Toxicity of coastal coccolithophores (Prymnesiophyceae, Haptophyta)

Over the last decade, certain coccolithophores have been the subject of extensive multidisciplinary research. Several species of coccolithophore, belonging mainly to the families Pleurochrysidaceae and Hymenomonadaceae, inhabit inshore coastal waters where they may occasionally bloom and hence impact aquaculture resources. The toxicity to Artemia salina larvae of 11 species of coccolithophore (nine coastal and two oceanic members of the order Coccolithales) was tested. For the nine coastal species, tests were conducted with rapidly growing and stationary phase cultures at a range of cellular concentrations and for two different exposure times (24 and 48 h). Five of the coastal species (four in the genus Pleurochrysis as well as Jomonlithus littoralis) were found to be toxic to A. salina nauplii. Allelopathic effects of a cell-free filtrate of a culture of a toxic coccolithophore were also tested on three flagellate microalgal species: Scrippsiella trochoidea, Tetraselmis sp. and Isochrysis galbana. Negative effects of the filtrate on growth rates and motility of S. trochoidea and Tetraselmis sp. were recorded, suggesting that the toxin of the coccolithophore tested could be an exotoxin similar to that produced by other non-calcifying members of the Prymnesiophyceae. The fact that certain coccolithophores were found to be toxic to invertebrates and were shown to exhibit allelopathic activity could imply negative effects at different trophic levels in coastal areas.