ALBERT

Description: Fluids entering the subduction zone play a key role in the subduction process. They cause changes in the dynamics and thermal structure of the subduction zone1, and trigger earthquakes when released from the subducting plate during metamorphism. Fluids are delivered to the subduction zone by the oceanic crust and also enter as the oceanic plate bends downwards at the plate boundary. However, the amount of fluids entering subduction zones is not matched by that leaving through volcanic emissions4 or transfer to the deep mantle, implying possible storage of fluids in the crust. Here we use magnetotelluric data to map the entire hydration and dehydration cycle of the Costa Rican subduction zone to 120 km depth. Along the incoming plate bend, we detect a conductivity anomaly that we interpret as sea water penetrating down extensional faults and cracks into the upper mantle. Along the subducting plate interface we document the dehydration of sediments, the crust and mantle. We identify an accumulation of fluids at ~20–30 km depth at a distance of 30 km seaward from the volcanic arc. Comparison with other subduction zones5–14 indicates that such fluid accumulation is a global phenomenon. Although we are unable to test whether these fluid reservoirs grow with time, we suggest that they can account for some of the missing outflow of fluid at subduction zones.

Description: Lavas erupted within plate interiors above upwelling mantle plumes have chemical signatures that are distinct from midocean ridge lavas. When a plume interacts with a mid-ocean ridge, the compositions of both their lavas changes, but there is no consensus as to how this interaction occurs1–3. For the past 15 Myr, the Pacific–Antarctic mid-ocean ridge has been approaching the Foundation hotspot4 and erupted lavas have formed seamounts. Here we analyse the noble gas isotope and trace element signature of lava samples collected from the seamounts. We find that both intraplate and on-axis lavas have noble gas isotope signatures consistent with the contribution from a primitive plume source. In contrast, nearaxis lavas show no primitive noble gas isotope signatures, but are enriched in strontium and lead, indicative of subducted former oceanic lower crust melting within the plume source5–7. We propose that, in a near-ridge setting, primitive, plumesourced magmas formed deep in the plume are preferentially channelled to and erupted at the ridge-axis. The remaining residue continues to rise and melt, forming the near-axis seamounts. With the deep melts removed, the geochemical signature of subduction contained within the residue becomes apparent. Lavas with strontium and lead enrichments are found worldwide where plumes meet mid-ocean ridges6–8, suggesting that subducted lower crust is an important but previously unrecognised plume component.

Description: Experiments have shown that ocean acidification due to rising atmospheric carbon dioxide concentrations has deleterious effects on the performance of many marine organisms(1-4). However, few empirical or modelling studies have addressed the long-term consequences of ocean acidification for marine ecosystems(5-7). Here we show that as pH declines from 8.1 to 7.8 (the change expected if atmospheric carbon dioxide concentrations increase from 390 to 750 ppm, consistent with some scenarios for the end of this century) some organisms benefit, but many more lose out. We investigated coral reefs, seagrasses and sediments that are acclimatized to low pH at three cool and shallow volcanic carbon dioxide seeps in Papua New Guinea. At reduced pH, we observed reductions in coral diversity, recruitment and abundances of structurally complex framework builders, and shifts in competitive interactions between taxa. However, coral cover remained constant between pH 8.1 and similar to 7.8, because massive Porites corals established dominance over structural corals, despite low rates of calcification. Reef development ceased below pH 7.7. Our empirical data from this unique field setting confirm model predictions that ocean acidification, together with temperature stress, will probably lead to severely reduced diversity, structural complexity and resilience Of Indo-Pacific coral reefs within this century

Description: The impact of solar activity on climate has been debated heatedly. Simulations with a climate model using new observations of solar variability suggest a substantial influence of the Sun on the winter climate in the Northern Hemisphere.

Description: The Southern Ocean is thought to be one of the most energetic regions in the world’s oceans. As a result, it is a location of vigorous diapycnal mixing of heat, salt and biogeochemical properties1, 2, 3. At the same time, the Southern Ocean is poorly sampled, not least because of its harsh climate and remote location. Yet the spatial and temporal variation of diapycnal diffusivity in this region plays an important part in the large-scale ocean circulation and climate4, 5, 6. Here we use high-resolution hydrographic profiles from Argo floats in combination with the Iridium communications system to investigate diapycnal mixing in the Southern Ocean. We find that the spatial distribution of turbulent diapycnal mixing in the Southern Ocean at depths between 300 and 1,800 m is controlled by the topography, by means of its interaction with the Antarctic Circumpolar Current. The seasonal variation of this mixing can largely be attributed to the seasonal cycle of surface wind stress and is more pronounced in the upper ocean over flat topography. We suggest that additional high-resolution profiles from Argo floats will serve to advance our understanding of mixing processes in the global ocean interior.

Description: The origin of the Christmas Island Seamount Province in the northeast Indian Ocean is enigmatic. The seamounts do not form the narrow, linear and continuous trail of volcanoes that would be expected if they had formed above a mantle plume1, 2. Volcanism above a fracture in the lithosphere3 is also unlikely, because the fractures trend orthogonally with respect to the east–west trend of the Christmas Island chain. Here we combine 40Ar/39Ar age, Sr, Nd, Hf and high-precision Pb isotope analyses of volcanic rocks from the province with plate tectonic reconstructions. We find that the seamounts are 47–136 million years old, decrease in age from east to west and are consistently 0–25 million years younger than the underlying oceanic crust, consistent with formation near a mid-ocean ridge. The seamounts also exhibit an enriched geochemical signal, indicating that recycled continental lithosphere was present in their source. Plate tectonic reconstructions show that the seamount province formed at the position where West Burma began separating from Australia and India, forming a new mid-ocean ridge. We propose that the seamounts formed through shallow recycling of delaminated continental lithosphere entrained in mantle that was passively upwelling beneath the mid-ocean ridge. We conclude that shallow recycling of continental lithosphere at mid-ocean ridges could be an important mechanism for the formation of seamount provinces in young ocean basins.

Description: Three new 22-membered macrolactone antibiotics, atacamycins A-C, were produced by Streptomyces sp. C38, a strain isolated from a hyper-arid soil collected from the Atacama Desert in the north of Chile. The metabolites were discovered in our HPLC-diode array screening and isolated from the mycelium by extraction and chromatographic purification steps. The structures were determined by mass spectrometry and NMR experiments. Atacamycins A, B and C exhibited moderate inhibitory activities against the enzyme phosphodiesterase (PDE-4B2), whereas atacamycin A showed a moderate antiproliferative activity against adeno carcinoma and breast carcinoma cells

Description: Ostreococcus is a marine picophytoeukaryote for which culture studies indicate there are 'high-light' and 'low-light' adapted ecotypes. Representatives of these ecotypes fall within two to three 18S ribosomal DNA (rDNA) clades for the former and one for the latter. However, clade distributions and relationships to this form of niche partitioning are unknown in nature. We developed two quantitative PCR primer-probe sets and enumerated the proposed ecotypes in the Pacific Ocean as well as the subtropical and tropical North Atlantic. Statistical differences in factors such as salinity, temperature and NO 3 indicated the ecophysiological parameters behind clade distributions are more complex than irradiance alone. Clade OII, containing the putatively low-light adapted strains, was detected at warm oligotrophic sites. In contrast, Clade OI, containing high-light adapted strains, was present in cooler mesotrophic and coastal waters. Maximal OI abundance (19 555±37 18S rDNA copies per ml) was detected in mesotrophic waters at 40 m depth, approaching the nutricline. OII was often more abundant at the deep chlorophyll maximum, when nutrient concentrations were significantly higher than at the surface (stratified euphotic zone waters). However, in mixed euphotic-zone water columns, relatively high numbers (for example, 891±107 18S rDNA copies per ml, Sargasso Sea, springtime) were detected at the surface. Both Clades OI and OII were found at multiple euphotic zone depths, but co-occurrence at the same geographical location appeared rare and was detected only in continental slope waters. In situ growth rate estimates using these primer-probes and better comprehension of physiology will enhance ecological understanding of Ostreococcus Clades OII and OI which appear to be oceanic and coastal clades, respectively. © 2011 International Society for Microbial Ecology. All rights reserved.

