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  • Other Sources  (428)
  • Articles (OceanRep)  (428)
  • Springer Nature  (263)
  • Oxford Univ. Press  (164)
  • American Meteorological Society
  • 1
    Publication Date: 2018-10-02
    Description: Population dynamics of major Baltic calanoid copepod species in the Gotland Basin during the last two decades were characterized by a decline of Pseudocalanus elongatus associated with declining salinities, and an increase of Temora longicornis and Acartia spp. potentially due to warmer conditions. Additionally this study investigated the effect of predation by the major planktivorous fish species herring (Clupea harengus) and sprat (Sprattus sprattus) for the period 1977–1996 in the Gotland Basin (Central Baltic Sea). Examination of consumption by these fish species in relation to copepod production estimates showed a switch by herring from consuming mainly CV/VI of P. elongatus and T. longicornis, to preying on CII of the latter copepod. This switch was potentially due to increased competition with the drastically increased sprat stock since the late 1980s. Further, an increased predation pressure by sprat on CV/CVI of both copepod species in spring resulted in higher copepod mortality rates. In consequence, based on these results we suggest that the increase in the sprat stock since the late 1980s contributed to a decline of P. elongatus, and additionally prevented an even more pronounced temperature-driven increase in the T. longicornis stock, as was observed for Acartia spp., which was not significantly consumed.
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  • 2
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    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 57 . pp. 300-309.
    Publication Date: 2019-09-23
    Description: Cod is the top piscivore predator in the Baltic Sea ecosystem. Based on stomach content data from 62 427 cod collected during 1977–1994 and food consumption rates, cannibalism in the Eastern and Western Baltic cod stocks has been quantified using multispecies virtual population analysis. In the Eastern Baltic stock, depending on model assumptions, an average of 25–38% of the 0-group and 11–17% of the 1-group were removed by predation by adults. Thus, between age 0 and age 2 a year class may lose on average about 31% and 44% of the initial number as a result of cannibalism. Cannibalism is lower in the Western Baltic. On average, 19% of the 0-group and 9% of the 1-group are consumed per year, i.e. 24% of the initial cohort is eaten before reaching age 2. Predation was most intense in 1978–1984, a period with high juvenile abundance and large adult stock sizes in both areas. Subsequently, stock, recruitment, and cannibalism declined steadily until the early 1990s and then increased again. Problems identified in relation to data compilation and estimation procedure are discussed with respect to their impact on estimates of cannibalism and stock– recruitment relationships
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  • 3
    Publication Date: 2017-10-10
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  • 4
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    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 63 (2). pp. 224-234.
    Publication Date: 2019-09-23
    Description: Gametes from five male and three female haddock ( Melanogrammus aeglefinus ) were crossed to produce 15 half-sibling families that were used to evaluate potential parental contributions to early life history variability. Larval morphology at 0 and 5 days post-hatch (dph) and time to starvation in the absence of food were examined. Maternal influences on larval standard length and yolk area were significant at 0 and 5 dph. Paternal effects on larval standard length were significant at 0 and 5 dph, whereas paternal effects on yolk area were only significant at 5 dph. Larval eye diameter was influenced by maternity at day 0 post-hatch and by both maternity and paternity at 5 dph. Myotome height of larvae was subject to maternal and paternal influences at 0 and 5 dph. Growth rate was significantly influenced by both paternity and maternity. Yolk utilization efficiency was significantly influenced by parental interaction, while the time taken for larvae to die in the absence of food was affected only by maternity. Results of this study not only confirm the importance of female contributions to larval development but also indicate a paternal influence on the development and the early life history success of marine fish.
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  • 5
    Publication Date: 2019-09-23
    Description: The seasonal development of oxygen concentrations in the deep water of a nearly permanently stratified station in Kiel Eight, which originates from inflows through the Great Belt and the Kattegat, was investigated. The bottom-water oxygen situation of an individual year was characterized by the apparent oxygen consumption rate from day 80 to day 260. The estimated consumption is poorly correlated with pelagic variables measured during the same year (winter-nutrient concentrations, DON, primary productivity, etc.). For the period 1979-1996, a significant correlation was found between oxygen consumption and average precipitation during the preceding 8 months (June-January). It is suggested that a considerable part of the production is transferred into the next year as particulate organic pool accumulated in, or on top of, the sediment rather than being immediately recycled.
