A preliminary study of tintinnid diversity in the NW Mediterranean Sea

Tintinnid diversity in surface waters was investigated in the Bay of Villef ranche in March, before the formation of the seasonal thermocline, and in M ay, following water column stratification. Tintinnid abundance was much gre ater in March (500 cells l(-1)), corresponding to a bloom of Stensomella ni valis, compared to May (30 cells l(-1)). Nonetheless, high numbers of speci es were encountered on both dates: 32 in March and 39 in May, respectively. Diversity was higher (H' = 2.5) for the May date with low tintinnid concen trations. We examined taxonomic diversity and morphological diversity. Vari ance of lorica length was correlated with taxonomic diversity, in contrast to variance of lorica diameter, which was nearly invariant. We suggest that either species with similar lorica diameters exploit different prey items or competition for prey items is not the dominant factor in structuring tin tinnid communities.