Oxygen deficiency and effects on bottom fauna in the eastern German Bight 1982
Dethlefsen, V.; von Westernhagen, H. (1983). Oxygen deficiency and effects on bottom fauna in the eastern German Bight 1982. Meeresforsch. Rep. Mar. Res. 30(1): 42-53
In: Meeresforschung = Reports on Marine Research. Berichte der Deutschen Wissenschaftlichen Kommission für Meeresforschung. G. Hempel: Kiel & Hamburg. ISSN 0341-6836, meer
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| Auteurs | | Top |
- Dethlefsen, V.
- von Westernhagen, H., meer
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| Abstract |
In August and September 1982 two cruises were carried out to investigate the extent and effects of 02-deficiencies in German and Danish coastal bottom waters. In two thirds of the more than 15000 km2 covered by the survey 02-content was less than 4 ml/1 (60% saturation); lowest values were near 1 ml/l. In bottom waters with low 02-contents pH-values were generally low (7.7). During the first cruise water in the area investigated was stratified, a thermocline was between 10-15 m above the bottom. In 02-deficiency areas (2-saturation around 10 % ) fish catches were low containing dead Agonus cataphractus, Pleuronectes platessa and Limanda limanda. When operating underwater TV dead fish (Agonus cataphractus; Callionymus lyra, Ammodytes sp. and flatfish) were detected lying dead on the bottom. Evaluation of underwater photography revealed the occurrence of dead benthic organisms in areas with low oxygen. The species were Ophiura albida and Venus striatula (paired empty valves). Possible causes for the occurrence of oxygen deficiencies are discussed and it is concluded that eutrophication processes in combination with adverse hydrographic and meteorological conditions have triggered low oxygen conditions in bottom waters. |
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