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  • 6
    Publication Date: 2018-06-05
    Description: Abundance, distribution, population structure, lipid content, lipid composition and reproductive and feeding activity of Rhincalanus nasutus were studied in the Gulf of Aqaba and in the northern Red Sea during RV “Meteor”-cruise M 44-2 in February/March 1999. Rhincalanus nasutus occurred in higher numbers in the Gulf of Aqaba (585 ind m−2) than in the northern Red Sea (254 ind m−2). Young developmental stages (nauplii, copepodite stages CI and CII) were absent. In the southern Gulf of Aqaba, the bulk of the population developed from stage CV to adult in the course of the 3-week study period. In contrast, immature CV stages dominated at the adjacent stations in the northern Gulf of Aqaba and in the northern Red Sea. Development was associated with the seasonal vertical migration from wintering mid-water layers and initiation of feeding starting as early as beginning of March in the southern Gulf of Aqaba. No upward migration was observed in the northern parts of the Gulf and in the northern Red Sea, where more than 90% of the females remained immature during our study. Lipids were dominated by wax esters in females and CV. The fatty acid and fatty alcohol compositions of females were very similar throughout the study region and period. Major fatty acids were 18:1(n−9), 16:1(n−7), 16:2(n−4) and 20:5(n−3). Our results support the previous reports of a seasonal dormancy of R. nasutus in the Gulf of Aqaba and suggest that the timing of vertical migration, feeding and maturation is closely coupled to the development of the spring bloom in oligotrophic subtropical waters.
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  • 7
    Publication Date: 2017-03-07
    Description: Retention or dispersion of larvae from the spawning grounds has been identified as one of the key processes influencing recruitment success in fish stocks. To examine the potential effects of transport on recruitment, numerical simulations were performed utilizing a three-dimensional physical oceanographic model of the Baltic Sea. Cod larvae were represented as Lagrangian drifters released in the deepwater region of the Bornholm Basin, the main spawning ground for Baltic cod. Simulations were performed for the major spawning seasons of 1993 and 1994, when annual and interannual variability of meteorological forcing was large. The principal goals of the modelling exercise were first to identify the physical processes influencing the demersal distribution of the early life stages and second to describe the transport of the pelagic stages in response to variations in windstress, thereby identifying the meteorological and hydrodynamic mechanisms influencing retention and/or dispersal. The results suggest that periods of low wind, especially from northern and eastern directions, retain early life stages of cod within the deepwater region of the Bornholm Basin. Periods of higher windstress and duration from the west and south resulted in a rapid transport of larvae into shallow coastal regions. Based on the results obtained from these drift experiments and a wind data time series from the meteorological station Christiansoe, a transport index has been developed, variations in annual retention/ dispersal have been identified, and comparisons with variations in recruitment success are presented.
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  • 8
    Publication Date: 2018-06-05
    Description: The abundance and vertical distribution of microcopepods sampled by nets with 55 μm mesh size was compared for two neighbouring but hydrographically different areas, the Gulf of Aqaba and the northernmost Red Sea, during spring 1999. The vertical structure of the total microcopepod communities differed considerably between the two regimes: In the stratified waters of the Red Sea, calanoids outnumbered oncaeids as well as oithonids at 0–100 m, whereas oncaeids dominated in all meso- and bathypelagic layers below 100 m deep. In the unusually deep vertically mixed waters of the Gulf of Aqaba, calanoids outnumbered each of the non-calanoid taxa as deep as 250 or 350 m, whereas the oncaeid dominated deep water community was restricted to depth ranges below 400 m. Dominant non-calanoid species in both areas were Oncaea bispinosa, Paroithona pacifica, Oithona simplex, Spinoncaea ivlevi, O. tregoubovi and O. cristata. O. scottodicarloi occurred in exceptionally high numbers in the northern Gulf. Pronounced differences between the two areas were found in the vertical distribution of poecilostomatoid species. By comparing the present results with published data from the central and southern Red Sea and other tropical and warm-temperate oceanic areas, intra- and inter-oceanic differences in the structure of microcopepod communities in oligotrophic areas are discussed. The high abundance and vertically extended range of calanoid copepods during spring appears to be a specific feature of the Gulf of Aqaba, indicating an unusual vertical succession in the trophodynamic structure of the copepod fauna in this area.
