ALBERT

Description: Effects of elevated temperature on the formation and subsequent degradation of diatom aggregates were studied in a laboratory experiment with a natural plankton community from the Kiel Fjord (Baltic Sea). Aggregates were derived from diatom blooms that developed in indoor mesocosms at 2.5 and 8.5 degrees C, corresponding to the 1993 to 2002 mean winter in situ temperature of the Western Baltic Sea and the projected sea surface temperature during winter in 2100, respectively. Formation and degradation of diatom aggregates at these 2 temperatures in the dark were promoted with roller tanks over a period of 11 d. Comparison of the 2 temperature settings revealed an enhanced aggregation potential of diatom cells at elevated temperature, which was likely induced by an increased concentration of transparent exopolymer particles (TEP). The enhanced aggregation potential led to a significantly higher proportion of particulate organic matter in aggregates at 8.5 degrees C. Moreover, the elevated temperature favoured the growth of bacteria, bacterial biomass production, and the activities of sugar- and protein-degrading extracellular enzymes in aggregates. Stimulating effects of rising temperature on growth and metabolism of the bacterial community resulted in an earlier onset of aggregate degradation and silica dissolution. Remineralization of carbon in aggregates at elevated temperature was partially compensated by the formation of carbon-rich TEP during dark incubation. Hence, our results suggest that increasing temperature will affect both formation and degradation of diatom aggregates. We conclude that the vertical export of organic matter through aggregates may change in the future, depending on the magnitude and vertical depth penetration of warming in the ocean.

Description: Models of multiple potentially limiting nutrients currently employ either multiplicative or threshold formulations, neither of which has a sound mechanistic explanation. Despite experimental evidence that lack of P severely constrains N assimilation, this mechanism has not been considered for constructing models of multi-nutrient limitation. We construct a phytoplankton optimal growth model linking C, chlorophyll (Chl), N, and P through a limitation chain in which P limits N assimilation, N limits photosynthesis and photosynthesis limits growth. The resulting formulation possesses characteristics of both multiplicative and threshold approaches and provides a mechanistic foundation for modelling multi-nutrient and light limitation of phytoplankton growth. The model compares well with experimental observations for a variety of unicellular phytoplankton species. It is suggested that the widely held view that N and P limitation act independently of each other is based on an invalid interpretation of experimental observations and that the transition from N to P limitation occurs over a wide range of colimitation rather than a sharply-defined transition point. If the species considered in this study are representative for marine phytoplankton, our model results indicate that most phytoplankton are colimited by N and P when inorganic N and P are simultaneously exhausted in the surface ocean. The model suggests that the close match between marine inorganic (Redfield) and phytoplankton N:P ratios results from optimal nutrient utilisation but does not indicate optimality of Redfield N:P.

Description: Generalist and opportunistic marine predators use flexible foraging behaviour to exploit prey bases that change in diversity and spatial and temporal distributions, Behavioural flexibility is constrained by characteristics Such as individual cognitive and physical capabilities, age, reproductive condition and central place foraging. To assess flexibility in the foraging tactics of a marine bird, we investigated the diets and foraging behaviour of the largest seabird predator in the North Atlantic Ocean. Northern gannets Sula bassana exploit abroad spectrum of pelagic prey that range in mass by more than 2 orders of magnitude, We investigated their foraging activity at their largest. offshore colony in the western Atlantic Ocean during 1998 to 2002, when they preyed primarily on shoals of spawning and post-spawning capelin Mallotus villosus, a small forage fish (similar to 15 g), and also on a much larger pelagic fish, post-smolt Atlantic salmon Salmo salar (similar to 200 g). Inter-annual dietary variation is associated with gannet and prey fish distributions. Landings of capelin at the colony by gannets were correlated with returns of larger foraging flocks from inshore, whereas landings of Atlantic salmon were associated with smaller flocks returning from offshore. Maximum foraging trip distances ranged from 20 to 200 km and averaged 57 +/- 12 (SE) km, consistent with distances to inshore capelin aggregations. When capelin abundance was low (in 2002), more gannets foraged offshore, preyed on large pelagic fishes (mostly Atlantic salmon) and exhibited the greatest dietary diversity. Though the Outbound portions of foraging trips were more sinuous than inbound routes, individual gannets exhibited general fidelity to foraging sites. These large avian predators used flexible foraging tactics to adjust to changing prey conditions and generate longer-term strategies to Lake advantage of diverse trophic interactions over a range of ocean ecosystems.

Description: Individual migratory schedules and wintering areas of northern gannets Morus bassanus were studied over 2 consecutive winters by deploying geolocation data loggers on breeding adults from the Bass Rock, UK. Northern gannets attended the breeding colony on Bass Rock until between 24 September and 16 October (median: 5 October). Afterwards, individual birds engaged in different migratory behaviour. Of the 22 birds tracked until at least December, 18% wintered in the North Sea and the English Channel, 27% in the Bay of Biscay and the Celtic Sea, 9% in the Mediterranean Sea and 45% off West Africa. Individual winter home ranges as measured by the 75% kernel density contours varied between 8 100 and 308 500 km(2) (mean = 134 000 km(2)). Several northern gannets migrated northwards from Bass Rock after leaving the colony for a stay of a few days to a few weeks, independent of whether they migrated to Africa or other southern areas later. Birds wintering off West Africa migrated to their wintering areas mostly within 3 to 5 wk, usually starting between early and late October. Most of these birds stayed off West Africa for a period of about 3 mo, where they remained in a relatively restricted area. Return migration was initiated between the end of January and mid-February, and took about as long as autumn migration. We conclude that individual gannets display very variable migratory behaviours, with discrete winter home ranges, and we infer that the migration habits of gannets may be changing in response to human impacts on marine ecosystems.

