ISSN:0020-9309    

DOI:10.1002/iroh.19910760302

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractAnalysis of phosphate and nitrate data recorded in the winter surface layer of the Baltic Sea from 1958 to 1989 indicate positive overall trends, although the rate of accumulation has decreased since 1978. The long term accumulation of these algal nutrients in the oxic deep water below the halocline has also decreased since 1977. Under anoxic conditions, however, the trend shown by the phosphate concentration is distinctly positive in recent times owing to phosphate remobilization from the sediment.The salinity has decreased in the surface water and even more rapidly below the halocline in the central Baltic basins during the period marked by the absence of major salt water inflows since 1977. The oxygen conditions have also deteriorated in the near‐bottom water layer during this time as shown by the considerable rise in the hydrogen sulphide concentrations. These changes, including the recent phosphate accumulation under anoxic conditions, can thus be considered natural rather than anthropogenic.The impact of long‐term variations in nutrients and hydrographic parameters is discussed with respect to the development of Baltic fish sto

ISSN:0020-9309    

DOI:10.1002/iroh.19910760303

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractSince the present quality state of the Wadden Sea is judged more discordantly than that of the North Sea, it is examined whether the Wadden Sea is a separate ecosystem. The nutrient load into the Wadden Sea and the trend of the load are assessed. Biological indicators of the ecological state of the Wadden Sea are examined with the result that there are signs of a bad as well as of a good state. This contradiction is assigned to the fact that quality standards are absent. Self‐protection mechanisms of the Wadden Sea are discussed with respect to their responsibility for the relatively good state. A qualitative model is proposed to explain the long‐term behaviour of the ecosys

ISSN:0020-9309    

DOI:10.1002/iroh.19910760304

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractThe relative contribution to the pelagic carbon flux of bacteria, autotrophic picoplankton (APP), and heterotrophic nano‐ and microplankton is highest in pristine oligotrophic waters. Increased nutrient loading stimulates picoplankton production but reduces the importance of the microbial food web. Not all microorganisms are affected in the same way by eutrophication and contaminant enrichment. In contrast to bacteria and heterotrophic nanoflagellates, the APP was found to be highly sensitive to heavy metal contamination. The changing significance of the microbial loop has far‐reaching consequences for the entire ecosystem including alterations occurring in the benthos. The structure and functioning of the microbial food web is similar in marine, brackish, and freshwater ecosyst

ISSN:0020-9309    

DOI:10.1002/iroh.19910760305

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19910760306

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractMicrobial food webs are responsible for the main carbon flow in shallow eutrophic estuaries of the Baltic Sea. Bacteria account for respirative use most of the autotrophic production. Bottom‐up influences are mainly directed to the phytoplankton. Massive increase of phytoplankton biomass has only little effect on the biomasses of the heterotrophic plankton. The investigated ecosystem obviously differs by its high bacteria/non‐bacteria heterotrophs‐relation from other aquatic ecosy

ISSN:0020-9309    

DOI:10.1002/iroh.19910760307

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractEutrophication of the nature is one of the most relevant problems for the human society today. In comparison to terrestrial and limnological ecosystems, however, the marine environment is affected with some exceptions of coastal waters in a minor degree. On the basis of data from 1976–1988 trend analysis for chlorophyll, primary production, zooplankton biomass and water transparency have been carried out for the Mecklenburg Bight and different areas of the Baltic proper.As expected from the longterm increase in the nutrient levels, also for some pelagic biological variables increasing trends could be observed. At least for chlorophyll they are significant in the 95% probability level for all investigated areas. Primary production shows also an increase, however, not significant for each subarea. For zooplankton nearly no changes could be observed. All data reflect a high interannual variability, which can partly be explained by meteorological and oceanological conditions. The results are discussed from an ecological point of view. The increase in phytoplankton variables is considered to be at least partly related to the eutrophication of the Balti

ISSN:0020-9309    

DOI:10.1002/iroh.19910760308

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractInvestigations on phytoplankton have been carried out in Baltic coastal waters, which are widely separated from the sea. Corresponding to their distance to the sea they differ in their trophic level. Annual phytoplankton production and a mean biovolume of 100‐200 g C · m−2and 2‐10 mm−3· 1−1respectively were found for the mesotrophic level, of 200‐400 g C · m−2and 10‐20 mm3· 1−1for the eutrophic level, and of 400‐600 g C · m−2and over 20 mm3· 1−1for the polytrophic level.In the course of nearly two decades of investigation a slight increase of phytoplankton biovolume, but no increase of primary production was recorded. Some changes in species composition are to be recognized in Greifswalder Bodden, if old literature is compared with recent data. In the Darss‐Zingst boddens a shift from Cyanobacteria dominance towards Chlorophyceae dominance has appeared for at least 5 years. This was on account of the disappearance ofGomphosphaeria pusilla, which is thought to be an indicator s

ISSN:0020-9309    

DOI:10.1002/iroh.19910760309

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractLongitudinal transects in the Schlei Fjord (Kiel Bight) revealed strong increases of microbiological parameters from the entrance towards the landlocked end of the fjord. In the inner part up to 14 × 106bacteria ml−1(microscopical count), 77 × 10−1saprophytic bacteria ml−1(plate count) and a thymidine incorporation rate of 0.436 nmol 1−1h−1were observed. The data were compared with earlier results from the same system and those from the nearby located Kiel Fjord. The observations indicate a very high degree of eutrophication in the Schlei Fjord and a lesser one in the Kiel Fjord. The significance of total bacterial numbers and numbers of saprophytic bacteria as indicators for eutrophication and contamination i

ISSN:0020-9309    

DOI:10.1002/iroh.19910760310

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractAnalysing the results of various authors recent studies in the pelagic region of the Baltic revealed that protozoan biomass is in the same range or even higher than metazooplankton biomass. The dominant groups of planktonic protozoans are heterotrophic pico‐ and nanoflagellates (various taxonomic groups), large heterotrophic flagellates (mainly dinoflagellates) and ciliates. Regularly the spring bloom of phytoplankton is accompanied by a maximum of protozoan biomass which declines in early summer as a result of intensive grazing pressure by metazooplankton and changing food conditions. The analysis of results from different stations indicated that biomasses of protozoans increase with an increasing degree of eutrophication. Several trophic levels within the microbial web should be added to the traditional view on the pelagic food web of the Baltic. Our knowledge regarding the quantitative aspect of the microbial matter flux of the Baltic is very limited up to now and complex ecological (and taxonomical) studies using standardized methods including all protozoan components are necessary. Protozoans (various trophic groups and levels), besides bacteria, should be viewed as the metabolically most active heterotrophic component in the pelagic region of the Baltic, their activity should increase with an increasing degree of eutrophicatio

ISSN:0020-9309    

DOI:10.1002/iroh.19910760311

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY