ALBERT

Description: Biological and fishery features of the waves of abundance of Illex argentinus in three fishery regions −52°S (shelf with 180–230 m depths in exclusive economic zone of Argentina—EEZA), 46° and 42°S (continental slope with 600–800 m depths off the EEZA) in April–June 1990 were studied. According to age analysis of 629 statoliths made aboard, age-length structure of each wave of abundance were determined. In April–June active spawning migrations of I. argentinus were observed from feeding grounds located in limits 50–52°S along the continental slope northwards through 46° and 42° fishery regions. Only winter-hatched squids (hatched from June to September of the previous year) took part in migrations which were observed as waves of abundance in all three regions. Each migratory wave of abundance consisted of 2–4 successive monthly generations. The start of spawning movement was corresponded with the age and maturity state of the squid. Squid of all monthly generations began migrating from the 52°S region at a mean age of approximately 250 days, passed through 46°S at mean age 280 days and through 42°S at mean age 295 days. Males migrated 2–3 weeks earlier than females of the same generation. Rates of somatic growth were very low during migrations from 52° to 46°S (RDGR - 0.13% mantle length (ML) in mature males and 0.2% ML in maturing females). During movement from 46° to 42°S and, obviously further, mature squids practically ceased somatic growth. Estimated rate of migrations was 23.2–28.9 km day−1 (including current velocity), or 26–30 cm s−1 (0.47 body length s−1). Spawning was considered to occur on the continental slope of Uruguay and Brazil north of 35°S in July–August. Methodical approaches of efficient determination of squid age, growth and stock structure by means of investigation of squid biological features and statolith microstructure in each distinguished wave of abundance were elaborated.

Description: Part of the spawning area of the squid, Loligo vulgaris reynaudii, was investigated over a 5-week period using a combination of hydroacoustic techniques, SCUBA dive transects and observations. Egg mass concentrations were identified by a Furuno FCY-663 echosounder, and these were positively confirmed by SCUBA diving. It was found that egg strands were concentrated into distinct, clumped spawning beds which were non-randomly distributed in the study area. Bottom substrata favored by spawning squid appeared to be sandy areas or low profile rocky reefs. The average number of eggs per strand was 148 (±37). This study examines different techniques to estimate numbers of squid eggs in the wild, which may have wider application. Two statistical techniques were used in an exploratory data analysis to estimate the total number of eggs present in the study area, using both random and non-random transect methods. A non-random technique of estimation on clearly defined egg bed areas was found to be the most appropriate, although egg number estimates to date are considered preliminary.

Description: Within the statoliths of the onychoteuthid squid Moroteuthis ingens captured off the southeast coast and the Chatham Rise (New Zealand} between 500 and 1239 m depth, there were conspicuous zones consisting of an inner opaque and outer translucent zone; these strikingly resembled zones observed in some teleost fish otoliths. There was no relationship between the number of increments within the opaque zone among individuals of different length and age, but the width of the opaque zone was negatively related to both mantle length and age. The smallest juveniles captured in bottom trawls had a narrow translucent zone relative to the opaque zone which suggested that the translucent zone is laid down after settlement and that settlement takes place probably at or before 160 mm mantle length in this species. This study suggests that the transition observed within the statolith microstructure of M. ingens represents a habitat change from an epipelagic habitat to a demersal habitat. Evidence for the hypothesis is drawn from analogous features observed within teleost otolith microstructure and from available information on Moroteuthis and Onykia

Description: The effects of feeding a prepared surimi diet (fish-based) and a prepared pelleted diet (shrimpbased) on the survival, growth and feeding rate of the cuttlefish Sepia officinalis L. were evaluated during a 45-day experiment. One hundred and twenty juveniles of laboratory cultured cuttlefish (74.5 ± 12.36 g) were divided into three treatments and were fed thawed shrimp (control), pellets or surimi. Survival rates on these diets were 95.0%, 67.5% and 22.5%, respectively. Preliminary data indicated that the low survival of cuttlefish fed surimi may have been caused by low levels of copper in their blood (131 vs 244 μg/ml) since copper is required for their respiratory blood pigment, hemocyanin. Instantaneous growth rates were 2.71 % body weight BW/day for cuttlefish fed raw shrimp, 0.33% BW/day for cuttlefish fed pellets, and 0.54% BW/day for cuttlefish fed surimi. The feeding rate of cuttlefish fed shrimp was high (6–8% BW/day). The feeding rate on pellets increased with time (from 〈 1 to 3% BW/day) but never reached the level for raw shrimp. The feeding rate on surimi increased to equal the rate for raw shrimp during days 1–30 (8 to 9% BW/day) and thereafter decreased (〈4% BW/day). In conclusion, there was a major distinction between the palatability of a prepared diet and the ability of that diet to support growth. Surimi was highly palatable but resulted in poor survival, suggesting low nutritional quality. In contrast, pellets were less palatable but produced maintenance growth. Development of practical surimi diets will require supplementation of the surimi with soluble micro- and macronutrients.

Description: The bathymetric distribution and relative abundance of cephalopods from the northern Tyrrhenian Sea have been investigated. The specimens were collected during six trawl surveys carried out from 1985 to 1987, between the isles of Elba and Giannutri. Cephalopods represented 9-17% of the total commercial catches. The depth of the catches ranged from 4 m to 635 m. The average catch per hour of the commercial species has been analysed. Eledone cirrhosa represents the most abundant species. Some observations on the biology of the most frequent species are given.

Description: Sepioteuthis lessoniana often are observed to come into inshore waters to lay egg capsules which are attached large seaweeds, sunken twigs and other substrata including man-made spawning beds. The egg capsules most commonly seen are exposed and contain 4-8 eggs (mode = 6) per capsule. However, in coral areas in Okinawa Islands, Sepioteuthis egg capsules have been discovered attached to the underside of dead tabletop corals, which lie upside down on the sea-floor. This type of egg capsule consistently contains two eggs per capsule. Unlike the typical S. lessoniana egg capsules found in seaweed bed or staghorn corals, they are deposited in a scattered fashion and never bundled together at the base. When exposed by a diver, they are easily attacked and eaten by fishes. The "usual" egg capsules are found in the period from April to May in Okinawa, while the latter type of capsules are found during June to October. Differences in spawning substrate and exposure, spawning seasons, the nature of eggs per capsule and arrangement of capsules suggests that S. lessoniana in Okinawa area is composed of two different infraspecific populations.

Description: Big specimens of Asperoteuthis acanthoderma and Megalocranchia sp. that were all landed at Okinawa area were investigated. Three specimens of A. acanthoderma (all fe- males) were measured 450-780 mm ML. Various characters exhibit those of a full grown stages than the type specimens which were 144.5 and 188 mm. Two specimens (also females) of Megalocranchia sp. were 1420+ and 1838 mm, respectively. This may be the largest record of the Cranchiidae except for the Antarctic Mesonychoteuthis.

Description: Statoliths of Loligo gahi were sampled in the fishery region 45–47°S on the Patagonian shelf during September 1989. Peculiarities of the growth zones in the ground statoliths of adults are described. Maximum age of large maturing and mature females (130–160 mm of mantle length, ML) was estimated to be 325–345 d, that of large mature males (250–290 mm ML) ranged from 360 to 396 d. The squid Loligo gahi d'Orbigny, 1835, occurs in temperate shelf and upper slope waters of the Atlantic and Pacific coasts of South America and is caught commercially by the international fleet in the southern part of the Patagonian shelf within the Falkland Islands Interim Conservation Zone (FICZ) (Roper et al., 1984; Csirke, 1987). Occasionally, dense shoals of L. gahi appear in the fishery region 45–47°S off the Exclusive Economic Zone of Argentina (EEZA) and have been caught in significant numbers by trawlers at depths of 120–150 m in September-October (Chesheva, 1990). Loligo gahi is a medium sized loliginid; in Falkland waters males attain 350 mm ML, females 210 mm ML (Hatfield, 1991), while in the fishery region 45–47°S maximum size is 260 mm and 160 mm, respectively (Chesheva, 1990). Patterson (1988) revealed two Falkland spawning stocks of L. gahi of unclear status, spring-spawners and autumn-spawners (austral seasons) and pointed out that the life span of squid of each stock lasted ~1 y. Recently Hatfield (1991) used statoliths to elucidate Patterson's (1988) estimations of age and growth of Falkland stocks of L. gahi and confirmed the 1-y duration of L. gahi's life span.

Description: Changes in marine ecosystems can be manifested in many different ways, on different temporal and spatial scales. Seabirds are top consumers in marine foodwebs and offer opportunities to detect and assess the biological effects of changes in physical parameters (sea-surface temperature [SST], salinity, depth of thermocline etc.) of the marine ecosystem. We compare six-eight years' of data on the biology (diet, and breeding success) of four species of seabird (arctic tern Sterna paradisaea and common tern S. hirundo, which feed at the sea surface; and Atlantic puffin Fratercula antica and razorbill Alca torda, which dive 30-60 m for their prey) breeding on Machias Seal Island (MSI) in the Bay of Fundy with both our own meteorological and oceanographic measurements, and with standard measurements from conventional sources. These are compared with fisheries data on changes in the main prey of all the seabirds concerned (juvenile or '0-group' herring Clupea harengus) which are the most direct link between the seabirds and the physical properties of the marine system. We explore relationships between seabird productivity and diet, and other aspects of both herring biology (larval surveys, and fat content) and oceanography (SST data from the island, and remotely sensed data from the entrance to the Bay of Fundy). Timing of laying by puffins followed SST variation at neither the local (MSI) nor regional scales, but at the scale of the North Atlantic, following the trend of populations breeding off northern Norway. The proportion of herring in the diet of terns over 6 years varied inversely with herring larval abundance the previous fall; this relationship was not statistically significant in the puffin and razorbill. A major new finding is the considerable (approximately 50%) inter-annual variation in the energy density (fat content) of juvenile herring that are the main seabird prey; breeding success of both species of tern varied in parallel with the energy density of juvenile herring in the diet until the last two years of the study, when sandlance (Ammodytes sp.) and euphausid shrimp predominated in the diet. Our long-term research approach combines traditional population monitoring (of numbers of breeding birds) with demographic, behavioural and environmental monitoring, to provide new understanding of the marine ecosystem as well as of seabirds.

Description: Ripe egg dimensions in the squid genus Illex are close to the minimum for cephalopods. The average diameter varies significantly depending on species (0.77–0.82 mm in I. coindeti , 0.75–0.88 mm in I. illecebrosus , and 0.96–1.04 mm in I. argentinus ), on geographical distribution intraspecifically, e.g. I. argentinus (0.96–0.97 mm in the shelf groups and 1.04 mm in the slope oceanic group), and between pre-spawning and spawning females of the summer-spawning shelf group of I. argentinus (0.97 and 0.92 mm, respectively). The potential fecundity (PF), defined as total oocyte stock both in the ovary and oviducts, depends on mantle length (ML in each species. It varies from 90 000 (ML = 150–160 mm) to 800 000 (ML = 230–250 mm) in I. coindeti , from 200 000 to 630 000 (ML = 220–280 mm) in I. illecebrosus , and from 75 000 (ML = 150–170 mm) to 1 200 000 (ML = 360–380 mm) in I. argentinus . It is possible to estimate the actual value of PF shortly before vitellogenesis begins and up to a start of spawning, when the diameter of the smallest oocytes exceeds 0.05 mm. The summer-spawning shelf females of I. argentinus release about of 70% of PF. Their spawning is intermittent and ripe egg production decreases over time with only a 50% replacement of the initial stock of vitelline oocytes and a decreasing volume of eggs at each release. Feeding activity decreases and the mantle wall and internal organs shrink once spawning commences. In spent animals, a degeneration of both vitelline and protoplasmic oocytes occurs. The squids genus Illex is one of typical r-strategists among the cephalopods.

Description: Viele Fischarten der Polarmeere schütz.eo sich vor dem Gefrieren durch die Synthese von makromolekularen Substanzen. Diese Moleküle sind meistens Proteine oder Glykoproteine (ANANfHANARA Y ANAN 1989). Die meisten antarlctischen Notolhenioidei sowie die arktischen und einige nord-boreale Dorschartige (Gadidae) besitzen sogenannte "antifreeze glycopeptides" (AFGP) der gleichen oder fast identischen Struktur. Dabei handelt es sich um Polymere verschiedener Länge des Glykotripeptids Alanin-Alanin-Threonin, wobei an jedes Threonin das Disaccharid Galaktose-N-Acetylgala.lctosamin gebunden ist. [...]

Description: Den Begriff 'Polynya' sucht man meist auch in anspruchsvollen Nachschlagewerken vergeblich. Er stammt aus dem Russischen und bezeichnet eine größere, sich über einen Zeitraum von Wochen bis Monaten erhaltende eisfreie Wasserfläche inmitten der zugefrorenen oder mit dichtem Treibeis bedeckten Meeresgebiete der Arktis und Antarktis. Ihre Größenausdehnung kann sich über hunderte und tausende von Quadratkilometern erstrecken. (...)

Description: This chapter records the benthonic foraminifera associated with a biogenic gas seep in the North Sea. A sample from an actively seeping site contains a benthonic foraminiferal assemblage statistically distinct from that of a control site. The distinctions are in terms of, firstly, abundance, diversity and dominance, secondly, taxonomic composition, and thirdly, proportions of epifaunal (surface-dwelling) and infaunal (sediment-dwelling) morphotypes.

Description: Productivity regime and phytoplankton size structure are described for two different epipelagic systems in the tropical/subtropical Northeast Atlantic Ocean investigated during 9–11 day drift studies in spring 1989 in the JGOFS North Atlantic Bloom Experiment, 18°N, 30°W and 33°N, 20°W. At the 18°N study site, an oligotrophic system was encountered. The water column above the main pycnocline at about 50–60 m depth was nutrient-depleted, and both chlorophyll and primary production displayed subsurface maxima at the nutricline. Picoplankton was the dominant size fraction, accounting for 78–90% of chlorophyll and 83–98% of primary production. Synechococcus-type coccoid cyanobacteria were the dominant picoplankters. The hydrographic situation was characterized by high small-scale variability; the most interesting feature was the intrusion of nutrient-depleted Subtropical Salinity Maximum Water into the euphotic zone, whose impacts on the productivity regime are discussed. At 33°N study site, a post-bloom situation was encountered. Although the euphotic zone was nutrient-depleted, higher amounts of larger phytoplankton were present, the contribution of picoplankton being 42–53% of chlorophyll and 42–86% of primary production. Over the course of the drift study, subsurface maxima of chlorophyll and productivity evolved, the contribution of picoplankton having increased. Picocyanobacteria again were the dominant picoplankters. At both study sites the profiles of abundance ratios of picocyanobacteria to picoeucaryotes cell numbers proved to be a useful tool to characterize water masses.

Description: Organic material entering the oceanic mesopelagic zone may either reenter the euphotic zone or settle into deeper waters. Therefore it is important to know about mechanisms and efficiency of substrate conversion in this water layer. Bacterial biomass, bacteria secondary production (BSP). extra­cellular peptidase activity (EPA) and particulate organic nitrogen (PON) were measured in vertical pro­files of the North Atlantic (46° N 18° W; 57° N 23° W) during the Joint Global Ocean Flux Study (JGOFS) cruise in May 1989. The magnitude of these parameters decreased differently with depth. The strong­est decreases were observed for bacterial production (3H-thymidine incorporation) and peptide turn­over (using the substrate analog leucine-methylcoumarinylamide). Bacterial biomass and peptidase potential activity were not reduced as much in the mesopelagic zone. Peptidase potential per unit cell biomass of mesopelagic bacteria was 2 to 3 times higher than that of bacteria in surface water. Nevertheless bacterial growth at depth was slow, due to slow actual hydrolysis. Values of theoretical PON hydrolysis were calculated from PON measurements and protein hydrolysis rates. These corre­sponded well to bacterial production rates, and the degree of correspondence increased from a factor of 0.63 (PON hydrolysis/ESP) in the mixed surface layer to 0.87 in the mesopelagic zone. Thus we hypothesized an effective coupling between particle hydrolysis and uptake of hydrolysate by bacteria, which depletes the deeper water of easily degradable substrates as hydrolysates usually are. The low enzymatic PON turnover rate of 0.04 d- 1 in the subeuphotic zone suggests that residence time of parti­cles within a depth stratum may be important for its contribution to export. storage and recycling of organic matter.