Description: We examined the influence of both season and hydrographic and meteorological factors on seabird abundance in the southern North Sea. Seabirds were counted from ships in a study area of 27.8 x 32.8 km on 407 d from 1990 to 2007. Two hydrographic and 5 meteorological parameters were taken from archived data. The relationships between bird abundance and abiotic parameters were investigated by generalised additive models for 3 distinct seasons. The species in the study area exhibited different seasonal patterns. While some species were present year-round, others occurred only at certain periods. Despite these substantial changes in abundances, the nature of the interactions between bird abundances and abiotic parameters did not vary much between seasons. All 5 meteorological and 2 hydrographic parameters significantly influenced the abundance of seabird species, though to a different degree. The single factors that most often had a significant influence in the single models were wind field, sea surface temperature anomaly, sea surface salinity anomaly and air pressure change. The quantitative composition of the seabird community differed significantly between onshore wind and offshore wind conditions. It is assumed that hydrographic parameters are relevant for the birds by determining their foraging habitats and that atmospheric parameters influence flight conditions during foraging and migration.

Description: Ecological stoichiometry can be a powerful tool to understand food web consequences of altered biogeochemical cycles as well as consequences of biodiversity loss on biogeochemistry and has proved to be a suitable framework to predict effects of consumers on the nutrient content of their prey. However, predictions from ecological stoichiometry have mainly been tested using single consumer species, whereas in most natural ecosystems several consumer species coexist. We conducted 2 outdoor mesocosm experiments with marine rock pool communities to test whether species richness and species combination of benthic invertebrates affected the nutrient content of periphyton. We independently manipulated 12 different consumer combinations ranging from 0 to 6 (2004) or 0 to 4 (2005) grazer species and measured the biomass and nutrient content of the algae. Grazers included 3 gastropods and 3 crustaceans. In 2005, we additionally analyzed animal nutrient content and N excretion rate. Algal biomass and C:N ratios decreased in the presence of grazers in both years, indicating that the remaining algae had higher internal N content. Also, both biomass (2004 and 2005) and C:N ratios (only 2004) decreased even further when grazer richness increased. In 2004, significant net diversity effects of grazer richness on periphyton C:N ratios indicated that periphyton N content under multispecies grazing could not be predicted from the effect of single species. In 2005, significant net diversity effects on C:N ratios were rare, but periphyton C:N ratios consistently decreased with increasing grazer excretion rate, indicating that higher nitrogen regeneration by grazers led to higher N incorporation by algae. The effects of species richness were mainly affected by the presence of one efficient grazer, the gastropod Littorina littorea. Our experiments indicate that non-additive intraguild interactions may qualitatively alter the stoichiometric effects of multispecies consumer assemblages.

Description: It is widely assumed that the production of secondary metabolites against grazing and fouling is costly for seaweeds in terms of metabolic energy and should therefore be reduced under conditions of resource limitation. Here we tested the hypothesis that anti-herbivore defenses and bioactivity against mussels in 4 brown seaweeds from northern-central Chile will be reduced when light is limited. In a 2 wk experiment, seaweeds were kept under different low-light conditions (~76 to 99% reduction of ambient sunlight) and grazing situations. Subsequently, we tested their anti-herbivore defense against a common amphipod grazer in feeding assays with living algal tissue and reconstituted food pellets. A standard test employing the production of byssus threads by mussels was furthermore used as an indicator for deterrents in crude algal extracts. All investigated seaweeds showed decreased growth under the stepwise light reduction. Lessonia nigrescens exhibited reduced defense ability under severe low-light conditions when living tissue was offered to the amphipod, probably caused by changes in the tissue structure or in nutritional traits. In Dictyota kunthii, L. trabeculata and Macrocystis integrifolia this effect was absent. None of the investigated seaweeds showed a clear effect of light reduction on chemically mediated defenses against the mesograzer and there was no effect of light limitation on the bioactivity against mussels. Thus, against general assumptions, chemical defense in the investigated seaweeds does not appear to be reduced under severe resource limitation. Results suggest that seaweeds may use different strategies of energy allocation to cope with low-light conditions.

Description: We describe an integrated database on European macrobenthic fauna, developed within the framework of the European Network of Excellence MarBEF, and the data and data integration exercise that provided its content. A total of 44 datasets including 465354 distribution records from soft-bottom macrobenthic species were uploaded into the relational MacroBen database, corresponding to 22897 sampled stations from all European seas, and 7203 valid taxa. All taxonomic names were linked to the European Register of Marine Species, which was used as the taxonomic reference to standardise spelling and harmonise synonymy. An interface was created, allowing the user to explore, subselect, export and analyse the data by calculating different indices. Although the sampling techniques and intended use of the datasets varied tremendously, the integrated database proved to be robust, and an important tool for studying and understanding large-scale long-term distributions and abundances of marine benthic life. Crucial in the process was the willingness and the positive data-sharing attitude of the different data contributors. Development of a data policy that is highly aware of sensitivities and ownership issues of data providers was essential in the creation of this goodwill.

