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  • Other Sources  (576)
  • Springer  (300)
  • AGU (American Geophysical Union)  (183)
  • Inter Research  (58)
  • Nature Publishing Group  (35)
  • 1995-1999  (386)
  • 1985-1989  (190)
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  • 1
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    Die Erde im Visier - Geowissenschaften an der Schwelle zum 21. Jahrhundert (1999)
    Springer
    In:  Heidelberg, Springer, vol. 113, no. XVI:, pp. 1-14, (ISBN 1-56670-263-3)
    Details
    Publication Date: 1999
    Keywords: Handbook of geophysics ; Seismology ; Seismics (controlled source seismology) ; Early warning systems (earthquakes, volcanic eruptions, tsunamis etc.) ; Earthquake hazard ; KTB ; ICDP ; IOcean Drilling Program ; climate ; Antarctica ; Nuclear explosion ; Volcanology ; GeodesyY ; satellites ; remote ; sensing ; gas ; hydrates ; Geothermics ; Energy (of earthquakes) ; potable ; water ; waste ; soils ; evolution ; Geol. aspects ; geotechnics ; Engineering geophys. ; ores
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Swimming depth of migrating silver eels Anguilla japonica released at seamounts of the West Mariana Ridge, their estimated spawning sites (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 186 . pp. 265-269.
    Details
    Publication Date: 2017-07-06
    Description: Five hormone-treated female Japanese silver eels Anguilla japonica were tagged with ultrasonic transmitters and released by submersible in the West Pacific at seamounts of the West Mariana Ridge, their supposed spawning grounds. Four eels were tracked for 60 to 423 min in the vicinity of the seamounts. They did not settle at the seamounts but swam at a mean speed of 0.37 m s-1 into open water above deep ground. Their mean swimming depth ranged from 81 to 172 m. Experiments suggest that pre-matured A. japonica migrate to their spawning grounds in temperate warm water and at shallow depths.
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  • 3
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    Influence of bacterial density on the exchange of phosphate between sediment and overlying water (1999)
    Springer
    In:  Hydrobiologia, 392 (1). pp. 55-63.
    Details
    Publication Date: 2016-04-18
    Description: Fluxes of phosphate across the sediment–water interface have been measured using inhibitors of bacterial activity sterilization and chloramphenicol and a control in order to quantify the influence of bacterial abundance on them. Results show that phosphate concentration in the interstitial water decreased when bacteria were present, in relation to treated aquaria. The measured (Jo) and theoretical fluxes (Jd) of phosphate also were higher when bacterial activity was suppressed. Mass balance calculated for Carbon, Nitrogen and Phosphorus in the sediment revealed a loss of theses compounds when bacterial activity was suppressed, and a net accumulation of Carbon and Phosphorus, and loss of Nitrogen under natural conditions.
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  • 4
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    Dynamics and history of the Laptev Sea and its continental hinterland : a summary (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamica and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 693-711. ISBN 3-540-65676-6
    Details
    Publication Date: 2015-03-31
    Description: Russian and German scientists have investigated the extreme environmental system in and around the Laptev Sea in the Siberian Arctic. For the first time a major comprehensive research program combining the efforts of several projects addressed both oceanic and terrestrial processes, and their consequences for marine and terrestrial biota, landscape evolution as well as land-ocean interactions. The primary scientific goal of the multidisciplinary program was to decipher past climate variations and their impact on contemporary environmental changes. Extensive studies of the atmosphere, sea ice, water column, and sea-floor on the Laptev Sea Shelf, as well as of the vegetation, soil development, carbon cycle, permafrost behaviour and lake hydrology, and sedimentationon Taymyr Peninsula and Severnaya Zemlya Archipelago were performed during the past years under a framework of joint research activities. They included land and marine expeditions during spring (melting), summer (ice free), and autumn (freezing) seasons. The close bilateral cooperation between many institutions in Russia and Germany succeeded in drawing a picture of important processes shaping the marine and terrestrial environment in northern Central Siberia in Late Quaternary time. The success of the projects, which ended in late 1997, resulted in the definition and establishment of a new major research effort which will concentrate on establishing a better understanding of the paleoclimatic and paleoenvironmental record of the area. This is important because it allows to be able to judge rates and extremes of potential future environmental changes.
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  • 5
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    The formation of high-grade ignimbrites, II: A pyroclastic suspension current model with implications also for low-grade ignimbrites (1999)
    Springer
    In:  Bulletin of Volcanology, 60 . pp. 545-567.
    Details
    Publication Date: 2018-05-29
    Description: Analogue experiments in part I led to the conclusion that pyroclastic flows depositing very highgrade ignimbrite move as dilute suspension currents. In the thermo–fluid–dynamical model developed, the degree of cooling of expanded turbulent pyroclastic flows dynamically evolves in response to entrainment of air and mass loss to sedimentation. Initial conditions of the currents are derived from column-collapse modeling for magmas with an initial H2O content of 1–3 wt.% erupting through circular vents and caldera ring-fissures. The flows spread either longitudinally or radially from source up to a runout distance that increases with higher mass flux but decreases with higher gas content, temperature, bottom slope and coarser initial grain size. Progressive dilution by entrainment and sedimentation causes pyroclastic currents to transform into buoyant ash plumes at the runout distance. The ash plumes reach stratospheric heights and distribute 30–80% of the erupted material as widespread co-ignimbrite ash. Pyroclastic suspension currents with initial mass fluxes of 107-1012 kg/s can spread for tens of kilometers with only limited cooling, although they move as supercritical, strongly entraining currents for the eruption conditions considered here. With increasing eruption mass flux, cooling during passage through the fountain diminishes while cooling during flow transport increases. The net effect is that eruption temperature exerts the prime control on emplacement temperature. Pyroclastic suspension currents can form welded ignimbrite across their entire extent if eruption temperature is To11.3.Tmw, the minimum welding temperature. High eruption rates, a large fraction of fine ash, and a ring-fissure vent favor the formation of extensive high-grade ignimbrite. For very hot eruptions produc ing sticky, partially molten pyroclasts, analysis of particle aggregation systematics shows that factors favoring longer runout also favor more efficient aggregation, which reduces runout. As a result, very high-grade ignimbrites cannot spread more than a few tens of kilometers from their source. In cooler pyroclastic currents, particles do not aggregate, and the sedimentation process may involve re-entrainment of particles, which potentially leads to more extensive cooling and longer runout; such effects, however, are only significant when net erosion of substrate occurs. Model results can be employed to estimate mass flux and duration of ignimbrite eruptions from measured ignimbrite masses and aspect ratios. The model also provides an alternative explanation of the observed decrease in H/Lratios with ignimbrite mass.
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  • 6
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    Frictionally modified flow in a deep ocean channel: Application to the Vema Channel (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C9). 21,123-21,136.
    Details
    Publication Date: 2018-04-17
    Description: The modification of the exchange flow in a deep southern hemisphere passage, resembling the Vema Channel, by frictionally induced secondary circulation is investigated numerically. The hydrostatic primitive equation model is a two-dimensional version of the sigma-coordinate Princeton Ocean Model. The time dependent response of a stratified along-channel flow, forced by barotropic or baroclinic pressure gradients, is examined. Near the bottom, where the along-channel now is retarded, there is cross-channel Ekman nux that is associated with downwelling on the eastern side and upwelling on the western side of the channel. In the presence of stratification the cross-channel flow rearranges the density structure, which in turn acts on the along-channel velocity via the thermal wind relation. Eventually the cross-isobath Ekman flux is shut down. In the case of baroclinically driven flow of Antarctic Bottom Water through the Vema Channel the model reproduces the observed shape of the deep temperature profiles and their cross-channel asymmetry. The model offers an explanation that is alternative or supplementary to inviscid multilayer hydraulic theory that;was proposed in earlier studies. It explains the extremely thick bottom boundary layers in the center and on the western slope of the channel. The deep thermocline is spread out in the west and sharpened in the east, and the coldest water is found on the eastern side of the deep trough; The modified density field reduces the along-channel flow near the bottom and focuses it into a narrow jet on the eastern side of the channel.
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  • 7
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    On the water masses and mean circulation of the South Atlantic Ocean (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 . pp. 20863-20833.
    Details
    Publication Date: 2018-04-17
    Description: We examine recent observations of water mass distribution and circulation schemes at different depths of the South Atlantic Ocean to propose a layered, qualitative representation of the mean distribution of flow in this region. This furthers the simple upper layer geostrophic flow estimates of Peterson and Stramma [1991]. In addition, we assess how well ocean general circulation models (GCMs) capture the overall structure of flow in the South Atlantic in this regard. The South Atlantic Central Water (SACW) is of South Atlantic origin in the subtropical gyre, while the SACW in the tropical region in part originates from the South Indian Ocean. The Antarctic Intermediate Water in the South Atlantic originates from a surface region of the circumpolar layer, especially in the northern Drake Passage and the Falkland Current loop, but also receives some water from the Indian Ocean. The subtropical South Atlantic above the North Atlantic Deep Water and north of the Antarctic Circumpolar Current (ACC) is dominated by the anticyclonic subtropical gyre. In the eastern tropical South Atlantic the cyclonic Angola Gyre exists, embedded in a large tropical cyclonic gyre. The equatorial part of the South Atlantic shows several depth-dependent zonal current bands besides the Angola Gyre. Ocean GCMs have difficulty capturing this detailed zonal circulation structure, even at eddy-permitting resolution. The northward extent of the subtropical gyre reduces with increasing depth, located near Brazil at 16°S in the near-surface layer and at 26°S in the Antarctic Intermediate Water layer, while the tropical cyclonic gyre progresses southward. The southward shift of the northern part of the subtropical gyre is well resolved in global ocean GCMs. However, high horizontal resolution is required to capture the South Atlantic Current north of the ACC. The North Atlantic Deep Water in the South Atlantic progresses mainly southward in the Deep Western Boundary Current, but some water also moves southward at the eastern boundary.
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  • 8
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    The intermediate depth circulation of the western South Atlantic (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 26 . 21,3329-21,3332.
    Details
    Publication Date: 2018-02-13
    Description: The subsurface oceanic circulation is an important part of the Earth climate system. Subsurface currents traditionally are inferred indirectly from distributions of temperature and dissolved substances, occasionally supplemented by current meter measurements. Neutrally-buoyant floats however, now enable us to obtain for the first time directly measured intermediate depth velocity fields over large areas such as the western South Atlantic. Here, our combined data set provides unprecedented observations and quantification of key flow patterns, such as the Subtropical Gyre return flow (12 Sv; 1 Sverdrup = 10(6)m(3)s(-1)), its bifurcation near the Santos Plateau and the resulting continuous narrow and swift northward intermediate western boundary current (4 Sv). This northward flowing water passes through complex equatorial flows and finally enters into the North Atlantic.
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  • 9
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    Equatorial currents and transports in the upper central Indian Ocean: Annual cycle and interannual variability (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C7). 15,495-15,514.
    Details
    Publication Date: 2018-04-17
    Description: The zonal circulation south of Sri Lanka is an important link for the exchange of water between the Bay of Bengal and the Arabian Sea. Results from a first array of three moorings along 80 degrees 30'E north of 4 degrees 10'N from January .1991 to March 1992 were used to investigate the Monsoon Current regime [Schott et al., 1994]. Measurements from a second array of six current meter moorings are presented here. This array was deployed along 80 degrees 30'E between 45'S and 5 degrees N from July 1993 to September 1994 to investigate the annual cycle and interannual variability of the equatorial currents at this longitude. Both sets of moorings contribute to the Indian Ocean current meter array ICM8 of the World Ocean Circulation Experiment. The semiannual equatorial jet (EJ) was showing a large seasonal asymmetry, reaching a monthly mean eastward transport of 35 Sv (1 Sv = 1 x 10(6) m(3) s(-1)) in November 1993, but just 5 Sv in May 1994. The Equatorial Undercurrent (EUC) had a maximum transport of 17 Sv in March to April 1994. Unexpectedly, compared to previous observations and model studies, the EUC was reappearing again in August 1994 at more than 10 Sv transport and was still flowing when the moorings were recovered. In addition, monthly mean ship drifts near the equator are evaluated to support the interpretation of the moored observations. Interannual variability of the EJ in our measurements and ship drift data appears to be related to the variability of the zonal winds and Southern Oscillation Index. The output of a global numerical model (Parallel Ocean Climate Model) driven by the winds for 1993/1994 is used to connect our observations to the larger scale. The model reproduces the EJ asymmetry and shows the existence of the EUC and its reappearance during summer 1994.
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  • 10
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    Profiles of ectoenzymes in the Indian Ocean: Phenomena of phosphatase activity in the mesopelagic zone (1999)
    Inter Research
    In:  Aquatic Microbial Ecology, 19 . pp. 139-148.
    Details
    Publication Date: 2016-05-26
    Description: Phosphatase (P-ase) activity was determined together with other extracellular enzyme activities, bacterial abundance and production rates during the 2 SW Monsoon process studies of the German JGOFS Arabian Sea Program. Water samples were collected along the cruise tracks from the equator to the upwelling region at the shelf edge off Oman. Depth profiles of P-ase activity were strikingly different from those of the other enzymes. While values of aminopeptidase and β-glucosidase generally decreased below the euphotic zone, P-ase increased by factors of 1 to 7. The relation between peptidase- and P-ase activity was from 4 to 21 at the surface and from 3 to 5 at 800 m depth. Because P-ase production (dissolved and cell-bound) in deep waters is mainly dependent on bacteria, P-ase activities per bacterial cell were calculated: these were, on average, 37 times higher at 800 m than at the surface. We also observed a positive correlation of P-ase activity with phosphate concentrations in the depth profiles below the euphotic zone, while this relationship was much more variable in the mixed surface layer. These observations suggest that C-limited bacteria in the deep strata did not primarily focus on the phosphate generated by their P-ase activity but on the organic C compounds which were simultaneously produced and which could probably not be taken up prior to the hydrolytic detachment of phosphate. It is hypothesised that a considerable part of the measured P-ase activity was dissolved (though it might have originated from bacteria). These enzymes may be important for the slow, but steady regeneration of phosphate and organic C in mesopelagic waters.
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  • 11
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    Stomach contents of sperm whales Physeter macrocephalus stranded in the North Sea 1990-1996 (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 183 . pp. 281-294.
