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.     

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.     

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.     

Scenario simulations of future salinity and ecological consequences in the Baltic Sea and adjacent North Sea areas–implications for environmental monitoring

Substantial ecological changes occurred in the 1970s in the Northern Baltic during a temporary period of low salinity (S). This period was preceded by an episodic increase in the rainfall over the Baltic Sea watershed area. Several climate models, both global and regional, project an increase in the runoff of the Northern latitudes due to proceeding climate change. The aim of this study is to model, firstly, the effects on Baltic Sea salinity of increased runoff due to projected global change and, secondly, the effects of salinity change on the distribution of marine species. The results suggest a critical shift in the S range 5–7, which is a threshold for both freshwater and marine species distributions and diversity. We discuss several topics emphasizing future monitoring, modelling, and fisheries research. Environmental monitoring and modelling are investigated because the developing alternative ecosystems do not necessarily show the same relations to environment quality factors as the retiring ones. An important corollary is that the observed and modelled S changes considered together with species’ ranges indicate what may appear under a future climate. Consequences could include a shift in distribution areas of marine benthic foundation species and some 40–50 other species, affiliated to these. This change would extend over hundreds of kilometres, in the Baltic Sea and the adjacent North Sea areas. Potential cascading effects, in coastal ecology, fish ecology and fisheries would be extensive, and point out the necessity to develop further the “ecosystem approach in the environmental monitoring”.     

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.     

Vertical migration of autotrophic micro-organisms during a vernal bloom at the coastal Baltic Sea – coexistence through niche separation

Vertical migration of two dinoflagellate species (Peridiniellacatenata and Scrippsiella hangoei) and a phototrophic ciliate(Mesodinium rubrum) were studied during the peak and decline of avernal bloom at the SW coast of Finland. During the diel cycle, part of thepopulations of P. catenata and M. rubrum wereobserved in the deeper layers with elevated nutrient concentrations, whileS. hangoei remained in the upper nutrient depleted mixed layer.Using a correspondence analysis the vertical distribution patterns of thespecies and chlorophyll a were examined over a temporal scale of hoursand weeks. The vertical migration was reflected in much higher variabilityin the depth distribution of P. catenata and M. rubrum over a diel scale, compared to S. hangoei. The analysisrevealed also significant differences in species specific depth distributionpatterns over both time scales. It is discussed that the co-existence of thetwo dominant dinoflagellate species during the vernal bloom is due to nicheseparation through behavioural adaptations. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Summer-autumn ichthyoplankton of the Sea of Okhotsk and the Sea of Japan and special traits of feeding of fish larvae and fry in 2003–2004

In summer-autumn of 2003–2004, the ichthyoplankton of the Sea of Okhotsk comprised 35 species. In this period the most widely distributed and numerous were larvae of the lord Hemilepidotus gilberti, the Pacific stout sand lance Ammodytes hexapterus, and the Sakhalin dab Limanda sakhalinensis. The maximum catches of fish larvae were attributed to coastal waters off eastern Sakhalin and to the shelf of the northern part of the Sea of Okhotsk. In November of 2003, the ichthyoplankton of the Sea of Japan was represented by fish larvae belonging mainly to the boreal ichthyocomplex. The catches consisted predominantly of larvae of the arabesque greenling Pleurogrammus azonus, the ronquil Bathymaster derjugini, and the rockfish Sebastes owstoni. Fish larvae and fry in the northwestern part of the Sea of Japan were caught principally within 43°–45° N and 137°–139° E above the depth 1500–2000 m. The food spectrum of fish larvae in the Sea of Okhotsk and the Sea of Japan comprised over 20 plankters of various size belonging to seven taxa. Irrespective of fish species, the food items common of all fish were copepods Pseudocalanus minutus and Oithona similis. The daily rations were calculated for mass species (Hemilepidotus gilberti, Ammodytes hexapterus, Hexagrammos stelleri, Pleurogrammus azonus, Bathymaster derjugini, and Sebastes owstoni). The larvae of all considered species in the Sea of Japan and in the Sea of Okhotsk fed predominantly in the light period of the day.     

Distribution of Ichthyoplankton in Relation to Specifics of Hydrological Regime off the Crimean coast (the Black Sea) in the Spring–Summer Season 2017

Journal of Ichthyology - The paper presents characteristics of the species composition, spatial distribution, and trophic interactions of ichthyoplankton and zooplankton in the spring–summer...     