Description: Reluctance to deposit data is rife among researchers, despite broad agreement on the principle of data sharing. More and better information will reach hitherto empty archives, if professional support is given during data creation, not in a project's final phase.

Description: How the chemical composition of sea water changes on its journey through the world’s oceans is poorly understood. Systematic measurements of dissolved trace metals across the Pacific Ocean suggest that these metals may help track sources and mixing of water masses.

Description: The Atlantic Ocean receives warm, saline water from the Indo-Pacific Ocean through Agulhas leakage around the southern tip of Africa. Recent findings suggest that Agulhas leakage is a crucial component of the climate system and that ongoing increases in leakage under anthropogenic warming could strengthen the Atlantic overturning circulation at a time when warming and accelerated meltwater input in the North Atlantic is predicted to weaken it. Yet in comparison with processes in the North Atlantic, the overall Agulhas system is largely overlooked as a potential climate trigger or feedback mechanism. Detailed modelling experiments—backed by palaeoceanographic and sustained modern observations—are required to establish firmly the role of the Agulhas system in a warming climate.

Description: Climate variability in the tropical Atlantic Ocean is determined by large-scale ocean–atmosphere interactions, which particularly affect deep atmospheric convection over the ocean and surrounding continents1. Apart from influences from the Pacific El Niño/Southern Oscillation2 and the North Atlantic Oscillation3, the tropical Atlantic variability is thought to be dominated by two distinct ocean–atmosphere coupled modes of variability that are characterized by meridional4, 5 and zonal6, 7 sea-surface-temperature gradients and are mainly active on decadal and interannual timescales, respectively8, 9. Here we report evidence that the intrinsic ocean dynamics of the deep equatorial Atlantic can also affect sea surface temperature, wind and rainfall in the tropical Atlantic region and constitutes a 4.5-yr climate cycle. Specifically, vertically alternating deep zonal jets of short vertical wavelength with a period of about 4.5 yr and amplitudes of more than 10 cm s−1 are observed, in the deep Atlantic, to propagate their energy upwards, towards the surface10, 11. They are linked, at the sea surface, to equatorial zonal current anomalies and eastern Atlantic temperature anomalies that have amplitudes of about 6 cm s−1 and 0.4 °C, respectively, and are associated with distinct wind and rainfall patterns. Although deep jets are also observed in the Pacific12 and Indian13 oceans, only the Atlantic deep jets seem to oscillate on interannual timescales. Our knowledge of the persistence and regularity of these jets is limited by the availability of high-quality data. Despite this caveat, the oscillatory behaviour can still be used to improve predictions of sea surface temperature in the tropical Atlantic. Deep-jet generation and upward energy transmission through the Equatorial Undercurrent warrant further theoretical study.

Description: Iron limits phytoplankton growth and hence the biological carbon pump in the Southern Ocean1. Models assessing the impacts of iron on the global carbon cycle generally rely on dust input and sediment resuspension as the predominant sources2, 3. Although it was previously thought that most iron from deep-ocean hydrothermal activity was inaccessible to phytoplankton because of the formation of particulates4, it has been suggested that iron from hydrothermal activity5, 6, 7 may be an important source of oceanic dissolved iron8, 9, 10, 11, 12, 13. Here we use a global ocean model to assess the impacts of an annual dissolved iron flux of approximately 9×108 mol, as estimated from regional observations of hydrothermal activity11, 12, on the dissolved iron inventory of the world’s oceans. We find the response to the input of hydrothermal dissolved iron is greatest in the Southern Hemisphere oceans. In particular, observations of the distribution of dissolved iron in the Southern Ocean3 (Chever et al., manuscript in preparation; Bowie et al., manuscript in preparation) can be replicated in our simulations only when our estimated iron flux from hydrothermal sources is included. As the hydrothermal flux of iron is relatively constant over millennial timescales14, we propose that hydrothermal activity can buffer the oceanic dissolved iron inventory against shorter-term fluctuations in dust deposition.

Description: The elemental stoichiometry of sea water and particulate organic matter is remarkably similar. This observation led Redfield to hypothesize that the oceanic ratio of nitrate to phosphate is controlled by the remineralization of phytoplankton biomass1. The Redfield ratio is used universally to quantitatively link the marine nitrogen and phosphorus cycles in numerous biogeochemical applications2,3,4. Yet, empirical and theoretical studies show that the ratio of nitrogen to phosphorus in phytoplankton varies greatly with taxa5,6 and growth conditions7,8,9. Here we present a dynamic five-box ecosystem model showing that non-Redfield utilization of dissolved nitrogen and phosphorus by non-nitrogen-fixing phytoplankton controls the magnitude and distribution of nitrogen fixation. In our simulations, systems dominated by rapidly growing phytoplankton with low nitrogen to phosphorus uptake ratios reduce the phosphorus available for nitrogen fixation. In contrast, in systems dominated by slow-growing phytoplankton with high nitrogen to phosphorus uptake ratios nitrogen deficits are enhanced, and nitrogen fixation is promoted. We show that estimates of nitrogen fixation are up to fourfold too high when non-Redfield uptake stoichiometries are ignored. We suggest that the relative abundance of fast- and slow-growing phytoplankton controls the amount of new nitrogen added to the ocean.

Description: Concerns about the slow pace of climate mitigation have led to renewed dialogue about solar-radiation management, which could be achieved by adding reflecting aerosols to the stratosphere1, 2, 3, 4, 5, 6. Modelling studies suggest that solar-radiation management could produce stabilized global temperatures and reduced global precipitation4, 5, 6. Here we present an analysis of regional differences in a climate modified by solar-radiation management, using a large-ensemble modelling experiment that examines the impacts of 54 scenarios for global temperature stabilization. Our results confirm that solar-radiation management would generally lead to less extreme temperature and precipitation anomalies, compared with unmitigated greenhouse gas emissions. However, they also illustrate that it is physically not feasible to stabilize global precipitation and temperature simultaneously as long as atmospheric greenhouse gas concentrations continue to rise. Over time, simulated temperature and precipitation in large regions such as China and India vary significantly with different trajectories for solar-radiation management, and they diverge from historical baselines in different directions. Hence, it may not be possible to stabilize the climate in all regions simultaneously using solar-radiation management. Regional diversity in the response to different levels of solar-radiation management could make consensus about the optimal level of geoengineering difficult, if not impossible, to achieve.

Description: The growth of oceanic plates at mid-ocean ridges, crustal accretion, occurs by a combination of magmatic and tectonic processes. Magmatic processes along ridges spreading at fast, intermediate and slowrates, continually add volcanic material to a centrally located spreading axis. This creates a narrowband of young volcanic rocks. However, at ridges spreading at ultraslow rates, diminished volcanism allows entire blocks of mantle to spread on the sea floor by tectonic processes. Remote imaging has advanced our observational understanding of crustal accretion, but temporal constraints are required to quantitatively understand ultraslow-spreading ridge construction. Here, we use U-series eruption ages of volcanic rocks collected from the ultraslow-spreading Southwest Indian Ridge. Unexpectedly, we find young volcanic eruption ages that are broadly dispersed throughout the rift valley, indicating that crustal accretion of young volcanic rocks is not confined to a narrow central spreading axis. As areas of young volcanism are observed close to distinct fault surfaces, we propose that the widely dispersed volcanism may result frommagma rising along faults. Our results indicate that axial-centric spreading models may not accurately describe crustal accretion at ultraslow-spreading ridges, prompting the re-evaluation of these models.

Description: Marine-derived fungi have been shown in recent years to produce a plethora of new bioactive secondary metabolites, some of them featuring new carbon frameworks hitherto unprecedented in nature. These compounds are of interest as new lead structures for medicine as well as for plant protection. The aim of this protocol is to give a detailed description of methods useful for the isolation and cultivation of fungi associated with various marine organisms (sponges, algae and mangrove plants) for the extraction, characterization and structure elucidation of biologically active secondary metabolites produced by these marine-derived endophytic fungi, and for the preliminary evaluation of their pharmacological properties based on rapid 'in house' screening systems. Some results exemplifying the positive outcomes of the protocol are given at the end. From sampling in marine environment to completion of the structure elucidation and bioactivity screening, a period of at least 3 months has to be scheduled.