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  • 9
    Publication Date: 2018-06-01
    Description: The seasonal development of bacteria was studied in the hypertrophic coastal lagoon Ciénaga Grande de Santa Marta (Caribbean coast of Colombia). This large but only 1.5 m deep lagoon is subject to strong seasonal variations of salinity from almost fully marine (April/May) to brackish conditions in October/November. Chlorophyll ranged from 6 to 182 μg L−1, and gross primary production amounted to 1690 g C m−2 per year. Total bacterial number (TBN) ranged from 6.5 to 90.5 × 109 cells L−1 and bacterial biomass (BBM) from 77 to 1542 μg C L−1, which are among the highest ever reported for natural coastal waters. Neither TBN nor BBM varied significantly with salinity, phytoplankton or seston concentrations. Only the bacterial mean cell volume showed a significant relation to salinity, being highest (0.066 μm3) during the period of increasing and lowest (0.032 μm3) during decreasing salinity. Bacterial protein accounted for 24% (19–26%) and phytoplankton protein for 57% (53–71%) of total seston protein. The ratio (annual mean) of bacterial carbon to phytoplankton carbon was 0.44 (range 0.04–1.43). At low phytoplankton abundance [chlorophyll a (Chl a) 〈 25 μg L−1], bacterial carbon was almost equal to phytoplankton biomass (i.e. the mean ratio was 1.04). In contrast, at Chl a 〉 100 μg L−1, BBM was low compared to phytoplankton biomass (the mean ratio was 0.16). In general, BBM varied less than phytoplankton biomass. Most probably, the missing correlation between bacterial and phytoplankton variables was due to (i) organic material partly derived from allochthonous sources serving as food resource for bacteria and (ii) a strong resuspension of bacteria from the sediment caused by frequent wind-induced mixing of the very shallow lagoon.
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  • 10
    Publication Date: 2017-11-14
    Description: Miocene Ignimbrite ‘A’ on Gran Canaria contains three compositional endmember fiamme types(two rhyolites and one trachyte) each of which crystallized distinct feldspar. Various textural and compositional criteria are interpreted as reflecting a complex scenario within the magma chamber in which the crystals formed. About 25–30% of the feldspar phenocrysts contain evidence for magma mixing in the form of (1) partial to severe dissolution–resorption rims, (2) distinct zones of drastically different compositions and (3) overgrowth textures on formerly resorbed crystals. Four major types of zoning in the oligoclase to anorthoclase feldspars of ignimbrite ‘A’ include a normal and a reversely zoned type and two complexly zoned types. The feldspars with normal and reverse zonation show only minor compositional amplitudes between individual zones (ΔAb, Or ∼4%), whereas the complexly zoned types show compositional differences between zones of up to 18 mol % Ab and 20 mol % Or and are commonly associated with an internal dissolution surface. Complex zoning with large compositional amplitudes and dissolution textures is taken as evidence of crystal movements within the magma and across compositional boundaries between magma batches. A multiple ‘step-cycle’ model, involving growth and transport of a crystal into another magma batch and its return to the original host magma, is suggested by the data. Moreover, feldspars from one rhyolite compositional group are found to be substantially elevated in δ18O, suggesting an input of a high δ18O component to this rhyolite. The other endmember rhyolite appears to be related to the endmember trachyte by mainly crystal fractionation of anorthoclase feldspar. This observation is consistent with trace element and rare earth element concentrations for the magma endmembers and their feldspars, where contamination led to a depletion in incompatible trace elements and light rare earth elements in the contaminated rhyolite and its feldspar phenocrysts. We suggest that the combination of textural and compositional variation in ternary feldspar of peralkaline rhyolitic systems is well suited to reconstruct dynamic processes such as magma mixing and contamination in evolving rhyolitic magma chambers.
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