Etude sédimentologique et méiobenthos d'un écosystème lagunaire modifié par un récif artificiel à vocation aquacole: l'acadja = Sediment nature and meiobenthos of an artificial reef (Acadja) used for extensive aquaculture
Guiral, D.; Gourbault, N.; Helleouet, M.-N. (1995). Etude sédimentologique et méiobenthos d'un écosystème lagunaire modifié par un récif artificiel à vocation aquacole: l'acadja = Sediment nature and meiobenthos of an artificial reef (Acadja) used for extensive aquaculture. Oceanol. Acta 18(5): 543-555
In: Oceanologica Acta. Elsevier/Gauthier-Villars: Montreuil. ISSN 0399-1784; e-ISSN 1878-4143, more
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| Authors | | Top |
- Guiral, D.
- Gourbault, N.
- Helleouet, M.-N.
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| Abstract |
In developing countries, recourse to extensive aquaculture systems based on the exploitation of natural aquatic food webs is currently the subject of considerable interest. In this connection, the construction of artificial reefs (known as Acadja) for the development on substrates of living communities, and the utilization of this new production to enhance fish growth have been evaluated in Côte d'Ivoire. This paper describes the granulometric, chemical and biological transformation of the sedimentary ecosystem as a consequence of this practice. In the artificial habitat, an increase in the sedimentation rate of the mineral fraction (definitive trapping of particle resuspension generated by the waves and induced by the wind) and of the organic fraction (direct and indirect sedimentation of the epiphytic biomass) constitutes the starting point of significant modifications in epibenthic communities. In the Acadja, the meiofauna, dominated by nematodes and copepods, is somewhat less diversified, some groups being absent or poorly represented (turbellarians, gastrotrichs, ostracods). These characteristics were confirmed by a specific study of the nematode assemblages. In fact, the relatively high diversity of the nematode community in the natural lagoon sediment (dominated seasonally by Paraphanolaimus, Anonchus et Daptonema) contrasts with low diversity in the Acadja sediment, where the community is always dominated by Theristus sp. This lower specific diversity generates a reduction of the trophic types. In the Acadja, only the non-selective detritus feeders colonize the fine and organic sediment. These sedimentological and ecological transformations, which affect the entire "brush park" (Acadja), induce a strong eutrophication of the benthic ecosystem. Sustainable fish production in such tropical lagoons, in an environment where anaerobic processes dominate (especially sulfato-reduction), calls for strategic spatio-temporal planning to take of account of this progressive eutrophication. |
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