Description: Whether the characteristics of tropical cyclones have changed or will change in a warming climate — and if so, how — has been the subject of considerable investigation, often with conflicting results. Large amplitude fluctuations in the frequency and intensity of tropical cyclones greatly complicate both the detection of long-term trends and their attribution to rising levels of atmospheric greenhouse gases. Trend detection is further impeded by substantial limitations in the availability and quality of global historical records of tropical cyclones. Therefore, it remains uncertain whether past changes in tropical cyclone activity have exceeded the variability expected from natural causes. However, future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6–34%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre. For all cyclone parameters, projected changes for individual basins show large variations between different modelling studies.

Description: The hydrographic properties of the North Atlantic Ocean changed significantly from 1950 to 2000: the subtropics warmed and became more saline, whereas the subpolar ocean cooled and freshened. These changes directly affect the storage of heat and fresh water in the ocean, but their consequences for ocean dynamics are determined by the resultant changes in seawater density. Here we use historical hydrographic data to show that the overall seawater density in the North Atlantic basin decreased during this 50-year period. As a result of these density changes, sea-surface heights changed in a spatially varying pattern with typical rates of 2 mm yr−1, in broad agreement with tide-gauge measurements. Melding the observed density fields within a numerical model we find a slight weakening in the overturning of the subtropical gyre by −1.5±1 Sv and a slight strengthening in the overturning of the subpolar gyre by +0.8±0.5 Sv. These gyre-specific changes run counter to the canonical notion of a single, basin-scale overturning cell and probably reflect interannual and decadal trends rather than any long-term climate trend. We conclude that gyre dynamics strongly affect temperature and salinity changes that translate into changes in the meridional overturning circulation.

Description: The Census of Marine Life has succeeded in raising awareness about marine biodiversity, and contributed much to our understanding of what lives where. But the project has fallen short of its goal to estimate species abundance.

Description: The ocean's nitrogen budget has escaped quantification. A modelling study shows how a small shift in the nitrate-to-phosphate uptake ratio of phytoplankton has a large effect on calculated nitrogen fixation rates.

Description: Dense water formed over the Antarctic continental shelf rapidly descends into the deep ocean where it spreads throughout the global ocean as Antarctic Bottom Water1, 2. The coldest and most voluminous component of this water mass is Weddell Sea bottom water1, 3, 4, 5, 6, 7. Here we present observations over eight years of the temperature and salinity stratification in the lowermost ocean southeast of the South Orkney Islands, marking the export of Weddell Sea bottom water. We observe a pronounced seasonal cycle in bottom temperatures, with a cold pulse in May/June and a warm one in October/November, but the timing of these phases varies each year. We detect the coldest bottom water in 1999 and 2002, whereas there was no cold phase in 2000. On the basis of current velocities and water mass characteristics, we infer that the pulses originate from the southwest Weddell Sea. We propose that the seasonal fluctuations of Weddell Sea bottom-water properties are governed by the seasonal cycle of the winds over the western margin of the Weddell Sea. Interannual fluctuations are linked to the variability of the wind-driven Weddell Sea gyre and hence to large-scale climate phenomena such as the Southern Annular Mode and El Niño/Southern Oscillation.

Description: Large amounts (estimates range from 70 Tg per year to 300 Tg per year) of the potent greenhouse gas methane are oxidized to carbon dioxide in marine sediments by communities of methanotrophic archaea and sulphate-reducing bacteria1, 2, 3, and thus are prevented from escaping into the atmosphere. Indirect evidence indicates that the anaerobic oxidation of methane might proceed as the reverse of archaeal methanogenesis from carbon dioxide with the nickel-containing methyl-coenzyme M reductase (MCR) as the methane-activating enzyme4, 5. However, experiments showing that MCR can catalyse the endergonic back reaction have been lacking. Here we report that purified MCR from Methanothermobacter marburgensis converts methane into methyl-coenzyme M under equilibrium conditions with apparent Vmax (maximum rate) and Km (Michaelis constant) values consistent with the observed in vivo kinetics of the anaerobic oxidation of methane with sulphate6, 7, 8. This result supports the hypothesis of ‘reverse methanogenesis’4, 9 and is paramount to understanding the still-unknown mechanism of the last step of methanogenesis. The ability of MCR to cleave the particularly strong C–H bond of methane without the involvement of highly reactive oxygen-derived intermediates is directly relevant to catalytic C–H activation, currently an area of great interest in chemistry10, 11, 12, 13.

Description: Instrumental records, proxy data and climate modelling show that multidecadal variability is a dominant feature of North Atlantic sea-surface temperature variations1–4, with potential impacts on regional climates. To understand the observed variability and to gauge any potential for climate predictions it is essential to identify the physical mechanisms that lead to this variability, and to explore the spatial and temporal characteristics of multidecadal variability modes. Here we use a coupled ocean–atmosphere general circulation model to show that the phasing of the multidecadal fluctuations in the North Atlantic during the past 600 years is, to a large degree, governed by changes in the external solar and volcanic forcings. We find that volcanoes play a particularly important part in the phasing of the multidecadal variability through their direct influence on tropical sea-surface temperatures, on the leading mode of northern-hemisphere atmosphere circulation and on the Atlantic thermohaline circulation. We suggest that the implications of our findings for decadal climate prediction are twofold: because volcanic eruptions cannot be predicted a decade in advance, longer-term climate predictability may prove challenging, whereas the systematic post-eruption changes in ocean and atmosphere may hold promise for shorter term climate prediction.

Description: RECENT advances in 40Ar/39Ar dating1,2 have made it possible to date individual K-feldspar grains from Pleistocene tephra, a capability that greatly improves the reliability and temporal resolving power of the method. Here we apply these new techniques to the dating of a phonolite tephra from the East Eifel volcanic field in West Germany, which is sandwiched between loess and palaeosol (alfisol) deposits, and which was therefore erupted during the transition from a glacial to an interglacial period. Our age estimate for this transition is 215±4 kyr (1 σ), which has important implications for the marine δ18O timescale and for models of global climate change during the Pleistocene. The results show that single-grain dating can detect and compensate for the large quantities of xenocrystic contaminants which are found in many tephra deposits. This technique could be used to date the tephra layers found in marine sediment cores and the results could greatly enhance the reliability of the marine δ18O timescale for more rigorous Fourier analysis testing of the Milankovitch hypothesis.

Description: ROOTH proposed that the Younger Dryas cold episode, which chilled the North Atlantic region from 11,000 to 10,000 yr BP, was initiated by a diversion of meltwater from the Mississippi drainage to the St Lawrence drainage system. The link between these events is postulated to be a turnoff, during the Younger Dryas cold episode, of the North Atlantic's conveyor-belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the North Atlantic region2. This turnoff is attributed to a reduction in surface-water salinity, and hence also in density, of the waters in the region where North Atlantic Deep Water (NADW) now forms. Here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from Orca Basin core EN32-PC4 which reveal a significant reduction in meltwater flow through the Mississippi River to the Gulf of Mexico from about 11,200 to 10,000 radiocarbon years ago. This finding is consistent with the record for Lake Agassiz which indicates that the meltwater from the southwestern margin of the Laurentide Ice Sheet was diverted to the northern Atlantic Ocean through the St Lawrence valley during the interval from ~11,000 to 10,000 years before present (yr BP).

Description: Abrupt changes in climatic conditions have been seen at high latitudes in the North Atlantic and the Antarctic at 13 kyr BP. It is important to determine whether this abrupt change was confined to high-latitude regions or whether it was global. Here we present results demonstrating an abrupt change in the rate and character of sedimentation in the South China Sea at the close of the last glacial period. Radiocarbon dating and its position in the oxygen isotope shift suggest that this change may be coincident with the changes found at high latitudes.

Description: Abrupt changes in climatic conditions have been seen at high latitudes in the North Atlantic1 and the Antarctic2,3 at 13 kyr BP. It is important to determine whether this abrupt change was confined to high-latitude regions or whether it was global. Here we present results demonstrating an abrupt change in the rate and character of sedimentation in the South China Sea at the close of the last glacial period. Radiocarbon dating and its position in the oxygen isotope shift suggest that this change may be coincident with the changes found at high latitudes.

