Abstract

The increase in distribution and frequency of Harmful Algal Blooms (HABs) worldwide are cause of social and environmental concern globally. In southern Chile, HAB episodes have caused great losses due to high fish mortalities in salmonid farms and native fauna, affecting biodiversity, local economies, and threatening food safety. The most damaging episodes of HABs in this region of the Pacific Ocean are associated to phytoplankton species producers of paralytic shellfish poison (PSP), but episodes caused by producers of Diarrheic Shellfish Poison (DSP) and other emergent lipophilic biotoxins have been increasingly detected. Sub-lethal toxic effects on mammals and the mechanisms of action described to date for DSP are diverse, although their impact on fish have been neglected. Using zebrafish (Danio rerio) as a model, we tested the effects of four lipophilic biotoxins: Okadaic acid, Dinophysis toxin-1, Dinophysis toxin-2, and Yessotoxin-1. We assessed the effects of sub-lethal concentrations on swim bladder inflation, touch response and locomotor activity on larvae, and the results suggest teratogenic impacts and/or neurotoxicity. Also, using fish expressing fluorescent proteins in a specific cell type and whole-mount staining, we detected changes in the distribution pattern of neutrophils and the amount of Goblet cells, suggesting an activation of the immune response of larvae. Finally, taking advantage of the zebrafish regenerative capacity, we used a tail-fin amputation protocol and detected a negative impact on tissue regeneration. These effects all together can have complex implications for environmental safety, biodiversity conservation and the salmon industry, since small amounts of toxins can probably increase susceptibility to other threats for fish, such as environmental pathogens.