Seasonal occurrence and role of protistan parasites in coastal marine zooplankton

13 pages, 7 figures, 1 tableThe prevalence of parasites and epibionts associated with zooplankton in coastal waters of the NW Mediterranean Sea was studied through fortnightly sampling from July 2003 to January 2005. The most commonly found parasites were dinoflagellates of the genera Syndinium and Blastodinium infecting a range of planktonic copepod species, for the most part females. The lethal parasite S. turbo was found in the calanoid copepod Paracalanus parvus all year round, but primarily during summer and autumn. Up to 7% of female P. parvus were visibly infected with S. turbo, corresponding to an estimated parasite-induced mortality rate of up to 0.15 d-1. The parasitic castrators Blastodinium spp. were generally found only from summer to late autumn. The most common Blastodinium species was B. mangini parasitizing the cyclopoid copepod Oncaea cf. scottodicarloi with up to 17% of females visibly infected. This corresponded to an estimated impairment of the reproductive rate of 0.16 d-1. The epibiotic diatom Sceptronema orientale infested on average 34% of adults of the harpacticoid copepod Euterpina acutifrons from late summer until early winter, but was absent during spring and early summer. Occurrence of the dinoflagellate Oodinium sp., a parasite of appendicularians, was seasonally very restricted with a peak of 14% of Oikopleura sp. infected in late summer. Other parasites such as Paradinium spp., Ellobiopsis spp. and the epibiotic diatom Pseudohimantidium pacificum were found more sporadically on various copepod species. The results indicate that parasitism in marine zooplankton is a common phenomenon that has the potential to play an important role in the population dynamics of marine zooplankton. © Inter-Research 2006A.S. was supported by the European Commission, Directorate General Research, through a Marie Curie Postdoctoral fellowship (Contract No. HPMF-CT-2002-01931), and by the Carlsberg Foundation (04-0134/20). E.S. was funded through the Spanish MCYT projects ZOOTRANSFER (REN2001-1693) and MICROROL (CTM 2004-02575/MAR)Peer Reviewe