Description: Perhaps the most significant event in the Cretaceous record of the carbon isotope composition of carbonate1,2, other than the 1–2.5 ‰ negative shift in the carbon isotope composition of calcareous plankton at the Cretaceous/Tertiary boundary3, is the rapid global positive excursion of ~2 ‰ (13C enrichment) which took place between ~91.5 Myr and 90.3 Myr (late Cenomanian to earliest Turonian (C/T boundary event))1,4,5. This excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon (TDC) reservoir resulting from an increase in rate of burial of 13C-depleted organic carbon, which coincided with a major global rise in sea level5 during the so-called C/T oceanic anoxic event (OAE)6. Here we present new data, from nine localities, which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the C/T boundary7,8 is nearly synchronous with that for carbonate and is widespread throughout the Tethys and Atlantic basins (Fig. 1), as well as in more high-latitude epicontinental seas. The postulated increase in the rate of burial of organic carbon may have had a significant effect on CO2 and O2 concentrations in the oceans and atmosphere, and consequent effects on global climate and sedimentary facies.

Description: The dynamic and production of a natural population of the rotifer Brachionus plicatilis (0.F. MÜLLER) were studied by regular field sampling at routine stations in the shallow Darss Zingst estuary, southern Baltic (3-7‰ S). Investigations of the horizontal distribution revealed significant population growth during the summer months at salinities above 3‰ S and at those stations characterized by high eutrophication. The first individuals hatch from resting eggs in May. Significant reproduction occurs from June to September, when temperatures are above 15° C. Mixis rates were highest during the exponential growth phase. Instantaneous rates of growth, birth, and mortality were estimated. Mean P/B ratios for the growing season were high (around 0.7 d-1) and were in the range of values obtained from mass cultures in the field under subtropical conditions. In Barther Bodden annual biomass production for 1982 was 1.1 g fw · m-3. In its natural habitat, B. plicatilis serves as a food source for fish juveniles and the mysid Neomysis integer, the seasonal dynamics of the rotifer population were not significantly affected by predators.

Description: Shrimps Crangon crangon L. were exposed to 5, 7.5, 10, 25 and 50 ppm of the anionic detergent alkylbenzene sulphonate (ABS) added to brackish water (7‰ salinity). The animals were incubated in these solutions from one to nine days at 15° C or 20° C. After 24 h and 108 h of incubation the activities of arylsulphatase (E.C. 3.1.6.1 ), acid phosphatase (E.C. 3.1.3.2) and cathepsin D (E.C. 3.4.4.23) were assayed in homogenates of the hepatopancreas. The influence of the detergent ABS on the moulting cycle of the shrimps was also investigated. The activity of all acid hydrolases assayed descreased by 20 % to 50 % in the experimental shrimps, depending on concentration of the pollutant, as compared with the control group. The moulting cycle of the shrimps exposed to the action of the detergent was shortened from 31 % to 51 %, and the body weight during one moulting cycle was reduced by 24 % to 36 %. Survival times were reduced in the animals exposed to the action of the detergent. Total mortality of the shrimps occurred after 194 h, in 5 ppm of ABS at 15° C and after 108 h in 50 ppm. The 96 h LC50 for shrimp Crangon crangon L. under laboratory conditions was estimated as 27 ppm of alkylbenzene sulphonate.

Description: Prior to 1975, average winter water nutrient concentrations at station Bokniseck in Kieler Bucht (Western Baltic} were 1.23 mmol/m3 total phosphorus and 12.7 mmol/m3 dissolved inorganic nitrogen. Nitrogen concentrations did not change until 1984. The mean of a few total phosphorus data from 1980-1984 is 1.94 mmol/m3. Mean nutrient concentrations in the area between the southern entrance of the Great Belt and Darss Sill increased between 1975 and 1984 from 0.8 to 1.6 mmol/m3 total phosphorus and from about 6 to 10 mmol/m3 inorganic nitrogen. Comparatively higher nutrient concentrations at Bokniseck station are correlated to higher salinity. However, no data are available on nutrient imports into Kieler Bucht with saline deep water. Unchanged nutrient concentrations at Bokniseck prior to 1975 are an argument against any dominant influence of anthroprogenic inputs which until 1974 increased to annually 1500 t of total phosphorus and 12700 t of total nitrogen, plus 5000 t of nitrogen from the atmosphere. Higher phosphorus concentrations 1980-1984 are correlated to severe oxygen deficiency in the deep water. Mobilization of phosphorus from sediments becoming anoxic could be the reason. Biota could be such sources and sinks of nutrients that influence the nutrient balance of Kieler Bucht. To sum up, there are several processes besides anthropogenic inputs that influence nutrient concentrations in water. An assessment of winter water nutrient concentrations alone is no adequate tool for the evaluation of the effects of anthropogenic nutrient inputs via rivers, sewage, land runoff, groundwater and from the atmosphere.

Description: Postglacial sequence of migration and extinction has been studied in a boring through 10 m deposits in Jutland, Denmark. The main profile contained freshwater and brackish water fauna in the bottom layer. Hydrobia ulvae was first recorded at -9.75 m. Next H. ventrosa was found together with H. ulvae. Then H. neglecta appeared, and all 3 species co-occurred at -8.75 m. At -4.95 m H. ulvae disappeared but H. ventrosa and H. neglecta were still abundant until a depth of -1.90 m. It is concluded that H. ulvae and H. ventrosa quickly colonized the Littorina Sea while H. neglecta may have arrived somewhat later. H. ulvae has the largest larval shell, especially in the Baltic, and H. ventrosa the smallest larval shell of the 3 species. The ecological significance of two markedly different shell forms of H. ulvae is discussed. Postglacial hydrobiids are compared with recent specimens of the 3 species.

Description: In situ measurements of the functional response (feeding, respiration and excretion) of Mytilus edulis and Ciona intestinalis showed that the effects of 2.5 µg 1-1 tributyl tin and 100 µg 1-1 cadmium on an assemblage of the two species was lower than what could be predicted from the response of the two species separately. This is explained by biological interactions between the species and by the fact that the two species may react in different ways to the same disturbance. Thus, results from single species tests seem inadequate for making predictions of pollution effects in marine environments, and tests should instead be carried out at the community or ecosystem level.

Description: In order to determine the time of settlement, growth and mortality of young bivalves, samples sieved on 250 µm screens were taken in parallel to ordinary samples (1 mm screen) in the western part of the Limfjord, Denmark. High densities of newly settled Corbula gibba (30000-67000/m2) and Abra alba (16000-22000/m2) in August 1986 were found at most stations. Growth of the juvenile Corbula gibba was very rapid and the specimens were retained by the 1 mm sieve a few weeks after settlement. Growth ceased in October at a length of 2.9-3.5 mm for Corbula gibba and 0. 7-2.1 mm for Abra alba. The juvenile bivalves suffered high mortality within the first month after settling. It is suggested that this mortality may be due to predation from epibenthic predators.

Description: Seawater samples for algal experiments and isolation of OHS (Dissolved Humic Substances) were taken in the Gdansk Bay during intense phytoplankton blooms. Bioassay experiments were conducted under controlled laboratory conditions with water containing natural phytoplankton communities. OHS was isolated from seawater by absorption on Amberlite XA0-2 according to the method of MANTOURA and RILEY (1975). It was found that the enrichment of the medium with OHS increased the production of chlorophyll a and cell numbers. OHS addition to the culture medium caused a change in the dominant species, especially in spring and summer phytoplankton. The results show that OHS influence not only the phytoplankton production but also the species succession by altering the species composition. The phenomenon of large phytoplankton blooms in coastal areas during the last decade should therefore be related (besides other physical, chemical and biological influences) to the presence of increasing concentrations of dissolved substances of the humic type.

