The limnetic zooplankton of a tropical floodplain lake: an enclosure experiment
Declerck, S.; Nwadiario, C.S. (1993). The limnetic zooplankton of a tropical floodplain lake: an enclosure experiment, in: Chardon, M. et al. Third Belgian Congress of Zoology, 5-6 November 1993. Belgian Journal of Zoology, 123(Suppl. 1): pp. 16
In: Chardon, M.; Goffinet, G. (Ed.) (1993). Third Belgian Congress of Zoology, 5-6 November 1993. Belgian Journal of Zoology, 123(Suppl. 1). University of Liège: Liège. 109 pp., more
In: Belgian Journal of Zoology. Koninklijke Belgische Vereniging voor Dierkunde = Société royale zoologique de Belgique: Gent. ISSN 0777-6276; e-ISSN 2295-0451, more
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Document type: Summary
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- Declerck, S., more
- Nwadiario, C.S.
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| Abstract |
During the dry season, the zooplankton community of the floodplain lake Iyi-Efi (Imo State, Nigeria; maximum depth: 3 m, surface: 46.000 m2) is dominated by small zooplankton at low densities. Due to low water levels, fishes are abundant. In order to estimate the impact of size selective fish predation on the peculiar structure of the zooplankton community, four polyethylene enclosures (cylinders with a length of 2.5 m and a diameter of 0.5 m) were established during the period 16/1 -7/2/’93. The enclosures were weekly sampled, as well as the lake itself. Probably due to the exclusion of fish, mean densities, biomass and body size increased already remarkably one week after the start of the experiment. The increase of total zooplankton biomass, at food levels hardly as high as those in the lake, indicate that food quantity is not a limiting factor in the lake's secondary production during the dry season. With the exception of the less conspicuous nauplii, the vertical distribution of the lake zooplankton revealed a strong preference for the turbid water layer near the bottom. This phenomenon may be explained as a behavioural adaptation to visual fish predation (1). In this respect, food distribution should not be considered as the cause, for chlorophyll a was found to be homogenously distributed, whereas primary production peaked at a depth of 0.4 m.(1) W. LAMPERT (1989). Functional Ecology. 3:321-27. |
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