Potentially toxic epiphytic Prorocentrum (Dinophyceae) species in Greek coastal waters

Five epiphytic Prorocentrum species have been identified after the examination of macrophyte, water column and sediment samples collected from 50 sites along North Aegean coastline (Greece) the period from August 2003 to December 2005. Two of the identified Prorocentrum species, P. borbonicum and P. levis, constitute new records for the Mediterranean Sea. Numerous specimens fitted the general description of P. lima exhibiting, however, great variability in several morphological characters, such as cell shape, length and width, number and shape of valve and marginal pores, making this species identification difficult and raising issues regarding its morphological identity. For this reason, all these identified morphotypes, are referred to as P. lima complex. Representatives of P. lima complex were the most abundant (up to 133,000 cells g(-1) fresh weight of macrophyte (fwm) on Cymodocea nodosa) among Prorocentrum species, followed by P. rhathymum (11,000 cells g(-1) fwm on C. nodosa). P. borbonicum was detected sporadically, while P. levis, P. rhathymum and P. emarginatum showed maximum cell densities in summer and autumn. P. lima complex representatives exhibited peak abundances at the end of November and/or December, while they were found in relatively high densities during summer and autumn. The temporal distribution of Prorocentrum species, combined with specific trends in substrate preference, may imply possible succession patterns and niche separation between potentially toxic dinoflagellates in epiphytic assemblages. Toxicological properties of Prorocentrum species were examined by means of protein phosphatase 2A inhibition assay and/or Artemia bioassay. Results concerning toxicity of Prorocentrum species constitute new information for the Mediterranean Sea, pointing out their potential role as diarrhetic shellfish poisoning (DSP) toxins producers. (C) 2008 Elsevier B.V. All rights reserved.