    Details
    Publication Date: 2018-05-08
    Description: Stomach contents of 17 sperm whales Physeter macrocephalus stranded in Scotland and Denmark during 1990-96 were analysed. All were sub-adult or adult males and stranded between November and March. They had presumably entered the North Sea during their southward migration from feeding grounds in Arctic waters. Other studies indicate that the majority of the whales were apparently healthy. The diet of these whales was found to consist almost entirely of cephalopods, principally squid of the genus Gonatus (hereafter 'Gonatus', but probably G. fabricii, an oceanic species characteristic of Arctic waters). The other prey species identified were also mostly oceanic cephalopods: the squids Histioteuthis bonnellii, Teuthowenia megalops and Todarodes sagittatus and the octopus Haliphron atlanticus. Although these results are consistent with other recent studies in the area based on single stranded whales, they differ from results of work on whales caught during commercial whaling operations in Icelandic waters (1960s to 1980s) in that little evidence of predation on fish was found in the present study. Remains of single individuals of the veined squid Loligo forbesi, the northern octopus Eledone cirrhosa and the saithe Pollachius virens provided the only possible evidence of feeding in the North Sea. We infer that sperm whales do not enter the North Sea to feed. The timing, and large and uniform sizes of the Gonatus species eaten (most had mantle lengths in the range 195 to 245 mm), as estimated from measurements of the lower beaks, and the seasonality of the strandings is consistent with the whales having fed on mature squid, possibly spawning concentrations--as has recently been reported for bottlenose whales. Assuming that the diet recorded in this study was representative of sperm whales during the feeding season, as much as 500000 t of Gonatus could be removed by sperm whales in Norwegian waters each year and up to 3 times that figure from the eastern North Atlantic as a whole. Evidence from other studies indicates that Gonatus is an important food resource for a wide range of marine predators in Arctic waters.
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  • 12
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    A new method for the determination of at-sea activity in sea turtles (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 185 . pp. 293-296.
    Details
    Publication Date: 2018-05-08
    Description: Interpretation of diving profiles of aquatic animals would be considerably enhanced by additional behavioural information. A new sensor is presented here which records animal movements. This sensor was tested on a captive loggerhead turtle Caretta caretta which showed similar activity patterns to free-living green turtles Chelonia mydas. A computer program with user-selectable options was developed to analyse the data consistently and rapidly. Using our sensor we calculated the total resting time, which differed by less than 5% from the real resting time when the sampling interval was 2 s. The method was additionally tested for different sampling intervals to find out its applicability for field studies.
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  • 13
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    Open-ocean convection: observations, theory and models (1999)
    AGU (American Geophysical Union)
    In:  Reviews of Geophysics, 37 (1). pp. 1-64.
    Details
    Publication Date: 2019-01-23
    Description: We review what is known about the convective process in the open ocean, in which the properties of large volumes of water are changed by intermittent, deep-reaching convection, triggered by winter storms. Observational, laboratory, and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales, the large-scale circulation of the ocean, and the prevailing meteorology. Two aspects make ocean convection interesting from a theoretical point of view. First, the timescales of the convective process in the ocean are sufficiently long that it may be modified by the Earth's rotation; second, the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability. Moreover, the convective and geostrophic scales are not very disparate from one another. Detailed observations of the process in the Labrador, Greenland, and Mediterranean Seas are described, which were made possible by new observing technology. When interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection, great progress in our description and understanding of the processes at work is being made.
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  • 14
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    Hydrothermal activity at Hook Ridge in the Central Bransfield Basin, Antarctica (1999)
    Springer
    In:  Geo-Marine Letters, 18 (4). pp. 277-284.
    Details
    Publication Date: 2017-06-29
    Description: Hydrothermal activity in the Central Bransfield Basin revealed an active low-temperature vent field on top of a submarine volcanic structure. A temperature anomaly was detected and the sea floor showed various patches of white silica (opal-A) precipitate exposures and some yellow–brown Fe-oxyhydroxide crusts. Enriched dissolved methane concentrations were encountered. Sediment was near 24°C just after the grab came on deck. No dense population of chemosynthetically based macrofauna known from other hydrothermal venting areas was present, except for pogonophora. The observations suggest that the sedimented hydrothermal field at Hook Ridge is a low-temperature end-member branch from a deeper hydrothermal source.
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  • 15
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    Diel variability of feeding activity in haddock (Melanogrammus aeglifinus) larvae in the East Shetland area, North Sea (1999)
    Springer
    In:  Marine Biology, 135 . pp. 361-368.
    Details
    Publication Date: 2018-06-06
    Description: Investigations of factors affecting feeding success in fish larvae require knowledge of the scales of variability of the feeding process itself and the indices used to assess this variability. In this study, we measured short-term (diel) variability in feeding rates of wild haddock (Melanogrammus aeglifinus) larvae four times per day during a 10-d cruise in the northern North Sea. Feeding activity was evaluated using indices of gut fullness, prey digestive state and biochemical measurements (tryptic enzyme activity). The gut fullness and the enzyme activity indices indicated moderate to high rates of food consumption throughout the cruise. Time series analysis of the three indices showed significant diel variability in all indices and enabled identification of significant lags between food uptake and peak digestive enzyme activity. The typical pattern of food consumption and digestion was characterized by maximal ingestion of prey early in the evening (19:00 hrs) and peak digestive enzyme activity at 01:00 hrs. The time scale over which enzyme activities reacted to prey ingestion was ca. 6 h, and is consistent with expectations from controlled laboratory experiments with other larval fish species. Significant diel variability in tryptic enzyme activity suggests that attempts to relate this measure of feeding success to other variables (e.g. food concentrations) should take care to accommodate natural cycles in feeding activity before making statistical comparisons.
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  • 16
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    The change from rifting to thrusting in the Northern Calcareous Alps as recorded in Jurassic sediments (1999)
    Springer
    In:  Geologische Rundschau, 87 . pp. 644-657.
    Details
    Publication Date: 2017-05-18
    Description: Facies analysis, fossil dating, and the study of the metamorphism in the Late Triassic to Early Cretaceous sedimentary successions in the central part of the Northern Calcareous Alps allow to reconstruct the tectonic evolution in the area between the South Penninic Ocean in the northwest and the Tethys Ocean with the Hallstatt Zone in the southeast. The Triassic as well as the Early and Middle Jurassic sediments were deposited in a rifted, transtensive continental margin setting. Around the Middle/Late Jurassic boundary two trenches in front of advancing nappes formed in sequence in the central part of the Northern Calcareous Alps. The southern trench (Late Callovian to Early Oxfordian) accumulated a thick succession of gravitatively redeposited sediments derived from the sedimentary sequences of the accreted Triassic–Liassic Hallstatt Zone deposited on the outer shelf and the margin of the Late Triassic carbonate platform. During a previous stage these sediments derived from sequences deposited on the more distal shelf (Salzberg facies zone of Hallstatt unit, Meliaticum), and in a later stage from more proximal parts (Zlambach facies zone of Hallstatt unit, Late Triassic reef belt). Low temperature–high pressure metamorphism of some Hallstatt limestones before redeposition is explained by the closure of parts of the Tethys Ocean in Middle to Late Jurassic times and associated subduction. In the northern trench (Late Oxfordian to Kimmeridgian) several hundred meters of sediment accumulated including redeposited material from a nearby topographic rise. This rise is interpreted as an advancing nappe front as a result of the subduction process. The sedimentary sealing by Tithonian sediments, documented by uniform deep-water sedimentation (Oberalm Formation), gives an upper time constraint for the tectonic events. In contrast to current models, which propose an extensional regime for the central and eastern Northern Calcareous Alps in the Late Jurassic, we propose a geodynamic model with a compressional regime related to the Kimmerian orogeny.
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  • 17
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    Clay mineral distribution in surface sediments of the Laptev Sea : indication for sediment provinces, dynamics and sources (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 587-599. ISBN 3-540-65676-6
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    Publication Date: 2015-04-08
    Type: Book chapter , NonPeerReviewed
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  • 18
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    Main structural elements of eastern Russian Arctic continental margin derived from satellite gravity and multichannel seismic reflection data (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 667-682. ISBN 3-540-65676-6
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    Publication Date: 2015-04-08
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  • 19
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    Microbial diversity in the marine sponge Aplysina cavernicola (formerly Verongia cavernicola) analyzed by fluorescence in situ hybridization (FISH) (1999)
    Springer
    In:  Marine Biology, 134 (3). pp. 461-470.
    Details
    Publication Date: 2015-08-27
    Description: We have employed electronmicroscopical methods (SEM, TEM) to document the microbial community associated with the marine sponge Aplysina cavernicola (formerly Verongia cavernicola, class Demospongiae). Five dominant bacterial types were identified, three of which resemble the morphotypes originally described by Vacelet (1975). One bacterial type possesses morphological properties that are characteristic of the genus Planctomyces. In addition, morphologically uniform bacteria which reside inside the nuclei of host cells were observed. Using in situ hybridization with fluorescently labelled rRNA probes directed against known bacterial groups, the phylogenetic affiliation of the mesohyl bacteria was assessed. It could be shown that the vast majority of mesohyl bacteria belongs to the domain Bacteria with a low GC content. Among the Bacteria, the delta-Proteobacteria were most abundant, followed by the gamma-Proteobacteria and representatives of the Bacteroides cluster. Clusters of Gram-positive bacteria with a high GC content were also found consistently in low amounts. No hybridization signal was obtained with probes specific to the domain Archaea, to the alpha- and beta-Proteobacteria and to the Cytophaga/Flavobacterium cluster. This study describes for the first time the application of the “top-to-bottom approach” using 16S rRNA probes and in situ hybridization to assess the microbial diversity in Aplysina sponges
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  • 20
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    Oceanographic causes for transarctic ice transport of river discharge (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 73-92. ISBN 3-540-65676-6
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    Publication Date: 2016-01-19
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  • 21
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    Distribution of pollen and spores in surface sediments of the Laptev Sea (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 577-585. ISBN 3-540-65676-6
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    Publication Date: 2015-04-08
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  • 22
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    Determination of depositional Beryllium-10 fluxesin the area of the Laptev Sea and Beryllium-10 concentrations in water samples of high northern latitudes (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 516-532. ISBN 3-540-65676-6
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    Publication Date: 2015-04-08
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  • 23
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    Planktic foraminifera in Holocene sediments from the Laptev Sea and the central Arctic Ocean : species distribution and paleobiogeographical implication (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 601-613. ISBN 3-540-65676-6
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    Publication Date: 2015-04-08
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  • 24
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    Step-like vertical structure formation due to turbulent mixing of initially continuous density gradients (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 93-99. ISBN 3-540-65676-6
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    Publication Date: 2015-04-08
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  • 25
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    Frazil ice formation during the spring flood and its role in transport of sediments to the ice cover (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 125-140. ISBN 3-540-65676-6
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    Publication Date: 2015-04-08
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  • 26
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    Oceanography: All change in the Arctic (1999)
    Nature Publishing Group
    In:  Nature, 397 (6718). pp. 389-391.
    Details
    Publication Date: 2015-07-16
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  • 27
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    Metabolism of nitrogen and sulfur in ectosymbiotic bacteria of marine nematodes (Nematoda, Stilbonematinae) (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 183 . pp. 149-158.
    Details
    Publication Date: 2015-08-27
    Description: Nematodes of the family Stilbonematinae are known for their highly specific association with ectosymbiotic bacteria. These worms are members of the meiofauna in marine, sulfide-rich sediments, where they migrate around the redox boundary layer. In this study, bacterial ectosymbionts of 2 species of marine nematodes, Stilbonema sp. and Laxus oneistus, were shown to be capable of the respiratory reduction of nitrate and nitrite (denitrification). The use of these alternative electron acceptors to oxygen by the bacteria allows the animals to migrate into the deeper, anoxic sediments, where they can exploit the sulfide-rich patches of the deeper sediment layers. The accumulation of thiols (sulfide, thiosulfate, sulfate and glutathione) in body tissues of the worms was determined following incubation in the presence of various electron donors (sulfide, thiosulfate) and acceptors (nitrate). In their chemoautotrophic metabolic potential, the ectosymbionts of the 2 nematode species were found to resemble the phylogenetically related, intracellular symbionts of macrofaunal hosts of deep-sea hydrothermal vents and other sulfide-rich habitats.
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  • 28
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    Glacial-interglacial records of the reflectance of sediments from the Norwegian-Greenland-Iceland Sea (Nordic seas) (1999)
    Springer
    In:  International Journal of Earth Sciences, 88 (2). pp. 325-336.
    Details
    Publication Date: 2018-05-28
    Description:  The reflectance of sediments (gray level) were measured on 11 sediment cores from the Norwegian–Greenland–Iceland Sea (Nordic seas). The analyzed time interval covers the past five glacial–interglacial cycles. Although the results demonstrate that the gray-level method has a potential for stratigraphic purposes, it is indicated that gray-level changes in the Nordic seas are not necessarily driven by variations in the content of biogenic calcite. A detailed comparison of gray-level values with contents of total CaCO3 (carbonate) and total organic carbon (TOC) reveals no overall causal link between these proxies. However, specific glacial core sections with layers containing organic-rich sediment clasts as a consequence of iceberg-rafting seem to correlate well with law gray-level values. Of those cores which show relatively high and comparable carbonate values in the last three main interglacial intervals (stages 11, 5.5, and 1), stage 11 is always marked by the highest gray-level values. A close inspection of the surface structure of the foraminiferal tests as well as the conduction of reflectance measurements on these tests leads to the conclusion that enhanced carbonate corrosion occurred during stage 11. The test corrosion not only affected the reflectance of the tests by making them appear whiter, it also seems responsible for the comparatively high gray-level values of the total sediment in stage 11. In contrast, the relatively low gray-level values found in stages 5.5, and 1 are not associated with enhanced test corrosion. This observation implies that variable degrees of carbonate corrosion can have a profound effect on total sediment reflectance.
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  • 29
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    Diatoms from surface sediments of the Saint Anna Trough (Kara Sea) (1999)
    Springer
    In:  In: Land-Ocean Systems in the Siberian Arctic : Dynamics and History. , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A. and Eicken, H. Springer, Berlin (u.a.), pp. 553-560. ISBN 3-540-65676-6
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    Publication Date: 2015-04-09
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  • 30
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    Tetrathionate production by sulfur-oxidizing bacteria and the role of tetrathionate in the sulfur cycle in sediments of the Baltic Sea (1999)
    Inter Research
    In:  Aquatic Microbial Ecology, 17 (3). pp. 255-265.
