Distribution of capsulated bacterioplankton in the North Atlantic and North Sea

In laboratory experiments, bacterioplankton were incubated under different nutrient conditions, and the percentage of bacteria exhibiting a polysaccharidic capsule (capsulated bacteria) and that of CTC (cyanotetrazolium chloride)-positive and therefore metabolically highly active bacteria were determined. In these seawater cultures amended with nutrients more than 95% of the CTC-positive cells exhibited a capsule. During two cruises, one to the North Atlantic and one to the North Sea, we investigated the distribution of capsulated bacteria throughout the water column. Capsulated bacteria were generally more abundant in eutrophic surface waters than in deeper layers or more oligotrophic regions. In the upper 100 m of the North Atlantic, about 6–14% of the total bacterioplankton community was capsulated, while in the layers below 100 m depth, 97% of the bacteria lacked a visible capsule. The percentage of capsulated bacteria correlated with bacterial abundance and production, and chlorophyll a concentration. Also, the bioavailability of DOC (dissolved organic carbon), estimated by the ratio between bacterial production and DOC concentration, significantly correlated with the percentage of capsulated bacteria. In the North Sea, the contribution of capsulated bacteria to the total number of bacteria decreased from the surface (3 m depth) to the near-bottom (25–35 m) layers from 20% to 14% capsulated bacteria. In the nearshore area of the North Sea, about 27% of the bacteria exhibited a capsule. Overall, a pronounced decrease in the contribution of capsulated bacteria to the total bacterial abundance was detectable from the eutrophic coastal environment to the open North Atlantic. Using this epifluorescence-based technique to enumerate capsulated bacterioplankton thus allowed us to routinely assess the number of capsulated bacteria even in the oceanic water column. Based on the data obtained in this study we conclude that almost all metabolically highly active bacteria exhibit a capsule, but also some of the metabolically less active cells express a polysaccharide capsule detectable with this method.     

Distribution patterns of bacterioplankton and chlorophyll-a in the German Wadden Sea

 In a first synoptic evaluation, the temporal and spatial distribution of bacterioplankton and chlorophyll-a were determined in the German Wadden Sea. Three surveys were undertaken in winter, spring, and summer of 1994 using up to eight ships simultaneously between the river Ems and Sylt island. Despite intensive hydrodynamic mixing of the Wadden Sea water, spatial gradients were obvious. The abundance of bacterioplankton ranged from 0.4 to 26×10⁵ ml^–1 and chlorophyll-a varied between <0.1 and 79 μg l^–1. In winter, relatively homogeneous distribution patterns of both parameters with small gradients were found. Highest chlorophyll-a values connected with a highly patchy structure were observed in spring, while in summer both total chlorophyll-a values and the complexity of the distribution pattern had decreased. In contrast, bacterial numbers increased steadily from January to July with the highest bacterial densities and greatest patchiness observed in summer. Moreover, in some regions of the Wadden Sea, a trophic succession of algae as carbon producers and bacteria as consumers was evident. Correlation analysis verified the relationship between bacteria and chlorophyll a, indicating bottom-up control of bacterial abundance in the northern part of the German Wadden Sea. Since the observed regression slope is remarkably low (0.12–0.46) compared to literature values (0.5–0.8), we suggest that the link between phytoplankton and bacteria found here is a special characteristic of the Wadden Sea as a transition zone between the coastal region and the outer North Sea. Received: 26 May 1998 / Accepted:12 November 1998     

Functioning of the Sea of Azov ecosystem

The structure and functioning of the Sea of Azov ecosystem have been studied. Based on the results of an analysis of the principal community components (phytoplankton, bacterioplankton, zooplankton, macrozoobenthos, and fish), the elements of balance equality and food utilization by the ecosystem components were calculated and schemes of their energy flow were constructed. The intensity and trends of production-destruction processes were characterized. It was revealed that the main energy flow in the Sea of Azov ecosystem passes through the detritus food web (81%). Along with eutrophication and sulfide pollution of bottom sediments, the impact of predatory ctenophore Mnemiopsis leidyi (A. Agassiz) determines to a considerable extent the pattern of the ecosystem’s transformation.     

The microphytobenthos of the Sea of Azov

This review examines the state of knowledge of microphytobenthos of the Sea of Azov. The insufficient number of floristic studies and the almost complete lack of quantitative data on populations and communities of microalgae in different marine ecotopes demonstrate the relevance of studying the microphytobenthos.     