Description: During the ‘Meteor’ Expedition 13 in July and August 1990 to the northern part of the Norwegian Sea off west Spitsbergen, 7 stations with a depth of 2000 m or more were sampled with Agassiz trawl or hyperbenthos sledge, 14 more with a large box corer. Sponges were found at 6 of the trawl stations and in 2 box cores. A total of 19 species occurred, most of which were new to the area. Eight of the species were encountered more often than the other 11. Literature review and check of unpublished samples showed that by distribution, frequency of occurrence or abundance these species can be defined as the typical sponge association of the Norwegian and Greenland abyssal sea. This sponge association has a wide occurrence over the deep Norwegian-Greenland seas and parts of the Arctic basins. The analysis of substrate utilization of the 8 core species shows that all of them are able to colonize soft bottom, even some that previously had been considered to be dependent on hard substrate exclusively. Alternative substrate utilization and, in some species, the adoption of an infaunallife style are judged to be major reasons for the success of these species in the deep sea. The infaunal life style of the species Thenea abyssorum, Trichostemma sol and Tentorium semisuberites is documented and population structure data are given for the first time.

Description: Siliceous sponge spicules are concurrently mentioned in deep-sea expedition reports as constituents of abyssal and bathyal sediments, al though generally comprising only a few percent of the single samples.

Description: Mesoscale fluctuations in the western tropical Atlantic are analyzed in Geosat altimetry sea surface height (SSH) and geostrophic velocity anomalies to investigate the role of eddies in the North Brazil Current (NBC) retroflection zone. The detachment of anticyclonic eddies from the NBC retroflection is observed during November through January, when the NBC retroflection into the North Equatorial Countercurrent (NECC) weakens and finally breaks down. These eddies are traced over more than 2 months between 50° and 60°W on their way toward the Caribbean, at average speeds of 15 cm s−1. In one case an apparent merger of two anticyclonic eddies occurs, one detached from the retroflection zone and one detached from the NECC. Cyclonic eddies are also observed but are generally less persistent. Mesoscale SSH variance just west of the retroflection increases by a factor of 2 from early summer to winter, mainly because of the anticyclonic eddies. Interhemispheric water mass transfer associated with the eddy flux out of the NBC retroflection may amount to an average transport of 3 Sv.

Description: Turbulence in the Planetary Boundary Layer has been a topic of research for a long time. Its theory, however, is hampered by the fact that we have fewer fundamental equations than unknowns when dealing with turbulent motions. The search for additional “laws” to match the number of equations with the number of unknowns in turbulence theory is commonly labelled the turbulent closure problem. Despite considerable effort, this problem has not been solved. There is a variety of approaches available. However, these have not converged towards a commonly accepted PBL theory, like the Monin-Obukhov similarity for the surface layer. The Working Group on Boundary Layer Dynamics and Air-Sea interaction of ICDM/IAMAP therefore invites the scientific community to discuss these problems and possible solutions. The present paper intends to stimulate such a discussion.

Description: The origin and the spreading of the shallow Mediterranean water core (Ms) in the Iberian basin is discussed with a quasi-synoptic hydrographic data set enhanced by chlorofluoromethane (CFM) measurements. Its characteristic density level is found to be σt = 27.4. Characterized by high temperature and CFM values, Ms enters the Iberian basin in the region of Cape St Vincent between depths of 500–750 dbar. A heat anomaly of 〉11.8 × 109 J m−2 is chosen as the boundary between the presence of Ms and the background field. The core is found in a tongue-like shape as well as in separate isolated eddies of both cyclonic and anticyclonic circulation. Using the optimum multiparameter analysis (Tomczak and Large, 1989, Journal of Geophysical Research, 94, 16141–16149), the North Atlantic Central Water (NACW), which mixes with the Mediterranean outflow to form Ms, turned out to be in the mean 1°C warmer and 0.11 saltier than in regions with minor Mediterranean influence. This points to the Gulf of Cadiz as the origin of Ms, where the Mediterranean oufflows is in contact with NACW of the appropriate characteristics.

Description: Gas chromatography-mass spectrometry (GC-MS) analyses of organic concentrates from eastern Mediterranean surface water show that dissolved fossil fuel residues are dominated by unsubstituted aromatic hydrocarbons and heterocyclic aromatics and thus resemble products of incomplete combustion. Deviating from this interpretation, preferential photochemical oxidation of alkyl-substituted aromatics is suggested as the principal causative mechanism, although, especially near land-based sources. the influence of combustion-derived unsubstituted aromatics is not defined. Total concentrations of dissolved aromatics as determined by GC-FID (flame ionization detection) and GC-MS from a limited data subset were in reasonable agreement with UV fluorescence measurements of dissolved/dispersed oil residues. The same preponderance of unsubstituted aromatics over their alkyl derivatives was found in extracts of the particulate phase, but concentrations were small relative to alkanes and/or alkenes of recent marine biosynthetic origin. CPI (carbon preference index) values of higher molecular weight n-alkanes indicated varying contributions of plant waxes to the particulate hydrocarbon pool. CPI values of corresponding dissolved n-alkanes were found to be near unity, indicating fossil fuel origin. Despite differences in higher molecular weight n-alkane CPI values and the predominance of recent biosynthetic aliphatics, the similarity of dissolved and particulate aromatic fractions suggests limited adsorption by particles of fossil fuel derived hydrocarbons and heterocyclics.

Description: Saudi Arabian coastal waters near sandy beaches, severely contaminated with crude oil released in Kuwait during the 1991 Gulf War, as well as underlying sediments and a few bivalves, were analysed to assess concentrations and composition of petrogenic hydrocarbon mixtures and structurally related oxidation products. Concentrations of dissolved oil residues determined by UV spectrofluorometry (UVF) near oil deposits on beaches did not exceed 3.5 μg l−1; concentrations dropped to approximately 1/10th of this value a few miles offshore. Gravimetric concentrations of unfractionated lipophilic material extracted from large volumes of seawater at the same stations were up to 10 times those determined by UVF. After chromatography on silica gel, individual petroleum hydrocarbons in the low polarity fractions and oxidation products in the polar fractions were characterized by their spectra (GC/MS) and quantitated by Selected Ion Monitoring (SIM) GC/MS. Concentrations of oxidation products (ketones, aldehydes, alcohols) of aromatic hydrocarbons exceeded those of their parent compounds by more than an order of magnitude. Significant concentrations were also found of the presumably pyrogenic triplett sensitizer anthraquinone. Contributions to polar fractions of water extracts by biosynthesized lipids were negligible. UVF determinations appear to underestimate concentrations of dissolved oil residues, because many oxidation products have lower fluorescence quantum yields than the respective parent hydrocarbons. Their ecotoxicological properties are unknown. Concentrations measured in sediments by UVF ranged from 13 to 540 μg g−1 dry wt and 0.5 to 103 μg g−1 as measured by gas chromatography with flame ionization detection (FID GC). Bivalves ranged from 0.8 to 1.5 μg mg−1 extractable organic matter (EOM) by UVF, and 0.1 to 0.3 μg mg−1 EOM by GC analysis. PAHs were identified in sediment and bivalve extracts by GC/MS and quantitated by SIM GC/MS. None of the relatively water soluble alkylbenzene photo-oxidation products found in water samples nor any higher molecular weight quinones could be detected in sediment extracts. However, ion chromatograms strongly suggest the presence of numerous high molecular weight aromatics in that matrix.

Description: The objective of the study was to produce a size-based matrix model of a Laminaria digitata (L.) Lamour. population. ‘Hard’ data for insertion in the matrix were collected in a 9 year cohort analysis of size and age specific survival and fertility for a stand in south west Nova Scotia, Canada. The product of the square matrix containing these values and a column vector containing the densities of size classes was used to project the size class structure one year later. The projected estimates were found to fit empirical estimates with some confidence. In contrast, an age-based fertility life table wrongly predicted a population declining in density by 45% per year. The study supports, in theory, the use of size-based matrix models for management of harvested stands. In reality, the amount of work required to obtain ‘hard’ data and the site specific nature of the projections may preclude the use of such an approach to broad scale management.

Description: Laboratory experiments were carried out to investigate the effect of protozoan, copepod and combined grazing on Phaeocystis biomass. Phaeocystis cf. globosa single cells were offered to 3 different protozoan species, to the calanoid copepod Temora longicornis, as well as to mixtures of both grazer types. The heterotrophic dinoflagellate Oxyrrhis marina and the oligotrich ciliate Strombidinopsis acuminatum ingested Phaeocystis at much higher rates than did the copepod. Nevertheless, protozoan growth and ingestion rates were submaximal, indicating Phaeocystis to be suboptimal food. The oligotrich ciliate Strombidium elegans did not feed on Phaeocystis. In grazing experiments with mixtures of both predator types, the decline of Phaeocystis single cells could be explained by protozoan grazing alone, implying no grazing by the copepods on Phaeocystis. Instead, copepods ingested the protozoans at high rates. Predation on 0. marina and S. acuminatum by T. longicornis resulted in a reduction of the total grazing pressure on Phaeocystis of 21 and 67 % respectively. We conclude that mesozooplankton predation on herbivorous ciliates and heterotrophic dinoflagellates, which consumed Phaeocystis cells, can considerably reduce the overall grazing pressure and may enhance Phaeocystis bloomng.