Description: In 1986 and 1987 a transect off SW Åland, N Baltic Sea was sampled for macrozoobenthos at 14 stations ranging from 1 to 226 m depth. In connection to this survey comparative samples were taken at a "standard depth" of 19-20 m at 2 additional stations to estimate variability in space and time. The data were analyzed for primary community parameters (i.e. no. of species, abundance and biomass) including spatial and temporal differences, and the information is evaluated in relation to topography and hydrography. A more detailed analysis using the dominant components of the zoobenthic communities illustrated some of the difficulties in monitoring of the marine zoobenthos. There were significant differences in abundances and biomasses even over short distances. The differences get even more pronounced when trying to relocate an exact station with another boat and using different grab types on the same station. This is exemplified by samples from a 19-meter station using a modified Olausen box corer and an Ekman-Birge type grab sampling on different days from different vessels; the primary community data obtained with both grabs was 10 vs. 10 species (with Pontoporeia affinis vs. Macoma balthica dominating), 1945 ± 529 vs. 2168 ± 385 ind/m2, and 21.6 ± 9.5 vs. 209.0 ± 45.3 g/m2, respectively. Similarily, samplings at stations less than 1 n. mile apart at 20 m depth using the Ekman-Birge grab yielded 2168 ± 385 and 7000 ± 607 ind/m2; a highly significant difference. The no. of species (10/13) and biomasses (209.0 ± 45.3/184 ± 89.0 g/m2) showed no significant differences. The data also showed some depth dependency, but there was no correlation (r=0.22) between abundance and biomass for the entire material pooled, illustrating the importance of always measuring both. When using keyspecies for monitoring purposes, their natural distribution should also be known, as the dominance-patterns shows clear gradients with depth and sediment type.

Description: During the winter 1984 and summer 1985, a series of limiting nutrient experiments (enrichment tests) were performed with coastal Baltic water by scientists from the German Democratic Republic, Poland and Sweden. The water used for the experiments was collected outside Warnemünde (GDR); Rostock (GDR}, Sopot (P) and Falsterbo (S). The bioassays were performed under similar laboratory conditions. Nitrogen was the potentially most limiting nutrient for phytoplankton biomass formation in coastal water from Rostock, Sopot and Falsterbo. During winter, before the spring phytoplankton bloom had started, phosphorus was the "most limiting" nutrient in the Rostock area. For the Warnemünde area, no clear limiting nutrient was found, except during July 1984, when nitrogen addition doubled the phytoplankton biomass. The lowest algal standing stocks were found for Warnemünde and Falsterbo, followed by Sopot. Extremely high chlorophyll-a values were found outside Rostock. Our results show that these coastal areas in the southern Baltic do not differ essentially from each other with respect to the most limiting nutrient (sensu Liebig), although their nutrient levels are quite different. Nutrient limitation experiments are discussed in the context of the assumed eutrophication of the Baltic.

Description: The paper presents the assumptions of a one-dimensional mathematical model of turbulent diffusion of marine suspensions, as well as the results of numerical investigations on the influence of dynamic conditions in a defined basin on the chlorophyll-a concentration. The influence of the duration and disappearance time of a disturbance, and the thickness of the layer disturbing uniform media of varying degrees of turbulence on the vertical distribution of the chlorophyll-a concentration is analysed.

Description: A large scale quantitative survey of the benthic vegetation of the Kiel Bight (Western Baltic Sea) has been performed by analysis of underwater television observations and samples obtained by SCUBA diving during 1985-86. This investigation was compared to a semiquantitative survey carried out in 1962-64 by SCHWENKE (1964, 1969). For the total study area (2571 km2), distinct changes in biomass and species composition have been observed. There is an increase of biomass above the 12 m level (probably with exception of the 6 m level) and a decrease below 12 m. Extensive Furcellaria lumbricalis populations have disappeared. Furcellaria lumbricalis has been replaced by Phyllophora truncata and Phycodrys rubens which are the predominant species at present. Among other possible causes for these changes, the role of commercial stone fishing and effects of increasing eutrophication in the Kiel Bight are discussed.

Description: The establishment of an initial association of marine benthos was investigated during a colonization experiment at the "Nordsee" research platform at 25 m depth, from April to December 1985 and 1986. Settlement and the early stages of succession were studied by taking monthly series of soft-bottom samples. Parallel to the experiment, recruitment in the natural habitat was studied at a reference station close to the platform. Number of species, density, diversity and evenness of the initial experimental association showed 3 different phases, similar to those described by RUMOHR (1980) as "pre-opportunistic, opportunistic and post-opportunistic" phases. These stages appear regularly during early succession, but, are subject to strong seasonal and annual variability. Heavy spatfalls of several species occurred in both years of the investigation; e.g. Tellina tabula, Echinocardium cordatum, juvenile ophiuroids of the genus Ophiura (mainly in 1985) and Scoloplos armiger, Mediomastus aff. fragilis and Abra sp. (1986). Total density attained maximum values of approx. 30,000 ind. per 0.1 m2. In the natural environment the colonization process was similar, but as in Kiel Bay, the densities were much lower than on the experimental substrates. The successional pattern and role of opportunists during early succession is discussed.

Description: Sven EKMAN (1876-1964), zoogeographer and limnologist in Uppsala, wrote significant articles on marine glacial relicts, drew up a proposal of the natural history division of the Baltic Sea and wrote the textbook "Tiergeographie des Meeres", first of its kind and later published in English as "Zoogeography of the Sea". - Adolf REMANE (1898-1976), zoosystematician and ecologist in Kiel, was one of the first to analyse the faunal composition and communities of the Baltic in "Die Tierwelt der Nord-und Ostsee". A pioneering textbook by him and C. SCHLIEPER "Biologie des Brackwassers" appeared also in English. REMANE found the interstitial habitat. He described numerous new Gastrotrichs, Rotifers and Archiannelids. - Carl SCHLIEPER (*1903), zoophysiologist in Kiel, is the founder of the "School of Baltic physiologists". Studies by him and his many students on salt water tolerance and osmoregulation, ionic and temperature adaptation and high pressure tolerance of aquatic animals are known world wide. He is the co-author of four textbooks. Sven G. SEGERSTRÅLE (*1899), zooecologist in Helsinki, initiated the yearly monitoring of the bottom fauna in coastal waters of Finland. He studied the systematics and ecology of amphipods, especially the genus Gammarus and Pontoporeia and biology of the mussel Macoma balthica. His descriptive articles on the Baltic Sea and studies on marine glacial relicts are well known.

Description: The effect of siderophores, cysteine and Na2EDTA in cultures of Chlorella vulgaris and Anabaena variabilis containing copper or cadmium, on the chlorophyll-a content, as well as on the rate of carbon fixation, has been investigated. Experiments on copper accumulation in Chlorella vulgaris cells grown in the presence of organic compounds have been also carried out. The siderophores, cysteine and Na2EDTA reduced the toxicity of copper and cadmium to axenic strains of algae and natural phytoplankton. No correlation between the toxic effect of copper and its bioavailability was observed.

Description: In the last 14 years, trapnet catches of the Baltic herring (Clupea harengus membras L.) have decreased drastically in the inner zones of the bays studied, but increased in the outer zones in the sea area of Turku, SW Finland. We deduce that the reasons for the decrease of catches have been eutrophication and sedimentation of the bays. The spawning grounds of the Baltic herring were studied by SCUBA-diving in the sea area of Turku in 1981-86. We studied 134 locations but found eggs in only 20 locations. Herring did not lay eggs on all suitable grounds, but regularly and intensively used some few locations from year to year. The most important spawning grounds were situated in the outer zones of the bays. We found eggs at 0-8 meters depth. In the inner parts of the bays, we did not find eggs with the exception of one shore, which is kept free of sediments by water currents. The spawning grounds comprised mainly sand and gravel. Most of them were covered by vegetation. Eggs were attached to Cladophora glomerata, Potamogeton perfoliatus, and red algae Furcellaria Jumbricalis and Phyllophora truncata. In the innermost zones of the bays the original littoral hard bottoms have changed to soft, muddy bottoms and consequently no eggs could be found there.

Description: In 1985 and 1986, a SW Finnish archipelago area was monitored for fish (using gillnets and seine), in order to investigate potential effects of salmonid fish farming on natural fish communities (population- and community level, growth and food choice). The results indicate some structural change eg. in total abundance and biomass values (increasing), on species composition (towards moore cyprinid-dominated communities), on growth rate (increasing) and food choice (increased proportions of fish consumed) of perch, and a general shift towards communities dominated by juveniles and small fish in areas influenced by fish farms.