    Details
    Publication Date: 2016-05-26
    Description: The role of tetrathionate in the sulfur cycle of Baltic Sea sediments was investigated in different habitats and under a variety of environmental conditions. Sediment profiles were recorded with regard to numbers of thiosulfate oxidizing bacteria, concentrations of sulfur compounds, and potential rates of thiosulfate oxidation. Products of thiosulfate oxidation were quantified in incubated sediment samples and in pure cultures. Evidence was found that tetrathionate is formed within these sediments, that sulfur oxidizing bacteria are present in considerable numbers, that these bacteria are of major importance in the oxidation of reduced sulfur compounds in their habitat, and that tetrathionate is an important oxidation product of these bacteria. Thiosulfate is oxidized by bacteria isolated from these sediments to varying proportions of tetrathionate, sulfate, and also elemental sulfur. In highly sulfidic sediments and in the presence of large amounts of organic matter, tetrathionate was present in sediment horizons in which thiosulfate and elemental sulfur also accumulated. A tetrathionate cycle is proposed to be active in natural marine and brackish water sediments in which, due to combined bacterial action and chemical reactions, a net oxidation of sulfide to elemental sulfur occurs in the presence of catalytic amounts of thiosulfate and tetrathionate.
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  • 31
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    An eddy permitting coupled physical-biological model of the North Atlantic. Part I: Sensitivity to advection numerics and mixed layer physics (1999)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 13 (1). pp. 135-160.
    Details
    Publication Date: 2017-06-06
    Description: Physical influences on biological primary production in the North Atlantic are investigated by coupling a four-component pelagic ecosystem model with a high-resolution numerical circulation model. A series of sensitivity experiments demonstrates the important role of an accurate formulation of upper ocean turbulence and advection numerics. The unrealistically large diffusivity implicit in upstream advection approximately doubles primary production when compared with a less diffusive, higher-order, positive-definite advection scheme.This is of particular concern in the equatorial upwelling region where upstream advection leads to a considerable increase of upper ocean nitrate concentrations. Counteracting this effect of unrealistically large implicit diffusion by changes in the biological model could easily lead to misconceptions in the interpretation of ecosystem dynamics. Subgrid-scale diapycnal diffusion strongly controls biological production in the subtropical gyre where winter mixing does not reach the nutricline. The parameterization of vertical viscosity is important mainly in the equatorial region where friction becomes an important agent in the momentum balance.
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  • 32
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    Control of macroalgal blooms at early developmental stages: Pilayella litoralis versus Enteromorpha spp (1999)
    Springer
    In:  Oecologia, 119 . pp. 46-54.
    Details
    Publication Date: 2017-10-09
    Description: Although blooms of opportunistic fast-growing macroalgae now occur frequently in coastal ecosystems affected by eutrophication, their initiation and control is little understood. Most previous studies have focused on the ecophysiology of adult algae only. We show that spores and/or germlings may represent critical stages in the life cycles and mass-developments of co-occurring opportunistic macroalgae in the Baltic (Pilayella littoralis and Enteromorpha spp.). We investigated the overwintering of spores, timing of germination, subsequent growth, and grazing on spores and germlings, in order to explain the initiation of mass blooms and species dominance patterns. In the field, Enteromorpha spp. showed 10- to 50-fold higher abundances of overwintering microscopic forms (up to 330 individuals cm-2) than P. littoralis. Moreover, we found continuous production of spores (up to 1.2 million settling spores m-2 h-1) from April to October in Enteromorpha spp., while there was evidence of only a short reproductive period in Pilayella. However, in spring, germlings and adults of P. littoralis appeared earlier in the field and reached a 10-fold higher biomass than Enteromorpha spp. In factorial laboratory experiments including temperature and light, there were clear differences in timing of germination. P. littoralis germinated at 5°C whereas Enteromorpha spp. required temperatures of 10-15°C for germination. In contrast, we detected only minor differences in growth response among adults of P. littoralis and Enteromorpha spp. Germination, not growth of adults, appeared to be the ecophysiological bottleneck for initiating mass spring development. Following the spring Pilayella bloom, Enteromorpha germlings occurred massively in the field (April-September), but rarely developed into adults. In laboratory feeding experiments we tested whether crustacean mesograzers common in summer may control development of Enteromorpha germlings. Both germination of settled spores and growth of germlings were reduced by 93-99% in the presence of grazers (Idotea chelipes and Gammarus locusta). Thus in addition to ecophysiological constraints, grazers, if present, may play a decisive role in the early life stages of macroalgal mass developments. These results mirror patterns of overwintering of seeds, germination control, seed and seedling predation in terrestrial plant communities.
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  • 33
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    Role of iron, light, and silicate in controlling algal biomass in subantarctic waters SE of New Zealand (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (13). 13395-13408 .
    Details
    Publication Date: 2017-11-24
    Description: Phytoplankton processes in subantarctic (SA) waters southeast of New Zealand were studied during austral autumn and spring 1997. Chlorophyll a (0.2–0.3 μg L−1) and primary production (350–650 mg C m−2 d−1) were dominated by cells 〈2 μm (cyanobacteria) in both seasons. The photochemical efficiency of photosystem II (Fυ/Fm) of cells was low (0.3), indicating physiological stress. Dissolved Fe (DFe) levels in surface waters were subnanomolar, and the molecular marker flavodoxin indicated that cells were iron stressed. In contrast, Subtropical Convergence (STC) and subtropical waters had higher algal biomass/production levels, particularly in spring. In these waters, DFe levels were 〉1 nmol kg−1, there was little evidence of Fe-stressed algal populations, and Fυ/Fm approached 0.60 at the STC. In addition to these trends, waters of SA origin were occasionally observed within the STC and north of the STC, and thus survey data were interpreted with caution. In vitro Fe enrichment incubations in SA waters resulted in a switch from flavodoxin expression to that of ferredoxin, indicating the alleviation of Fe stress. In another 6-day experiment, iron-mediated increases in chlorophyll a (in particular, increases in large diatoms) were of similar magnitude to those observed in a concurrent Si/Fe enrichment; ambient silicate levels were 4 μM. A concurrent in vitro Fe enrichment, at irradiance levels comparable to the calculated mean levels experienced by cells in situ, resulted in relatively small increases (approximately twofold) in chlorophyll a. Thus, in spring, irradiance and Fe may both control diatom growth. In contrast, during summer, as mean irradiance increases and silicate levels decrease, Fe limitation, Fe/Si colimitation, or silicate limitation may determine diatom growth.
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  • 34
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    A box model for the paleoceanography of the Black Sea (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters (26). pp. 497-500.
    Details
    Publication Date: 2018-02-13
    Description: The evolution of the Black Sea's salinity after the opening of the Bosporus about 7500 years ago is investigated using a simple two-box model. The model consists of watermass and salt conservation equations, and allows for changes in halocline depth. The paleoceanographic box model is forced by present-day Mediterranean inflow and outflow, and atmospheric forcings. Analytic solutions for the evolution of the box volumes are given. Model salinities reach 90% of their the present-day values in both boxes about 2,500 years after the opening of the Bosporus. The evolution of the salinities is shown to be almost independent of the evolution of the box volumes, and the results are compared with the existing paleoceanographic proxy records.
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  • 35
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    Greenhouse gases in cold water filaments in the Arabian Sea during the Southwest Monsoon (1999)
    Springer
    In:  Naturwissenschaften, 86 . pp. 489-491.
    Details
    Publication Date: 2017-03-07
    Description: The distribution of partial pressure of carbon dioxide and the concentrations of nitrous oxide and methane were investigated in a cold water filament near the coastal upwelling region off Oman at the beginning of the southwest monsoon in 1997. The results suggest that such filaments are regions of intense biogeochemical activity which may affect the marine cycling of climatically relevant trace gases
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  • 36
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    Volatile halogenated hydrocarbons over the western Pacific between 43° and 4°N (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Atmospheres, 104 . pp. 1663-1678.
    Details
    Publication Date: 2017-11-24
    Description: A spectrum of halogenated hydrocarbon compounds in marine air masses were surveyed over an area in the western Pacific between 43°N, 150°E and 4°N, 113°E in September 1994. The ship's track between northern Japan and Singapore traversed three climatic zones of the northern hemisphere. Recently polluted air, clean marine air derived from the central Pacific Ocean from different latitudes, and marine air from the Indonesian archipelago were collected. Tetrachloroethene and trichloroethene of anthropogenic origin, brominated halocarbons as tribromomethane, dibromochloromethane and bromodichloromethane of anthropogenic and natural sources, and other trace gases were measured in the air samples. Very sparse data on the distribution of these compounds exist for the western Pacific atmosphere. The distribution patterns of the compounds were related to synoptic-scale meteorology, spatial conditions, and origin of the air masses. Anthropogenic and natural sources for both chlorinated and brominated substances were identified. Tetrachloroethene and trichloroethene concentrations and their ratios identify anthropogenic sources. Their mixing ratios were quite low compared to previously published data. They are in agreement with expected low concentrations of photochemically active substances during autumn, with an overall decrease in concentrations toward lower latitudes, and with a decrease of emissions during recent years. Strong evidence for a natural source of trichloroethene was discovered in the tropical region. The concentrations of naturally released brominated species were high compared to other measurements over the Pacific. Gradients toward the coasts and elevated concentrations in air masses influenced by coastal emissions point to significant coastal sources of these compounds. The trace gas composition of anthropogenic and natural compounds clearly identified the air masses which were traversed during the cruise.
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  • 37
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    The Importance of flow in the Mozambique Channel to seasonality in the greater Agulhas Current system (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 26 . pp. 3321-3324.
    Details
    Publication Date: 2018-02-13
    Description: The temporal variability of the greater Agulhas Current system has important climatological consequences. Some recent results have suggested that this variability contains a large seasonal component, due to changes in the circulation at latitudes poleward of Madagascar only. A model simulation shows that the contribution of Tropical Surface Water to Agulhas Current waters, via the Mozambique Channel, also has a distinct seasonal characteristic that is brought about by the seasonal wind stress over the tropical Indian Ocean. This simulated flow through the Channel contributes substantially to the seasonality of the Agulhas Current. This model result is shown to be not inconsistent with available hydrographic observations.
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  • 38
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    Factors influencing seaweed responses to eutrophication: Some results from EU-project EUMAC (1999)
    Springer
    In:  Journal of Applied Phycology, 11 . pp. 69-78.
    Details
    Publication Date: 2018-06-15
    Description: Seaweed responses to eutrophication and their role in coastal eutrophication processes were compared at 8 different sites along the European coasts from the Baltic to the Mediterranean as part of the EU-ENVIRONMENT Project Marine Eutrophication and benthic Macrophytes (EUMAC). Structural and functional changes of marine benthic vegetation typical of eutrophic waters, in particular mass development (blooms) of certain seaweeds, are not merely the result of increased nutrient loading, but must be attributed to complex interactions of primary and secondary effects during the eutrophication process. Due to species-specific physiological properties of the algae (nutrient kinetics, growth potential, light, temperature requirements), the combined effects of abiotic and biotic factors on juvenile or adult developmental stages control the development of algal blooms in different ways. In particular the role of light, temperature, water motion and oxygen depletion, as well as of grazers, on early and adult developmental stages of the algae are considered. The result are discussed in the context of coastal eutrophication control and management
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  • 39
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    Introduction to special section: World Ocean Circulation Experiment: South Atlantic results (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C9). pp. 20859-20861.
    Details
    Publication Date: 2018-04-17
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  • 40
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    Foraging behaviour and reproductive success in Magellanic penguins (Sphensicus magellanicus): a comparative study of two colonies (1999)
    Springer
    In:  Marine Biology, 133 . pp. 381-393.
    Details
    Publication Date: 2018-06-07
    Description: During the breeding season 1996/97 we compared the foraging and diving behaviour of adult Magellanic penguins (Spheniscus magellanicus), growth rates of their chicks and their breeding success at two colonies in the south of Chile. One of the colonies is located on Magdalena Island in the Strait of Magellan, where a commercial fishery existed several years ago; the other, on the shores of the yet unexploited Otway Sound. Thirty adult Magellanic penguins were equipped with time–depth recorders (TDR) to investigate their behaviour at sea. In each colony 15 adults returning from the sea were stomach flushed to analyse dietary composition. Chicks of TDR-nests and of 12 additional control nests were weighed regularly. Foraging effort was significantly higher at Magdalena than at Otway. The Magdalena-birds usually remained at sea overnight and foraged with a mean duration of 18 h, whereas the penguins of Otway Sound foraged during 1-d trips with a mean duration of only 9 h. Compared to Magdalena, penguins at Otway dived shallower (mean depth 14.9 vs 16.5 m), shorter (mean duration 57.8 vs 64.3 s) and showed more searching and feeding as opposed to travelling activity (on average 69 vs 55%) during the foraging trips. Compared to other breeding locations both colonies were characterised by high chick growth rates, high fledging body masses (〉3 kg) and early fledging date (after 70 to 80 d), and a very high reproductive success of 〉1.75 chicks per breeding pair. Comparison of the diet (almost exclusively sprats) with former investigations suggests for both areas an unchanged food structure over the last decade. The results in both colonies indicate ample food availability in the season 1996/97. However, compared to the much smaller Otway colony, penguins on Magdalena have to cope with more competition for food. Therefore, future prey limitation, through resumed fishery operations or effects of El Niño, might affect the penguin population on the island more negatively than in Otway Sound.
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  • 41
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    A tropical bird in the Artic (The Cormorant paradox) (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 188 . pp. 305-309.
    Details
    Publication Date: 2018-05-08
    Description: Seabirds, like all marine endotherms, have to compensate for the extensive cooling effect of water when diving. Alone among them, cormorants (Phalacrocoracidae) have a wettable plumage and are predicted to require disproportionately large amounts of food to balance heat losses. These piscivorous birds are thus thought to have a detrimental impact on fish stocks. However, we show here that even in great cormorants from Greenland, which dive in water at 3 to 7°C, daily food intake is lower than for well-insulated European seabirds. Despite their wettable plumage, cormorants thus appear to manage their energy budgets in a remarkably efficient way. Nevertheless, the specific foraging strategies which enable this performance make cormorants dependent on high prey density areas, a feature that should be taken into account by future management plans.
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  • 42
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    Predation on cephalopods by Antarctic fur seals, Arctocephalus gazellae, at two localities of the Scotia Arc, Antarctica (1999)
    Springer
    In:  Polar Biology, 21 . pp. 59-63.
