Species richness and distribution of benthic tidal flat fauna of the Banc d'Arguin, Mauritania

• Published in: Oceanologica acta 1999, Vol.22 (2), p.233-243
• Main Authors: Wijnsma, Gerard, Wolff, Wim J, Meijboom, André, Duiven, Piet, De Vlas, Jaap
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Banc d'Arguin; benthos; bethos; Biological and medical sciences; diversity; diversité; Fundamental and applied biological sciences. Psychology; Institute for Forestry and Nature Research; Instituut voor Bos- en Natuuronderzoek; limicole; Marine; Sea water ecosystems; shorebirds; Synecology
• ISSN: 0399-1784
• DOI: 10.1016/S0399-1784(99)80048-6

The Banc d'Arguin in Mauritania, West Africa, is an area of tidal flats and shallow inshore waters bordering the sandy desert of the Sahara. The project Banc d'Arguin 1985–1986 investigated predominantly benthic biomass and production, the same data allow investigation of the species diversity and the distribution of the tidal flat fauna of the Banc d'Arguin. We sieved and analysed 410 core samples (diameter 10 cm) from 82 locations with 0.6 mm mesh size. A total of 111 taxa were identified. Polychaeta were most diverse with 42 species belonging to 20 families. Other large species groups were Gastropoda (20 species, 14 families), Amphipoda (14 taxa, 8 families) and Bivalvia (15 species, 10 families). Densities ranged from 152 to 5635 ind. m −2, with an average of 1404 ind. m −2. Six taxa accounted for more than half of the total density. H' values were generally low with values ranging from 0 to 2.78 nats. Low evenness values indicated a high degree of dominance. The total density was independent of any sediment characteristic, probably because of the large range of species. Densities of dominant species did show a correlation with sediment size. A fraction of the individuals could have been lost with our use of a 0.6 mm sieve. Many species occurred only at a few stations. An explanation for this could be that stations are dominated by different species, while the diversity within a station is relatively low. The occurrence of opportunistic species supports this explanation. The Banc d'Arguin is a reversed estuary, and the stress caused by high temperatures and salinity could result in opportunistic assemblages. The (theoretical) high turnover rate of these opportunistic assemblages could be the key to the importance of the Banc d'Arguin for wintering shorebirds. Le Banc d'Arguin, à l'ouest de l'Afrique, est une région de vasières et d'eaux littorales peu profondes en bordure des sables désertiques du Sahara. Le programme Banc d'Arguin 1985–1986 avait pour thème la biomasse benthique et la production, la diversité spécifique et la répartition de la faune dans la zone des marées du Banc d'Arguin. Des prélèvements, au nombre de 410 (diamètre 10 cm) ont été effectués en 82 stations, filtrés (maille 0,6 mm) puis analysés. Au total, 111 taxons ont été identifiés. Les polychètes présentent la plus grande diversité avec 42 espèces appartenant à 20 familles. Viennent ensuite les gastropodes (20 espèces, 14 familles), les amphipodes (14 taxons, 8 familles) et les b