Description: As part of the NOAA/ROPME/MSRC sponsored assessment of the coast of Saudi Arabia, heavily impacted by the large oil spills of the 1991 Gulf War, we measured benthic community respiration (R) and primary production (P) rates in shallow subtidal basins near heavily oiled coastlines. Study sites were located in zones predicted to be basins of maximum deposition of any oiled sediments likely to wash off the adjacent coast and in reference bays predicted to be clean and unaffected. We measured oxygen exchange using in situ benthic respirometers and analysed petroleum hydrocarbon (PHC) levels in the near surface sediments at five stations. We concentrated our efforts in mud habitats to complement related studies in seagrass habitats. Measured community R rates ranged from a low of 700 μM m2 h−1 in coarse sand sediments with total organic carbon content (TOC) of only 0.16% of dry wt to the highest rate of 2184 μm m−2 h−1 in finer mud-sand habitats with 0.39% TOC. All measured rates were in the range of literature values for shallow marine sediments at temperatures of 17 to 19°C. Sediment oil content was 13–540 μg g−1 dry wt by ultraviolet fluorescence (UVF) analysis and 0.5–103 μg g−1 by gas chromatography (GC). Benthic P rates, calculated as light minus dark changes in dissolved oxygen, ranged from a low of 1162 μm m−2 h−1 at the most heavily oiled site to a high of 5216 μm m−2 h−1 at less oiled sites. While a weak inverse relationship between benthic P and sediment oil content was not significant statistically due to the small number of samples, a significant inverse relationship was found between the ratio of production to respiration (P/R) and the total petroleum content of the sediments by UVF. The effect appears to be driven more by differences in production than an effect on respiration which showed little relationship with either oil content or productivity. We conclude that within 1 year after the oil grounded on the intertidal sands of Saudi Arabia, the levels of oil in subtidal benthic sediments had decreased in most habitats to levels that did not show community stress by our oxygen measurements. Rather, long term damage to benthic subtidal habitats was limited only to enclosed bays adjacent to the most heavily oiled coastlines. Preliminary estimates of yearly P converted to carbon units indicates that the shallow mud sediments of the Gulf are at least as productive as most oligotrophic water columns. Since benthic habitats covered by seagrass, algae beds or coral reefs are likely to have even higher production rates, we conclude that benthic processes contribute significantly to the overall carbon flux in the Gulf ecosystem.

Description: A method for the collection of large-volume samples of oceanic particles is described. Near-surface seawater is pumped from below the ship to a continuous-flow centrifuge at rates of up to 1.2 m3 h−1. The seawater is in contact with polyethylene, polypropylene, Teflon and titanium materials only. The retention efficiency of the centrifuge for marine particles is the same as for standard membrane filters, as shown by comparisons with separate samples from Go-Flo bottles. The pumping system is non-contaminating with respect to both particulate and dissolved species. Several subsampling facilities for additional chemical constituents and other parameters can be supplied simultaneously due to the modular design of the system and the high flow rates

Description: Climatological data sets are used to estimate the amount of water changing temperature and salinity at the sea-surface owing to air-sea exchanges. Considering this conversion as a function of sea-surface temperature and salinity leads to the definition of a conversion vector, which represents mass sources and sinks for each water type. The vector representation shows graphically the way the shape of the temperature-salinity relation is driven at the surface by the air-sea heat and fresh water fluxes.

Description: Current measures of microbe‐mediated biogeochemical processes in sediments were examined for their potential use as indicators of heavy metal ecotoxicity in both river sediments and bacterial cultures. Assays were carried out with HgCl2, CuSO4, and 3CdSO4 · 8H2O added to sediment samples and bacterial cell suspensions at concentrations ranging from 0.1 to 10 mM and 0.1 μM to 1 mM, respectively. Chemoautotrophic CO2 fixation by Elbe River sediment microbiota was most sensitive to Hg2+ and Cd2+, but not to Cu2+. Among the estimates of heterotrophic productivity, incorporation of leucine into cellular protein showed clearer dose responses than incorporation of thymidine into bacterial DNA. Thymidine incorporation was highly resistant to and even stimulated by metal ions, particularly in starved and anaerobic cultures of a test strain of Vibrio anguillarum. Similar metal ion induced “overshoot” responses beyond the levels of untreated controls were noted for mineralization of 14C‐glucose by V. anguillarum and, in the case of Cd2+, also in sediment. As a less complex measure of microbial respiratory activity, succinate dehydrogenase (SDH) showed normal dose responses without stimulatory effects, as long as bacterial cell homogenates were assayed. Despite this result, it is concluded that levels of SDH in natural sediment microbiota are inevitably affected by metal‐induced processes of selection and enzyme synthesis, and would thus fail to provide an appropriate measure of metal ecotoxicity. The final conclusion is that current parameters of microbial production and activity often reveal dose responses that do not fulfill basic requirements of ecotoxicity testing in metal‐polluted sediments.

Description: The benthic response to the sedimentation of particulate organic matter (POM) was investigated during 1985–1990 at 47°N, 20°W (BIOTRANS station). The first noticeable annual sedimentation of phytodetritus, as indicated by chlorophyll a concentrations in the sediment, occurred as early as late April-early May. Maximum amounts were found in June–July. Two different sedimentation pulses to the sea bed are described that demonstrate interannual variation: the occurrence of salp faecal pellets early in the year 1988 and the massive fall out of a plankton bloom in summer 1986, which deposited approximately 15 mmol C m−2. The benthic reaction to POM pulses was quite diverse. The mega-, macro- and meiobenthos showed no change in biomass, whereas bacterial biomass doubled between March and July. This corresponds to a seasonal maximum of total adenylate biomass. The relative abundance of Foraminifera among the meiobenthos increased during the summer. Benthic activity (ATP, ratio ATP/ETSA), as well as in situ sediment community oxygen consumption rates (SCOC), showed distinct seasonal maxima in July–August of 0.75 mmol C m−2 day−1. Based on SCOC and the carbon demand for growth, a benthic carbon consumption of 0.94 mmol C m−2 day−1 was estimated. This represents about 1.1% of spring bloom primary production and 9.6% of the export flux beneath the 150 m layer, measured during the North Atlantic Bloom Experiment. Bacteria and protozoans colonizing the epibenthic phytodetrital layer were responsible for 60–80% of the seasonal increase in SCOC. The strong reaction of the smaller benthic size groups (bacteria, protozoans) to POM pulses stresses their particular importance for sediment-water interface flux rates.

Description: Sediments of 13 piston cores from opposite continental slopes of the South China Sea, off southern China and Sabah (northern Borneo), were analyzed by sedimentological methods and dated by oxygen isotope stratigraphy. Sediments mostly consist of hemipelagic clay with 20% carbonate off Sabah and 40% off China. We calculated terrigenous and carbonate accumulation rates for up to 11 time-slices from the Holocene to oxygen-isotope stage 6. Terrigenous accumulation rates generally increase with water depth and reach a maximum at the middle slope off Sabah and at the lower continental slope off China. During glacial and interglacial times this distribution pattern did not markedly change, despite an increase of accumulation rates for glacial periods by a factor of 2 to 5 compared to interglacial periods. Rates are negatively correlated with positions of sea level, which controls the partition of fluviatile terrigenous material for deposition on shelf, slope, and abyssal plain. Carbonate accumulation rates are higher off China by a factor of 2 compared to Sabah, probably indicating higher calcareous plankton productivity.

Description: Salzreiches Wasser, das durch die Straße von Gibraltar aus dem Mittelmeer in den Atlantik strömt, wird dort verwirbelt und driftet teilweise als rotierende Salzlinse in etwa 1000 Meter Tiefe manchmal mehr als zwei Jahre lang bis zu 1000 Kilometer weit, ehe es sich endgültig mit dem Atlantikwasser vermischt.