High-Antarctic regular sea urchins – the role of depth and feeding in niche separation

Regular sea urchins of the families Cidaridae and Echinidae are widespread and sympatrically occurring epibenthic species in Antarctic waters. Food preference and water depth distribution of the five most abundant species (Ctenocidaris gigantea, C. spinosa, Notocidaris mortenseni, Sterechinus antarcticus, S. neumayeri) were analysed based on trawl and photograph samples. Both diet and water depth contribute to niche separation among these species. All sea urchins consume bryozoans and sediment, but echinids feed predominantly on diatoms in the fluff, when available. Cidarids do not consume diatoms, most likely owing to morphological constraints; their typical food consists of sponges and hydroids. C. spinosa and S. neumayeri prefer shallow water depths, whereas N. mortenseni and S. antarcticus prefer deeper regions. C. gigantea is the most variable species regarding food composition and living depth.     

How does eutrophication affect different life stages of Fucus vesiculosus in the Baltic Sea? – a conceptual model

During the last few decades the perennial seaweed Fucus vesiculosus L. has rapidly declined in large parts of the Baltic Sea. Indirect effects of eutrophication, such as increased turbidity, sedimentation, grazing and occurrence of filamentous algae, have generally been suggested as major factors causing the decline. It is only recently, however, that the effects of these factors have been experimentally tested and here we summarise these results in a new conceptual model. In many areas, it might be desirable to enhance the recovery of Fucus artificially, as the natural rate of re-establishment of this important macroalga is limited both in time and space. To be able to optimise and evaluate the potential of restoring Fucus belts in eutrophicated areas, we need to know how eutrophication affects critical steps in its life cycle, such as the attachment, germination and early growth of germlings. We suggest that more attention should be given to the survival of early post-settlement stages in Fucusas they are crucial for the maintenance and re-establishment of populations. We also stress that the two reproductive periods that the species exhibits are included in discussions concerning effects of eutrophication on Fucus, as it is likely that the outcome of reproduction will differ between the two reproductive periods. In the new conceptual model we distinguish between the effects on adult and juvenile life stages and we add the two reproductive strategies of Fucus.     

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.     

Transport and accumulation of sediment and contaminants in the Lagoon of Kuršiųmarios (Lithuania) and Baltic Sea

In this paper an overview is given of earlier work on transport, deposition AND transformation of suspended matter, and contaminants (metals, hydrocarbons) in Lithuanian coastal waters as well as in other parts of the Baltic Sea. The Lithuanian river Nemunas dischargesc. 600.10⁶ kg suspended matter into the Kuršių Marios Lagoon annually, of which two thirds are accumulated in the lagoon. The remainder is exported to the Baltic Sea through the Klaipéda Strait influencing biological activity in the coastal zone. Sedimentation rate in Kuršių Marios Lagoon is estimated at 3.2 mm y⁻¹. In the last 50 years the surface area of the lagoon decreased by 0.7 km² y⁻¹. Concentration profiles of metals and hydrocarbons were measured in the Kuršių Marios Lagoon, the Baltic proper, and in the Gulf of Finland. Among hydrocarbons both anthropogenic and compounds from natural sources are present. It is argued that correct interpretation of concentration horizons in sediment may be hampered by various processes,e. g. early sedimentogenesis and diagenesis, and cyclic salinity changes in the Baltic Sea.     

Age and growth of the round goby Neogobius melanostomus in the Gulf of Gdańsk several years after invasion. Is the Baltic Sea a new Promised Land?

The ages of 8 to 23·5 cm total length (L(T)) round goby Neogobius melanostomus collected monthly during 2006 and 2007 in the Gulf of Gdańsk (Baltic Sea) ranged from 2 to 6 years, with age class 4+ years dominant. Males were larger at age than females. The fastest growth occurred in the first 2 years of life in both sexes. Females were heavier at a given L(T) than males, but only for fish > c. 15 cm. A strong relationship between N. melanostomus otolith size and fish size was found, with no difference between males and females, and a significant relationship between fish growth rate and otolith growth rate, which enabled backcalculation of growth rates. Marginal increment width analysis confirmed the periodicity of annual ring formation in otoliths and showed that the most intense opaque zone formation occurs in July to August, while hyaline zone formation starts as early as September to October. It was concluded that the N. melanostomus that have colonized the southern Baltic Sea exhibit the largest size and longest life span ever recorded for this species.     