    Details
    Publication Date: 2021-06-16
    Description: The cephalopod remains from 206 Antarctic fur seal (Arctocephalus gazella) scats collected at Mossman Peninsula, South Orkney Islands (n = 105) and at Stranger Point, South Shetland Islands (n = 101) contained 148 beaks (57 lower and 91 upper). The lower beaks were sorted and measured. Identification of 33 of the lower beaks that were collected at Mossman Peninsula revealed two squid species, Brachioteuthis ?picta (n = 26) and Psychroteuthisglacialis (n = 7), with lower rostral lengths (LRL) of 2.0–3.5 mm, and 1.0–2.5 mm, respectively. Identification of 15 of the lower beaks collected at Stranger Point revealed the same squid species, with the LRL of B. ?picta ranging from 3.0–3.4 mm (n = 9), and that of P. glacialis from 2.0 to 3.5 mm (n = 6). Estimated squid sizes and wet masses indicate that Antarctic fur seals feed on the small sub-adult squid which inhabit the surface layers. We have compared the squid diet estimated for the seals with that reported for its congeners in lower latitudes and other Antarctic seals, and conclude that cephalopods do not form an important food resource for Antarctic fur seals.
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  • 43
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    Groundwater seepage in the marine environment. Role for mass flux and bacterial activity (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 178 . pp. 169-177.
    Details
    Publication Date: 2018-05-08
    Description: In Eckernförde Bay (western Baltic Sea) pockmark structures are induced by groundwater seeping out of the sediment. On 3 occasions in winter and spring 1993-94 we investigated the influence of groundwater on the reduction of salinity, on porewater chemistry, and on bacterial activities (methane oxidation and sulphate reduction). In 2 out of 3 sampling campaigns groundwater discharge could be detected. The concentration gradients of Cl- and SO4= are moved towards the sediment surface by the vertical advection of groundwater during seep times. Without groundwater discharge the porewater chemistry resembled the control site. Compared to the control site, the methane oxidation and sulphate reduction rates were elevated at the pockmark site, reaching maximum values of 49 and 269 µmol l-1 d-1 respectively. The groundwater venting from the pockmark had an end member composition of 80 mM Na+, 1.0 mM Ca++ and was depleted in Mg++. Due to mixing of these major cations along the groundwater/seawater interface, no CaCO3 precipitation was found around the pockmark site.
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  • 44
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    Occurence of trichodinid ciliates (Peritricha: Urceo-lariidae) in the Kiel Fjord, Baltic Sea, and its possible use as biological indicator (1999)
    Springer
    In:  Parasitology Research, 85 . pp. 726-732.
    Details
    Publication Date: 2018-01-19
    Description: Investigations on the occurrence of trichodinid ciliates from fish caught in the Kiel Bight and Kiel Fjord (western Baltic Sea) were carried out between September 1996 and March 1997. Smears of the gills, fins, and skin of 120 Gadus morhua and 92 Platichthys flesus caught by fish traps and trammel nets revealed the presence of trichodinid ciliates. According to the fish species and locality, different prevalences and densities of trichodinid ciliates were found. Fish caught in the Kiel Bight revealed a lower prevalence of trichodinid ciliates on their gills (P. flesus 74.2%, G. morhua 3.8%) in comparison with fish of the same species and size caught in the Kiel Fjord (P. flesus 75.0%, G. morhua 26.2%). In both areas, P. flesus was more heavily infested than G. morhua. Seasonal changes in the prevalence of infestation of P. flesus between autumn and winter in the Kiel Fjord are proposed to be linked to an increase in bacterial biomass during winter. The fish ecology in combination with the total number of bacteria in the fish environment is discussed as an important factor influencing the abundance of trichodinid ciliates. The present data suggest the use of trichodinid ciliates as an indicator for eutrophication in brackish-water environments.
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  • 45
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    Interbasin deep water exchange in the western Mediterranean (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C10). 23,495-23,508.
    Details
    Publication Date: 2018-04-17
    Description: Owing to its nearly enclosed nature, the Tyrrhenian Sea at first sight is expected to have a small impact on the distribution and characteristics of water masses in the other basins of the western Mediterranean, The first evidence that the Tyrrhenian Sea might, in fact, play an important role in the deep and intermediate water circulation of the entire western Mediterranean was put forward by Hopkins [1988]. There, an outflow of water from the Tyrrhenian Sea into the Algero Provencal Basin was postulated in the depth range 700-1000 m, to compensate for an observed inflow of deeper water into the Tyrrhenian Sea. However, this outflow, the Tyrrhenian Deep Water (TDW), was undetectable since it would have hydrographic characteristics that could also be produced within the Algero-Provencal Basin. A new data set of hydrographic, tracer, lowered Acoustic Doppler Current Profiler (LADCP), and deep float observations presented here allows us now to identify and track the TDW in the Algero-Provencal Basin and to demonstrate the presence and huge extent of this water mass throughout the western Mediterranean. It extends from 600 m to 1600-1900 m depth and thus occupies much of the deep water regime. The outflow from the Tyrrhenian is estimated to be of the order of 0.4 Sv (Sv=10(6) m(3) s(-1)), based on the tracer balances. This transport has the same order of magnitude as the deep water formation rate in the Gulf of Lions. The Tyrrhenian Sea effectively removes convectively generated deep water (Western Mediterranean Deep Water (WMDW)) from the Algero-Provencal Basin, mixes it with Levantine Intermediate water (LIW) above, and reinjects the product into the Algero-Provencal Basin at a level between the WMDW and LIW, thus smoothing the temperature and salinity gradients between these water masses. The tracer characteristics of the TDW and the lowered ADCP and deep float observations document the expected but weak cyclonic circulation and larger flows in a vigorous eddy regime in the basin interior
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  • 46
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    On the determination of characteristics of the interior ocean dynamics from radar signatures of oceanic internal solitary waves (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 . 30,039-30,046.
    Details
    Publication Date: 2018-04-17
    Description: In this paper we discuss two different methods of inferring characteristics of the interior ocean dynamics from radar signatures of internal solitary waves visible on synthetic aperture radar (SAR) images. The first one consists in the recognition and the interpretation of sea surface patterns of internal solitary waves; the second one consists in the analysis of the modulation depth of the normalized radar backscattering cross section (NRCS) associated with internal solitary waves. For this purpose we consider a data set composed of SAR and in situ measurements carried out from 1991 to 1997 in the region of the Strait of Messina. The recognition and the interpretation of sea surface patterns of internal solitary waves in the Strait of Messina can be used to study characteristics of the density distribution in the area: The internal wave field varies with seasonal variations in the vertical density stratification and with remotely induced variations, i.e., variations induced by the larger-scale circulation, in the horizontal density distribution. In order to inquire into the possibility of inferring parameters of the interior ocean dynamics by analyzing the modulation of the NRCS associated with internal solitary waves, several numerical simulations are carried out using a radar imaging model. These simulations are performed by assuming different wind conditions and internal wave parameters. It is shown that an accurate knowledge of wind conditions is crucial for deriving internal wave parameters and hence parameters of the interior ocean dynamics from the modulation of measured NRCS associated with internal solitary waves.
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  • 47
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    Immunological and molecular probes to detect phytoplankton responses to environmental stress in nature (1999)
    Springer
    In:  In: Molecular Ecology of Aquatic Communities. , ed. by Zehr, J. P. and Voytek, M. A. Developments in Hydrobiology, 138 . Springer, Berlin, Germany, pp. 177-198. ISBN 978-94-010-5827-8
    Details
    Publication Date: 2018-06-29
    Description: Recent advances in using immunological and nucleic acid probes to detect the effects of environmental stress on phytoplankton growth rate and yield are reviewed here. The rationale for this approach is discussed in the context of the general response observed from microorganisms grown under stress imposed by various environmental factors. Retrenchment, or the observed down-regulation of metabolic processes under nutrient deficiency, is categorized as a general response that is of limited use in designing probes to stress induced by a specific nutrient. In contrast, compensation and the increase capacity for nutrient acquisition are specific responses that appear more promising for the development of such probes. Methods and approaches used to design immunological and nucleic acid probes for stress imposed by nutrient deficiency are reviewed. Specific examples for iron and nitrogen limitation are presented to demonstrate the potential use of nutrient stress indicators in natural populations of phytoplankton. Finally, the limitations of this approach and the importance of understanding the regulation of the genes and proteins used to prepare the probes are emphasized.
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  • 48
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    Influence of transparent expolymer particles (TEP) on sinking velocity of Nitzschia closterum aggregates (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 182 . pp. 69-76.
    Details
    Publication Date: 2018-05-08
    Description: Sinking velocities of more than 300 Nitzschia closterium aggregates were determined during roller table incubation using digital image analysis. To examine the influence of transparent exopolymer particles (TEP) on aggregate settling speed, 3 experiments with different ratios of TEP to cell volume concentration were conducted. The results showed that, for N. closterium aggregates without TEP, sinking velocity (U) was significantly related to the equivalent spherical diameter (ESD) of the aggregates, yielding U (cm s-1) = 1.89 (ESD, cm)0.55. The higher was the specific TEP content of an aggregate, the lower was the sinking velocity and the less pronounced was the size versus velocity relationship. Excess densities (Δρ) of aggregates were derived from velocity measurements and 3-dimensional fractal dimensions (D3) of aggregates were calculated from scaling properties of Δρ. Values for D3 never exceeded 2 and fit well to values of the 2-dimensional fractal dimension (D2) attained from image analysis.
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  • 49
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    Ecology of Pseudoterranova decipiens (Krabbe, 1878) (Nematoda: Anisakidae) from Antarctic waters (1999)
    Springer
    In:  Parasitology Research, 85 . pp. 638-646.
    Details
    Publication Date: 2018-01-19
    Description: The present study provides further data on the occurrence of Pseudoterranova decipiens in fish from two different sampling sites in the Antarctic. A total of 690 fish belonging to 33 species from the eastern Weddell Sea and 322 fish belonging to 12 species from the South Shetland Islands were examined. Altogether, 23 fish species were found to be infested and 11 new host records could be established. P. decipiens occurred at a water depth of between 80 and 820 m. Chaenocephalus aceratus and Notothenia coriiceps from the South Shetland Islands were the species with the highest prevalence (95%) and intensity (2-194 and 1-121, respectively) of infestation. Both are transport hosts, which mainly feed on benthic nototheniid fish species and accumulate the nematodes. Bathypelagic, pelagic, or mainly euphausid feeding fish species were only lightly infested, if at all. This demonstrates the benthic life cycle of P. decipiens in the Antarctic. The preferred site of infestation was the body cavity and the liver; no specimen could be isolated from the fish musculature. This might be explained by the low water temperatures. The infestation of fish from the Weddell Sea was distinctly lower than that of fish around the South Shetland Islands. Besides possible differences in final host populations at the two localities studied, the loss of eggs and larvae under the eastern Weddell Sea shelf ice and over the continental slope and differences in the availability of the first intermediate and macroinvertebrate hosts led to a lower level of infestation. Another role, although nondecisive, may be played by the reduced time of development and infectivity of eggs and larvae, respectively, in the extremely cold waters of the Weddell Sea. P. decipiens is not a rare but, rather a well-established parasite of the Antarctic fauna, which demonstrates the ability of this cosmopolitan species to complete its life cycle even under conditions of subzero temperatures.
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  • 50
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    Stable isotope fractionation by phytoplankton in response to daylength, growth rate, and CO2 availability (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 184 . pp. 31-41.
    Details
    Publication Date: 2018-05-08
    Description: Stable carbon isotope fractionation (ε p) of 7 marine phytoplankton species grown in different irradiance cycles was measured under nutrient-replete conditions at a high light intensity in batch cultures. Compared to experiments under continuous light, all species exhibited a significantly higher instantaneous growth rate (μi), defined as the rate of carbon fixation during the photoperiod, when cultivated at 12:12 h, 16:8 h, or 18:6 h light:dark (L/D) cycles. Isotopic fractionation by the diatoms Skeletonema costatum, Asterionella glacialis, Thalassiosira punctigera, and Coscinodiscus wailesii (Group I) was 4 to 6o/oo lower in a 16:8 h L/D cycle than under continuous light, which we attribute to differences in μi. In contrast, ε p in Phaeodactylum tricornutum, Thalassiosira weissflogii, and in the dinoflagellate Scrippsiella trochoidea (Group II) was largely insensitive to daylength-related differences in instantaneous growth rate. Since other studies have reported growth-rate dependent fractionation under N-limited conditions in P. tricornutum, μi-related effects on fractionation apparently depend on the factor controlling growth rate. We suggest that a general relationship between εi and μi/[CO2,aq] may not exist. For 1 species of each group we tested the effect of variable CO2 concentration, [CO2,aq], on isotopic fractionation. A decrease in [CO2,aq] from ca 26 to 3 µmol kg-1 caused a decrease in ε p by less than 3o/oo. This indicates that variation in μi in response to changes in daylength has a similar or even greater effect on isotopic fractionation than [CO2,aq] in some of the species tested. In both groups ε p tended to be higher in smaller species at comparable growth rates. In 24 and 48 h time series the algal cells became progressively enriched in 13C during the day and the first hours of the dark period, followed by 13C depletion in the 2 h before beginning of the following light period. The daily amplitude of the algal isotopic composition (δ13C), however, was 〈=1.5o/oo, which demonstrates that diurnal variation in δ13C is relatively small.
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  • 51
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    On the influence of submarine ridges on translation and stability of Agulhas rings (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C4). pp. 7897-7906.
    Details
    Publication Date: 2019-09-23
    Description: A series of experiments with a quasi‐geostrophic model have been carried out to investigate the influence of topographic obstacles on the translatory movement of Agulhas rings. The rings were initialized as Gaussian‐shaped anomalies in the stream function field of a two‐layer ocean at rest. Bottom topography consisted of a meridional ridge of constant height in the middle of the quadratic model domain. The vertical ring structure, the initial ring position, and the height of the ridge were varied. The general northwestward movement of the model eddies has been shown to be modified toward a more equatorward direction by encountering the upslope of the ridge. Sufficient topographic heights and strong slopes can even block the eddies and force them toward a pure meridional movement. During their translation the eddies lose their vertical coherence. After about 150 days the eddy can only be detected by the surface signal, while the lower layer eddy is dispersed by the radiation of Rossby waves. The passage of “young” (regarding the time between their initialization and their contact with the ridge) and energetic eddies is accompanied by the observation of along‐slope currents of significant strength. These may be due to the rectification of radiated Rossby waves at the topographic slope. Only eddies with a significant dynamic signal in the lower layer are influenced by the bottom topography. Strong, shallow eddies over deep lower layers can cross the ridge without strong modification of their translatory movement.
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  • 52
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    Modelling Sea-Ice Roughness in the Arctic (1999)
    Springer
    In:  In: Ice Physics and the Natural Environment. , ed. by Wettlaufer, J. S., Dash, J. G. and Untersteiner, N. NATO ASI Series, 56 . Springer, Heidelberg, Germany, pp. 341-346.
