Vol. 43 No. 2, 2004

Spatial and Temporal Structure of Planktonic Copepods in the Bay of Tunis (Southwestern Mediterranean Sea)

Mohamed Néjib Daly Yahia¹, Sami Souissi^2,* and Ons Daly Yahia-Kéfi³

¹Laboratory of Environment Bio-monitoring, Hydrology and Planktonology Research Group, University of Sciences of Bizerta, Zarzouna, Bizerta 7021, Tunisia.Fax: +21672590566. E-mail: nejib.daly@fsb.rnu.tn
²Ecosystem Complexity Research Group, University of Sciences and Technologies of Lille. CNRS-UMR 8013 ELICO, Marine Station, B.P. 80. Wimereux 62930, France.
³Hydrology and Planktonology Research Group, Tunisian Agronomic National Institute, 43 Avenue Charles Nicolle, Tunis 1082, Tunisia. Fax: 216-717-99391. E-mail: dalyyahya.ons@inat.agrinet.tn

Mohamed Néjib Daly Yahia, Sami Souissi and Ons Daly Yahia-Kéfi (2004) The community of pelagic copepods of the Bay of Tunis was studied using a grid of 14 stations regularly sampled 24 times between December 1993 and November 1995. A previously published regionalization of this bay, based on its hydrological structure leading to a description of 4 functionally different zones, was considered in this study. In the bay, copepods dominated the mesozooplankton, and spatial heterogeneity of both abundance and species composition was detected. There were 2 principal gradients: i) from coastal to offshore stations and ii) from the southwestern to the northeastern portions of the bay. In total, 52 pelagic copepod species were recorded in the bay during this study. The families of Acartiidae, Paracalanidae, Centropagidae, and Oithonidae dominated, each of which was represented by 5 species. The most abundant copepods were represented by the following species ranked according to their dominance: Oithona nana, O. helgolandica, O. plumifera, Centropages kroyeri, Clausocalanus arcuicornis, Acartia clausi, Euterpina acutifrons, and Microsetella rosea. Their contribution to total copepod abundance varied between 65% and 100% during the study. These 8 dominant species comprised the neritic community of copepods in the bay. Another community of copepods in the bay was characterized by the following oceanic species: Acartia danae, Centropages chirchiae, Mesocalanus tenuicornis, Mecynocera clausi, Candacia armata, Eucalanus crassus, and Oithona plumifera. This community was particularly evident in the central and northeastern parts of the bay, where copepod diversity was significantly higher compared to the coastal zones.

Key words: Mediterranean, Bay of Tunis, Copepod distribution, Diversity structure.

*Correspondence: Fax: +33-3-21992901. E-mail: Sami.Souissi@univ-lille1.fr