Description: Deep-sea whale falls create sulfidic habits Supporting chemoautotrophic communities, but microbial processes underlying the formation Of Such habitats remain poorly evaluated. Microbial degradation processes (sulfate reduction, methanogenesis) and biogeochemical gradients were studied in a whale-fall habitat created by a 30 t whale carcass deployed at 1675 m depth for 6 to 7 yr on the California margin. A variety of measurements were conducted including photomosaicking, microsensor measurements, radio-tracer incubations and geochemical analyses. Sediments were Studied at different distances (0 to 9 in) from the whale fall. Highest microbial activities and steepest vertical geochemical gradients were found within 0.5 m of the whale fall, revealing ex situ sulfate reduction and in vitro methanogenesis rates of up to 717 and 99 mmol m(-2) d(-1), respectively. In sediments containing whale biomass, methanogenesis was equivalent to 20 to 30%, of sulfate reduction. During in vitro sediment studies, sulfide and methane were produced within days to weeks after addition of whale biomass, indicating that chemosynthesis is promoted at early stages of the whale fall. Total sulfide production from sediments within 0.5 m of the whale fall was 2.1 +/- 3 and 1.5 +/- 2.1 mol d(-1) in Years 6 and 7, respectively, of which similar to 200 mmol d(-1) were available as free sulfide. Sulfate reduction in bones was much lower, accounting for a total availability of similar to 10 mmol sulfide d(-1). Over periods of at least 7 yr, whale falls can create sulfidic conditions similar to other chemosynthetic habitats Such as cold seeps and hydrothermal vents.

Description: Latitudinal clines in species diversity in limnic and terrestrial habitats have been noted for well over a century and are consistent across many taxonomic groups. However, studies in marine systems over the past 2 to 3 decades have yielded equivocal results. We conducted initial analyses of the MarBEF (EU Network of Excellence for Marine Biodiversity and Ecosystem Function) database to test for trends in local and regional diversity over the latitudinal extent of European continental-shelf waters (36° to 81°N). Soft-sediment benthic macrofauna exhibit little evidence of a latitudinal cline in local (α-) diversity measures. Relationships with water depth were relatively strong and complex. Statistically significant latitudinal trends were small and positive, suggesting a modest increase in diversity with latitude once water-depth covariates were removed. These results are consistent regardless of whether subsets of the database were used, replicates were pooled, or component taxonomical groups were evaluated separately. Local and regional diversity measures were significantly and positively correlated. Scientific cooperation through data-sharing is a powerful tool with which to address fundamental ecological and evolutionary questions relating to large-scale patterns and processes.

Description: This study examines whether or not biogeographical and/or managerial divisions across the European seas can be validated using soft-bottom macrobenthic community data. The faunal groups used were: all macrobenthos groups, polychaetes, molluscs, crustaceans, echinoderms, sipunculans and the last 5 groups combined. In order to test the discriminating power of these groups, 3 criteria were used: (1) proximity, which refers to the expected closer faunal resemblance of adjacent areas relative to more distant ones; (2) randomness, which in the present context is a measure of the degree to which the inventories of the various sectors, provinces or regions may in each case be considered as a random sample of the inventory of the next largest province or region in a hierarchy of geographic scales; and (3) differentiation, which provides a measure of the uniqueness of the pattern. Results show that only polychaetes fulfill all 3 criteria and that the only marine biogeographic system supported by the analyses is the one proposed by Longhurst (1998). Energy fluxes and other interactions between the planktonic and benthic domains, acting over evolutionary time scales, can be associated with the multivariate pattern derived from the macrobenthos datasets. Third-stage multidimensional scaling ordination reveals that polychaetes produce a unique pattern when all systems are under consideration. Average island distance from the nearest coast, number of islands and the island surface area were the geographic variables best correlated with the community patterns produced by polychaetes. Biogeographic patterns suggest a vicariance model dominating over the founder-dispersal model except for the semi-closed regional seas, where a model substantially modified from the second option could be supported.

Description: Submarine mud volcanism represents an important. pathway for methane from deeper reservoirs to the surface, where it enters the benthic carbon cycle. To quantify overall methane release from the Captain Arutyunov mud volcano (CAMV) and to assess the contribution of macrobenthic seep organisms to the regulation of the benthic methane flux, we linked water column methane concentrations, seabed methane emission and pore water geochemistry to the spatial distribution of seep biota. Prominent organisms of the CAMV seep biota were 3 different species of frenulate tubeworms. Seabed methane emission ranged from 0.001 to 0.66 mmol m(-2) d(-1). Dense patches of tubeworms were associated with the lowest seabed methane emission. Elevated methane emission was associated with a sporadic distribution of tubeworms and the occurrence of numerous mud clasts. Despite the presence of a large subsurface methane reservoir, the estimated total methane release from CAMV was low (0.006 x 10(6) mol yr(-1)). In addition to direct methane consumption by Siboglinum poseidoni, the tubeworms likely contribute to the retention of methane carbon in the sediment by affecting bacterial communities in the proximity of the tubes. The siboglinids create new meso-scale habitats on the sediment Surface, increasing habitat heterogeneity and introducing niches for bacterial communities.

Description: Epibacterial communities on thalli of the algal species Fucus serratus, Fucus vesiculosus, Laminaria saccharina, Ulva compressa, Delesseria sanguinea and Phycodrys rubens were analysed using 16S ribosomal RNA gene-based DGGE. Individuals of all species were collected in the Kiel Fjord (Baltic Sea) and in the rocky intertidal of Helgoland (North Sea). DGGE gels as well as cluster and multidimensional scaling analysis based on the DGGE band patterns of the epibacterial community showed significant differences between the epibacterial communities on the investigated algal species both in the Baltic and North Seas. Epibacterial communities differed less between regions than between host species, and were more similar on closely related host species. Results give the first evidence for lineage-specific bacterial associations to algal thalli. Furthermore, the results suggest that these algal species may control their epibiotic bacterial communities.