Radioecological problems in coastal landscapes of the Sea of Azov

The features of the spatial distribution, of the migration, and of the accumulation of natural (232Th) and manmade (137Cs) radioactive nuclides in the coastal landscapes of the Sea of Azov are studied. It was shown, that the specific activity of 232Th in the accumulation of the so-called "black sands" was shown as high as 6000 Bq/kg, that increases the natural geochemical background in 200 times. The impact of aerial transfer of the "black sands" on 232Th migration and accumulation in the soil-plant system was clarified. The 232Th distribution down the soil profile suggests that the "black sands" are likely the product of the erosion of the coastal parent materials enriched by natural radionuclides. In general, the specific activity of 137Cs in the beach sand is not high and it is close to the background (global fallout) value. It was determined that 137Cs content in the coastal ecosystems is connected only by aerial pathway as a part of global and Chernobyl-born fallout.     

Community differentiation of bacterioplankton in the epipelagic layer in the South China Sea

The South China Sea (SCS) is the largest marginal sea in the western tropical Pacific Ocean and is characterized by complex physicochemical environments. To date, the biogeographic patterns of the microbial communities have rarely been reported at a basin scale in the SCS. In this study, the bacterial assemblages inhabiting the epipelagic zone across 110°E to 119°E along 14°N latitude were uncovered. The vertical stratification of both bacterial taxa and their potential functions were revealed. These results suggest that the water depth‐specific environment is a driver of the vertical bacterioplankton distribution. Moreover, the bacterial communities were different between the eastern stations and the western stations, where the environmental conditions were distinct. However, the mesoscale eddy did not show an obvious effect on the bacterial community due to the large distance between the sampling site and the center of the eddy. In addition to the water depth and longitudinal location of the samples, the heterogeneity of the phosphate and salinity concentrations also significantly contributed to the variance in the epipelagic bacterial community in the SCS. To the best of our knowledge, this study is the first to report that the variability in epipelagic bacterioplankton is driven by the physicochemical environment at the basin scale in the SCS. Our results emphasize that the ecological significance of bacterioplankton can be better understood by considering the relationship between the biogeographic distribution of bacteria and the oceanic dynamics processes.     

Interannual Variability of Lipids and Fatty Acids in Azov Anchovy Engraulis encrasicolus maeoticus (Engraulidae) under Current Salinization of the Sea of Azov

Journal of Ichthyology - The work examines the food supply of the Azov anchovy Engraulis encrasicolus maeoticus in 2006–2013, while the level of salinity of the Sea of Azov was rising from...     

Taxonomic composition and interannual variations in numerical density of meroplankton in the Sea of Azov

This paper presents data on the taxonomic composition and dynamics of numerical density of meroplankton in the Sea of Azov. Studies performed in June 2003–2005 revealed benthic invertebrate larvae of 26 taxa: Polychaeta, 7; Cirripedia, 1; Decapoda, 5; Gastropoda, 5; and Bivalvia, 8. Meroplankton was dominated by larvae of species that are able to endure considerable concentrations of pollution by labile sulfides in bottom sediments and eutrophication: Mytilaster lineatus, Cerastoderma sp., Abra ovata (Philippi), Hydrobia acuta (Gastropoda), and Amphibalanus improvisus (Cirripedia). The spatial and temporal variations in the structure of dominant species and numerical abundance of meroplankton in the Sea of Azov are likely to be associated with water temperature fluctuations, pelagic predators, and eutrophication. Under anthropogenic stress and predation pressure, most larvae of benthic invertebrates are apparently unable to complete metamorphosis and contribute to recruitment to parental populations. Thus, the numerical density of meroplankton in the Sea of Azov can significantly vary, even over one month.     

Heterogeneity in the nutrient limitation of different bacterioplankton groups in the Eastern Mediterranean Sea

The heterotrophic bacterial community of the Eastern Mediterranean Sea is believed to be limited by phosphorus (P) availability. This observation assumes that all bacterial groups are equally limited, something that has not been hitherto examined. To test this hypothesis, we performed nutrient addition experiments and investigated the response of probe-identified groups using microautoradiography combined with catalyzed reporter deposition fluorescence in situ hybridization. Our results show contrasting responses between the bacterial groups, with Gammaproteobacteria being the group more affected by P availability. The Roseobacter clade was likely colimited by P and nitrogen (N), whereas Bacteroidetes by P, N and organic carbon (C). In contrast, SAR11 cells were active regardless of the nutrient concentration. These results indicate that there is high heterogeneity in the nutrient limitation of the different components of the bacterioplankton community.     

