Diversity and abundance of “Pelagibacterales” (SAR11) in the Baltic Sea salinity gradient

The candidate order “Pelagibacterales” (SAR11) is one of the most abundant bacterial orders in ocean surface waters and, periodically, in freshwater lakes. The presence of several stable phylogenetic lineages comprising “Pelagibacterales” correlates with the physico-chemical parameters in aquatic environments. A previous amplicon sequencing study covering the bacterial community in the salinity gradient of the Baltic Sea suggested that pelagibacteral subclade SAR11-I was replaced by SAR11-IIIa in the mesohaline region of the Baltic Sea. In this current study, we investigated the cellular abundances of “Pelagibacterales” subclades along the Baltic Sea salinity gradient using catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH). The results obtained with a newly designed probe, which exclusively detected SAR11-IIIa, were compared to CARD-FISH abundances of the marine SAR11-I/II subclade and the freshwater lineage SAR11-IIIb (LD12). The results showed that SAR11-IIIa was abundant in oligohaline–mesohaline conditions (salinities 2.7–13.3), with maximal abundances at a salinity of 7 (up to 35% of total Bacteria, quantified with a universal bacterial probe EUB). As expected, SAR11-I/II was abundant (27% of EUB) in the marine parts of the Baltic Sea, whereas counts of the freshwater lineage SAR11-IIIb were below the detection limit at all stations. The shift from SAR11-IIIa to SAR11-I/II was confirmed in the vertical salinity gradient in the deeper basins of the Baltic Sea. These findings were consistent with an overlapping but defined distribution of SAR11-I/II and SAR11-IIIa in the salinity gradient of the Baltic Sea and suggested the adaptation of SAR11-IIIa for growth and survival in mesohaline conditions.     

A metabarcoding analysis of the wrackbed microbiome indicates a phylogeographic break along the North Sea–Baltic Sea transition zone

Sandy beaches are biogeochemical hotspots that bridge marine and terrestrial ecosystems via the transfer of organic matter, such as seaweed (termed wrack). A keystone of this unique ecosystem is the microbial community, which helps to degrade wrack and re-mineralize nutrients. However, little is known about this community. Here, we characterize the wrackbed microbiome as well as the microbiome of a primary consumer, the seaweed fly Coelopa frigida, and examine how they change along one of the most studied ecological gradients in the world, the transition from the marine North Sea to the brackish Baltic Sea. We found that polysaccharide degraders dominated both microbiomes, but there were still consistent differences between wrackbed and fly samples. Furthermore, we observed a shift in both microbial communities and functionality between the North and Baltic Sea driven by changes in the frequency of different groups of known polysaccharide degraders. We hypothesize that microbes were selected for their abilities to degrade different polysaccharides corresponding to a shift in polysaccharide content in the different seaweed communities. Our results reveal the complexities of both the wrackbed microbial community, with different groups specialized to different roles, and the cascading trophic consequences of shifts in the near shore algal community.     

Isolation and characterization of phage–host systems from the Baltic Sea ice

In search for sea ice bacteria and their phages from the Baltic Sea ice, two ice samples were collected from land-fast ice in a south-west Finland coastal site in February and March 2011. Bacteria were isolated from the melted sea ice samples and phages were screened from the same samples for 43 purified isolates. Plaque-producing phages were found for 15 bacterial isolates at 3 °C. Ten phage isolates were successfully plaque purified and eight of them were chosen for particle purification to analyze their morphology and structural proteins. Phage 1/32 infecting an isolate affiliated to phylum Bacteroidetes (Flavobacterium sp.) is a siphovirus and six phages infecting isolates affiliated to γ-Proteobacteria (Shewanella sp.) hosts were myoviruses. Cross titrations between the hosts showed that all studied phages are host specific. Phage solutions, host growth and phage infection were tested in different temperatures revealing phage temperature tolerance up to 45 °C, whereas phage infection was in most of the cases retarded above 15 °C. This study is the first to report isolation and cultivation of ice bacteria and cold-active phages from the Baltic Sea ice.     

Estimating Competition between Wildlife and Humans–A Case of Cormorants and Coastal Fisheries in the Baltic Sea

Cormorants and other wildlife populations have come in real or perceived conflicts with humans over exploited fish stocks. From gut contents of cormorants, and using an extension of the Catch equation, we estimated the degree of short term competition between great cormorants and coastal fisheries in two areas along the Swedish Baltic Sea. Cormorants consumed 10 and 44%, in respective area, of the fish biomass of six fish species harvested by humans; eel, flounder, herring, perch, pike, and whitefish. On average, cormorants consumed smaller individuals than harvested in fisheries. But for perch, cod and flounder, cormorants consumed harvestable sized fish corresponding >20% of human catches. Our competition model estimated the direct decrease in fisheries catches due to cormorant predation to be <10% for all species except flounder (>30%) and perch (2–20%). When also including the indirect effects of cormorant predation on smaller fish that never reached harvestable size, the estimated decrease in fisheries catches at least doubled for perch (13–34%) and pike (8–19%). Despite large uncertainties, our model indicates that cormorants may locally have a direct impact on human catches of at least flounder, and when incorporating indirect effects also on perch and pike. The study indicates that the degree of competition between cormorants and humans varies substantially between areas. We also included economical values in the model and concluded that for the commercially most important species, eel and cod, the estimated economic impact of cormorants on fisheries was low.     

Degradation of Crude Oil and PAHs in Iron–Manganese Concretions and Sediment from the Northern Baltic Sea

The ability of different sea bottom types to recover from oil contamination under oxic and anoxic conditions is poorly known in the brackish Baltic Sea. We carried out microcosm experiments to examine the capacity of iron–manganese concretions and sediment to remove petroleum compounds at 10°C. The biological degradation potential of polycyclic aromatic hydrocarbons (PAHs) was indicated by the 1000-fold increase in the copy numbers of PAH-degradation genes resulting in 2.2 × 10⁶ gene copies g^?1 DW. In the experiments 35?81% of the crude oil and 96% of PAHs disappeared through abiotic and biotic pathways, and there was little difference between the concretions and sediment. Bacterial community analysis revealed that the bacterial sequences obtained from the oil-treated concretions were affiliated to groups typical for concretions and metal-rich environments, whereas oil-treated sediment sequences were similar to those originating from sediments and oil-contaminated environments. The high frequency of concretion clones affiliated with specific taxonomic groups of α-, β-, γ-, and δ-proteobacteria may indicate the existence of new clades of bacteria within the Rhizobiales and Rhodospirillales of the α-proteobacteria, Burkholderiales—incertae sedis of the β-proteobacteria, Chromatiales of the γ-proteobacteria and the Syntrophobacteriales of the δ-proteobacteria. Our study suggests that concretions and bottom sediment maintain rich, distinct bacterial communities under oil exposure that have the potential to remove petroleum compounds in oxic and anoxic conditions.     

Nitrogen budgets of the Polish agriculture 1960–2000: implications for riverine nitrogen loads to the Baltic Sea from transitional countries

The Oder and the Vistula rivers are responsible for about 25% of the total riverine nitrogen input to the Baltic Sea and of this 60% have been estimated to originate from diffuse sources. In this study we have tested the hypothesis that changes in agricultural practices in Poland have changed the riverine nitrogen export from the rivers Oder and Vistula to the Baltic Sea. We calculated agricultural long-term nitrogen budgets (1960–2000) for the catchments of the Oder and the Vistula rivers. Poland went through severe economical changes in the early 1990s, which led to a drastic decrease in fertilizer consumption. The role of the calculated nitrogen surplus as an eutrophication capacitor and the potential to reduce this important capacitor to improve the environmental state of the Baltic Sea is discussed. N surplus for the entire country showed a maximum in 1980 (58 kg ha⁻¹ sown area⁻¹) and it dropped to 39 kg ha⁻¹ sown area⁻¹ in 2000. The surplus was, however, up to two times lower than that in other transitional countries, and much lower than in Western Europe with intensive agriculture. An observed decrease in nitrogen concentrations in both Polish rivers is not ascribed to drop in fertilizer use, but it results from nutrient removal in municipal wastewater treatment plants with tertiary treatment facilities. Comparison of trends in nitrogen concentrations in different transition countries indicates that factors other than reduced fertilizer application influenced the inertia of the water quality response. Hence, the potential to reduce diffuse nitrogen emissions from agriculture by reducing fertilization is constricted in areas with low-nitrogen surplus. In transitional countries like Poland the largest potential for nutrient reductions seem to be in improving the connectivity to waste water treatment plants with tertiary treatment.     