Description: The cirrate octopod Stauroteuthis syrtensis is a mesopelagic species commonly collected in the North Atlantic. Individuals were observed at depths 〉600 m and typically within 100 m of the bottom in three ~900 m deep canyons indenting the southern edge of Georges Bank. When first sighted, most octopods were floating passively with their webbed arms gathered into a small ball. When disturbed, they expanded their webs to form a ‘balloon’ shape, swam slowly by sculling their fins, pulsed their webs like medusae and, in some cases, streamlined their arms and webs and moved away smoothly by rapidly sculling their fins. The bodies of 9 octopods comprised 92 to 95% water, with tissue containing 9 to 22% carbon (C) and 2 to 4% nitrogen (N). These values were similar to those reported for medusae and ctenophores. Oxygen (O2) consumption rates of 4.6 to 25.8 µmol O2 g–1 C h–1 were within ranges reported for medusae, ctenophores, and deep-water cephalopods. The stomachs of S. syrtensis, dissected immediately after capture, contained only the calanoid copepod Calanus finmarchicus. Calculations indicated that S. syrtensis need 1.3 to 30.1 ind. d–1 of C. finmarchicus to meet their measured metabolic demand. Excretion rates (0.3 to 12.4 µg NH4+ g–1 C h–1 and 0.06 to 4.83 µg PO43– g–1 C h–1) were at least an order of magnitude lower than rates reported for other octopods or gelatinous zooplankters. O:N ratios (11 to 366) suggested that S. syrtensis catabolized lipids, which may be supplied by C. finmarchicus. Vertical distribution, relatively torpid behavior and low metabolic rates characterized S. syrtensis as a benthopelagic and relatively passive predator on copepods.

Description: The North Pacific Ocean population of the neon flying squid Ommastrephes bartramii, which undertakes seasonal north–south migrations, consists of autumn and winter–spring spawning cohorts. We examined life history differences between the 2 cohorts in relation to the oceanographic environment. The differences could be explained by seasonal north–south movements of the following 2 oceanographic zones: (1) the optimum spawning zone defined by sea surface temperatures; and (2) the food-rich zone defined by the position of the transition zone chlorophyll front (TZCF). The 2 cohorts use the food-rich zone in different phases of their life cycles. The spawning grounds for the autumn cohort occur within the subtropical frontal zone (STFZ), characterized by enhanced productivity in winter due to its proximity to the TZCF, whereas the spawning grounds for the winter–spring cohort occur within the subtropical domain, which is less productive. As the TZCF shifts northward in spring, the autumn cohort continues to occur in the productive area north of the TZCF, whereas the winter–spring cohort remains in the less productive area to the south until it migrates into productive waters north of the TZCF in the summer or autumn. Consequently, the autumn cohort grows faster than the winter–spring cohort during the first half of its life cycle, whereas the winter–spring cohort grows faster during the second half. This growth pattern may be responsible for differing migration patterns; males of the autumn cohort do not have to migrate given their early fast growth in the STFZ, whereas those of the winter–spring cohort must migrate to the food-rich subarctic frontal zone to compensate for their slow growth. These biological and ecological differences between the 2 cohorts suggest flexibility of their life history response to oceanographic environments.

Description: Highly stratified marine ecosystems with dynamic features such as fronts or clines in salinity, temperature, or oxygen concentration challenge an individual’s ability to select suitable living conditions. Ultimately, environmental heterogeneity organizes the spatial distributions of populations and hence the spatial structure of the ecosystem. Our aim here is to present a method to resolve small-scale distribution on an individual level, as needed for the behaviorally-based prediction of habitat choice and limits. We focused on the small-scale vertical distribution of cod Gadus morhua L. in the Bornholm Basin, central Baltic Sea, during spawning time in 2 years with different vertical thermohaline and oxygen stratifications. Individual cod were identified by echotracking of real-time in situ hydroacoustic distribution data. In order to resolve and identify hydrographic preferences and limits, ambient parameters including temperature, salinity, and oxygen concentration as well as expected egg-survival probability were individually allocated to each fish. The vertical distribution of hydroacoustically identified fish was compared to data simultaneously recorded by data storage tags attached to cod. The results showed a clear influence of ambient salinity and oxygen concentration on the distribution pattern and distributional limitation of cod during spawning time, and also consistency of data storage tag-derived distribution patterns with those based on individual echotracking. We therefore consider this method to be a useful tool to analyze individual behavior and its implications for the population’s spatial distribution in stratified environments.

Description: Phytoplankton supply the base of the marine food web and drive the biogeochemical cycles of carbon and nutrients. Over much of the ocean, their growth is limited by their uptake of nitrogen (as nitrate), which has most commonly been described by the hyperbolic Michaelis-Menten (MM) equation. However, the lack of a theory to explain variations in MM constants has hindered our ability to predict the response of marine ecosystems to changes in environmental conditions. The MM equation fits data from short-term experiments well, but does not agree with steady-state experiments over wide ranges of nutrient concentrations. In contrast, the recently developed optimal uptake kinetics (OU) does agree with the latter and can also describe the observed pattern of MM half-saturation constants from field. experiments. OU kinetics explains the observed pattern of N uptake as the result of a general physiological trade-off between nutrient uptake capacity and affinity. The existence of a general trade-off would imply a relatively high degree of predictability in the response of nutrient uptake to changing nutrient concentrations and thus provide a basis for predicting effects of climate change on marine ecosystems and biogeochemical cycles.