Biogeography of pelagic bacterioplankton across an antagonistic temperature-salinity gradient in the Red Sea

The Red Sea is a unique marine ecosystem with contrasting gradients of temperature and salinity along its north-to-south axis. It is an extremely oligotrophic environment that is characterized by perpetual year-round water column stratification, high annual solar irradiation, and negligible riverine and precipitation inputs. In this study, we investigated whether the contemporary environmental conditions shape community assemblages by pyrosequencing 16S rRNA genes of bacteria in surface water samples collected from the northeastern half of this water body. A combined total of 1855 operational taxonomic units (OTUs) were recovered from the 'small-cell' and 'large-cell' fractions. Here, a few major OTUs affiliated with Cyanobacteria and Proteobacteria accounted for ～93% of all sequences, whereas a tail of 'rare' OTUs represented most of the diversity. OTUs allied to Surface 1a/b SAR11 clades and Prochlorococcus related to the high-light-adapted (HL2) ecotype were the most widespread and predominant sequence types. Interestingly, the frequency of taxa that are typically found in the upper mesopelagic zone was significantly elevated in the northern transects compared with those in the central, presumably as a direct effect of deep convective mixing in the Gulf of Aqaba and water exchange with the northern Red Sea. Although temperature was the best predictor of species richness across all major lineages, both spatial and environmental distances correlated strongly with phylogenetic distances. Our results suggest that the bacterial diversity of the Red Sea is as high as in other tropical seas and provide evidence for fundamental differences in the biogeography of pelagic communities between the northern and central regions.     

Mollusks of the Utlyuk Liman (Sea of Azov): A Review of Species Composition with Remarks on Distribution and Ecology

Summarized data on the fauna composition, distribution, and ecology of gastropod and bivalve mollusks of the Utlyuk Liman in the northwestern part of the Sea of Azov is presented. The total number of mollusk species identified was 63; 43 species belonged to the class Gastropoda, and 20 species, to the class Bivalvia. The distribution of mollusks in the liman has extremely irregular character, whereas the distribution of species along the marine shore of Biryuchii Ostrov spit is more homogeneous. Euryhaline Mediterranean species represent the core of liman malacofauna; some taxa of the Ponto-Caspian zoogeographical complex (Dreissena polymorpha and species of the genus Theodoxus) and invader species from distant sea basins (Mya arenaria and Anadara inaequivalvis) were also identified.     

The role of zooplankton in the functioning of the Taganrog Gulf ecosystem in the Sea of Azov

The taxonomic composition, distribution of biomass and seasonal variability of zooplankton were studied in various areas of the Taganrog Gulf of the Sea of Azov. The structural-functional transformation of zooplankton was analyzed for ecosystems of various levels of organization (the hypereutrophic central and eutrophic western parts). Unusually strong water blooming caused by cyanobacteria and the pressure of predatory comb jelly results in the elimination of zooplankton, the simplification of the trophic web, and the loss of the ecosystem’s capacity for biotic self-purification. The considerable participation of microzooplankton, especially that of tintiniids, in the metabolism of the Taganrog Gulf ecosystem is one of the important features of its sustainable functioning.     

Modelling viral impact on bacterioplankton in the North Sea using artificial neural networks

The temporal variability of the viral impact on bacterioplankton during the summer-winter transition in the North Sea was determined and artificial neural networks (ANNs) were developed to predict viral production and the frequency of infected bacterial cells (FIC). Viral production and FIC were estimated using a virus-dilution approach during four cruises in the southern North Sea between July and December 2000 and an additional cruise in June 2001. Supplementary data such as bacterial production, and bacterial and viral abundance were collected to relate changes in FIC and viral production to the dynamics of other biotic parameters. Average viral abundance varied between 4.4 x 10(6) ml(-1) in December and 29.8 x 10(6) ml(-1) in July. Over the seasonal cycle, viral abundance correlated best with bacterial production. Average bacterial abundance varied between 0.5 x 10(6) ml(-1) in December and 1.3 x 10(6) ml(-1) in July. Monthly average values of FIC ranged from 9% in September to 39% in June and the average viral production from 11 x 10(4) ml(-1) h(-1) in December to 35 x 10(4) ml(-1) h(-1) in July. The data set was used to develop ANN-based models of viral production and FIC. Viral production was modelled best using sampling time, and bacterial and viral abundance as input parameters to an ANN with two hidden neurons. Modelling of FIC was performed using bacterial production as an additional input parameter for an ANN with three hidden neurons. The models can be used to simulate viral production and FIC based on regularly recorded and easily obtainable parameters such as bacterial production, bacterial and viral abundance.     

