Dinoflagellate cyst production at a coastal Mediterranean site

To assess the diversity and seasonality of dinoflagellate cyst production, surface sediment and trap samples were studied in the Gulf of Naples (Medit erranean Sea). A total of 59 different cyst morphotypes were recorded. At t he stations within the 70 m isobath, sediment assemblages were dominated by calcareous Peridiniales (66-79%), while at the deepest stations non-calcar eous Peridiniales attained the highest percentages (40-49%). The sediment t rap sampling, carried out fortnightly over two annual cycles, revealed high production rates (up to 1.7 x 10(6) cysts m(-2) day(-1)) from spring to la te autumn of both years, with a distinct seasonal production pattern. Altho ugh rather similar in species composition, the total cyst flux differed mar kedly between the 2 years (1.26 and 0.55 x 10(8) cysts m(-2) year(-1), resp ectively). Species-specific production patterns were observed: some species formed cysts over several months, others in restricted periods of the year . Cyst-forming species constituted a small part of the planktonic dinoflage llate populations recorded in the area. A coupling between the trap materia l and surface water plankton was observed for calcareous Peridiniales. This sampling approach allowed the detection of some species never recorded bef ore in the gulf, including two potentially toxic species: Alexandrium ander soni and Gymnodinium catenatum-like species.