Description: Die häufigsten vulkanischen Volatilen sind H2O, CO2, SO3 und Halogene. Zusammensetzung, Menge und Injektionsraten von vulkanischen Gasen und Partikeln in die Troposphäre und Stratosphäre hängen ab von der chemischen Zusammensetzung eines Magmas, dem plattentektonischen Milieu sowie Eruptionsmechanismen und Eruptionsraten. Über 90% der eruptierten Magmen sind basaltischer Zusammensetzung mit niedriger Viskosität, relativ geringen Volatilengehalten und meist niedrigen Eruptionsraten sowie wenig explosiven Eruptionen überwiegend entlang der mittelozeanischen Rücken in großen Wassertiefen. Magmen in Inselbögen und Subduktionszonen an Kontinenträndern sind H2O-reich, in anderen plattentektonischen Milieus überwiegt in basaltischen Magmen CO2. In mafischen Magmen ist CO2 schlecht löslich und kann daher schon mehrere Kilometer unter der Erdoberfläche als Gasphase aus einem Magma entweichen. Felsische (hochdifferenzierte) Magmen, H2O-reich und CO2-arm, eruptieren oft hochexplosiv, insbesondere an Subduktionszonen, und mit hohen Eruptionsraten, z.B. El Chichón (Mexiko, 1982) und Pinatubo (Philippinen, 1991). Ihre Eruptionssäulen (Gas-/Partikelgemische) können bis ca. 40 km Höhe erreichen und sind Hauptlieferant der in die Stratosphäre injizierten Gasmengen.

Description: Structural, physical property, and magnetic data from Ocean Drilling Program Site 808 in the Nankai Trough, Japan, indicate that both sediment loading and plate convergence have driven dewatering and consolidation in this region. Evidence for this interpretation is provided by a migrated seismic reflection profile, computed tomography of core-scale structures, magnetic susceptibility and P-wave velocity data, and experimental studies of Site 808 samples. These data also show that the strain (including volume change) resulting from plate convergence is partitioned into both penetrative deformation structures as well as more discrete, core-scale structures with finite displacements. These core-scale structures range from relatively subtle, kink-like deflections of the primary phyllosilicate fabric to sharp discontinuities with probable displacements much greater than the dimensions of the core barrel. Although all of the structures acted at least in part as dewatering conduits, evidence of concentrated fluid flow in this region of the prism is limited to a narrow interval almost 150 m above the décollement (located at between 946 and 965 mbsf). This interval correlates with the middle of a hemipelagic sequence above the décollement that appears to have thinned, apparently through dewatering, relative to a more seaward section. Thinning and dewatering appear to have been induced by deposition of a more clastic sedimentary sequence (the outer marginal trench-wedge sediments) that grades upward into a coarse-grained trench-fill sequence. Importantly, the hemipelagic sequence below the décollement appears to have thinned very little, suggesting that these sediments are underconsolidated and overpressured. This interpretation is consistent with porosity measurements from below the décollement. Microscopic and submicroscopic studies of sediments from within the décollement record a cyclic deformation sequence of displacement-brecciation-porosity collapse and compaction that may also reflect deformation of an overpressured sequence. Finally, the structural, physical property, and magnetic data also yield kinematic and geometric results consistent with the present convergent vector between the Philippine Sea Plate and Eurasia. These data indicate a shortening direction that trends between 308° and 315°, consistent with plate convergent vectors that trend between 310° and 314°.

Description: Shipboard laboratory index property data, shore-based consolidation tests, and in-situ stress and pore-pressure measurements are used in this study to constrain the stress conditions at ODP Site 808, Nankai Trough. Results of these tests are presented along with additional intepretations of porosity rebound and permeability. The sediment at Site 808 is highly affected by excess fluid pressures throughout the sediment column. Excess fluid pressure is severe below the major fault boundary, the decollement. The in-situ measurement of lateral stresses, which are shallow in the sediment section, confirms that the principal stress direction is rotated from a "normal" basin-type condition where the principal stress direction is vertical.

Description: The Vema Channel represents a prominent location for the nortward flow of bottom water in the subtropical western South Atlantic. A recent multibeam echo-sounding survey of the Vema Sill on board F.S. Meteor revealed a narrow and shallow portion of the Vema Channel at 31°12′S, 39°24′W, the Vema Sill. The survey also showed the remarkably asymmetric shape of the sill region, suggesting an interaction between the bottom flow and the shape of the channel.

Description: The total transport of Antarctic Bottom Water across the Rio Grande Rise, including the western boundary, the Vema Channel, and the Hunter Channel is estimated from hydrographic measurements across these pathways. The contribution of the Vema Channel is greatest at 3.9 × 106 m3 s−1, which is very close to earlier estimates. The western boundary current contribution is 2.0 × 106 m3 s−1 and that of the Hunter Channel 0.7 × 106 m3 s−1. The lower values outside the Vema Channel are offset by the important source of mass they form to the lower density classes of bottom water. About 40% of the flow is concentrated in the highest density class representing the source of Weddell Sea Deep Water to the Brazil Basin. The flow structure is characterized by horizontal and vertical recirculation.

Description: Hydrographic observations from the Iberian Basin demonstrate the variability of water masses in upper and intermediate layers. The surveyed area embraces the internal front between water masses from higher latitudes and the Mediterranean outflow, exhibits several isolated Mediterranean eddy (meddy) structures at middepth, and displays the virtual source region for the Mediterranean Water (MW) tongue off the Portuguese continental slope. The description is enhanced by additional chlorofluoromethane measurements, which show anomalously high concentrations at middepth, due to mixing of MW with the overlying Atlantic waters in the Gulf of Cadiz. The geostrophic stream function shows several meddylike features that not only are remarkably extended in the depth range of the MW, but are also correlated with surface height anomalies.

Description: In the subtropical belt highly productive ecosystems are formed by coral reefs in oligotrophic seas. Towards more eutrophic conditions, coral reefs diminish and are subsequently replaced by highly productive kelp forests. In high latitudes framework constructing carbonate production is enhanced by the growth of branching coralline algae which predominantly generate maerl-type deposits. On a global view, these coralline algal ecosystems show an island-like distribution pattern within the phaeophytic kelp belt. Compared to kelp ecosystems, coralline-algaldominated ecosystems have low rates of productivity. Therefore, it is reasonable to seek the pronounced competitive value of the extremely slow-growing corallines. Due to their low annual growth increment, the coralline algae studied are very endangered by abiotic physical disturbances and by overgrowth of rapidly growing filamentous algae or sessile invertebrates. To overcome fouling pressure and storm-triggered physical disturbances, coralline algae thrive well in wave-sheltered headlands or skerry areas and generate characteristic ‘denuded areas’ by intense herbivory. This general distributional pattern is also true for high-boreal to subarctic coralline algal bioherms in northern Norway. Such a complex biological feedback maintains a high potential of self-regulation or self-organization in the algal reef bioherms. The different proponents involved in feedback processes include bacterial colonization, diatom microfouling and selective induction of larval metamorphosis. The negative impact of diatom microfouling and the important role of herbivores are relevant activities in the feedback system on a microscopic scale. Macroscopically, intense herbivory on coralline algae create denuded conditions, which are a widespread phenomenon in coralline algal ecosystems.

Description: Sediments undergoing accretion in trench-forearc systems are subjected to conditions of large lateral thrusting. This stress regime controls the mechanism of faulting as well as the yield and strength properties of the sediment. Understanding them is therefore crucial for the construction of quantitative models of sediment dynamics in convergent margin settings. For this purpose triaxial and oedometer tests were performed on six whole-round core samples recovered from Site 808 from depths between 173 and 705 mbsf. Samples from five depth intervals were subjected to a triaxial test program that was primarily designed to define yield and strength behavior. Test specimens were cut parallel and normal to the core axis. Additional five oedometer tests with similarly prepared specimens were performed on samples from four depth intervals to evaluate the directional state and degree of sediment compaction. Test results show that the degree of sediment compaction is higher than expected from overburden. This overcompaction increases with depth. A well-developed mechanical anisotropy is evident in all samples tested, regardless of their depth and lithology. Values of yield limit, stiffness, and shear strength are up to 40% higher in the horizontal direction compared to the vertical direction. In addition the test data demonstrate that the axis of the volumetric yield loci have rotated into extensional stress field. This verifies that the mechanical state of sediment in the accretionary wedge is controlled by in-situ stress conditions of extensional nature. The coefficients of lateral stress inferred suggest that the extensional stress regime becomes increasingly effective with depth.