Description: The effects of towed fishing gear on benthic fauna are under intense scrutiny and evidence is growing that trawling may significantly affect benthic communities in the North Sea. Most studies explore the current fauna or compare today’s situation with that of 2 or 3 decades ago, when North Sea-wide information on benthos and fishing became available. However, in the North Sea, extensive mechanised trawling began more than a century ago. This study compared historical and recent records in order to explore potential long-term links between changes in the epibenthos and fishing. Based on reconstructed species lists from museum specimens, we compared epibenthos data from 1902 to 1912 with those from 1982 to 1985 and 2000. We analysed changes in average taxonomic distinctness (AvTD), a biodiversity indicator, and changes in biogeographical species distributions. Landings data were collated for round- and flatfish caught in the northern, central and southern North Sea from 1906 to 2000 as proxies for total otter and beam trawl effort, respectively. These indicate that the southern and much of the central North Sea were fished intensively throughout the 20th century, whilst the northern North Sea was less exploited, especially in earlier decades; exploitation intensified markedly from the 1960s onwards. For epibenthos, the mean AvTD decreased significantly from the 1980s to 2000, when it was below expected values in 4 ICES rectangles, 3 of these located in heavily trawled areas. Biogeographical changes from the beginning to the end of the century occurred in 27 of 48 taxa. In 14 taxa, spatial presence was reduced by 50% or more, most notably in the southern and central North Sea; often these were long-lived, slow-growing species with vulnerable shells or tests. By contrast, 12 taxa doubled their spatial presence throughout the North Sea. Most biogeographical changes had happened by the 1980s. Given that other important environmental changes, including eutrophication and climate change, have gained importance mainly from the 1980s onwards, we have concluded that the changes in epibenthos observed since the beginning of the 20th century have resulted primarily from intensified fisheries.

Description: Physical and chemical properties of the water column, along with meteorological conditions were examined for their relationship with phytoplankton biomass in the Irminger Sea during late autumn and early winter. Data were collected during 2 cruises to the region in November and December 2001 and November 2002. Phytoplankton biomass was approximated by (chl a) concentrations within the water column. When examined during autumn and winter alone, the Irminger Sea was suitably described as one biogeochemical region responding to varying meteorological forcing. Hydrographic differences within the region were not observed to have a significant effect on phytoplankton growth during this period. Strong correlations with latitude were seen in chl a concentrations, physical conditions (including mixed layer depth) and meteorological forcing (including net heat flux). Variability in autumn/winter phytoplankton growth conditions appears to be driven by light limitation modulated by meteorological forcing. The temporal and spatial scales of locations sampled in 2001 represent a progression in the physical and biological conditions from late autumn to early winter. Along this ‘virtual transect’, a baseline value of approximately 0.1 mg m–3 is seen in the mean chl a concentrations within the mixed layer. We postulate that convection provides a mechanism for reduction of net losses of phytoplankton, by helping to keep phytoplankton within the mixed layer. Under such conditions, a deeper and therefore more accurate estimation of the critical depth would be valid. Evidence of the extended maintenance of phytoplankton within the mixed layer is presented in the form of the relative dominances of different phytoplankton groups.

Description: Bacteria were isolated seasonally from the Mediterranean sponges Chondrilla nucula and Petrosia ficiformis and screened for antibacterial activities. Selected isolates were taxonomically identified by 16S rRNA gene sequencing. A total of 416 different bacterial strains were isolated, 60 (14.4%) of which displayed variable degrees of antimicrobial activity. Of the bioactive strains, 58.3% were able to inhibit Staphylococcus aureus, 6.7% were active against Bacillus subtilis, 11.7% against both Enterococcus faecalis and Escherichia coli, 38.3% against Pseudoalteromonas atlantica and 33.3% against Pseudomonas elongata. 16S rRNA gene sequence analysis showed that 2 isolates, 1 from seawater samples and 1 from P. ficiformis, were most closely related to Bacillus subtilis (99% similarity) and that another isolate from P. ficiformis was most closely related to a previously described sponge-associated Alphaproteobacterium NW001 (98% similarity). Two isolates from C. nucula were most closely related to Brachybacterium paraconglomeratum (99% similarity) and Shewanella algae (89% similarity). The high percentage of bioactive isolates derived from the 2 sponges suggests that marine microorganisms, whether animal-associated or planktonic, are promising sources for drug discovery.

Description: We investigated connections between subtropical Atlantic climate variability, atmospheric conditions in the European Alpine region (45 to 47° N and 5 to 8° E) and the interannual variability of the thermal conditions in the largest body of freshwater in Western Europe (Lake Geneva). The long-term water temperature was related to climate variability by means of a multivariate regression model. Results revealed atmospheric connections that have been elusive so far, and showed that over the period from 1959 to 2000, summer thermal conditions in Lake Geneva appear tightly linked to the long-term variability of the subtropical Atlantic climate. The multivariate model revealed high skills and tight correlations, which suggest the possibility of assessing future thermal changes in Lake Geneva from the Atlantic climate variability. The implications of such climatic forcing on the functioning of the pelagic ecosystem in Lake Geneva were illustrated by analysing the long-term changes in abundance of the summer-dominant carnivorous cladocerans Bythotrephes longimanus and Leptodora kindtii during the period 1974 to 2000. Again, the multivariate model revealed high skills and excellent correlations between the interannual changes in abundance of these species and the variability of summer climate. Our approach provides a general understanding of the interrelations between large- and regional-scale climates, local environmental conditions and the ecological responses in Lake Geneva during summer, and is therefore applicable to other retrospective studies.

Description: Bimodal depth distribution patterns observed for sprat Sprattus sprattus larvae in previous field studies conducted in the deep basins of the Baltic Sea have led researchers to hypothesise that larval sprat condition was depth-dependent. We examined this hypothesis by measuring morphological, biochemical and otolith-based proxies for nutritional condition in sprat larvae collected in discrete 5 m depth intervals from the surface to the bottom in the central Bornholm Basin. Similar to earlier studies, larval sprat were most abundant in 2 depth strata (0 to 10 and 65 to 75 m). Their nutritional condition in surface and deep waters was not uniformly expressed by the different indices. For example, sprat larvae from 0 to 10 m could not be distinguished from conspecifics caught at 65 to 75 m by a long-latency condition proxy (otolith-based growth rates). Similarly, a medium-latency proxy (RNA:DNA) did not suggest differences in condition between the depths. However, short-latency proxies (protein:standard length and DNA:dry weight) supported the depth-dependent condition hypothesis. The lack of correspondence and pitfalls associated with the use and interpretation of multiple condition indices (e.g. the influences of temperature and body size) are discussed and recommendations to strengthen these various metrics are provided.

