A survey of cryptomonad diversity and seasonality at a coastal Mediterranean site

The composition and seasonal cycle of the cryptomonad community were investigated at a coastal station in the Gulf of Naples (Mediterranean Sea) from March 2002 to March 2004. Serial dilution cultures were established from samples collected fortnightly in surface waters and single species abundances were estimated as most probable number. For species identification, unialgal cultures obtained by further dilution were analysed with light and scanning electron microscopy and spectrophotometry. Additional data collected at the same station and from other Mediterranean areas are also presented. Sixteen different morphs were recognized from 103 cultures. These included Plagioselmis prolmiga, Proteomonas sulcata (haplomorph and diplomorph), Rhinomonas pauca, R. reticulata, Rhodomonas salina, R. cf. marina, Storeatula major, Teleaulax cf. acuta. Seven other morphs belonging to the genera Cryptochloris, Hemiselmis, Rhodomonas and Storeatula did not fit the descriptions of any described species, demonstrating a high rate of unknown diversity in the group. Total cryptomonad abundance showed peaks in spring summer and autumn of both years. Some species were recorded occasionally, others (P. prolonga) throughout the year, still others (Hemiselmis sp., P. sulcata, R. pauca and R. reticulata) only at certain times of the year, the occurrence pattern recurring in both years. The species-specific occurrence patterns and the seasonal succession suggest that these species differ in their ecological requirements.