Ecosystem based modeling and indication of ecological integrity in the German North Sea—Case study offshore wind parks

Human exploitation and use of marine and coastal areas are apparent and growing in many regions of the world. For instance, fishery, shipping, military, raw material exploitation, nature protection and the rapidly expanding offshore wind power technology are competing for limited resources and space. The development and implementation of Integrated Coastal Zone Management (ICZM) strategies could help to solve these problems. Therefore, suitable spatial assessment, modeling, planning and management tools are urgently needed. These tools have to deal with data that include complex information on different spatial and temporal scales. A systematic approach based on the development of future scenarios which are assessed by combining different simulation models, GIS methods and an integrating set of ecological integrity indicators, was applied in a case study in the German North Sea. Here, the installation of huge offshore wind parks within the near future is planned. The aim was to model environmental effects of altered sea-use patterns on marine biota. Indicators of ecological integrity were used to assess altering conditions and possible ecosystem shifts ranging from systems’ degradations to the development of highly productive and diverse artificial reef systems. The results showed that some ecosystem processes and properties and related indicators are sensitive to changes generated by offshore wind park installations while others did not react as hypothesized.     

Isotopic evidence of environmental changes during the Devonian–Carboniferous transition in South China and its implications for the biotic crisis

The Devonian–Carboniferous (D–C) transition coincides with the Hangenberg Crisis, carbon isotope anomalies, and the enhanced preservation of organic matter associated with marine redox fluctuations. The proposed driving factors for the biotic extinction include variations in the eustatic sea level, paleoclimate fluctuation, climatic conditions, redox conditions, and the configuration of ocean basins. To investigate this phenomenon and obtain information on the paleo-ocean environment of different depositional facies, we studied a shallow-water carbonate section developed in the periplatform slope facies on the southern margin of South China, which includes a well-preserved succession spanning the D–C boundary. The integrated chemostratigraphic trends reveal distinct excursions in the isotopic compositions of bulk nitrogen, carbonate carbon, organic carbon, and total sulfur. A distinct negative δ¹⁵N excursion (~−3.1‰) is recorded throughout the Middle Si. praesulcata Zone and the Upper Si. praesulcata Zone, when the Hangenberg mass extinction occurred. We attribute the nitrogen cycle anomaly to enhanced microbial nitrogen fixation, which was likely a consequence of intensified seawater anoxia associated with increased denitrification, as well as upwelling of anoxic ammonium-bearing waters. Negative excursions in the δ¹³C_carb and δ¹³C_org values were identified in the Middle Si. praesulcata Zone and likely resulted from intense deep ocean upwelling that amplified nutrient fluxes and delivered ¹³C-depleted anoxic water masses. Decreased δ³⁴S values during the Middle Si. praesulcata Zone suggests an increasing contribution of water-column sulfate reduction under euxinic conditions. Contributions of organic matter produced by anaerobic metabolisms to the deposition of shallow carbonate in the Upper Si. praesulcata Zone is recorded by the nadir of δ¹³C_org values associated with maximal △¹³C. The integrated δ¹⁵N-δ¹³C-δ³⁴S data suggest that significant ocean-redox variation was recorded in South China during the D–C transition; and that this prominent fluctuation was likely associated with intense upwelling of deep anoxic waters. The temporal synchrony between the development of euxinia/anoxia and the Hangenberg Event indicates that the redox oscillation was a key factor triggering manifestations of the biodiversity crisis.     

Distribution of denitrifying bacterial communities in the stratified water column and sediment–water interface in two freshwater lakes and the Baltic Sea