Description: The occurrence of the ctenophore Mnemiopsis leidyi as a new invasive species in the Baltic Sea and the potential consequences for fish stock recruitment was investigated in spring 2007. The study focused on the Bornholm Basin, which serves as the major spawning ground for cod and sprat, the commercially most important fish stocks in the Baltic. The distribution pattern of M. leidyi revealed a substantial overlap with cod eggs. The observed predation of M. leidyi on eggs has the potential to alter the recruitment success of cod, which is the top predator in the system and, thus, to change the Baltic food-web structure.

Description: We investigated the nutritional condition of larval fishes caught in daily ichthyoplankton hauls in the ‘Helgoland Roads’ (54°11.18’N and 07°54.00’E) from February to June 2004. We concentrated on larvae of dab Limanda limanda and lesser sandeel Ammodytes marinus in order to compare early life stages of iteroparous and nearly semelparous fish. We analysed length, weight and RNA:DNA ratios as a proxy for condition of the larvae. The relationship between larval nutritional condition and larval size provided an indication of condition-selective mortality due to a loss of larvae in poor condition from the larger size-classes. For the sandeel, larvae in good condition were present in all size-classes, whereas for the dab maximum larval condition increased with increasing size. Variability in both standard length and condition was high in the 2 species during their planktonic stage. Both species showed good nutritional condition in the early to mid portion of the recruitment period and declines in condition in late April. This was more pronounced in larval dab, which showed a higher dependency on feeding conditions than larval sandeel. Together, these findings indicate a more conservative strategy of early life stages of the nearly semelparous sandeel compared with the iteroparous dab.

Description: The present study quantifies the spatial heterogeneity of the environmental conditions associated with successful spawning by cod Gadus morhua in the Bornholm Basin. Quarterly means from 1989 to 2003 of the thickness of reproductive volume that enabled egg survival indicate that most favourable spawning conditions were located in the central area, inside the 80 m isobath. On average, spatial patterns were similar in the second and third quarters, but with overall lower thicknesses of reproductive volume and less horizontal extension of conditions suitable for egg survival in the third quarter. The observed basin-wide variation in thickness of reproductive volume and oxygen content inside this volume can result in marked horizontal differences in oxygen-related egg mortality, especially during stagnation years. The spawning habitat selected by adult Baltic cod in the Bornholm Basin was characterised by comparing data on egg abundance with environmental variables measured concurrently with egg collection. A clear preference for spawning at locations in the deep basin is evident after both inflow events, as well as for stagnation periods. In consequence, the closed area for fishing implemented in the Bornholm Basin during the main spawning periods from 1995 to 2003, although located in the northern centre of the basin, did not necessarily ensure undisturbed spawning in stagnation years.

Description: We monitored the dynamics of extracellular organic matter in 3 mesocosms: one dominated by a heterotrophic (microbial) community with negligible autotrophic activity (net heterotrophic system), a second where a small Phaeocystis bloom developed (production and loss almost balanced), and a third harboring a large diatom bloom (net autotrophic system). In all mesocosms, meso- and macroscopic heterotrophic organisms were excluded to primarily study extracellular organic matter production and turnover by specific algae and microbial loop organisms, respectively. Concentration and composition of dissolved organic matter (DOM), i.e. dissolved organic carbon (DOC), monosaccharides and total carbohydrates (MCHO and TCHO), free and combined neutral carbohydrates (DFCHO and DCCHO), as well as free and combined amino acids (DFAA and DCAA) were measured. In addition, net and gross community production rates were determined to calculate C-budgets. Whereas concentrations and composition of MCHO differed very little among the 3 mesocosms, dynamics of TCHO, DFCHO, and DCCHO differed significantly. Concentrations of DFAA were higher in both algal mesocosms compared to the heterotrophic system, and composition of DFAA was significantly different in the Phaeocystis and Diatom tanks. The composition and concentration of DCAA, however, were similar in all 3 mesocosms. Total dissolved carbohydrates and amino acids comprised a substantial fraction of the DOC pool. Dynamics of these DOC fractions, however, could only partly explain those of DOC, implying either that other dissolved compounds were important for overall C-cycling, or that microbial degradation of DOM affects the detection of carbohydrates and protein components.

