| Autor: |
Hickel, Wolfgang |
| Předmět: |
|
| Zdroj: |
ICES Journal of Marine Science / Journal du Conseil; Aug1998, Vol. 55 Issue 4, p600-609, 10p, 1 Chart, 7 Graphs |
| Abstrakt: |
Variability in micro- and nanoplankton biomass in the German Bight is described based on 34 annual cycles measured five times week−1 near the island of Helgoland. Sources of variability include not only succession of plankton populations within the seasonal cycle but also changes in the hydrographic structure of the nearby stratified water masses of the outer German Bight. The expected effect of increasing inorganic nutrient concentrations (eutrophication) on long-term changes of phytoplankton stocks could not be determined definitively, because of the overriding effect of hydrographic changes. Indications for eutrophication effects – frequent plankton blooms and oxygen depletion in the bottom water due to accumulated organic particles – are restricted to the outer German Bight. Diatoms and flagellates exhibit different seasonal cycles, with particularly large inter-annual fluctuations in the summer dinoflagellate stocks. Nanoplankton populations appear to have increased sharply at the end of the 1970s. As other plankton and abiotic factors have changed in the southern North Sea at the same time, possible larger-scale events must be considered as well as regional causes. [ABSTRACT FROM PUBLISHER] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