    Details
    Publication Date: 2020-03-30
    Description: The variability of sea ice in the polar regions is an important factor in the climate system particularly because of its strong influence on heat and freshwater transports as well as momentum exchange between ocean and atmosphere. To describe these effects accurately ice conditions need to be known over long time periods and wide regions. Models are able to produce such data but need to be verified by observations (Lemke et al., 1998). One classical model variable which can be validated quite well with remote sensing methods (SMMR, SSM/I) is the ice coverage. Modelled ice drift can be verified by comparing observed and simulated drift trajectories (Kreyscher et al., 1998). Ice thickness observations, however, are only rarely available from drillings, sonar measurements and laser altimeter recordings. Keywords
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  • 53
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    Is the CTC dye technique an adequate approach for estimating active bacterial cells? (1999)
    Inter Research
    In:  Aquatic Microbial Ecology, 17 (2). pp. 207-209.
    Details
    Publication Date: 2016-05-26
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  • 54
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    Dynamics, estimation and impact of South Atlantic inter-ocean exchange (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C9). pp. 20885-20910.
    Details
    Publication Date: 2017-11-24
    Description: Interocean exchange of heat and salt around South Africa is thought to be a key link in the maintenance of the global overturning circulation of the ocean. It takes place at the Agulhas Retroflection, largely by the intermittent shedding of enormous rings that penetrate into the South Atlantic Ocean. This makes it extremely hard to estimate the inter ocean fluxes. Estimates of direct Agulhas leakage from hydrographic and tracer data range between 2 and 10 Sv (1 Sv = 106 m3 s−1). The average ring shedding frequency, determined from satellite information, is approximately six rings per year. Their associated interocean volume transport is between 0.5 and 1.5 Sv per ring. A number of Agulhas rings have been observed to cross the South Atlantic. They decay exponentially to less than half their initial size (measured by their available potential energy) within 1000 km from the shedding region. Consequently, most of their properties mix into the surroundings of the Benguela region, probably feeding directly into the upper (warm) limb of the global thermohaline circulation. The most recent observations suggest that in the present situation Agulhas water and Antarctic Intermediate Water are about equally important sources for the Benguela Current. Variations in the strength of these may lead to anomalous stratification and stability of the Atlantic at decadal and longer timescales. Modeling studies suggest that the Indian-Atlantic interocean exchange is strongly related to the structure of the wind field over the South Indian Ocean. This leads in the mean to a subtropical supergyre wrapping around the subtropical gyres of the South Indian and Atlantic Oceans. However, local dynamical processes in the highly nonlinear regime around South Africa play a crucial role in inhibiting the connection between the two oceans. The regional bottom topography also seems to play an important role in locking the Agulhas Currents' retroflection. State-of-the-art global and regional “eddy-permitting” models show a reasonably realistic representation of the mean Agulhas system; but the mesoscale variability and the local geometrical and topographic features that determine largely the interocean fluxes still need considerable improvement. In this article we present a review of the above mentioned aspects of the interocean exchange around South Africa: the estimation of the fluxes into the South Atlantic from different types of observations, our present level of understanding of the exchanges dynamics and forcing, its representation in state-of-the-art models, and, finally, the impact of the Indian-Atlantic fluxes on regional and global scale both within the Atlantic Ocean and in interaction with the overlying atmosphere.
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  • 55
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    Increased El Niño frequency in a climate model forced by future greenhouse warming (1999)
    Nature Publishing Group
    In:  Nature, 398 (6729). pp. 694-697.
    Details
    Publication Date: 2021-02-25
    Description: The El Niño/Southern Oscillation (ENSO) phenomenon is the strongest natural interannual climate fluctuation1. ENSO originates in the tropical Pacific Ocean and has large effects on the ecology of the region, but it also influences the entire global climate system and affects the societies and economies of manycountries2. ENSO can be understood as an irregular low-frequency oscillation between a warm (El Niño) and a cold (La Niña) state. The strong El Niños of 1982/1983 and 1997/1998, along with the more frequent occurrences of El Niños during the past few decades, raise the question of whether human-induced 'greenhouse' warming affects, or will affect, ENSO3. Several global climate models have been applied to transient greenhouse-gas-induced warming simulations to address this question4, 6, but the results have been debated owing to the inability of the models to fully simulate ENSO (because of their coarse equatorial resolution)7. Here we present results from a global climate model with sufficient resolution in the tropics to adequately represent the narrow equatorial upwelling and low-frequency waves. When the model is forced by a realistic future scenario of increasing greenhouse-gas concentrations, more frequent El-Niño-like conditions and stronger cold events in the tropical Pacific Ocean result
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  • 56
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    Origins of the midlatitude Pacific decadal variability (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 26 (10). pp. 1453-1456.
    Details
    Publication Date: 2018-02-13
    Description: Analysis of multiple climate simulations shows much of the midlatitude Pacific decadal variability to be composed of two simultaneously occurring elements: One is a stochastically driven, passive ocean response to the atmosphere while the other is oscillatory and represents a coupled mode of the ocean‐atmosphere system. ENSO processes are not required to explain the origins of the decadal variability. The stochastic variability is driven by random variations in wind stress and heat flux associated with internal atmospheric variability but amplified by a factor of 2 by interactions with the ocean. We also found a coupled mode of the ocean‐atmosphere system, characterized by a significant power spectral peak near 1 cycle/20 years in the region of the midlatitude North Pacific and Kuroshio Extension. Ocean dynamics appear to play a critical role in this coupled air/sea mode.
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  • 57
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    Modes of climate variability as simulated by a coupled general circulation model. Part I: ENSO-like climate variability and its low-frequency modulation (1999)
    Springer
    In:  Climate Dynamics, 15 (8). pp. 605-618.
    Details
    Publication Date: 2016-09-08
    Description:  The El Niño-Southern Oscillation (ENSO) is investigated in a multicentury integration conducted with the coupled general circulation model (CGCM) ECHAM3/LSG. The quasiperiodic interannual oscillations of the simulated equatorial Pacific climate system are due to subsurface temperature anomaly propagation and a positive atmosphere-ocean feedback. The gravest internal wave modes contribute to the generation of these anomalies. The simulated ENSO has a characteristic period of 5–8 years. Due to the coarse resolution of the ocean model the ENSO amplitude is underestimated by a factor of three as compared to observations. The model ENSO is associated with the typical atmospheric teleconnection patterns. Using wavelet statistics two characteristic interdecadal modulations of the ENSO variance are identified. The origins of a 22 and 35 y ENSO modulation as well as the characteristic ENSO response to greenhouse warming simulated by our model are discussed.
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  • 58
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    Pacific thermocline bridge revisited (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 26 (9). p. 1329.
    Details
    Publication Date: 2018-02-13
    Description: The coupling on decadal time scales of the mid‐latitude and tropical Pacific via an oceanic ‘bridge’ in the thermocline is investigated using ocean general circulation model hindcasts and a coupled ocean atmosphere model. Results indicate that in the tropics decadal anomalies of isopycnal depth are forced by Ekman pumping and are largely independent of the arrival of subducted anomalies in the thermocline that originate in the mid‐latitudes of either hemisphere. In the coupled model, temperature anomalies on isopycnals show little coupling from the tropics to the northern hemisphere, but are lag correlated between southern hemisphere mid‐ and low‐latitudes. However, anomaly magnitudes on the equator are small. These results suggest that the oceanic ‘bridge’ to the northern hemisphere explains only a small part of the observed decadal variance in the equatorial Pacific. Coupling to the southern mid‐latitudes via temperature anomalies on isopycnals remains an intriguing possibility.
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  • 59
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    Interdecadal interactions between the tropics and midlatitudes in the Pacific Basin (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 26 (5). p. 615.
    Details
    Publication Date: 2018-02-13
    Description: Analysis of global climate model simulations and observations suggest decadal, midlatitude changes in and over the North Pacific cause decadal modulation of the El Niño‐Southern Oscillation. This coupling between the two geographic regions is via atmospheric, not oceanographic, teleconnections. In essence, large scale changes in the circulation of the atmosphere over the Pacific Basin, while largest in midlatitudes, have a significant projection onto the wind field overlying the equatorial regions. These low frequency wind changes precondition the mean state of the thermocline in the equatorial ocean to produce prolonged periods of enhanced or reduced ENSO activity. The midlatitude variability that drives equatorial impacts is of stochastic origin and, although the magnitude of the signal is enhanced by ocean processes, likely unpredictable.
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  • 60
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    Marine diversity shift linked to interactions among grazers, nutrients and propagule banks (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 185 . pp. 309-314.
    Details
    Publication Date: 2018-05-08
    Description: Diverse coastal seaweed communities dominated by perennial fucoids become replaced by species-poor turfs of annual algae throughout the Baltic Sea. A large-scale field survey and factorial field experiments indicated that grazers maintain the fucoid community through selective consumption of annual algae. Interactive effects between grazers and dormant propagules of annual algae, stored in a 'marine seed bank', determine the response of this system to anthropogenic nutrient loading. Nutrients override grazer control and accelerate the loss of algal diversity in the presence but not in the absence of a propagule bank. This implies a novel role of propagule banks for community regulation and ecosystem response to marine eutrophication.
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  • 61
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    Competition between benthic cyanobacteria and diatoms as influenced by different grain sizes and temperatures (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 187 . pp. 77-87.
    Details
    Publication Date: 2019-09-23
    Description: An experimental laboratory set-up was used to study the influence of different grain size compositions and temperatures on the growth of benthic cyanobacteria and diatoms, and on the competition between these 2 groups. Monospecific cultures of 3 species of cyanobacteria (Merismopedia punctata, Microcoleus chthonoplastes, Oscillatoria limosa), and of 2 species of benthic diatoms (Phaeodactylum tricornutum and Nitzschia sp.) were used. The organisms were cultured in 100 ml flasks filled with medium and 3 different kinds of sediment: (1) Sand (fine sand, 63 to 200 µm), (2) Mud-I (mixed fine sand and mud 〈63 µm in the ratio 80:20 wt %), (3) Mud-II (mixed fine sand and mud in the ratio 50:50 wt %). Experimental temperatures were 10, 15 and 25°C. At 10°C and 15°C, both diatom species achieved the highest biomass on the sediments of the finest grain size (50 wt % 〈 63 µm) while cyanobacteria achieved low biomass levels. Coarsening of sediments at the same temperature levels revealed a gradually lower biomass of the diatoms. Particularly on sand, the diatoms never reached the same concentrations of chlorophyll a as on mud. The cyanobacteria, on the other hand, had the highest biomass on sand at 15°C. In the competition experiments the benthic diatom species Nitzschia sp. dominated all types of sediments at 10°C and 15°C. The experiments at 25°C were dominated by the filamentous cyanobacterium M. chthonoplastes. This indicates the importance of abiotic conditions for the distribution and abundance of benthic phototrophic micro-organisms.
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  • 62
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    The Asian decapod Hemigrapsus penicillatus (de Haan, 1835) (Grapsidae, Decapoda) introduced in European waters: status quo and future perspectives (1999)
    Springer
    In:  Helgoland Marine Research, 52 . pp. 359-366.
    Details
    Publication Date: 2018-05-28
    Description: The Asian decapod Hemigrapsus penicillatus (de Haan, 1835) was first recorded in European waters in 1994. The first specimens were collected in the estuary of Charente Maritime on the west coast of France close to La Rochelle. The current range in Europe covers Spanish shallow water habitats of the Bay of Biscay to areas north of La Rochelle (France). Densities of up to 20 specimens per square metre occur. This species has a high temperature and salinity tolerace and will expand its distribution in European waters. It is not clear whether this crab was introduced by shipping in ballast water or as a fouling organism. Based on a study of ship hull fouling in German dry docks this account provides evidence that hull fouling is a likely vector for the introduction of this crab. In August 1993, six juvenile specimens of H. penicillatus were removed from the hull of a car-carrier. After its journey from Japan into European waters this vessel docked in the port of Bremerhaven (Germany) for a routine inspection and coating with antifouling paint.
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  • 63
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    Comparison of multivariate patterns: different taxonomic levels in macrofaunal analysis vs.sediment profiling imagery (SPI) (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 190 . pp. 125-132.
    Details
    Publication Date: 2018-05-08
    Description: The multivariate patterns resulting from analyses of macrobenthic abundance data at different taxonomic levels are compared to the pattern derived from various measurements obtained through sediment profiling imagery (SPI). A time-series data set from 1 station in Kiel Bay (Western Baltic) at 22 m depth including macrobenthic and SPI replicates covering 8 yr (1989 to 1996) was analyzed by means of multidimensional scaling (MDS) ordination. The macrobenthos data showed similar patterns, and there was little information loss, with decreasing taxonomic resolution from species to phylum level. The multivariate pattern in the SPI data was not significantly correlated to any of the macrofaunal patterns. However, macrofaunal and SPI patterns seemed to be complementary since they emphasized different aspects of the long-term succession in the Southern Baltic Sea. While macrofaunal patterns were sensitive to anoxia events, changes of SPI-recorded seabed characteristics were primarily related to physical disturbances possibly due to variations in fishing intensity.
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  • 64
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    Sea ice dynamics in the Weddell Sea simulated with an optimized model (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C5). pp. 11151-11162.
    Details
    Publication Date: 2019-09-23
    Description: The advection of sea ice and associated freshwater/salt fluxes in the Weddell Sea in 1986 and 1987 are investigated with a large‐scale dynamic‐thermodynamic sea ice model. The model is validated and optimized by comparison of simulated sea ice trajectories with observed drift paths of six buoys deployed on the Weddell Sea ice. The skill of the model is quantified by an error function that measures the deviations of simulated trajectories from observed 30‐day sea ice drift. A large number of sensitivity studies show how simulated sea ice transports and associated freshwater/salt fluxes respond to variations in physical parameterizations. The model reproduces the observed ice drift well, provided ice dynamics parameters are set to appropriate values. Optimized values for the drag coefficients and for the ice strength parameter are determined by applying the error function to various sensitivity studies with different parameters. The optimized model yields a mean northward sea ice volume export out of the southern Weddell Sea of 1693 km3 in 1986 and 2339 km3 in 1987. This shows the important role of sea ice transport for the freshwater budget of the Weddell Sea and gives an indication of its high interannual variability.
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  • 65
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    Anaerobic methane oxidation associated with marine gas hydrates: Superlight C-isotopes from saturated and unsaturated C20 and C25 irregular isoprenoids (1999)
    Springer
    In:  Naturwissenschaften, 86 (6). pp. 295-300.
