Abstract:
Toxic marine micro-algae that form harmful algal blooms can have serious human health impacts worldwide. New species are rapidly being described and their associated toxins isolated and characterised. A high level of within-species variation calls for specific testing and examination of isolates from different regions. The benthic dinoflagellate genera Ostreopsis and Gambierdiscus produce some of the most toxic natural known compounds, including palytoxin, ciguatoxin, and maitotoxin (and associated analogues). These toxins are associated with incurable human poisoning syndromes such as ciguatera fish poisoning through consumption of contaminated finfish. The aim of the study was to assess the toxicity of algal extracts containing known marine biotoxins (as determined by LC-MS analysis) using two bioassay models. Extracts of twelve Ostreopsis and Gambierdiscus isolates (originating from the Cook Islands, New Caledonia, Australia and New Zealand) were characterised using LC-MS methods to determine toxin content. Five out of seven Ostreopsis extracts were classified as palytoxin or palytoxin analogue producers. One Gambierdiscus extract produced ciguatoxins and one maitotoxin, with all five producing maitotoxin-3. The extracts were then tested in the zebrafish (Danio rerio) fish embryo toxicity (FET) the sea urchin (Evechinus chloriticus) fertilisation and developmental assays. The FET assay showed a toxic response to four out of five Gambierdiscus extracts with no response to any Ostreopsis extracts. Urchin fertilisation was not significantly affected by the presence of any of the algal extracts. Urchin larval development was significantly affected by two of the five Gambierdiscus extracts tested and partially affected by one of the seven Ostreopsis extracts. These results show the potential of these two bioassays as screening tools for marine algal biotoxins.