Description: Complete penetration of frontal thrust and décollement of the Nankai Trough accretionary complex in Site 808 during ODP Leg 131 provided a wealth of structural observations and physical property data. In this paper possible mechanisms are discussed that could be responsible for the development of irregular downhole trends in acoustic anisotropy observed in Site 808. After various steps of data reduction and screening, a paleomagnetic reorientation procedure is applied to a selected group of physical property data sets. This facilitates the integration of the observed changes in physical properties with the geotectonic framework at the deformation front of the Nankai Trough accretionary complex. The paleomagnetic database was employed in the reconstruction of directional properties of acoustic velocities of the Lower Shikoku Basin sedimentary sequence, which is divided by a sharply defined décollement into an accreting and a subducting portion. P-wave velocity anisotropies derived from paleomagnetically oriented samples in the upper part of this 420-m-thick hemipelagic sequence show maximum values in the direction parallel and normal to the inferred vector of plate convergence (31O°-315°). No preferred orientation of P-wave velocity anisotropy is found in the subducting part of the sequence. The preferred direction of maximum anisotropy parallel to the convergence vector is also in accordance with the true direction of the observed macro- to mesoscale structural features in Site 808. Microfractures and microcracks forming as stress relief and tensile fractures in cores of semilithified sediment normal and perpendicular to the maximum horizontal stress are discussed as control mechanisms for the development of the observed anisotropy pattern.

Description: While marine snow aggregates were devoid of Phaeocystis in 1989, a large fraction of the Phaeocystis biomass was associated with aggregates two years later. This discrepancy corresponds to a significant difference in aggregate size between the two years studied, interpreted to be a consequence of different levels of turbulent mixing. Phaeocystis colonies remained freely suspended during 1989 when aggregates were small, and adhered loosely to the large aggregates observed forming during 1991. Overall, the aggregation potential of Phaeocystis was low in comparison to diatoms. Independent of the degree of aggregation, sedimentation was the dominant loss factor of Phaeocystis biomass from the upper layer

Description: Live observations, cytological characteristics and biometrical measurements on Miliolinella subrotunda (Montagu, 1803) sampled from the northern and southern Atlantic Ocean are presented.M. subrotunda facultatively constructs a long, detritic tube lifting the test several millimeters above the sediment surface. A thickened conical base anchors the construction on the sediment surface and a long, flexible tube protrudes into the velocity profile of the bottom currents. The miliolid test is placed on top, surrounded by the uppermost part of the tube. This construction allows the organisms to feed in the particle stream above the sediment surface. In comparison to species living in and on the surface sediments,M. subrotunda apparently shows higher nutritional values in food ingested and larger amounts of reserve substances. Characteristics of the shape and structure that reduce drag on the tubes include a broadened conical base, a flexible tube, and a rounded top. From biometrical measurements it is concluded, that the tubes are constructed over a short period of their ontogeny.

Description: The Houtman Abrolhos Islands, situated at the western passive margin of the Australian continent, consist of a series of shelf-edge coral reefs. The central platforms of the reefs are Late Pleistocene in age and are generally some 3–5 m above present sea level. The uppermost part of the Last Interglacial reefs normally has an upward-shallowing sequence, consisting of coral framestone, coralline algal bindstone and skeletal grainstone to rudstone. This sequence represents deposition in water depths of less than 2 m, and provides a good indicator of sea level. High-precision mass-spectrometric dates of corals from the Abrolhos reefs, including dates obtained from drill cores, arological, isotopic and stratigraphic criteria are established for the selection of suitable samples for dating and for assessing the reliability of dates. Using the screened dates and the stratigraphic evidence, the timing and character of the sea level variations of the Last Interglacial in the Abrolhos region are examined. The data show that sea level of the Last Interglacial in the Abrolhos was 4 m below its present height by ca. 134 ka BP and probably reached about 2 m above present height at ca. 133 ka BP. The exact time at which sea level reached its peak (6 m above present sea level) cannot be determined from our data. But it is clear that the sea level high stand of the Last Interglacial lasted until ca. 116 ka BP and that for much of the Last Interglacial sea level at the Abrolhos was at a height of about 4 m above its present level

Description: Cruise POS-199 was a first expedition under Project ODER to investigate the geological and sedimentological situation in an area east of the island of Riigen, where the submarine valley of the river Oder discharges into the southern Arkona-Basin. Using acoustic methods (3.5 kHz, Boomer, and Sidescan Sonar) in a closely-spaced grid of survey lines (2 sm apart in E-W trending profiles), we located accumulations of mud (Schlick) in an area characterized generally by sand deposition and -redeposition. Mud deposition is restricted to the deepest parts of the pre-transgressional river valley and to water depths below 20 mbsl. These accumulations of mud were sampled by box coring and gravity coring (where successful) and subsampled onboard ship for investigation of physical properties and subsequent analyses in shorebased laboratories. Future analyses will include sedimentological, radiochemical, micropaleontological and geochemical analyses to establish the dispersal, sedimentation and transformation of natural and manmade substances in the Oder depositional system.

Description: In den letzten Jahrzehnten sind aus Untersuchungen im Meer umwälzende Vorstellungen zur erdgeschichtlichen Entwicklung von Ozeanen und Kontinenten erwachsen. Marine Sedimente und ozeanische Kruste werden mitsamt ihren Porenwässern laufend den Kontinenten angegliedert. Marine Sedimentgesteine und ihre frühere Umwelt können besser gedeutet werden, wenn man heutige Vorgänge im Meer dazu heranzieht. Ozeanische Sedimente sind in ihrer detaillierten zeitlichen Abfolge zu hervorragenden Archiven für die Erdgeschichte geworden. Einige neuer Beispiele sollen dies verdeutlichen.

Description: Surface sediments from a transect across the mid-ocean ridge north of Iceland (Kolbeinsey Ridge) have been analyzed according to their compositional, textural and hydromechanical characteristics. The results were used to reconstruct sediment formation and depositional processes. The ridge sediments are dominated by volcaniclastic particles of hyaloclastic and pyroclastic origin. These particles show a wide variety in size, shape and density. Single-grain settling velocities of the different glass types reveal the suitability of this parameter as a reflector of the particle properties of size, shape and density, which are also known to be relevant to grain transport. Observations concerning different current expositions of central ridge sediments, combined with the parameters of settling velocity distribution, grain-size distribution and sediment particle composition, were applied to distinguish between transport association with rare, easily movable glass shards and poorly sorted sediments in sheltered ponds. A bimodal settling velocity distribution of steep ridge-flank sediments probably indicates the effect of sediment admixture from poorly sorted mass flows. Alternating coarse- and fine-grained layers characterize the transition between ridge-glass sands and the ridge-adjacent plain, which is dominated by slow-settling pelagic material.

Description: Based on the vector character the treatment of the three-dimensional seismic wavefield becomes complex. With the exploitation of converted wave-modes the acquisition of vectorwavefield data is effective, especially in the wide-angle range. Consequently shear waveacquisition with conventional sources, including marine sources, is possible and only multicomponent seismometers are required. Using this method wide-angle recordings of high quality were obtained within the BABEL-project (Baltic and Bothnian Echoes from the Lithosphere). However the processing of such vector-wavefield data raises the question of how to decompose the wavefield in its single modes. This thesis classifies the separation techniques, which have been presented in the literature, and shows a strong connection between polarization and separation of the seismic wavefield. Taking wide-angle data into particular consideration a discussion of these methods demonstrates the general applicability provided that equidistant traces are available. It is found out with the Controlled Orientation - a further developed method for the automatic reorientation of three-component recordings - that the alignment of refraction seismic data to the direction of the P-wave first arrival is not reliable because of the nearly vertical incidence. However it turns out, that the correction of the apparent angle of incidence need not be considered. With the processive realization of equidistant traces it is demonstrated that the amplitude character for the analysis of polarization is preserved. Therefore a multi-trace procedure can be implemented, which is in a position to process effectively long offset three-component data based on a two-dimensional operator window. This two-dimensional polarization-filter works data-adaptively for the determination of polarization parameters and is superior to the conventional method of Montalbetti and Kanasewich (1970). Three-component wide-angle data are used to illustrate the improvements obtained in noise reduction and in wave-mode separation using this technique .

Description: THE vestimentiferan tubeworm Riftia pachyptila is found around hydrothermal vent areas in the deep sea. Intracellular bacterial chemoautotrophic symbionts use the oxidation of sulphide from the effluent of the vents as an energy source for CO2 fixation. They apparently provide most or all of the nutritional requirements for their gutless hosts1–5. This kind of symbiosis has since been found in many other species from various other phyla from other habitats6–9. Here we present results that the bacteria of R. pachyptila may cover a significant fraction of their respiratory needs by the use of nitrate in addition to oxygen. Nitrate is reduced to nitrite, which may be the end product (nitrate respiration)10 or it may be further reduced to nitrogen gas (denitrification)11. This metabolic trait may have an important role in the colonization of hypoxic habitats in general by animals with this kind of symbiosis.