Description: The effect of phytoplankton on the other compartments of a simple microbial loop consisting of dissolved matter, bacteria and nanoflagellates was investigated in three 1000 l mesocosms. These mesocosms were inoculated with a natural bacterial community and (1) no other additions (No Addition tank), (2) Phaeocystis globosa (Phaeocystis tank), or (3) 2 diatom species (Diatom tank). During the 20 d experiment, autotrophic activity was negligible in the No Addition tank. In contrast a small P. globosa bloom developed in the Phaeocystis tank and a large diatom bloom dominated the Diatom tank. In this paper we describe the experiment, the changes in chlorophyll a and heterotrophic nanoflagellate concentrations, as well as the cycling of nitrogen, phosphorus, and silica. Then we provide a synthesis of the structure and functioning of the microbial loops in these 3 systems using cluster analysis, a statistical pattern recognition tool. The goal was to test the hypothesis that differences in the resident phytoplankton populations would be reflected in (1) the composition and concentration of dissolved organic matter, (2) the composition of the bacterial community, (3) the food web, and (4) the cycling of elements and organic matter. In all 3 mesocosms, nitrate and silicic acid remained abundant. Orthophosphate was preferred by diatoms, whereas Phaeocystis appeared to prefer dissolved organic phosphorus. The hypothesis that phytoplankton composition shapes the structure and functioning of the microbial loop was partially supported: 6 d after inoculation each mesocosm exhibited a distinct organic matter signature. After 10 to 12 d, concentrations of heterotrophic nanoflagellates were high enough to exert significant grazing pressure in all 3 mesocosms. A parallel shift in bacterial community composition was visible in all mesocosms at this time, possibly reflecting grazing pressure. The food-web structure developed divergently in the 3 mesocosms during the second half of the experiment. Differences in biochemical cycling between mesocosms were predominantly driven by the large quantitative differences in autotrophs.

Description: We used data collected at 〉 60 stations over a 10 yr period to build the carbon budget of the plankton community in the euphotic layer of the Eastern North Atlantic Subtropical Gyre (NASE). Autotrophic biomass exceeded microbial heterotrophic biomass by a factor of 1.7. Mean ( SE), integrated chlorophyll a concentration and net particulate primary production (PP) were 17 +/- 1 Mg m(2) and 271 +/- 29 mg C m(-2) d(-1), respectively. Protist grazing on phytoplankton represented 〉 90% of PP. Bacterial production (BP) was 17 +/- 3 mg C m(-2) d(-1). In vitro O-2-evolution experiments indicated that net community production was -65 +/- 16 mmolO(2) m(-2) d(-1), while community respiration (CR) averaged 124 +/- 13 mmolO(2) m(-2) d-1, equivalent to 1324 +/- 142 mg C m(-2) d(-1). However, the sum of the respiration rates by each microbial group, estimated from their biomass and metabolic rates, ranged from 402 to 848 Mg C m(-2) d-1. Therefore, CR could not be reconciled with the respiratory fluxes sustained by each microbial group. Comparison between estimated gross photosynthesis by phytoplankton (481 to 616 mg C m(-2) d-1) and the sum of respiration by each group suggests that the microbial community in the NASE province is close to metabolic balance, which would agree with the observed O-2 supersaturation in the euphotic layer. Taking into account the mean open-ocean values for PP, BP, CR and bacterial growth efficiency, we show that bacteria account for approximately 20% of CR. Our results suggest that the view that bacteria dominate carbon cycling in the unproductive ocean must be reconsidered, or else that in vitro incubations misrepresent the real metabolic rates of one or several microbial groups.

Description: This study explores the date of first otolith increment formation in Baltic sprat Sprattus sprattus and relates the onset of maturity at Age 1 to the larval traits that are tied to the formation of the first increment. From the otolith microstructure analyses in larvae we found that regular deposition of increments is closely related to larval length, the first clear increment being identified at 16 mm length. Otolith distance from the centre to the first clear increment was independent of temperature, whereas the width of subsequent regular increments increased with increasing temperatures. These results are interpreted in the context of the interaction of larval length, somatic growth and environmental temperature. The date of first increment formation was further estimated in mature and immature Age 1 sprat caught from 1998 to 2000 using a technique that we developed, based on the effect of temperature on larval-stage otolith microstructure after first increment formation. The overall result was that larvae that reach the length of 16 mm early (late) in the season in warm years are more (less) likely to mature the following year. In cold years, like 1998, the probability of maturating at Age 1 was independent of the date at which larvae became 16 mm long, and other processes such as juvenile growth rates, feeding conditions and year-class abundance are suggested as factors that may influence the onset of maturity.

Description: Pronounced environmental trends across fronts suggest that the otolith chemistry of oceanic fish can resolve zones on either side, promoting application to population questions at similar spatial scales. Trace and minor elements laid down immediately prior to capture - along the edges of otoliths from Patagonian toothfish Dissostichus eleginoides - discriminated frontal zones in the Antarctic Circumpolar Current in the Southwestern Atlantic Ocean. Mean values differentiated sampling areas by up to 2.6 standard deviations, suggesting: (1) otolith Mg/Ca enrichment related to fish activity around the Burdwood Bank; (2) Mn/Ca enrichment associated with South America; (3) Sr/Ca linked to the presence of Circumpolar Deep Water; and (4) Ba/Ca to nutrient production and mixing. In the Polar Frontal Zone, meanders or eddies may account for affinities with neighbouring sampling areas, bringing water from the Subantarctic and Antarctic Zones onto the North Scotia Ridge. Moreover, fish age showed a significant relationship with depth and improved cross-validation by 14%, giving 85% classification rates to South American and Antarctic regions, and 57 to 83% to areas along the Patagonian Shelf. These results indicate that otolith chemistry reflects hydrography, detecting oceanic gradients across the slope of continental shelves and between zones separated by strong trends like fronts.

Description: Statoliths of the gonatid squid Gonatus fabricii from Disko Bay, West Greenland, were analysed by laser ablation inductively coupled plasma mass-spectrometry (LA-ICP-MS) to determine the concentrations and spatial distributions of 9 minor and trace elements (Sr, Ba, Mg, U, Zn, Mn, Y, Zr, Na). Element composition was assigned in situ to distinct statolith regions, corresponding to ontogenetic stages of an individual squid’s life. Significant variations in concentrations of all measured elements except Na were found between different regions of the statolith. Variations in Ba/Ca ratios suggest that juveniles inhabit surface waters, while larger specimens move to deeper waters. U/Ca and Sr/Ca ratios increased towards the outer statolith region, suggesting migration of adult squid into colder waters. Mg/Ca ratios decreased progressively from the core to the edge, most likely related to changes in protein concentrations in their microstructure during ontogenesis. This study is one of the first to apply LA-ICP-MS to cephalopod statoliths. Our results emphasise the strong potential of spatially resolved statolith analyses to gather information on life history, migrations and habitat use of cephalopods.