    Details
    Publication Date: 2019-09-23
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  • 66
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    Ecology: Competition and coexistence (1999)
    Nature Publishing Group
    In:  Nature, 402 . pp. 366-367.
    Details
    Publication Date: 2017-02-28
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  • 67
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    Asian small-clawed otters: resting and swimming metabolic rates (1999)
    Springer
    In:  Journal of Comparative Physiology B - Biochemical Systemic and Environmental Physiology, 169 (2). pp. 100-106.
    Details
    Publication Date: 2018-05-29
    Description: Open-flow oxygen and carbon dioxide respirometry was used in Neumünster Zoo (Germany) to examine the energy requirements of six Asian small-clawed otters (Amblonyx cinerea) at rest and swimming voluntarily under water. Our aim was to compare their energy requirements with those of other warm-blooded species to elucidate scale effects and to test whether the least aquatic of the three otter species differs markedly from these and its larger relatives. While at rest on land (16 °C, n = 26), otters (n = 6, mean body mass 3.1 ± 0.4 kg) had a respiratory quotient of 0.77 and a resting metabolic rate of 5.0 ± 0.8 Wkg−1(SD). This increased to 9.1 ± 0.8 Wkg−1 during rest in water (11–15 °C, n = 4) and to 17.6 ± 1.4 Wkg−1 during foraging and feeding activities in a channel (12 °C, n = 5). While swimming under water (n = 620 measurements) in an 11-m long channel, otters preferred a speed range between 0.7 ms−1 and 1.2 ms−1. Transport costs were minimal at 1 ms−1 and amounted to 1.47 ± 0.24 JN−1 m−1 (n = 213). Metabolic rates of small-clawed otters in air were similar to those of larger otter species, and about double those of terrestrial mammals of comparable size. In water, metabolic rates during rest and swimming were larger than those extrapolated from larger otter species and submerged swimming homeotherms. This is attributed to high thermoregulatory costs, and high body drag at low Reynolds numbers.
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  • 68
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    Anthropogenic CO〈sub〉2〈/sub〉 and CFCs in the North Atlantic Ocean - a comparison of man-made tracers (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 26 . pp. 2065-2068.
    Details
    Publication Date: 2018-02-13
    Description: We compare estimates of the anthropogenic CO2 content of seawater samples from the subpolar North Atlantic Ocean calculated on the basis of a back-calculation technique with measurements of the chlorofluorocarbon CFC-11. Estimated anthropogenic CO2 concentrations are in the range 10–80 µmol kg-1, while CFC-11 concentrations cover the full range from below detection limit to 〉 5 pmol kg-1 in waters at atmospheric equilibrium. The majority of the data points show a linear correlation between anthropogenic CO2 concentrations and CFC-11 saturation, which can only be explained by the strongly advective nature of the North Atlantic Ocean. Only deep eastern basin samples deviate from this general observation in that they show still significant concentrations of anthropogenic CO2 where CFC-11 is no longer detectable. In order to remove the influence of the Revelle factor reflected in the anthropogenic CO2 concentrations we have calculated 'excess' pCO2, showing an even tighter linear correlation with atmospheric equilibrium concentrations of CFC-11.
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  • 69
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    Anthropogenic CO〈sub〉2〈/sub〉 Inventory of the Indian Ocean (1999)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 13 . pp. 179-198.
    Details
    Publication Date: 2018-03-15
    Description: This study presents basin-wide anthropogenic CO2 inventory estimates for the Indian Ocean based on measurements from the World Ocean Circulation Experiment/Joint Global Ocean Flux Study global survey. These estimates employed slightly modified ΔC* and time series techniques originally proposed by Gruber et al. [1996] and Wallace [1995], respectively. Together, the two methods yield the total oceanic anthropogenic CO2 and the carbon increase over the past 2 decades. The highest concentrations and the deepest penetrations of anthropogenic carbon are associated with the Subtropical Convergence at around 30° to 40°S. With both techniques, the lowest anthropogenic CO2 column inventories are observed south of 50°S. The total anthropogenic CO2 inventory north of 35°S was 13.6±2 Pg C in 1995. The inventory increase since GEOSECS (Geochemical Ocean Sections Program) was 4.1±1 Pg C for the same area. Approximately 6.7±1 Pg C are stored in the Indian sector of the Southern Ocean, giving a total Indian Ocean inventory of 20.3 ±3 Pg C for 1995. These estimates are compared to anthropogenic CO2 inventories estimated by the Princeton ocean biogeochemistry model. The model predicts an Indian Ocean sink north of 35°S that is only 0.61–0.68 times the results presented here; while the Southern Ocean sink is nearly 2.6 times higher than the measurement-based estimate. These results clearly identify areas in the models that need further examination and provide a good baseline for future studies of the anthropogenic inventory.
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  • 70
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    Methane in the northern Atlantic controlled by microbial oxidation and atmospheric history (1999)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 26 (5). pp. 587-590.
    Details
    Publication Date: 2018-02-13
    Description: During May - August, 1997, the distributions of dissolved methane and CCl3F (CFC11) were measured in the Atlantic between 50° and 60°N. In surface waters throughout the region, methane was observed to be close to equilibrium with the atmospheric mixing ratio, implying that surface ocean methane is tracking its atmospheric history in regions of North Atlantic Deep Water formation. Despite the different atmospheric history and ocean chemistry of CH4 and CFC11, their spatial distribution patterns in the water column are remarkably similar. One-dimensional distributions have been simulated with an advection-diffusion model forced by the atmospheric histories. The results suggest that the similar patterns result from the increasing input of CH4 and CFC11 to newly formed deep waters over time, combined with the effect of horizontal mixing and the oxidation of methane on a 50 year time scale.
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  • 71
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    Three-dimensional space utilisation in a marine predator (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 183 . pp. 263-273.
    Details
    Publication Date: 2018-05-08
    Description: Diving seabirds should evolve a variety of foraging characteristics which enable them to minimize energy expenditure and to maximize net energy gain while searching for prey underwater. In order to assess the related ecological adaptations in a marine predator, we studied the at-sea distribution and the diving behaviour of 23 cormorants Phalacrocorax carbo (Linnaeus) breeding at the Chausey Islands (France) using VHF-telemetry and data loggers recording hydrostatic pressure. Birds foraged within an area of approximately 1131 km2 situated north-east of the breeding colony. This zone represents only 25% of the maximal potentially available area that the birds may utilize considering their maximum foraging range of 35 km. Individual birds remained within restricted individual foraging areas (on average 18 and 10% of the total utilized area in 1994 and 1995, respectively) throughout the study period. Moreover, the cormorants studied conducted an average of 42 dives per foraging trip, lasting for an average of 40 s (maximum 152 s), and reached an average maximum dive depth of 6.1 m (maximum 32 m) with median descent and ascent angles calculated to be 18.7° and 20.3°, respectively. Overall, 64% of all dives were U-shaped dives and 36% V-shaped dives. We use these results to demonstrate how both specialization and opportunism may support the remarkably high foraging efficiency of this marine predator.
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  • 72
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    The good, the bad, and the ugly: a critical look at species and their institutions from a user's perspective (1999)
    Springer
    In:  Reviews in Fish Biology and Fisheries, 9 . pp. 375-378.
    Details
    Publication Date: 2016-09-14
    Description: Over the past eight years my colleagues and I have been involved in a major project to make key information on fishes available to users, especially in developing countries (Froese and Pauly, 1998; http://www. fishbase.org/). There are about 25 000 species of fishes in the world of which over 7 000 are used by humans as food, for sport or as pets. Dealing with such large numbers meant that we depended heavily on taxonomic works to ensure that we assigned relevant information to the correct species. Eight years through the project we have covered 22 000 species, 40 000 synonyms, 80 000 common names, and 14 000 references. We have worked with over 300 collaborators, among them many taxonomists, and we have visited many museums. In this contribution I present our experiences in the catchy categories of ‘good’, ‘bad’, and ‘ugly’, not to offend anyone, but to provoke reactions that hopefully will lead to some of the changes that we as users of taxonomic information would like to see.
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  • 73
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    Little-studied arc-backarc system in the spotlight (1999)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 80 (32). pp. 353-359.
    Details
    Publication Date: 2016-06-07
    Description: A research cruise has documented changes in rift tectonics, volcanism, and hydrothermalism along the least studied and most enigmatic sector of a crustal complex in the southwest Pacific Ocean. Results from the longitudinal transect are expected to provide insight into processes involving the Kermadec arc-Havre backarc (KAHB) system, a continuum from oceanic spreading to continental rifting at a convergent plate boundary KAHB forms the central sector of an active, 2000-km arc-backarc complex between Tonga and New Zealand (Figure 1). The expedition also engaged in the first comprehensive survey of submarine vents in the Taupo Volcanic Zone (TVZ) at the south end of the KAHB system. Identified in the off-shore segment of TVZ were three major hydrothermal vent areas associated with late Quaternary fault structures. Data from the expedition and from other recent research in the same area addressed questions concerning the type of hydrothermal venting, magmatic heterogeneity along and across KAHB, the style of backarc rifting, and tectonic and magmatic consequences of anomalous terranes colliding with the subduction margin.
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  • 74
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    Some aspects of ocean heat transport by the shallow, intermediate and deep overturning circulations (1999)
    AGU (American Geophysical Union)
    In:  In: Mechanisms of global climate change at millenial time scales. , ed. by Clark, P. U. Geophysical monograph, 112 . AGU (American Geophysical Union), Washington, D.C., pp. 1-22. ISBN 0-87590-095-X
    Details
    Publication Date: 2020-08-04
    Type: Book chapter , NonPeerReviewed
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  • 75
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    Land-Ocean Systems in the Siberian Arctic : Dynamics and History ; with 301 Figures, 6 in Colour and 85 Tables (1999)
    Springer
    In:  , ed. by Kassens, H., Bauch, H. A., Dmitrenko, I. A., Eicken, H., Hubberten, H. W., Melles, M., Thiede, J. and Timokhov, L. A. Springer, Berlin (u.a.), XI, 711 pp. ISBN 3-540-65676-6
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    Publication Date: 2019-09-24
    Type: Book , NonPeerReviewed
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  • 76
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    Fecundity of the chokka squid Loligo vulgaris reynaudii on the southeastern coast of South Africa (1999)
    Springer
    In:  Marine Biology, 135 (2). pp. 315-319.
    Details
    Publication Date: 2021-06-17
    Description: Potential fecundity in Loligo vulgaris reynaudii was estimated to be about 17 000 eggs, calculated as the total number of discernible oocytes in the ovary and oviduct. Squid were observed to spawn up to 8140 eggs over a 36 h period in captivity. First estimations of actual fecundity are therefore between 8000 and 17 000 eggs. Factors complicating a more accurate estimation of actual fecundity in this species include difficulties with aquarium maintenance, their behaviour of spawning over a protracted period and in multiple sites, and atretic oocytes observed in both developing and mature ovaries. Detailed morphological and histological analysis of gonads collected at regular intervals over a complete spawning season will allow a more precise calculation of actual fecundity.
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  • 77
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    Diving behaviour of female northern rockhopper penguins, Eudyptes chrysocome moseleyi , during the brooding period at Amsterdam Island (Southern Indian Ocean) (1999)
    Springer
    In:  Marine Biology, 134 (2). pp. 375-385.
    Details
    Publication Date: 2021-06-17
    Description: The pattern and characteristics of diving in 14 female northern rockhopper penguins, Eudyptes chrysocome moseleyi, were studied at Amsterdam Island (37°50′S; 77°31′E) during the guard stage, using electronic time–depth recorders. Twenty-nine foraging trips (27 daily foraging trips and two longer trips including one night) with a total of 16 572 dives of ≥3 m were recorded. Females typically left the colony at dawn and returned in the late afternoon, spending an average of 12 h at sea, during which they performed ∼550 dives. They were essentially inshore foragers (mean estimated foraging range 6 km), and mainly preyed upon the pelagic euphausiid Thysanoessa gregaria, fishes and squid being only minor components of the diet. Mean dive depth, dive duration, and post-dive intervals were 18.4 m (max. depth 109 m), 57 s (max. dive duration 168 s), and 21 s (37% of dive duration), respectively. Descent and ascent rates averaged 1.2 and 1.0 ms−1 and were, together with dive duration, significantly correlated with dive depth. Birds spent 18% of their total diving time in dives reaching 15 to 20 m, and the mean maximum diving efficiency (bottom time:dive cycle duration) occurred for dives reaching 15 to 35 m. The most remarkable feature of diving behaviour in northern rockhopper penguins was the high percentage of time spent diving during daily foraging trips (on average, 69% of their time at sea); this was mainly due to a high dive frequency (∼44 dives per hour), which explained the high total vertical distance travelled during one trip (18 km on average). Diving activity at night was greatly reduced, suggesting that, as other penguins, E. chrysocome moseleyi are essentially diurnal, and locate prey using visual cues.
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  • 78
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    Comparative analysis of some morphometric characters in two Sepiolids: Sepietta Neglecta (NAEF, 1916) and Sepietta Oweniana (Orbigny, 1840) (1999)
    Springer
    In:  In: Advancing Research on Living and Fossil Cephalopods. , ed. by Olóriz Saéz, F. and Rodríguez-Tovar, F. J. Springer, Boston, MA, pp. 17-21, 5 pp. ISBN 978-1-4615-4837-9
    Details
    Publication Date: 2021-05-11
    Description: The comparative morphometric analysis, which has proved valuable in vertebrates for the identification of features needed for further clarification of classifications, is lacking in the greater part of cephalopod literature (Voss, 1977; Roper, 1983). The taxonomy of sepiolids, especially that of Sepiola and Sepietta species, is quite difficult in practice (Naef, 1923; Mangold and Boletzky, 1987; Nesis, 1987; Guerra, 1992). In most cases the mantle has to be cut open to expose the organs of the mantle cavity, and the comparison of several specimens of different species and of both sexes is recommended (Bello, 1995). Adult and sub-adult males can be identified from the hectocotylous, females from the bursa copulatrix, inside the mantle cavity. In Sepietta neglecta and Sepietta oweniana the currently known characters are not sufficient to identify the females because both their external and internal morphology are identical (Guerra, 1992; Bello, 1995). The only difference referred to by Naef (1923) is that the tentacles of S. neglecta are smaller than those of S. oweniana and bear much smaller suckers. However this is evident only when specimens of equal size from the two species are examined together. The purpose of this paper is to verify whether the length of tentacular clubs, the thickness of tentacles and the diameter of club suckers reflect the growth rate, and are significantly different for the two species to define relative indices.