Description: Recruitment and survival of Nereis diversicolor and Corophium volutator was studied in an artificial Saltwater Lagoon in the Danish Wadden Sea. The two species were the most successful colonizers of this lagoon and they have temporarily accounted for more than 80 % of the benthic individuals. Predation by waders, emigration and a low salinity in winter(〈2‰) appeared to be important regulators of the population sizes. Various field experiments have been performed to examine the effect of selected infaunal species on recruitment of C. volutator and N. diversicolor. The density of recruits of C. volutator was negatively affected by adult individuals of its own species, by C. arenarium, by Macoma balthica, and by Nereis diversicolor. C. arenarium was the only species that had a negative effect on N. diversicolor. At the intertidal flat a high recruitment of both, C. volutator and N. diversicolor, took place within cages enclosing the natural fauna, while the density of recruits on the adjacent bottom was low. The importance of epibenthic predators and cage artifacts on the density of recruits is discussed.

Description: The influence of eutrophication on the occurrence of the red algae Furcellaria lumbricalis and Phyllophora truncata was studied in the sea area of Turku. Due to increased sediment load and planktonic production, light penetration in the water has decreased in the northern parts of the study area. Furthermore, the quality of the sea bottom has changed. Plots of 1 m2 (N = 100} in the upper littoral zone (0.5-6 m} were studied by SCUBA diving, in order to investigate the factors controlling the occurrence of the red algae. Two transects were situated in the eutrophicated area, and two in the reference area. In the plots, the percentage cover of each plant species and of Mytilus edulis was documented, and the Secchi disc visibility and depth was measured. The numerical data were analyzed by correlation analysis and stepwise multiple regression analysis (BMDP2R}. In the eutrophicated area, abiotic factors (percentage cover of plain bottom and bottom quality} explained 81.28 % of the variation of red algae cover. In the reference area, the biotic factors (total number of species and Mytilus cover in %} were the most important factors, explaining 66.4 % of red algae cover.

Description: Major inflows of saline water into the Baltic Sea have a significant impact on the oceanological regime of the deep water in the central basins. Such events show seasonal characteristics, which are investigated here for the 80-year period from 1897 to 1976. The characteristic properties - i.e. salinity, temperature, density and oxygen concentration of the water bodies entering the Baltic during major inflows are analyzed for the first time. The significance of the season of the inflow event for its effects on the oceanological conditions in the deep water is discussed.

Description: 12-year quantitative phytoplankton data collected in the Tvarminne sea area in June-August from 1972-1985 were analysed in relation to environmental data collected at the same time. This was done by principal component analysis followed by canonical correlation analysis. A phytoplankton species succession which took place parallel to the increase in temperature was found to be the most important factor causing variation in species composition. The second most important factor was a change in phytoplankton species composition from the early 1970's towards the 1980's. This followed the same pattern as nutrient levels and total phytoplankton biomass. The species primarily responsible for the change were nanoplanktonic forms, such as unidentified flagellates, Cryptomonas spp., Monoraphidium contortum and Microcystis reinboldii, and a heterotroph, Ebria tripartita. It was concluded that this was due to increased levels of total phosphorus and organic load in the Gulf of Finland. Short-term weather conditions had no significant effect on species composition.

Description: The history of studies of benthic flora and fauna in the Northern Baltic Sea (N of 58° N, including the Gulfs) is briefly reviewed from the early naturalists of the Linnaean period (mid-18th century) to the early 1970's.

Description: Fish eggs and larvae were sampled during 1970 and 1971 at approximately monthly intervals in the Kiel Bay using a Bongo-Net. Samples of 0.5 mm mesh net were considered in this study. At every station temperature and salinity were measured. The most abundant fish eggs were of sprat origin, followed by flounder, cod and plaice. Spawning areas of this species are also described. Fish larvae showed high abundance from June to August with gobies predominance. Commercially important species such as herring, cod and plaice were present in low numbers. Species exceeding the 5 % relative proportion level (tow-year average) were herring, sprat, rockling, gobies and gunnel.

Description: The Bornholm Basin has a distinct hydrographical pattern in terms of temperature, salinity and oxygen. Due to the strong differences in density, there is a strong vertical stratification of water masses and ichthyoplankton as well. The vertical distribution of fish eggs and larvae was investigated in a period of 27 hours at an anchor station. Samples were taken at three hours intervals with a closing net. The species composition of fish eggs and fish larvae in (), both in percent, was found to be 79.7 (84.0) sprat, 17.5 (15.0) cod, 1.3 (0.6) rockling, 1.5 (0.4) flounder and 7.3 dead eggs. To control for water masses around the station, double oblique hauls with a ring net were performed, as well as measurements of temperature and salinity. The vertical distribution of sprat and cod eggs showed considerable differences. Sprat eggs were most abundant in the upper 40 metres, whereas cod eggs were found only from 40 metres downwards. The few eggs of rockling and flounder showed a weak accumulation between 40 to 65 metres. Sprat and cod larvae were present throughout the whole water column, decreasing in numbers with depth. The maximum abundance overlapped for sprat and cod between 40 to 65 metres. However, sprats were also common in the upper layer, in which cod were present in small numbers only. The larvae of rockling and flounder were generally scarce and not found in every sample. No aggregation was obvious at certain depth levels.

Description: Predation on zoobenthos by fish was studied on Åland, northern Baltic Sea, in a shallow, semi-isolated bay (Station 1) and an outer area (Station 2) which is in direct connection with the bay. The fish sampling was done under an one year-cycle (May-November 1984 - May-June 1985) with a standardized multimesh set of gillnets. The fish samples for community analysis were taken once a month (May-November 1984 - May-June 1985). Stomach samples of perch (Perca fluviatilis, L.), roach (Rutilus rutilus, L.) and ruffe (Acerina cernua, L.) were collected five times during the sampling period representing the spring-, summer- and autumn-seasons. The fish species studied are the most important predators on benthic macroinvertebrates in this area. Calculations of the annual food consumption were done on the basis of field data and literature values. The soft bottom infauna was monitored throughout the study to get accurate measures of the standing stock. Roach was the most abundant and important bottom feeder in the study areas. It consumed 64 to 73 % of the total amount of benthic food taken. Roach preyed heaviest on molluscs. Perch preyed mainly on crustaceans (at St. 2) and insect-larvae (at St. 1). It consumed about 24 to 35 % of the total amount of fish predation. Ruffe is principally an obligate benthic feeder consuming mainly insect-larvae, crustaceans and polychaetes. The abundances of ruffe were low in the study areas, and the quantities consumed were marginal on an annual basis. The total consumption calculated was 999 kg/ha at St. 2 and 349 kg/ha at St. 1 during the summer season (May-November). Consumption is significantly higher in the outer area (St. 2) mainly due to higher fish abundances and benthic biomass in this area. The consumption values are equivalent to about 9 to 31 % of the annual secondary benthic production in the area studied. The fish consumed a significant proportion of the benthic standing stock, but simultaneous experiments in the lab and field have shown that the structuring effect of fish-predation on the benthic community is small. The ecological relevance of the fish/benthos couplings on shallow soft bottoms are further emphasized.

Description: In static toxicity tests, the effects of HgCl2 and of an organic mercury complex on the mortality of Neomysis integer and Pomatoschistus microps were determined under various temperature and salinity conditions. Definite species-specific differences with respect to combined temperature, salinity and mercury effects were found. The toxicity of the organic mercury complex exceeded that of HgCl2 by a factor of 20 in the case of N. integer, and by a factor of 30 in the case of P. microps. By means of continuous respiration and activity measurements on N. integer (the more sensitive species) under organo-mercury contamination at different environmental conditions (temperature, salinity and pO2), reproducible sublethal concentrations were determined. For this species, a direct relationship was found between mercury contamination levels, increase in activity, and oxygen uptake.

Description: On the occasion of the celebrations of the 50th year of existence of the biological station at Hiddensee (1982), the 150th jubilee year of the Zoological Institute of the Ernst-Moritz-Arndt-University in Greifswald (1986), and the 25th year of existence of an independent marine biological research and training facility at the University of Rostock (1985), a short overview is given of the development of biological science in the Baltic Sea in the Hither Pomerania and Mecklenburg region. It will become clear that the initiative for brackish water research arose at the University of Greifswald, with algological studies concentrated at Hiddensee and zoological-ecological work in Greifswald itself. Effective and successful marine biological research and teaching at the University of Rostock started with the establishment of the Department of Marine Biology (1960), where university marine biological activities are now concentrated as a result of the university reform (1968).