We have studied the distribution and community composition of denitrifying bacteria in the stratified water column and at the sediment–water interface in lakes Plußsee and Schöhsee, and a near-shore site in the Baltic Sea in Germany. Although environmental changes induced by the stratification of the water column in marine environments are known to affect specific populations of denitrifying bacteria, little information is available for stratified freshwater lakes and brackish water. The aim of the present study was to fill this gap and to demonstrate specific distribution patterns of denitrifying bacteria in specific aquatic habitats using two functional markers for the nitrite reductase (nirK and nirS genes) as a proxy for the communities. The leading question to be answered was whether communities containing the genes nirK and nirS have similar, identical, or different distribution patterns, and occupy the same or different ecological niches. The genes nirK and nirS were analyzed by PCR amplification with specific primers followed by terminal restriction fragment length polymorphism (T-RFLP) and by cloning and sequence analysis. Overall, nirS-denitrifiers were more diverse than nirK-denitrifiers. Denitrifying communities in sediments were clearly different from those in the water column in all aquatic systems, regardless of the gene analyzed. A differential distribution of denitrifying assemblages was observed for each particular site. In the Baltic Sea and Lake Plußsee, nirK-denitrifiers were more diverse throughout the water column, while nirS-denitrifiers were more diverse in the sediment. In Lake Schöhsee, nirS-denitrifiers showed high diversity across the whole water body. Habitat-specific clusters of nirS sequences were observed for the freshwater lakes, while nirK sequences from both freshwater lakes and the Baltic Sea were found in common phylogenetic clusters. These results demonstrated differences in the distribution of bacteria containing nirS and those containing nirK indicating that both types of denitrifiers apparently occupy different ecological niches.     

Biological monitoring of fish and crustaceans in the Wadden Sea — potential and problems

Monitoring of fish and crustaceans in the Wadden Sea (WS) must cope with rapid changes in distribution patterns, access to certain areas and gear efficiency. Application and limitations of a variety of fishing devices (fyke nets, gill nets, enclosures, stow nets, purse seines, beam trawls, push nets, beach seines, bottom trawls, pelagic trawls) are discussed with regard to different objectives of monitoring. Furthermore, the validity of data from three current monitoring programmes is also discussed. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988)     

Planktic foraminifera from the mid-Cretaceous (Barremian–Early Albian) of the North Sea Basin: Palaeoecological and palaeoceanographic implications

A marine Cretaceous succession (Barremian–Albian) of a cored borehole (BGS 81/40), located in the Central North Sea Basin, has been examined with respect to its planktic and benthic foraminiferal content, as well as for calcareous nannofossils. The distribution patterns of foraminifera and calcareous nannofossils allow for a two fold division of the investigated interval. (1) The Barremian–earliest Aptian interval, which reflects a marine, temporary restricted setting. This is indicated by sporadic occurrences of planktic foraminifera with very rare planispiral forms suggesting short-term connections of the Boreal and Tethyan Realms. The benthic foraminiferal assemblages indicate aerobic, sometimes dysaerobic bottom-water conditions. High abundances of nannoconids in the Barremian suggest enhanced stratification and/or warm, oligotrophic surface water. (2) The late Aptian–early Albian interval, which was characterised by an open-oceanic environment with cool and aerobic surface water conditions. Planktic foraminifera are more abundant and diverse than in the lower interval. Trochospiral hedbergellids dominate the foraminiferal assemblages. The episodic occurrences of planispiral, clavate and trochospiral-flattened planktic morphotypes indicate the existence of a seaway between the Boreal and the Tethyan Realms. Aerobic to dysaerobic bottom-water conditions are suggested by the composition of the benthic foraminiferal assemblages. High abundances of cool-water taxa within the calcareous nannofossil assemblages indicate a cooling trend across the latest Aptian and earliest Albian.     

Measurement of δ15N in macroalgae stored in an environmental specimen bank for regional scale monitoring of eutrophication in coastal areas

The use of stored samples of macroalgae (Fucus ceranoides, Fucus spiralis and Fucus vesiculosus) to monitor contamination of coastal areas was evaluated. The samples, collected from sampling sites (SS) along the entire coast of Galicia (NW Spain) in 5 sampling surveys carried out between 1990 and 2007, were stored in an Environmental Specimen Bank (ESB). The δ¹⁵N was measured in the macroalgal tissues as an indicator of eutrophication. A decrease in δ¹⁵N (p < 0.05) was observed in all species (except for F. vesiculosus in 2007) in successive surveys. δ¹⁵N values were higher in macroalgae from interior zones of the estuaries than in macroalgae collected from the open sea. The method was sensitive enough to detect variations in δ¹⁵N signatures and SS with anomalous values, and to compare trends in contamination on a regional scale. The method is therefore a useful tool for the establishment of environmental improvement programmes (e.g. European Framework Directives) and monitoring surveys.     

