Seasonal variations in tintinnid abundance and species composition were studied weekly for 4 yr at a coastal site in the Gulf of Naples (Tyrrhenian Sea). Of the 57 identified tintinnid species, only 7 accounted for 81% of tintinnid abundance. Recurrent seasonal patterns were observed for the most common species. The characteristics of the tintinnid community over this 4 yr study are similar to those reported for tintinnid assemblages at the same study site in 1984-85 in terms of total abundance, species composition and timing of the dominant species. According to reports in the literature the persistence in time of the dominant tintinnid species appears to be a general feature, a sort of 'fingerprint' of each area. In contrast, in the Gulf of Naples only Tintinnopsis beroidea, reported as dominant in 1934, continues to be dominant in this area today; the other dominant species of the 1930s were rarely found during this study. Changes and persistence of tintinnid species in the Gulf of Naples are discussed in relation to major changes in phytoplankton populations in the period 1984 to 2000. Chlorophyll concentrations integrated over the whole water column are now only 50% of the former values and only 34% of former surface values. We also compare our findings to reports from other coastal sites to evaluate the distribution of key tintinnid species, in particular for the western Mediterranean Sea. KEY WORDS: Tintinnids · Diversity · MediterraneanResale or republication not permitted without written consent of the publisher

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