南海北部海域春季浮游细菌和病毒空间分布及其影响因素

应用流式细胞检测技术测定了2014年春季南海北部海域浮游细菌和病毒丰度,研究了其水平和垂直分布特征并对其与环境因子的相关性进行了分析。结果表明,调查海区浮游细菌和病毒丰度分别介于1.28×10~4—9.96×10~5个/m L和4.69×10~5—5.39×10~7个/m L之间,二者丰度随水深的增加基本呈现逐渐下降的趋势,而水平分布趋势不明显。浮游细菌和病毒丰度与温度、p H和溶解氧显著正相关,与水深、盐度、活性磷酸盐、硅酸盐、硝酸盐和总氮则呈显著负相关关系(P0.01),说明该海域细菌和病毒数量受到上述环境因子的共同调控。分析浮游细菌和病毒的相互关系发现,VBR(Virus to bacteria ratio)平均32.23,最小值位于S11站位25m层,最大值则位于S7站位75m层,分别为4.80和264.63,VBR值小于100的站位占到调查站位总数的95.6%。VBR值除与细菌呈显著负相关关系外(P0.01),与其它环境因子相关性不明显(P0.05),说明该海区细菌是病毒的主要寄主,病毒可能主要是以噬菌体的状态存在。     

Diel changes in bacteriochlorophyll a concentration suggest rapid bacterioplankton cycling in the Baltic Sea

Aerobic anoxygenic phototrophs were recently found to constitute a significant portion of the marine microbial community. These bacteria use bacteriochlorophyll-containing reaction centers to perform photoheterotrophic metabolism. A new instrument for routine measurements of both chlorophyll a and bacteriochlorophyll a was used for monitoring anoxygenic phototrophs in the Baltic Sea in late summer 2003. Bacteriochlorophyll a concentration ranged from 8 to 50 ngl(-1), with an average bacteriochlorophyll/chlorophyll ratio of 4.2 x 10(-3). Moreover, diel trends in bacteriochlorophyll a signals were observed, with a distinct decline occurring during daylight hours. Based on laboratory measurements this phenomenon was ascribed to the complete inhibition of bacteriochlorophyll synthesis by light, which, in combination with a concurrent turnover of the cells, resulted in a pigment decline. Following this explanation, we postulate that bacteriochlorophyll a can serve as a natural 'pulse-and-chase' marker, allowing estimation of the mortality rates of anoxygenic phototrophs from the rates of pigment decline. Based on this assumption, we suggest that the Baltic photoheterotrophic community was characterized by high turnover rates, in a range of 0.7-2 d(-1).     

南黄海潮汐锋对浮游细菌生物量分布的影响

2 0 0 1年 5月 16～ 2 3日、6月 10～ 2 4日和 2 0 0 2年 6月 5～ 12日 ,利用“北斗号”船只对南黄海鱼产卵场进行了 3次专项调查。研究了潮汐锋断面叶绿素 a浓度、浮游细菌生物量的分布 ,目的是阐明潮汐锋的存在对浮游细菌生物量分布的影响。3个航次中的叶绿素 a浓度变化范围分别是 0 .0 6～ 2 .34mg/ m3(2 0 0 1- 0 5 )、0 .0 8～ 0 .9mg/ m3(2 0 0 1- 0 6 )、0 .14～ 3.0 4 mg/ m3(2 0 0 2 - 0 6 )。 3航次的聚球藻 (Synechococcus spp.)蓝细菌生物量变化范围分别为 7.6 2～ 2 2 .0 6 mg C/ m3(2 0 0 1- 0 5 )、8.5 3～2 7.5 2 mg C/ m3(2 0 0 1- 0 6 )、0 .6 9～ 5 5 .90 m g C/ m3(2 0 0 1- 0 6 )。异养细菌生物量变化范围分别为 7.5 6～ 5 1.82 mg C/ m3(2 0 0 1-0 5 )、8.5 4～ 2 4 .77mg C/ m3(2 0 0 1- 0 6 )、3.12～ 10 .0 5 mg C/ m3(2 0 0 2 - 0 6 )。而聚球藻蓝细菌对浮游植物总生物量的贡献 (CB:PB)平均值分别为 :5 8% (2 0 0 1- 0 5 )、77% (2 0 0 1- 0 6 )、31% (2 0 0 2 - 0 6 )。结果表明 :南黄海鱼产卵场在春末夏初 (5～ 6月份 ) ,叶绿素 a浓度最大值及次大值主要分布在锋区及其邻近的层化区2 0 m以浅位置 ;聚球藻蓝细菌生物量最大值主要分布于锋区及层化区表层和水体中层 ;异养