Primary production, nutrients, and size spectra of suspended particles in the southern North Sea
Gieskes, W.W.C. (1972). Primary production, nutrients, and size spectra of suspended particles in the southern North Sea. NIOZ-rapport, 1972(16). Nederlands Instituut voor Onderzoek der Zee: Texel. 39, 7 pp.
Part of: NIOZ-rapport. Netherlands Institute for Sea Research (NIOZ): Den Burg. ISSN 0923-3210
The effect of nutrient enrichment from the Rhine on some major characteristics of the phytoplankton ecosystem of Dutch coastal waters was studied with 14C, liquid scintillation and Coulter Counter techniques. The magnitude of primary production in the most eutrophic waters closest to shore and the Rhine mouth was found to be affected by turbidity, rather than by concentration of nutrients only. That the annual production cycle starts later in onshore waters than in the clear offshore water mass is probably also due to turbidity. Primary production of dissolved organic matter was at times up to 20% of the total carbon fixed per square meter. It is suggested that filtrate radio-activity is to a large, though unknown, extent derived from labelled organic compounds of the mucus of colony-forming species like Phaeocystis globosa and Chaetoceros socialis. The nutrient regime and degree of eutrophication, but also other factors like stratification, turbulence, and light conditions seem to control the community structure and species composition of the populations, and therewith the amount of primary productivity. Diatom productivity in the Dutch coastal water mass can be high even in summer, in spite of a near-depletion of silicate already early in spring. This can be so because silicate concentrations may periodically rise, e.g. in stratified water due to the dominance of dinoflagellates in the primary producer populations , or after periods with certain climatic-hydrographic conditions when diatoms may sink out of the euphotic zone .
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