Reports of Harmful algal Blooms (HAB) have increased worldwide as a result of enhanced growth and eutrophication as well as improved monitoring programs and climate change . Several species of HAB pause a threat to human health as well as commercial fish and shellfish. Among HAB-forming dinoflagllates of cosmopolitan occurrence , Alexadrium catenella produces saxitoxins responsible for Paralytic Shellfish Poisoning (PSP) and allelochemicals of undetermined nature responsible for mass mortalities of aquatic organisms. Dinophysis acuminata is another HAB-forming dinoflagellate with a global distribution responsible for Diarrheic Shellfish Poisoning (DSP) which causes economic loss due to closures of shellfish productions.
Alexandrium catenella has been forming recurrent blooms in USA, notably in the Gulf of Maine, Alaska and California. Recent studies have shown that A . catenella has been expanding along the West Coast of the USA up to the Arctic region. This species has been associated with contamination of shellfish with PSP, which hampers shellfish aquaculture production, but also with mass mortalities of fish. Blooms of Dinophysis and associated toxins are an emerging threat to human health and aquaculture in North America, as documentation of these blooms has increased, notably in USA.
Several studies have dealt with PSP accumulation and detoxification in shellfish. Studies with DSP kinetics in shellfish have been rare due to difficulties in culturing Dinophysis species and maintaining large scale cultures for feeding experiments. Studies on the impacts of Alexanrium and especially Dinophysis on fitness of shellfish are less frequent . In the present study, we report results of the effects of A . catenella on a commercial shellfish species using reproduction as a model experimental study. We tested the effects of A . catenella on severa l developmental stages of the Japanese pearl oyster and compared its effects to several other species of the genus Alexandrium , producers and non-producers of PSP. We also report our results of the effects of Dinophysis acuminata on the reproduction of the Japanese pearl oyster and compare it with other species of Dinophysis tested from monoclonal cultures.
Our results show that all tested species have negative effects on reproduction of the shellfish species which warrant further studies of the impacts of uncharacterized allelochemicals of both Alexandrium and Dinophysis on shellfish as well as fish of commercial importance, especially that the aquaculture sector is being further developed in USA.