Description: Shrimps (Crangon crangon L.) were exposed to 5, 7.5, 10, 25, or 50 ppm of light fuel oil, heavy fuel oil or crude oil at 15° C or 20° C with aeration. The mortality was recorded. It was found that light fuel oil was the most toxic and crude oil the least toxic.

Description: The genus Enteromorpha Link is one of the most common algae in the Gulf of Gdańsk. The literature mentions that several Enteromorpha species occur in the western part of the Gulf of Gdańsk. The material for analysis was collected in the littoral zone down to a depth of 1 m in the Gulf of Gdańsk and on the open Baltic coast once a month from April to November 1986. The taxonomical characters, the nature of the bottom sediments and the sampling season were used for describing OTUs. 6 dissimilarity coefficients and 7 clustering methods were employed. The two principal clusters and some intermediate OTUs are shown on the dendrograms. The difference between these two clusters lies in the morphological characters. In one of them, the filaments are unbranched, without prolification, and the cells are multilateral and rounded, setting in random fashion; in the second one the filaments are branched, and the cells are rectangular, setting in an orderly manner along the main axis and the branches. The remaining characters, especially the quantitative ones do not seem to be important from the cluster analysis point of view.

Description: Cadmium, lead, copper, chromium and zinc contents were determined in otoliths of the cod Gadus morhua L. from the Southern Baltic. It was shown that the levels of these heavy metals fluctuated during the period of investigation (1969-1985). It was found that levels of Cd, Cu, Cr and Zn decreased with age and age-dependent morphometric parameters, while the amount of lead increased. Sex of cod did not affect the level of bioaccumulation of these five trace elements in the otoliths. With the exception of Cu no differences were found between heavy metal contents in otoliths of cod from the Gdańsk and Bornholm Deep.

Description: Following a mass mortality of the demersal fish population in Kiel Fjord due to anoxic water conditions throughout the water column, the occurrence of mass aggregations of the free-living marine nematode Pontonema vulgare on dead fish, jellyfish (Aurelia aurita, Cyanea capillata) and starfish (Asterias rubens), and in weakened mussels (Mytilus edulis) was observed by SCUBA diving and documented through underwater photography as early as two days after the incident occurred. P. vulgare not only survived the anoxic conditions which prevailed for severals days, but also took advantage of these circumstances to prey upon dead or weakened animals on the sediment. These observations confirm previous reports of a possible role of Pontonema vulgare as a scavenger in the form of mass aggregations in areas of acute oxygen depletion and sediments of high organic content. Positive thigmotaxis is assumed to cause aggregations of Pontonema vulgare upon brown sediments and on webs of Beggiatoa spec. in oxic water with no apparent prey as a cause. Their chemoreceptive sense, thigmotactic aggregation behavior, ability to withstand adverse oxygen conditions, and their broad feeding spectrum are responsible for the success of this species in an extreme environment.

Description: Based on data collected at 7 stations 4 times a year in 1985 and 1986, composition and distribution of meiobenthic communities in the Polish part of the Szczecin Lagoon, a eutrophic and polluted water body connected with the Baltic Sea, is presented. The data show a tendency to reduced total meiobenthos densities and diversity from the lower to upper reaches of the lagoon. The meiobenthic communities studied were dominated by nematodes, ostracods ranking second in numerical importance. Harpacticoid copepods were most abundant at the outer stations which are influenced by Baltic inflows. Most of the 10 harpacticoid species recorded in the lagoon were found at the outer stations (lower reaches) as well. Similarity analysis allowed to separate three zones within the lagoon: (1) the outer zone, its stations showing most abundant and diverse meiobenthic communities; (2) the innermost zone (upper reaches) with the least abundant and qualitatively impoverished communities; and (3) the intermediate zone.

Description: An approach to monitoring the availability of oxygen to benthic marine invertebrates in the sediment is presented on the basis of biochemical analyses of metabolites of species from Kiel Bight. In Halicryptus spinulosus, Astarte borealis and Arctica islandica several metabolites of anaerobic metabolism were examined for their suitability as indicator substances of the oxygen availability. The amino acids aspartic acid and alanine seem to be useful only as indicators of short-term anaerobiosis, whereas glycogen and succinate together may indicate the overall duration of long-term anaerobiosis. The time course of glycogen depletion and of the increase of succinate concentrations in the tissues is correlated to the duration of experimentally induced anaerobiosis. Analyses of freshly captured Halicryptus spinulosus reflect the occurrence of long-term anaerobiosis at the sampling site in Kiel Bight during the end of summer and early autumn. Succinate concentrations in these worms and the depletion of glycogen came close to the values of specimens kept in the laboratory under anoxic conditions for 40 days (at 10°C).

Description: On the basis of long-term investigations, the course of seasonal variations of mean daily primary production and mean chlorophyll-a concentration in the Southern Baltic waters are presented. The mean annual primary production of the Gdańsk Deep, Bornholm Deep and the Gotland Deep amounted to 124.4 gC m-2, 88.8 gC m-2 and 107.2 gC m-2, respectively. The primary production of the Southern Baltic in 1986 was higher than in 1985, and higher than the long-term mean value. The mean annual production for the Southern Baltic in 1986 amounted to 130 gC m-2. On the basis of long-term observations of primary production and chlorophyll-a of the Southern Baltic, certain upward trends in phytoplankton production were observed.

Description: The nutrient situation in eutrophic shallow coastal water systems is characterized by particular features. In addition to water exchange with the open sea, interactions at the sediment/water interface play a significant role. With the help of investigation on phosphate sorption/desorption balances and on the denitrification capacity of shallow coastal waters, the following general conclusions can be made: The phosphate concentrations in the water are primarily determined by physico-chemical reactions with the sediment, and less by the rhythm of the phytoplankton primary production. Through intensive interactions between sediment and water, a phosphate "equilibrium" concentration which fluctuates very little is maintained over the whole year. High primary production rates are possible at these low equilibrium concentrations of phosphate. The phosphate sorption capacity of sediments is a characteristic parameter of shallow systems. Sediments with a high organic matter content exhibit the highest phosphate sorption capacities. With the development of nearly anearobic conditions, nitrate reduction can occur at a rate, when the appropriate amount of nitrate is made available to the reaction. Under optimal conditions for nitrate reduction, nitrate concentration is also not a parameter characterizing the nature of the water body.

Description: During 1982, 1983 and 1984 numbers of planulae within the oral arms of the common jellyfish Aurelia aurita were counted, and the organic content of the larvae was determined through C/N analysis. The total numbers of larvae produced by females of the same size increased during the period of investigation by a factor of 4-5, and a good linear correlation between the amount of larvae and body weight of the females were observed. In contrast, the averaged carbon content of the planulae decreased from 0.68 µg C per individual in 1982 to 0.28 µg C per individual in 1984. On average, larvae represented 17% of the carbon content of a female in 1982, 25% in 1983 and 37% in 1984. Partitioning of this organic matter among larvae differed from year to year: low numbers of planulae with a high organic content were observed in 1982, very high numbers with a low organic content in 1984, and intermediate in 1983. Thus breeding behaviour of the common jellyfish seems to be a complex process and there is evidence that medusae abundance and estimated food availability ragulate reproduction in Aurelia aurita populations.

Description: The energy content of Mysis mixta from the Southern Baltic in relation to its body weight was studied in June, August and October 1986, and April and May 1987. In June, immature animals (4-13 mm) and adult females (18-25 mm) dominated. The same composition was found in August, although the size had changed: the immature animals ranged from 10 to 21 mm and adult females from 21 to 30 mm. A more homogeneous population ranging from 12 to 22 mm was found in October. Males occurred in large numbers only in autumn. The dry weight was 15.04 % of the wet weight, and included 8.18% ash. The relationship between dry weight and body length fitted the power function W = 0.714 L2.835. The average energy content of M. mixta was high: 24.748 Jmg-1 OW and 27.055 Jmg-1 AFDW.There was no significant difference in energy content between adult females and males in October, when both sexes were present. Energy content per dry weight increased with the size of the animals. M. mixta obtained in the study area showed similar energy content to each other.