Description: Nontransform offsets are a fundamental aspect of the offset geometry exhibited along the mid-oceanic ridge system, independent of spreading rate. Along the slow/intermediate opening (〈40 mm/y full rate) Mid-Atlantic Ridge these offsets of the ridge axis range in length from less than 10 km to approximately 30 km and vary in age offset from 0.5 to 2.0 m.y. The variable morphotectonic geometries associated with these discontinuities indicate that horizontal shear strains are accommodated by both extensional and strike-slip tectonism and that the geometries are unstable in time. In many cases, there appears to be an evolutionary relationship between transform fault boundaries and nontransform offsets as the result of prolonged differential asymmetric spreading between adjoining ridge segments. The finite element method is used to study the complex stress field associated with these small-offset discontinuities of ridges with slow (30 mm/y) and fast (100 mm/y) total opening rates. A plane stress plate model examines the variation in the horizontal tectonic stress field produced by offsets with different lengths and changes in the ratio of a ridge-normal tensile stress resisting plate separation to a shear stress resisting relative plate motion along the discontinuity. The predicted fault patterns based on the calculated stress field are compared with seafloor observations in terms of the morphotectonic patterns and evolution of nontransform offsets. For a slow spreading rate, the analysis shows that all structural geometries observed can be modeled by a range of offset lengths (5, 10, 20, 30, and 40 km) and by a ridge-normal stress 3 to 5 times greater than the discontinuity shear stress. These findings suggest that nontransform offsets are zones of mechanical weakness relative to the surrounding lithosphere. An offset length between 10 and 20 km is predicted to be the threshold length for maintaining a transform fault geometry. As inferred from ridge axis morphology, there seems to be a strong link between the magnitude of the stress ratio and the time varying magmatic activity along and between ridge segments. While our models are consistent with a weak discontinuity shear stress relative to the ridge-normal stress to explain the geometries of nontransform offsets of slow-spreading centers, a weaker ridge-normal stress to discontinuity shear stress most closely models the development of an overlapping spreading center geometry, the distinctive geometry of nontransform offsets of spreading centers opening at fast rates. This difference is attributed to magma supply along-axis, relatively continuous for fast-spreading centers and intermittent for slow-spreading centers, and a preexisting zone of mechanical weakness linked to the evolution of nontransform offsets from transform faults on slow-spreading centers.

Description: Accurately weighed aliquots of the ∼ 500-Ma-old interlaboratory standard hornblende MMHb-1 were mixed with known quantities of a ∼ 100 Ma-old Himalayan biotite and subjected to normal Full-size image (〈1 K) incremental heating analysis. The addition of the biotite created monotonically increasing apparent ages, similar to profiles interpreted as showing Ar diffusive loss in the literature. The release of Ar from biotite dominates the low-temperature portion of the spectra and lowers the observed age. Lower Ca/K ratios in the first increments are consistent with contamination, but do not distinguish the composition of the contaminant phase. A large number of published amphibole “diffusive loss” profiles may, in fact, be due to contamination by biotite or other phases which release Ar at low extraction temperatures.

Description: On a transect between 20° and 70°S in the eastern Atlantic Ocean and Weddell Sea, water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon (δ13CΣCO2). These measurements were compared to δ13C values determined on live specimens of the benthic foraminifer Fontbotia wuellerstorfi and closely related genera from the same stations. In addition, at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured. General deepwater and bottom-water mass circulation patterns as inferred from the δ13CΣCO2 are in close agreement with those known from other nonconservative tracers. Very low δ13C values of upper Circumpolar Deep Water (〈0.3‰ Pee Dee belemnite (PDB)) in the Polar Front region and the eastern limb of the Weddell gyre coincide with nutrient maxima. However, a significant decoupling of the dissolved phosphate signal from the δ13CΣCO2 signal is indicated in the abyssal Weddell Sea. We attribute this to temperature-dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom-water formation. Multiple corer water from the sediment/water interface is slightly δ13C depleted relative to deepwater and bottom-water δ13ΣCO2. The surface sediment organic carbon δ13C is 3 to 4‰ lower south of the Polar Front than north of it, and the δ13Corg in freshly accumulated phytodetritus is 3 to 4‰ lower than surface sediment organic carbon δ13C. Comparison of live F. wuellerstorfi δ13C and related genera with bottom-water δ13CΣCO2 exhibits at most stations between the Subtropical Front (≈41°S) and the southern boundary of the Antarctic Circumpolar Current (≈55°S) a significant lowering of foraminiferal δ13C values. Compilation of a mean last glacial/interglacial δ13C amplitude (Δδ13C) from six published southern ocean cores results in a shift of −0.99± 0.13‰ PDB; this shift is greater than that in all other regions. However, all of these cores are from positions close to Recent oceanic fronts. Thus, for these peripheral areas of the southern ocean, we suggest about half of the glacial/interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production.

Description: Paragenetic mineral assemblages have been established based on mineralogical, chemical, and isotope (S, Pb) studies, and the sequence of deposition has been defined in hydrothennal sulfide structures in a typical back-arc basin. The ores in the Manus basin have a prominent Zn specialization (sphalerite, würtzite, and fe-sphalerite). An association of Fe-spbalerite and galena with Ag sulfosalts is noted that is not characteristic of typical midocean ridge hydrothennal systems. The average 34S in the sulfide minerals is 3.5%o, which corresponds to the medium-temperature sphalerite stage in hydrothermal mineral fonnation. It is suggested that the metal source is located in the relatively acid rocks of the island-arc tholeiitic series and possibly in sediments.

Description: Einleitung Vor drei Jahrzehnten bahnte sich in den Erdwissenschaften ein Umschwung an, der nur mit der wissenschaftlichen Revolution verglichen werden kann, die Charles Darwin mit seinen Ideen zur Evolution der Biosphäre auslöste. Mit den Theorien der Spreizung der Ozeanböden und der Plattentektonik wurde die Evolution der Lithospähre völlig neu durchdacht.

Description: Chemoautotrophic bacteria live symbiotically in gills of Lucinoma aequizonata, an infaunal clam inhabiting an oxygen-poor environment. These intracellular symbionts respire nitrate, i.e. they use nitrate instead of oxygen as a terminal electron acceptor in the respiratory chain. Nitrate is only reduced to nitrite and not further to nitrogen gas. Nitrate is respired by the symbionts under fully aerobic conditions at the same rate as under anaerobic conditions. The bacterial symbionts contain a nitrate reductase that is associated with the membrane-containing fraction of the symbiont cell and that is sensitive to respiratory inhibitors; both features are consistent with the respiratory role of this enzyme. A review of nitrate reductase in chemoautotrophic syrnbionts suggests that nitrate respiration may be common among these symbioses. Symbiont nitrate reductase may be an ecologically important factor permitting the survival of animal hosts in oxygen-poor environments.

Description: Growth of the shallow-water gorgonian Lophogorgia ceratophyta was investigated in an infralittoral station located in La Spezia Gulf, Ligurian Sea. Mean annual height growth rate was estimated to be 2.57 cm · a-1. The fractal dimension of the colonies was found to gradually evolve in complexity, exhibiting a simpler branching pattern in younger specimens. The maintenance of a low, invariable ramification complexity as an optimal choice in managing relationships between water and the colony's living tissues is also discussed.

Description: Five Barrow Group (Berriasian to Valanginian) siliciclastic sequences are described from the North-West Shelf, Australia, and calibrated against global third-order (?eustatically-mediated) cycles. Particular emphasis is placed on the sedimentological (core, wireline log) and palaeontological (micropalaeontological, palynological) characterization of constituent systems tracts.

Description: Outer membrane (OM), cytoplasmic membrane (CM) and intracytoplasmic membranes (ICM) from the halophilic phototrophic purple sulphur bacterium Ectothiorhodospira mobilis 9903 were purified and characterized. The three membrane fractions were significantly different in regard to protein profiles on SDS-PAGE, and to the composition of amino acids, fatty acids and lipids. The presence of lipoproteins, the occurrence of lyso-phosphatidyl-ethanolamine and an increased content of saturated and short-chain fatty acids are characteristic properties of the OM. CM and ICM fractions are different on the basis of buoyant density, of protein profiles and amino acid composition, and due to the presence of succinate dehydrogenase activity in CM. In addition, CM and ICM showed significant differences in pigment content and absorption spectra.