The extensive bloom of alternate-stage Prymnesium polylepis (Haptophyta) in the Baltic Sea during autumn–spring 2007–2008

During autumn 2007, an unusual increase in an algal species belonging to the order Prymnesiales was observed throughout the Baltic Sea Proper during routine national monitoring. Electron microscopical examination of the blooming species showed two types of flat scales – small and large – that resembled those of the alternate stage of Prymnesium polylepis. No spine-bearing scales were found. The 18S rDNA sequence data (n?=?20, c. 1500?bp) verified the species identification as P. polylepis. There was up to 0.5% (7?bp) variability in the P. polylepis partial 18?S rDNA sequences from the Baltic Sea. These environmental sequences differed by 0–0.35% (0–4?bp) from cultured P. polylepis (isolate UIO036), and by 1.0–3.7% from other available Prymnesium sequences. The number of cells assumed to be P. polylepis began to increase in October 2007 coincidently with significantly calm and dry weather, and at their maximum the cells accounted for over 80% of the total phytoplankton biovolume in December–January. During February–April 2008, 95% of the Prymnesiales cells were in the size class of P. polylepis (>6?µm). The species attained bloom concentrations (>1?×?10⁶?cells?l^–1) from March to May 2008. The species was observed throughout the Baltic Sea, except the Bothnian Bay, Gulf of Riga and the Kattegat. No toxic effects of the bloom were observed.     

The round goby (Neogobius melanostomus) in the Gulf of Gdańsk – a species introduction into the Baltic Sea

In recent years, information concerning the awareness of organisms accidentally introduced into the Baltic Sea has substantially improved. Non-indigenous Estuarine and Marine Organisms (NEMO's) are hazardous for the Baltic ecosystem. Currently, about one hundred species are identified as accidentally or intentionally introduced into the Baltic Sea. Ballast waters and escape from aquaculture are the most important invasion vectors. During the last decade, an invasion of the round goby (Neogobius melanostomus) – a Ponto-Caspian fish species has been observed in the Gulf of Gdańsk. The first record of this fish in the Baltic Sea is from 1990. Early detection of the invader enabled the study of population growth and changes in the area. The first years of invasion were characterized by low numbers of individuals and a limited distribution. Later, the round goby gradually colonized all shallow waters in the western part of the Gulf of Gdańsk. Initially the fish inhabited stony and rocky habitats, but later it also occupied sandy bottoms. The round goby is now the dominating fish species in most of the shallow waters of the Gulf of Gdańsk. Two main factors account for the successful invasion of this fish in the region: the state of ecosystem at the time of the invasion and the biological features of N. melanostomus. In the late 1980s, the shallow waters of the Gulf of Gdańsk were almost devoid of piscivorous fishes. Concurrently, bivalves (a preferred prey of the round goby) have increased. Important is also parental care of laid eggs and reproductive strategy. Population growth potential enables the colonization of nearby regions. The first round gobies in the Vistula Lagoon were collected in 1999 and colonization of other Baltic Sea areas is anticipated.     

Mortality of Herring Eggs on Different Algal Substrates (Furcellaria spp. and Cladophora spp.) in the Baltic Sea – An Experimental Study

In the Baltic Sea, herring (Clupea harengus membras) spawns in the littoral zone, where its eggs are attached to algae or vascular plants. Field studies indicate that egg mortality can be very high (up to 100%) in eggs that are attached to red algae (Rajasilta et al., 1989, 1993). Because high mortality can be due to allelochemical effects of the algae, we studied the mortality of herring eggs on different algal substrates experimentally. Four types of substrates were tested: fresh Cladophora and Furcellaria, and Furcellaria that had decomposed six days or 23 days. The incubation time in the experiments was 3 days and incubation temperature 12–13 ^oC (ca. 700–800 h-degrees). The results were in accordance with observations made in field studies and indicated significant differences among the substrate types. In eggs attached to fresh Cladophora, mortality was significantly lower (mean=2.8%; n=20) than in those attached to Furcellaria, independently of the treatment of the algae. The highest values of mortality (mean=14.4%; n=20) were found in eggs attached to Furcellaria that had decomposed over a six days’ period. This suggested that Furcellaria contain some chemical substances, which can cause mortality in herring embryos and the effect seems to be dependent on the state of decomposition of the algae.     

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...