Description: We investigated the larval feeding ecology of sprat Sprattus sprattus L., an important commercial fish species in the Central Baltic Sea. We collected seasonally resolved larval abundance and gut content as well as zooplankton data, with the goal of identifying mechanisms leading to variability in larval survival. Our results show sprat larvae feed progressively on larger food items as they grow during the season depending on their size and the composition of the available prey. We found first-feeding larvae early in the spawning season to prey exclusively upon microplankton. Small larvae fed mainly upon nauplii of the copepods Acartia spp., Temora longicornis and Centropages hamatus (ca. 65%), whereas larger larvae consumed up to 80% Acartia spp. copepodites and adults, as well as cladocerans. Trends in sprat larval diets were to a large degree explainable by selective feeding. Feeding success and gut fullness increased linearly with larval size. Trophic niche breadth increased linearly until larvae reached a predator size of 16 mm, after which it decreased. We explain the latter decline by a restricted size spectrum of prey available to larger sprat larvae, which points towards the importance of considering the structure of the zooplankton community when evaluating the predator size to niche breadth relationship. Our results suggest first-feeding Baltic sprat larvae to be always food-limited, while larger larvae are not. We hypothesize medium-sized sprat larvae to be the life stage that has the potential to cause most of the interannual variability in sprat larval survival, which is dependent on a match between larval production and the state of the plankton cycle.

Description: Representatives of the phylum Bacteroidetes are repeatedly reported to be abundant members of oceanic bacterioplankton, probably because of their ability to degrade complex organic matter. 16S rDNA analysis was performed in order to address the importance of this phylum in a highly oligotrophic region such as the Eastern Mediterranean Sea and to investigate its distribution patterns and community composition. A new antisense primer was designed for PCR and used in combination with the general eubacterial sense primer 27F to specifically target Bacteroidetes representatives. Data were correlated with water depth and water mass properties. Denaturant gradient gel electrophoresis (DGGE) analysis and sequencing of environmental clone libraries revealed specific distribution patterns. A major fraction of the sequences was assigned to the AGG58 cluster, a branch of yet uncultured members of the Bacteroidetes lineage. Our results demonstrate a considerable diversity within the Bacteroidetes lineage in the oligotrophic Eastern Mediterranean Sea. Differing water mass properties are considered to be of major relevance for the spatial distribution with depth; several environmental clone sequence clusters could be specifically assigned to a defined water mass or to the deep waters of investigated locations. Depth-specific distribution of Bacteroidetes is demonstrated for the first time by the results of this study.

Description: The effect of methane seepage from sediments harbouring shallow gas hydrates on standing stocks and the distribution pattern of meiobenthic organisms, in particular Nematoda and Rotifera, was studied at about 800 m water depth at Hydrate Ridge, Cascadia subduction zone, off Oregon. The presence of shallow gas hydrates, buried only a few 10s of centimetres below the sediment surface, was indicated by extensive bacterial mats of chemosynthetic Beggiatoa sp. and clam fields of the bivalve mollusk Calyptogena spp. Mean abundances of meiobenthic organisms integrated over the upper 10 cm of the sediment were highest (1294 ind. 10 cm–2) at clam fields, closely followed by control sediments least affected by gas hydrates (1199 ind. 10 cm–2) and lowest in sediments covered with bacterial mats (762 ind. 10 cm–2). Average meiobenthic biomass was highest at the clam field site (262.2 µg C 10 cm–2), 210.4 µg C 10 cm–2 at the control site and very low in sediments covered with bacterial mats (61.4 µg C 10 cm–2). The dominant taxa of meiobenthic organisms at the investigated sites were nematodes and, unexpectedly, Rotifera that are almost unknown from the deep marine habitat. In terms of abundance, rotifera dominated the meiobenthic community in gas-hydrate-influenced sediments, while control sediments and deeper basins adjoined to Hydrate Ridge were dominated by nematodes. Nematodes were concentrated in the sediment surface at all sites, whereas rotifers were almost evenly distributed at all depths, with a slight preference for deeper sediment horizons. The horizontal as well as vertical distribution of nematodes and rotifers is likely to be determined by competition or predation, and by the high adaptive capability of rotifers to highly sulphidic and anoxic conditions. Estimates of meiobenthic carbon turnover in relation to the bulk organic carbon supply indicate that, in contrast to other meiobenthic communities in cold seep environments, the meiobenthos in the studied gas-hydrate-containing sediments do not benefit from the excess availability of organic carbon via the chemoautotrophic food web. This may be because, for most meiobenthic organisms (other than rotifers), tolerance mechanisms are overwhelmed by the deleterious environmental conditions of reduced oxygen availability and extremely high sulphide fluxes.

Description: Nitrification in aquatic sediments is catalyzed by bacteria. While many autecological studies on these bacteria have been published, few have regarded them as part of the benthic microbial food web. Ciliates are important as grazers on bacteria, but also for remineralization of organic matter. We tested the hypothesis that ciliates can affect nitrification. Experiments with Baltic Sea sediments in laboratory flumes, with or without the addition of cultured ciliates, were conducted. We found indication of a higher nitrification potential (ammonium oxidation) in one experiment and increased abundances of nitrifying bacteria in treatments with ciliates. This is likely due to higher nitrogen availability caused by excretion by ciliates and enhanced transport processes in the sediment.