Plant–soil relationships in fragments of Mediterranean snow-beds: ecological and conservation implications

We investigated the spatial structures of soil properties and snow-bed vegetation, and their relationships, in southern Italy. We analyzed data on 26 plant species and 10 soil traits from adjacent 1 × 1 m plots in two snow-bed patches. Measures of spatial autocorrelation revealed striking spatial structures for plant cover and soil properties at both sites. Bivariate statistics and Mantel tests highlighted a significant correlation between spatial patterns of plants and soil in the study sites. Canonical correspondence analysis related such relationships to an ecological gradient connecting soil properties and plant assemblages in this unusual ecological context. Among the variables significantly related to plant patterns is the soil organic matter, which is recognized as being sensitive to global warming. Our analyses suggest that soil dynamics due to increasing temperature may promote the replacement of species typical of southern snow-bed ecosystems by more mesophilous plants.     

The ecological role of moss in a polar desert: implications for aboveground–belowground and terrestrial–aquatic linkages

The McMurdo Dry Valleys of Antarctica is one of the coldest and driest habitats on the planet. As vascular plants are absent in this region, moss is the main form of aboveground primary production with a potentially important contribution to biogeochemical cycling, yet little is known about their ecological role. To determine the relationship between moss and soil properties relevant to biogeochemistry, we sampled both from a variety of locations in the Dry Valleys. Moss presence was compared to soil properties, and we measured the plasticity of moss stoichiometry (C:N:P) across gradients in nutrient availability. Results demonstrate that many soil properties significantly differed with moss presence, particularly conductivity and pH, but there is no strong evidence that this is caused by the moss presence and not the conditions inherent to the microsites where moss was found. There is great variability in moss stoichiometry, with some significant differences between sites, but generally variability within sites is larger than variation among sites. Results suggest that the main source of moss nutrients is from the soil, rather than water, but correlations with any one nutrient source are weak, suggesting a great deal of plasticity in moss stoichiometry and nutrient uptake.     

Effects of temperature on egg and larval survival of cod (Gadus morhua) and sprat (Sprattus sprattus) in the Baltic Sea – implications for stock development

Hydrobiologia - Stock development of cod and sprat, two major fish species in the Baltic Sea, is linked by trophic interactions. Depending on recruitment success the Baltic may be pushed towards...     

Iron–Manganese Concretions Sustaining Microbial Life in the Baltic Sea: The Structure of the Bacterial Community and Enrichments in Metal-Oxidizing Conditions

The abundant deposits of spherical iron-manganese concretions in the Gulf of Finland are colonized by bacteria in vast numbers. Communities on the surface and in the porous interior have formed two separate clusters, in accordance with their genetic differences. The overall bacterial community in the concretions was highly diverse, representing 12 phyla. Half of the bacteria were affiliated with the most common classes of Proteobacteria, while a third of the bacteria were unclassified. Cloned 16S rRNA-gene sequences of the concretion bacteria showed high scores for similarity to the sequences obtained from sea sediments, metal-rich environments, and ocean crust. The clone library of native concretions was not dominated by known Fe- and Mn-oxidizing species. Known Mn-oxidizing bacteria Sphingomonas, Pseudomonas, and Bacillus were enriched in experiments with Mn²⁺-containing liquid media, whereas Prosthecobacter (Verrucomicrobia) and Rheinheimera were enriched in semisolid media possibly better simulating the natural conditions in the concretions. In a corresponding experiment, the Fe²⁺-oxygen gradient favored the enrichment of Shewanella baltica and Thalassolituus oleivorans, which are known to reduce Fe and to degrade petroleum hydrocarbons, respectively. An individual spherical concretion forms a microcosm for a diverse microbial community having potential to oxidize Fe and Mn as shown in cultivation experiments. Therefore, bacteria may significantly affect the formation of the concretions in the Gulf of Finland.     

Production characteristics of bacteria and phytoplankton in the Sea of Okhotsk and Bering Sea during spring–summer

Production parameters for bacterioplankton were assessed during the spring–summer period in the western parts of the Sea of Okhotsk and the Bering Sea, as well as in northwestern Pacific Ocean. The lowest values of bacterial production were observed in early June during the spring phytoplankton bloom (0.08 mg C day^–1 m^–3), while the maximum values (up to 55 mg C day^–1 m^–3) occurred in late July?early August, 1.5 to 2 months after the bloom. The concentration of dissolved organic matter, the substrate for bacterioplankton, was assessed using satellite data. The ratio between bacterial and primary production in the surface samples varied from 0.5% at the peak of phytoplankton bloom to 180% at the peak of bacterioplankton development.