Description: Shrimps Crangon crangon L., acclimated in the laboratory for 24 h in brackish water (7‰ salinity), were incubated in solutions of anionic detergent alkylbenzene sulphonate (ABS) in concentrations of 5 - 50 ppm. After 24 h or 96 h of incubation, preparations of hepatopancreas were stained and examined by light or transmission electrone microscopy. The light microscopy examination revealed a flattening of the duct cells, pyknotic nuclei in these cells, fine granular secretions in the ducts of the gland, and cellular infiltration. The transmission electron microscopy examination revealed an impairment and destruction of the lysosomal and mitochondrial membranes of the hepatopancreas cells in the shrimps exposed to alkylbenzene sulphonate.

Description: In spring, summer and autumn enclosure experiments were performed in the central part of the Arkona Sea. The natural water with the plankton community was enriched by nutrients to about winter levels, and to the double of these concentrations. In spring and summer, the phytoplankton responded with rapid uptake of nutrients and an increase in primary production and biomass. In autumn, the uptake of nutrients was also fast, whereas productivity did not increase, and biomass only in diatoms. Not only did the production increase with higher nutrient supply, but also the productive season was prolonged. This fact is of importance for the function of the pelagic system in the Baltic, because the biomass and nutrients remaining after the spring bloom determine to a great extent the productivity of the whole year.

Description: A bioenergetic model was parameterized for herring (Clupea harengus) using information available in the literature. In this model, all components of the energy budget are functions of temperature and fish weight. The model is used to simulate herring growth and consumption in a coastal area of the northern Baltic proper. Simulated seasonal growth curves restrained to fit one weight per age class are similar to observed growth curves, indicating the importance of temperature in determining herring growth rates in the Baltic. Calculated food consumption and conversion efficiencies are compared with other published estimates.

Description: Knowledge of how phytoplankton responds to nutrient inputs is essential for water management and for minimizing eutrophication. Only processes that are deterministic, i.e. that can respond as algorithms, are controllable. The study area is the chain of inshore waters (so-called Bodden) south of the Darss-Zingst peninsula - shallow eutrophic waters of estuarine character in the Southern Baltic. Monitoring programmes and laboratory experiments have revealed an annual periodicity of the phytoplankton and of the physico-chemical factors influencing it. On the basis of these results, experiments were carried out in enclosures to study the effects of nutrient loading on phytoplankton. The purpose was to test the feasibility of influencing phytoplankton development under field conditions during the transition period from late spring to mid-summer. This contribution presents results from the 1985 shallow water enclosure experiments (FLAK 85) which demonstrate that - the scale of phytoplankton reactions and the species involved are stochastic in character and are governed by stochastic interactions between meteorological events and water exchange processes in the chain of Bodden; - all processes affecting phytoplankton growth are deterministic in character, conforming to simple batch theories: simultaneous addition of nitrogen and phosphorus favours green algae, and in exceptional cases one algal species became dominant; - nutrient loadings do not affect the time of transition to the mid-summer phytoplankton population, the most important regulating factor obviously being temperature.

Description: The investigation area, Himmerfjarden Bay situated at the Swedish coast of the northern Baltic Proper, receives waste water from a sewage treatment plant. Phosphorus is efficiently reduced in the sewage treatment resulting in a high N : P ratio (≈ 65 : 1) in the discharge. In the near future also the nitrogen discharge will be reduced, and it is teared that a lowered N : P ratio in the receiving waters may favour an undesired increase of nitrogen fixing blue-green algae. This study is focussed on the development of a common nitrogen fixing species in the area, Aphanizomenon flos-aquae, at varied nutrient loadings in 1983-85. The biomass as well as the number of heterocysts was low near the treatment plant and increased with increasing distance from the sewage discharge. The low biomass and number of heterocysts in Himmerfjarden Bay is interpreted as an effect of competition with other algae and of low level of phosphorus relative to nitrogen, i.e. unfavourable conditions for nitrogen fixation. The abundance of Aphanizomenon was highest in 1984 when the phosphorus load was higher than in the other years of investigation. As a tentative conclusion it is suggested that nitrogen fixing algae may increase as a result of reduction in the nitrogen discharge to Himmerfjarden Bay in the future. At the reference station outside the Bay, nutrient conditions favoured nitrogen fixing algae, as interpreted from an inorganic N:P ratio less than 10:1 during the summers of the investigation period. Here the variation in biomass between the years was mainly due to the variaton in water temperature; Aphanizomenon was most abundant during the warm summer of 1984 and less abundant during the cold summer of 1985. A significant correlation was obtained between the heterocyst frequency and concentration of inorganic phosphorus in the trophogenic layer at the reference station.

Description: In the Bornholm Basin cod eggs occur exclusively in the intermediate and deep water layers, because their buoyancy is insufficient for allowing them to float in the low salinity surface layer. In the lower range of their vertical distribution they can be exposed to low oxygen contents, which might affect their mortality thus influencing recruitment. At three cruises carried out during the main spawning season of cod in the Bornholm region, hydrographic measurements were made and ichthyoplankton samples were taken by means of a Bongo net and a multiple opening/closing zooplankton sampler. In the middle and at the end of May large numbers of cod eggs were found especially in the north-eastern part of the Bornholm Basin, whereas in the middle of June considerable frequencies were observed only in the southeast. The eggs were concentrated at depths of 60 to 75 m, but they occurred also below that depth range down to the bottom. In this lower part of the water column an intermediate minimum of the oxygen concentration was observed with values of less than 1 ml/l. Due to the increase of specific gravity during embryonic development of cod the older egg stages were relatively more abundant in the deeper water, which caused them to be more exposed to low oxygen levels than the younger ones. Instantaneous daily mortality rates (Z} were estimated by comparing the daily production of a given stage during the first survey with that of its corresponding stage during the second survey. For two cohorts the Z-values amounted to 0.314 and 0.322, respectively. An extrapolation for the entire incubation period leads to an overall egg mortality of 99.9 %.

Description: In this study, we evaluate whether it is possible to distinguish the effects of eutrophication from other, i.e. hydrographical, factors affecting zooplankton. We illustrate our arguments with examples from an old set of zooplankton data which includes 9-year records on mesozooplankton and hydrography collected from Seili, off the south coast of Finland. The present study shows that hydrographic changes override or mask, at least in the time period studied, possible eutrophication effects.

Description: Considerable amounts of nutrients enter as a result of human activity the Western Baltic Sea in the form of discharge or seepage from land or as atmospheric input. Benthic macrophytes which preferably inhabit the nutrient recipient shallow near-shore areas, and where they often constitute the major primary producers may thus play an important role in eutrophication processes by uptake and accumulation of nutrient elements, enhanced primary production and following degradation of the produced organic material. Nutrient uptake, binding capacity and limitation as well as nutrient dependent growth of the two community forming seaweeds Phycodrys rubens and Fucus vesiculosus have been investigated and related to the seasonal patterns of the nutrient conditions in their respective habitats. Nutrient concentrations, both phosphorus and nitrogen, in the algal beds are markedly higher than in the surface water of the open Kiel Bight. In general, the seaweeds seem not to be nutrient limited under natural conditions except for nitrogen in Phycodrys during summer. Nutrient tissue contents are saturated only for nitrogen during winter. The significance of these findings is discussed in view of the observed increasing nutrient levels and changes of the vegetation in the Kiel Bight.

Description: Hurricanes and other strong storms can cause important decreases in sea surface temperature by means of vertical mixing within the upper ocean, and by air–sea heat exchange. Here we use satellite-derived infrared images of the western North Atlantic to study sea surface cooling caused by hurricane Gloria (1985). Significant regional variations in sea surface cooling are well correlated with hydrographic conditions. The greatest cooling (up to 5°C) occurred in slope waters north of the Gulf Stream where the seasonal thermocline is shallowest and most compressed; moderate cooling (up to 3 °C) occurred in the open Sargasso Sea where the thermocline is deeper and more diffused; little or no cooling occurred in shallow coastal waters (bottom depth less than 20 m) which were isothermal before the passage of hurricane Gloria. There is a pronounced right-side asymmetry of sea surface cooling with stronger (by a factor of 4) and more extensive (by a factor of 3) cooling found on the right side of the hurricane track. These qualitative results are consistent with the notion that vertical mixing within the upper ocean is the dominant sea surface cooling mechanism of hurricanes.

Description: There is now clear evidence that changes in the Earth's climate may be sudden rather than gradual. It is time to put research into the build-up of carbon dioxide in the atmosphere on a better footing.