|Some reflections about the structure of the pelagic zone of the brackish Lake Grevelingen (SW-Netherlands)|
Bakker, C. (1978). Some reflections about the structure of the pelagic zone of the brackish Lake Grevelingen (SW-Netherlands). Hydrobiol. Bull. 12(2): 67-84
In: Hydrobiological Bulletin. Netherlands Hydrobiological Society: Nieuwersluis. ISSN 0165-1404, more
Food webs; Plankton; Succession (ecological); Netherlands, Grevelingen L. [gazetteer]; Brackish water
The seasonal succession of the plankton in the marine brackish Lake Grevelingen, a closed sea arm in the S.W.-Netherlands, comprises the initial stagessensu Margalef and is characterized by predominantly small phytoplankton (flagellates, diatoms) and zooplankton (rotifers, tintinnids, copepods), maintaining relatively high levels of production from early spring (February) to late summer (September). The structure of the plankton in the course of seasonal succession is in agreement with the concepts of Margalef.
Simplification of the pelagic food web in Lake Grevelingen has occurred as a consequence of the elimination of the tides. Some examples are given in relation to the composition of the phyto- and zooplankton and of its significance. The occurrence of rotifer-dominated zooplankton blooms in early spring is emphasized.
Closed sea arms such as Lake Grevelingen, showing the same morphometry as the previous tidal estuary, contain extended shallow areas which influence strongly the pelagic zone. The abundance in the zooplankton of larval stages of several littoral-benthic species demonstrate these influences clearly. The shallows of the lake, occupied by eelgrass beds (Zostera marina) in summer, influence the pelagic zone in several ways: large quantities of detritus are given off after the growing season, sheltered habitats are supplied for small pelagic animals, and eelgrass leaves represent a substrate for epifauna species.