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  • 79
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    Spawning cycle of onychoteuthid squids in the southern Indian Ocean:new information from seabird predators (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 188 . pp. 93-104.
    Details
    Publication Date: 2021-06-17
    Description: Cephalopods play an important role in the trophic web of the Southern Ocean, but little information is available on their biology. The 2 largest sub-Antarctic seabirds, the king penguin Aptenodytes patagonicus and the wandering albatross Diomedea exulans, feed primarily on squids during the austral winter at the Crozet Islands. We examined a large number of accumulated cephalopod beaks in the stomach of these birds together with some undigested items; first, to understand how these 2 predators share the squid resource during winter, a period of supposed low food availability, and, second, to use a diving and a flying seabird as biological samplers of Southern Ocean cephalopods. Individuals of the family Onychoteuthidae formed the bulk of the squid diet, accounting for 72.6 and 57.0% of the number of lower beaks in samples from king penguins and wandering albatrosses, respectively. Seven different species were identified, the 3 main squids being Kondakovia longimana (38.8 and 28.0% by number for penguins and albatrosses, respectively), Moroteuthis ingens (13.5 and 26.2%) and M. knipovitchi (20.1 and 2.3%). Both seabirds preyed upon the same cephalopod species, but penguins primarily took small- to medium-sized juveniles (99.0% of the onychoteuthids) and albatrosses preyed on larger adult specimens (96.0%). Fresh remains indicated that adult K. longimana and M. ingens were mature individuals which, as shown by satellite tracking of albatrosses, were taken over the slope and nearby oceanic waters surrounding the archipelago. The present study indicates that mating/spawning of K. longimana and M. ingens occurs in Crozet waters during the winter months. It also extends the biogeography of K. longimana to north of the Antarctic Polar Front, in the Polar Frontal Zone, where it has not previously been recorded.
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  • 80
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    Behavioral aspects of sperm competition in cuttlefish, Sepia officinalis (Sepioidea: Cephalopoda) (1999)
    Springer
    In:  Marine Biology, 134 (4). pp. 719-728.
    Details
    Publication Date: 2021-06-18
    Description: Sexual selection studies in cephalopods indicate that sperm competition is a central feature of their mating systems, yet this has not been studied experimentally in any detail. In 1998 we staged 20 matings of the cuttlefish, Sepia officinalis L., in the laboratory. Males rapidly initiated mating in the “head-to-head” position, with no apparent courtship. Mating lasted an average of 10 min (range 7 to 14 min). For the first 6 min (on average 63% of the mating duration), the male flushed strong jets of water directly at the female's buccal membrane, which sometimes resulted in the expulsion of parts of spermatangia placed there in recent matings. Then, in a single discrete movement that lasted an average of only 14 s, the male's modified fourth left arm – the hectocotylus – wrapped around a single large bundle of spermatophores (ca. 150 to 300) and transferred them to the female's buccal membrane. For the remainder of the mating (average 3 min, range 1.5 to 5.0 min), the hectocotylus repeatedly broke the spermatophores open, and manipulated them, so that sperm were released and many spermatangia were attached along the ventral buccal membrane, near the paired seminal receptacles. Approximately 140 spermatangia were attached in rows 3 to 5 deep around the ventral buccal membrane in a single mating; the rest were usually discarded during mating. Histology revealed that each of the seminal receptacles consists of a series of sperm storage bulbs connected by a central duct, which leads to a single pore at the surface of the buccal membrane. Baseline data on sperm motility were obtained, but the mechanism by which sperm enter the seminal receptacle remains unknown. Females seemed to initiate termination of mating, then males guarded their mates temporarily. These results, combined with other recent laboratory experiments, provide evidence that sperm competition may be a major feature of the mating system of S. officinalis.
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  • 81
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    Carbon- and oxygen-isotope composition of the cuttlebone of Sepia officinalis : a tool for predicting ecological information? (1999)
    Springer
    In:  Marine Biology, 133 (4). pp. 651-657.
    Details
    Publication Date: 2021-06-18
    Description: Analysis of the isotope composition of calcareous structures of marine organisms has proved useful in providing biological data. The present study constitutes the first detailed work undertaken on the isotope composition of coleoid cephalopods. We analysed the carbon- and oxygen-isotope composition [δ13C (CO2− 3) and δ18O (CO2− 3), respectively] of the cuttlebone aragonite of wild and cultivated specimens of Sepia officinalis Linnaeus, 1758. δ13C (CO2− 3) ranged from −2.94 to 1.00‰, δ18O (CO2− 3) from −0.18 to 2.08‰. The carbon-isotope composition is not in equilibrium with the carbon species of the ambient seawater, and does not reflect the deposition of CaCO3 in seawater. The potential influence of environmental factors and biological processes on the carbon-isotope composition of the cuttlebone is discussed. In contrast to δ13C, the oxygen-isotope composition of cuttlebone aragonite appears to be in isotopic equilibrium with the ambient seawater. Seasonal changes in isotopic temperature revealed by our analyses agreed with changes in the temperature of the ambient seawater. CaCO3 was deposited all year round. A maximum life span of 2 yr, a year-round spawning season, and variable growth rates among and within individuals have been inferred from the isotopic temperatures.
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  • 82
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    Exploitation of the marine environment by two sympatric albatrosses in the Pacific Southern Ocean (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 177 . pp. 243-254.
    Details
    Publication Date: 2021-06-17
    Description: The marine habitat exploited by black-browed Diomedea melanophrys and grey-headed albatrosses D. chrysostoma breeding at Campbell Island, New Zealand, was studied using satellite telemetry. Data were analysed in relation to the bathymetry and sea-surface temperature of the foraging zones. Black-browed albatrosses spent 55% of their time on the Campbell Plateau but also carried out long foraging trips to the Polar Front and Antarctic Zone at a distance of over 2000 km. They relied heavily on juvenile Micromesistius australis, a schooling fish, during foraging trips to the shelf but over oceanic waters the squid Martialia hyadesi was the main prey taken. Grey-headed albatrosses spent 71% of their time foraging over the deep waters of the Polar Frontal Zone where M. hyadesi comprised over 90% of the mass of prey taken. No satellite-tracked birds fed over the shelf, but data from the duration of foraging trips and dietary analysis suggests that shelf-feeding is important for this species. Significant inter-species differences in the time spent in neritic and oceanic zones show that black-browed albatrosses are reliant primarily on shelf resources while grey-headed albatrosses are primarily oceanic feeders. In addition, the 2 species overlapped little in the zones used over oceanic waters, with black-browed albatrosses feeding in more southerly waters than grey-headed albatrosses. However, both species feed on M. hyadesi when foraging in association with the Polar Front.
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  • 83
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    Ontogenetic changes in morphometric and reproductive indices of the squid Gonatus fabricii (Oegopsida, Gonatidae) in the Norwegian Sea (1999)
    Springer
    In:  Polar Biology, 22 (6). pp. 357-365.
    Details
    Publication Date: 2021-07-26
    Description: Ontogenetic changes in morphometric and reproductive indices were studied using 166 individuals of the arctic gonatid squid Gonatus fabricii (7.3–322 mm pen length) collected in the southern part of the Norwegian Sea. Body proportions and consistency of the mantle and fins did not change in maturing and mature males. In contrast, during maturation the females first lost their tentacles, then the horny rings of their 4th arm suckers, and the muscular part of their body turned watery and gelatinous. Unlike most squid, G. fabricii females start mating at maturity stage III, and all but one female at stage IV had mated, as well as all spent females. Females had high values of both gonadosomatic index and maturity indices compared to those of the North Pacific gonatids, whereas gonadosomatic index values of males were low, probably due to slow functioning of both testis and spermatophoric gland, and long accumulation of spermatophores in the Needham's sac. It is suggested that the breakdown of female body tissues is an adaptation for a deepwater bathypelagic “brooding” of the negatively buoyant egg-mass caused by the high specific density of the secretion from the nidamental glands in gonatids.
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  • 84
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    Highly Variable Microsatellites in the California Market Squid Loligo opalescens (1999)
    Springer
    In:  Marine Biotechnology, 1 (4). pp. 403-406.
    Details
    Publication Date: 2021-08-24
    Description: Attempts to study the genetic population structure of cephalopods are impeded by the low levels of genetic variation in these species. We have developed polymerase chain reaction (PCR) primers for six hypervariable microsatellite markers in order to analyze the molecular population structure in the Californian market squid Loligo opalescens. Each of these genomic loci has been cloned and fully sequenced. Here we report the sequence and properties of the six PCR primer sets for the amplification of hypervariable microsatellites. Heterozygosity levels in six squid samples from different locations are high for all loci tested.
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  • 85
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    Influence of oceanographic variability on recruitment in the Illex argentinus (Cephalopoda:Ommastrephidae) fishery in the South Atlantic (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 183 . pp. 159-167.
    Details
    Publication Date: 2021-06-23
    Description: The fishery for Illex argentinus in the Southwest Atlantic is subject to large inter-annual variability in recruitment strength. In this paper we attempt to build a predictive model using sea surface temperature (SST) to examine links between recruitment to the Falkland Islands fishery and environmental variability during the juvenile and adult life history stages. SST data from the National Center for Atmospheric Research (NCAR) were found to be comparable with near-surface data derived from in situ expendable bathy-thermograph (XBT) profiles in the southern Patagonian shelf. Variation in SST during the early life stages appears to be important in determining recruitment of I. argentinus. SST in the hatching grounds of the northern Patagonian shelf during the period of hatching (particularly June and July) was negatively correlated with catches in the fishery in the following season. SST anomaly data from positions in the Pacific and Southwest Atlantic were used to examine teleconnections between these areas. Links were seen at a lag of 2 yr between the Pacific and southern Patagonian shelf, and at about 5 yr between the Pacific and northern Patagonian shelf. This is consistent with SST anomalies associated with El Niño in the Pacific propagating around the globe via the Antarctic Circumpolar Wave (ACW). Predicting cold events via teleconnections between SST anomalies in the Pacific and Atlantic would appear to have the potential to predict the recruitment strength of I. argentinus in the Southwest Atlantic.
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  • 86
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    Vampire blood: respiratory physiology of the vampire squid (Cephalopoda: Vampyromorpha) in relation to the oxygen minimum layer (1999)
    Springer
    In:  Experimental Biology Online, 4 (1). pp. 1-10.
    Details
    Publication Date: 2021-07-05
    Description: The functional properties of the haemocyanin ofVampyroteuthis infernalis (Cephalopoda: Vampyromorpha), measured at 5 °C, are reported and discussed in relation to hypoxia. The oxygen affinity of this haemocyanin (P50=0.47−0.55 kPa) is higher than any previously measured for a cephalopod. The high cooperativity (n50=2.20−2.23) and Bohr coefficient (−0.22) suggest a true transport function for this haemocyanin. This high-affinity haemocyanin, in conjunction with moderate gill diffusion capacity, provides a sufficient oxygen gradient from the environment to the blood to support the low routine oxygen consumption rate of V. infernalis.
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  • 87
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    Movements and diving behavior of weaned Weddell seal ( Leptonychotes weddellii ) pups (1999)
    Springer
    In:  Polar Biology, 21 (1). pp. 23-36.
    Details
    Publication Date: 2021-06-11
    Description: Between 1993 and 1995, the diving behavior and movement patterns of 23 weaned Weddell seal pups (Leptonychotes weddellii) were tracked in the Ross Sea. Antarctica, using satellite-linked time-depth recorders. Regression analyses revealed that for seals of between 8 and 27 weeks old, age was poorly correlated with the dive depth, duration, or frequency. However, changes in dive parameters suggested that Weddell seal pups were attempting to maximize dive time, but the manner in which this was done depended on age and time of day. Movement patterns indicated that most Weddell seal pups left their natal area by the end of February, and traveled north along the Antarctic continent coastline. Several individuals returned to McMurdo Sound, but others were last located more than 400 km from McMurdo. Routes followed suggest that pups can use the pack ice habitat, but prefer to remain closer to the coastline than do adults.
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  • 88
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    Microsatellite analysis of genetic diversity in the squid Illex argentinus during a period of intensive fishing (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 187 . pp. 171-178.
    Details
    Publication Date: 2021-06-24
    Description: Levels of genetic diversity and population differentiation were examined in temporally (1990 to 1997) and geographically separated samples of the argentine short-finned squid Illex argentinus using 7 microsatellite loci. Number of alleles (mean number of alleles per locus over all samples = 24.1) and heterozygosity (mean observed heterozygosity per sample = 0.84) were high for all samples, indicating that these loci have a greater potential utility for investigating population genetic structure than allozyme markers used in previous studies. Genetic diversity did not differ significantly between samples taken 5 yr after commencement of the fishery (1990) and those collected during a period of progressively intense fishing pressure (1994 and 1997). Several small but significant differences in between-sample genetic variation (FST) were observed, but these could not confirm the previous suggestion of cryptic species or several well-defined stocks within the fished population.
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  • 89
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    Confirmation of serial spawning in the chokka squid Loligo vulgaris reynaudii off the coast of South Africa (1999)
    Springer
    In:  Marine Biology, 135 (2). pp. 307-313.
    Details
    Publication Date: 2021-06-17
    Description: Ovary maturation and spawning in the chokka squid Loligo vulgaris reynaudii were investigated by collecting squid from across their distributional range on the southeastern coast of South Africa between 1992 and 1993. Based on histological examination of the ovarian tissue and the separation of multiple modes in oocyte size-frequency distribution, ovary development was characterised by eight distinct stages. Our study confirms serial spawning in L. v. reynaudii.
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  • 90
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    Introduced marine species of the North Sea coasts (1999)
    Springer
    In:  Helgoland Marine Research, 52 . pp. 219-234.
    Details
    Publication Date: 2018-05-28
    Description: About 80 non-indigenous species are assumed to have been introduced into the North Sea by transoceanic shipping and aquaculture. The number is certainly underestimated as most small organisms received insufficient attention at the species level. Also, the seafaring tradition of the North Sea countries is much longer than our biological surveys are. Most exotic invertebrates originate from the western Atlantic and were introduced by shipping, while most algae stem from the Pacific and came with the introduced oysters. A peak of newcomers was observed in the 1970s. Most of the arrivals became established in brackish environments, at harbor sites and in the vicinity of oyster farms, fouling on hard substrates or living as epibionts. A few live in sediments, are holoplanktonic or are parasites. At the open coast, approximately 6% of the macrobenthic species are exotics, while in estuaries their share is up to 20%. Most exotics have been encountered in the southern North Sea first, and many did not spread further north. About 25% of the established non-natives are widespread and attain locally high abundances. As a consequence, some inshore habitats are entirely dominated by exotics. The overall effect on the ecosystem seems to be more additive than one of displacement. This suggests that the coastal biota of the North Sea are quite capable of accommodating newcomers. However, this is no guarantee that the next introduced species may not cause severe ecological change or economic harm. There is a need to minimize the risk of unintentional introductions by ballast water treatment and by adhering to quarantine procedures in aquaculture. Current research on exotics in the North Sea is regarded as inadequate for proper evaluation and management requirements.
