The trophic role of birds in the Grevelingen estuary, The Netherlands, as compared to their role in the saline Lake Grevelingen
Wolff, W.J.; van Haperen, A.M.M.; Sandee, A.J.J.; Baptist, H.J.M.; Saeijs, H.L.F. (1976). The trophic role of birds in the Grevelingen estuary, The Netherlands, as compared to their role in the saline Lake Grevelingen, in: Persoone, G. et al. (Ed.) Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 2. Population dynamics of marine organisms in relation with nutrient cycling in shallow waters. pp. 673-689 In: Persoone, G.; Jaspers, E. (Ed.) (1976). Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 2. Population dynamics of marine organisms in relation with nutrient cycling in shallow waters. European Marine Biology Symposia, 10(2). IZWO/Universa Press: Wetteren. ISBN 90-6281-002-0. 712 pp., more In: European Marine Biology Symposia., more |
| Available in | Authors | | Document type: Conference paper
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| Authors | | Top | - Wolff, W.J., more
- van Haperen, A.M.M.
- Sandee, A.J.J.
| - Baptist, H.J.M., more
- Saeijs, H.L.F., more
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| Abstract | The Grevelingen estuary (140 km² ; tidal amplitude 2.6 m) was dammed up in May 1971. Since then a semi-stagnant saline lake (106 km²) replaced the former estuary. Based on regular counts of all waterfowl in the area the trophic role of birds has been quantified. Before May 1971 ducks, waders and gulls were the most important species in the estuary, consuming mainly benthic flora and fauna. In the saline lake fish-eating birds, e.g. grebes, cormorants and mergansers, came to the fore, and the waders declined dramatically. The predation pressure was calculated from census data and the standard metabolism was multiplied by a constant factor 5 to obtain consumption. Thus it was found that the predation of the benthic fauna was 3.4g ash-free dry wt/m²/year in the estuary, and 1.0g/m²/year in the lake. The predation of the fish fauna was 0.01g/m²/year in the estuary and 0.4g/m²/year in the lake. Herbivore consumption rose from 0.1 g ash-free dry wt/m²/year in the estuary to 2.7 g/m²/year in the lake, although the differences may be partly explained by a decrease in the primary and the secondary production of the water, this also means that the predation by birds on the benthic fauna in an estuary is favoured by the daily emersion of large areas of tidal flats. The total level of consumption is maintained by a shift from secondary consumers to primary consumers. |
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