Description: The Platanar volcanic center is dominated by a calc-alkaline, basalt-andesite-dacite-rhyolite magma series with unusual LREE enrichment. Adjacent and overlapping the calc-alkaline rocks are the most alkaline basalts found along the volcanic front of Central America. These basalts are mafic, LIL- and LREE-enriched transitional to alkaline basalts. Several are found on the north flank of Platanar in the Aguas Zarcas region, where there are nine cinder cones and a few isolated flows. However, they are also found in isolated lava outcrops at least as far south as Porvenir volcano along the volcanic front. The addition of mafic alkaline magmas with high La/Yb and low Ba/La into the Platanar magma chamber or chambers may contribute to the LREE-enriched character of the Platanar basaltic andesites and andesites. At Platanar the field and geochemical evidence suggest mixing between calc-alkaline and alkaline magmas, a process that has probably occurred throughout the development of the Cordillera Central of Costa Rica. The presence of negative Ce anomalies in several of the calc-alkaline lavas also make the Platanar complex very unusual compared to the rest of the Central American volcanic front. In the center of the Platanar complex is the Chocosuela caldera, an apparent remnant of an avalanche caldera created by the collapse in the Middle Pleistocene of an ancestral stratovolcano toward the NNW in a directed blast-type eruption. Rhyolite is present as pumice lapilli in pyroclastic flow deposits outside the caldera rim. Whole lapilli analyses span the daciterhyolite range. The previous eruption of high silica tephra as pyroclastic flows, the current long dormant period and the repeated occurrence of earthquake swarms on the flanks of the Platanar complex make it a candidate for volcanic hazard mapping, detailed geological mapping and emergency planning.

Description: The abundance and sedimentation of acantharia and their cysts was recorded in the water column and sediment traps in the East Greenland Sea in August-September 1990. Although acantharia constituted 〈1% of total suspended particulate organic carbon (POC) in the water column, up to 90% (average 55%) of the POC sedimenting in 100 m was present in the form of acantharian cysts during a 9 day drift experiment. Rapid dissolution of strontium sulphate, of which their shells and spines are constructed, was evidenced by their disappearance with depth in the water column, maximum dissolution occurring between 500 and 1000 m water depth. Mass encystment and sedimentation of this single group of sarcodine protozoa can have dramatic effects on, the measurement of particulate fluxes in the open ocean, and may be a recurrent phenomenon in the eastern North Atlantic.

Description: What limits phytoplankton growth in nature? The answer is elusive because of methodological problems associated with bottle incubations and nutrient addition experiments. We are investigating the possibility that antibodies to proteins repressed by a specific nutrient can be used as probes to indicate which nutrient limits photosynthetic carbon fixation in the ocean. The diatom Phaeodactylum tricornutum Bohlin and the chlorophyte Dunaliella tertiolecta Butcher were grown in batch cultures in artificial seawater and f/2 nutrient lacking either phosphorus, iron, or nitrogen. Chlorosis was induced by nutrient limitation in both species with the exception of phosphorus‐limited D. tertiolecta. The synthesis and appearance of specific proteins were followed by labeling with 14C‐bicarbonate. Nutrient limitation in general leads to a decrease in the quantum efficiency of photosystem II, suggesting that deficiency of any nutrient affects the photosynthetic apparatus to some degree: however, the effect of nitrogen and iron limitation on quantum efficiency is more severe than that of phosphorus. A crude fractionation of the soluble and membrane proteins demonstrated that the large proteins induced under limitation by phosphorus and iron were associated with the membranes. However, small iron‐repressible proteins were located in the soluble fraction. Isolation with anion‐exchange chromatography and N‐terminal sequencing of iron‐repressible, 23‐kDa Proteins from D. tertiolecta, P. tricornutum, and Chaetoceros gracilis revealed that these small soluble proteins have strong homology with the N‐terminal sequence of flavodoxins from Azotobacter and Clostridium. The identity of the flavodoxin from D. tertiolecta was confirmed by immunodetection using antiflavodoxin raised against Chlorella. Flavodoxin was detected only under iron deprivation and was absent from nitrogen‐and phosphorus‐limited algae. Flavodoxin is a prime candidate for a molecular probe of iron limitation in the ocean. The requirements to confirm its utility in nature are discussed.

Description: Etwa ein Drittel des von Menschen freigesetzten Treibhausgases Kohlendioxid (CO2) reichert sich in der Atmosphäre an und verstärkt dort den Treibhauseffekt. Zwei Drittel dieses Eintrags werden der Atmosphäre wieder entzogen und an anderer Stelle deponiert. Doch nur für etwa die Hälfte des wieder gebundenen Kohlendioxids kennen wir bisher die Senken. Wo bleibt der Rest? Um Aussagen über den Verbleib weiterer CO2-Emissionen und damit über die zukünftige Entwicklung des Treibhauseffektes machen zu können, bedarf es der Lösung des Kohlenstoffrätsels.

Description: Moored Acoustic Doppler Current Profilers (ADCPs) were used to analyse the daily vertical zooplankton migration and its seasonality. One-year records of vertical velocity and acoustic backscatter were obtained at four stations in the Greenland Sea. Both parameters exhibited a diurnal cycle typical for vertically migrating zooplankton. Upward and downward migration occured in short periods approximately 5 h long, and peak migration velocities were around 1.5 cm s−1. Similar structures were observed at all four mooring sites in the 200–300 m depth range. Farther down, between 1000 and 1400 m, no daily migration was observed. Strong seasonal variations are evident, and both the phase and intensity of the migration pattern change with daylight as the season progresses. In summer and during the polar night the migration became very weak and was only detectable in the displacement of scattering layers. When the day/ night contrast was large, intense upward or downward motion was accompanied by sloping backscatter isopleths. We observed two main scattering layers, a deep layer that varies in depth with season and an almost invariable shallow scattering layer at about 150 m depth. The deep layer was interpreted as the “resting depth” of the migrating plankter, and the latter as their “feeding horizon”. Changes in the “resting depth” from about 400 m in autumn and spring to about 200 m in winter lead to seasonal variations in the migration distance. This behaviour is discussed with respect to environmental conditions.

Description: Three data types are compared in the low-current-velocity regime in the southeastern North Atlantic, between 12-degrees-N and 30-degrees-N, 29-degrees-W and 18-degrees-W: Geosat altimetric sea level and derived surface geostrophic velocities, shallow current meter velocities, and dynamic heights derived from hydrographic data from cruises 4, 6, and 9 of the research vessel Meteor. The four current meter daily time series, at depths around 200 m, were smoothed over 1 month; the altimetric geostrophic velocities were computed from sea surface slopes over 142 km every 17 days. The correlation coefficients between the current meter and altimetric geostrophic velocities range between 0.64 and 0.90 for the moorings near 29-degrees-N but between 0.32 and 0.71 for the two around 21-degrees-N; the associated rms discrepancies between the two measurement types range between 1.5 and 4.4 cm/s, which is 49% to 127% of the rms of the respective current meter time series. Dynamic heights relative to 1950 dbar for the months of November 1986 (d(M4)), November 1987 (d(M6)), and February 1989 (d(M9)) were computed from Meteor cruises 4, 6, and 9. Both dynamic heights and altimetric heights (h(M4), h(M6), h(M9)) were averaged over 1-degrees boxes for the duration of each cruise. Differences d(M4) - d(M6) and d(M9) - d(M6) were computed only at bins where at least one station from both cruises existed, Assuming that dynamic heights d in dynamic centimeters are equivalent to sea level h in centimeters, the standard deviation sigma of the differences ((h(M4) - h(M6)) - (d(M4) - d(M6))) and corresponding M9 - M6 values was 2.1 cm. This value (squared) is only 13% of the (5.8 cm)2 variance of the dynamic height differences and is indistinguishable from the 2.7- to 5.6-cm natural variability of sea level in the area expected between the times when the ship and the satellite sampled the ocean. The areally averaged discrepancy for M9 - M6 was only 0.7 cm, but the corresponding value for M4 - M6 was 5.2 cm. A systematic difference between the water vapor corrections used before and after July 1987 is responsible for the M4 - M6 difference. The average M4 - M6 discrepancy is only 0.1 cm using the Fleet Numerical Oceanography Center correction, with a standard deviation of 3.1 cm. In spite of the underlying differences in sampling and physics, including unknown barotropic components not included in our hydrographic dynamic heights, and in data errors, including water vapor, ionospheric, and orbital effects on the altimetry, consistent interannual changes of the mean sea level from the independently obtained altimetric and hydrographic data sets are obtained, and correlated seasonal changes in surface currents are observed with both altimetry and current meters.