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  • 91
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    Intermediate water in the Brazil-Malvinas Confluence Zone: A Lagrangian view (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 104 (C9). 21,063-21,082.
    Details
    Publication Date: 2018-04-27
    Description: The subsurface flow within the subantarctic and subtropical regions around the Brazil-Malvinas (Falkland) Confluence Zone is studied, using daily hydrographic and kinematic data from four subsurface floats and a hydrographic section parallel to the South American shelf. The float trajectories are mapped against sea surface flow patterns as visible in concurrent satellite sea surface temperature (SST) images, with focus on the November 1994 and October/November 1995 periods. The unprecedented employment of Lagrangian θ-S diagrams enables us to trace the advection of patches of fresh Antarctic Intermediate Water (AAIW) from the Confluence Zone into the subtropical region. The fresh AAIW consists of a mixture of subtropical AAIW and Malvinas Current core water. Within the subtropical gyre, these patches are discernible for extended periods and drift over long distances, reaching north to 34°S and east to 40°W. The cross-frontal migration of quasi-isobaric floats across the Confluence Zone from the subtropical to the subantarctic environment is observed on three occasions. The reverse process, float migration from a subpolar to a subtropical environment was observed once. These events were located near 40°S, 50°W, the site of a reoccurring cold core feature. Subsurface float and SST data comparison reveals similarities with analogous observations made in the Gulf Stream [Rossby, 1996] where cross-frontal processes were observed close to meander crests. The limited number of floats of this study and the complex structure of the Brazil-Malvinas Confluence Zone, however, restricts the analysis to a description of two events.
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  • 92
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    Nitrous oxide in the deep waters of the world's oceans (1999)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 13 . pp. 1127-1135.
    Details
    Publication Date: 2018-03-15
    Description: We present a compilation and analysis Of N2O data from the deep-water zone of the oceans below 2000 m. The N2O values show an increasing trend from low concentrations in the North Atlantic Ocean to high concentrations in the North Pacific Ocean, indicating an accumulation of N2O in deep waters with time. We conclude that the observed N2O accumulation is mainly caused by nitrification in the global deep-water circulation system (i.e., the “conveyor belt”). Hydrothermal and sedimentary N2O fluxes are negligible. We estimate the annual N2O deep-water production to be 0.3 ± 0.1 Tg. Despite the fact that the deep sea below 2000 m represents about 95% of the total ocean volume, it contributes only about 3–16% to the global open-ocean N2O production. A rough estimate of the oceanic N2O budget suggests that the loss to the atmosphere is not balanced by the deep-sea nitrification and pelagic denitrification. Therefore an additional source of 3.8 Tg N2O yr−1 attributed to nitrification in the upper water column (0–2000 m) might exist. With a simple model we estimated the effect of changes in the North Atlantic Deep Water (NADW) formation for deep-water N2O. The upper water N2O budget is not significantly influenced by variations in the N2O deep-water formation. However, the predicted decrease in the NADW formation rate in the near future might lead to an additional source of atmospheric N2O in the range of about 0.02-0.4 Tg yr−1. This (anthropogenically induced) source is small, and it will be difficult to detect its signal against the natural variations in the annual growth rates of tropospheric N2O.
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  • 93
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    A model for growth of steep-sided vent structures on the Endeavour Segment of the Juan de Fuca Ridge: Results of a petrologic and geochemical study (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research - Solid Earth, 104 (B10). pp. 22859-22884.
    Details
    Publication Date: 2018-04-12
    Description: Petrologic and geochemical studies of vent solids from the Main Endeavour Field (MEF) and the High Rise Field (HRF), Juan de Fuca Ridge, demonstrate that the steep‐sided vent structures characteristic of these sites form dominantly by flange growth, combined with diffuse flow through sealed portions of structures, and incorporation of flanges into structures. Geochemical calculations suggest that the prevalence of amorphous silica and flanges in Endeavour deposits is the result of conductive cooling of vent fluids that have high concentrations of ammonia. At Endeavour, as the temperature of vent fluid decreases, ammonia‐ammonium equilibrium buffers pH and allows more efficient deposition of sulfide minerals and silica from fluids that have a higher pH than conductively cooled ammonia‐poor fluids present at most other unsedimented mid‐ocean ridge vent sites. Deposition of silica stabilizes flanges and allows structures to attain large size. It also leads to diffuse flow and further conductive cooling by reducing the permeability and porosity of the structures and of feeder zones, thus decreasing entrainment of seawater. Most inactive vent samples recovered from areas peripheral to the HRF and MEF are similar to barite + silica rich samples from the Explorer Ridge and Axial Seamount and likely formed from precipitation of silica and barite on a biological substrate. Active white smoker chimneys from the Clam Bed Field, located south of the HRF, are pyrrhotite rich and likely formed from vent fluids that are depleted in Zn and Cd and enriched in Pb and Ba relative to fluids exiting trans‐Atlantic geotraverse (TAG) and Cleft Segment white smoker chimneys.
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  • 94
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    Possible predictability in overflow from the Denmark Strait (1999)
    Nature Publishing Group
    In:  Nature, 397 . pp. 243-246.
    Details
    Publication Date: 2017-02-28
    Description: The overflow and descent of cold dense water from the Denmark Strait sill-a submarine passage between Greenland and Iceland-is a principal means by which the deep ocean is ventilated, and is an important element in the global thermohaline circulation. Previous investigations of its variability-in particular, direct current measurements(1,2) in the overflow core since 1986-have shown surprisingly little evidence of long-term changes in now speed. Here we report significant changes in the overflow characteristics during the winter of 1996-97, measured using two current-meter moorings and an inverted echo sounder located at different depths in the fastest part of the now. The overflow warmed to the highest monthly value yet recorded (2.4 degrees C), and showed a pronounced slowing and thinning at its lower margin. We believe that the extreme warmth of the overflow caused it to run higher on the continental slope off east Greenland, so that the lower current meters and the echo sounder were temporarily outside and deeper than the fast-flowing core; model simulations appear to confirm this interpretation, We suggest that the extreme warmth of the overflow is a lagged response to a warming upstream in the Fram Strait three years earlier (caused by an exceptional amplification of the winter North Atlantic Oscillation). If this is so, over-now characteristics may be predictable.
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  • 95
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    The predominantly facultative nature of epibiosis: experimental and observational evidence (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 187 . pp. 59-66.
    Details
    Publication Date: 2019-08-29
    Description: Epibiosis is a spatially close association between 2 or more organisms belonging to the same or different species. Through direct and indirect interactions, this association has major effects on the species involved and on community dynamics. When the effects are predominantly beneficial for epibiont and basibiont, coevolution can be expected to lead to associational specificity. Circumstantial evidence, however, suggests that many epibionts are non-specific substratum-generalists. In this arti-cle, we investigate the commonness of specificity in epibiotic associations. In a first approach, we inves-tigated the in situ recruitment preferences of potential epibionts when choosing between artificial and living substrata. After exposure for 3 wk in early summer, an early successional community had estab-lished, comprising cyanobacteria, diatoms, sesslle colonial ciliates and red algae. All species recruited on almost all substrata available. However, artificial substrata were usually preferred over living sur-faces. Consequently, the species studied are class~fied as facultative epibionts. An analysis of a list of over 2000 epibiotic associations corroborated these results, the majority of described 'epibionts' are not basibiont-specific and generally occur on non-living substrata as well. Also, basibiont species usually bear more than 1 epibiont species. Relative to each other, epibionts and basibionts are characterised by a typical set of life history traits. We conclude that specific and obligate epibionts are rare. Their scarcity is discussed in view of multilevel antifouling defences and presumptive evolutionary transi-tions from epibiosis towards endoparasitism or endosymbiosis.
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  • 96
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    Endogenous circatidal rhythm in the Manila clam Ruditapes philippinarum (Bivalvia: Veneridae) (1999)
    Springer
    In:  Marine Biology, 134 . pp. 107-112.
    Details
    Publication Date: 2018-06-07
    Description: Manila clams, Ruditapes philippinarum, removed from their natural environment and maintained for 9 weeks in continuously immersed conditions exhibited a clear endogenous circatidal rhythm in oxygen consumption. The clams exhibited a semidiurnal rhythmicity in oxygen consumption after showing a diurnal pattern in the first few days (5 to 7 d) of the experiment. The results of the present study indicate that activity rhythms of clams are controlled not only by exogenous factors, but also by an endogenous circatidal periodicity.
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  • 97
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    Reptilian diving: highly variable dive patterns in the green turtle (Chelonia Mydas) (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 185 . pp. 101-112.
    Details
    Publication Date: 2018-05-08
    Description: Diving reptiles, unlike most diving birds and mammals, return infrequently to the surface to breathe. Spending the bulk of their lives underwater, they are likely to have developed a large variety of specific behavioural patterns different from those of their warm-blooded counterparts. However, for technical reasons, underwater behaviour of these aquatic reptiles remains poorly understood. In this study green turtles Chelonia mydas nesting on Cyprus (Eastern Mediterranean) were equipped with multi-channel data loggers monitoring diving behaviour and activity (via a logger-integrated 3-D compass which served as an activity sensor) during the inter-nesting interval. Data from 2 turtles for 2 consecutive inter-nesting intervals were available for detailed dive analysis. Both turtles showed highly variable dive patterns ranging from travelling subsurface dives to specific dive types such as U- (mainly resting and foraging dives), S- (a form of energy saving swimming) and V-dives. The green turtles stayed near the coast throughout the study, dived no deeper than ca 25 m, but remained underwater for up to ca 40 min. The recordings of the activity sensor revealed high activity levels (less than 20% resting d-1) during the whole inter-nesting period which was attributed to extensive foraging. The combination of both the activity data and the dive data showed that the turtles were engaged in travelling movements for 46% of the inter-nesting time spent underwater, foraged for 34% and rested for 12% of the time. We discuss the physiological, ecological and conservation implications of these results.
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  • 98
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    Use of observed ice crystal sizes and shapes to calculate mean-scattering properties and multispectral radiances: CEPEX April 4, 1993, case study (1999)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Atmospheres, 104 (D24). pp. 31763-31779.
    Details
    Publication Date: 2018-01-24
    Description: During the Central Equatorial Pacific Experiment, ice crystal sizes and shapes were measured in an outflow anvil. A habit (i.e., column, bullet rosette, Koch fractal polycrystal, sphere) was assigned to each particle using a self-organized neural network based on simulations of how the maximum particle dimension and area ratio varied for random orientations of these crystals. Average ice crystal size and shape distributions were calculated for 25 km long segments at six altitudes using measurements from a two-dimensional cloud probe for crystals larger than 90 μm and a parameterization for smaller crystals based on measurements from the Video Ice Particle Sampler (VIPS). Mean-scattering properties were determined by weighting the size and shape dependent single-scattering properties computed with ray-tracing algorithms according to scattering cross-section. Reflectances at 0.664, 0.875, 1.621, and 2.142 μm were then calculated using a Monte Carlo radiative transfer routine. Although these reflectances agree reasonably with those measured by the MODIS airborne simulator (MAS) above the anvil, uncertainties in cloud base and system evolution prevent a determination of whether ray-tracing or anomalous diffraction theory better predict reflectance. The calculated reflectances are as sensitive to the numbers and shapes of crystals smaller than 90 μm as to those of larger crystals. The calculated reflectances were insensitive to the classification scheme (i.e., neural network, discriminator analysis, and previously used classification scheme) for assigning particle shape to observed crystals. However, the reflectances significantly depended on assumed particle shape.
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  • 99
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    The family Ectothiorhodospiraceae (1999)
    Springer
    In:  In: The Prokaryotes. An evolving electronic resource for the microbiological community. A Handbook on the Biology of Bacteria. Ecophysiology, Isolation, Identification, Applications. , ed. by Dworkin, M., Falkow, S., Rosenberg, E., Schleifer, K. H. and Stackebrandt, E. Springer, New York. 3
    Details
    Publication Date: 2012-02-28
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  • 100
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    Microzooplankton grazing and nitrogen supply of phytoplankton growth in the temperate and subtropical North East Atlantic (1999)
    Inter Research
    In:  Marine Ecology Progress Series, 189 . pp. 93-104.
    Details
    Publication Date: 2018-05-08
    Description: Serial dilution experiments were conducted on JGOFS-North Atlantic cruise of RV 'Meteor' M36/2 at a 20° W transect in June and July 1996 to assess the role of microzooplankton grazing and nitrogen supply in controlling phytoplankton stocks in the subtropical and temperate northeast Atlantic. Rates of microzooplankton grazing ranged from 0.08 d-1 at 54° N to 0.53 d-1 at 40° N and mean growth rates of phytoplankton ranged from 0.19 d-1 at 54° N to 0.75 d-1 at 40° N. Both rates were positively related to seawater temperature, whereas the apparent growth yield of phytoplankton declined with increasing temperature from 0.19 µg chl a dm-3 d-1 at 54° N to 0.01 µg chl a dm-3 d-1 at 33° N. Complete nitrogen saturation of phytoplankton growth indicated light or non-nitrogenous limitation at the nitracline at 47° N and in the deep chlorophyll maximum at 33° N, whereas in the mixed layer at 47° N and 54° N the ambient nitrogen supply was sub-saturated and yielded 63 and 39% of nitrogen- saturated growth. Nitrogen supply of phytoplankton growth was dominated by external and cellular sources in nitrate-rich waters of the mixed layer at 54° N and at the nitracline at 47° N, whereas nitrogen regeneration dominated at the nitrate-depleted surface waters at 47° N. However, in the deep chlorophyll maxima at 33° N and 40° N phytoplankton growth was primarily maintained by nitrogen regeneration, although external nitrogen was sufficiently available. The recycling efficiency of the microbial community was defined as the ratio of regenerated growth yield to herbivorous grazing loss. Efficiencies of ~100% under post-bloom situations indicated tight coupling of predation, nitrogen supply and phytoplankton growth. We suggest that microzooplankton grazing has a high potential for nitrogen supply and biomass control of phytoplankton communities during summer in the temperate and subtropical northeast Atlantic.
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