The interaction of aquatic organisms (Mytilus Sp.) with harmful algal blooms: Composition, distribution and metabolism of lipophilic marine biotoxins in the Austral Pacific fjords

Abstract

For years, marine resources have been an important part of human development due to the high nutritional contribution they possess. Mussels sp. are the most consumed species in the world. As a result of requirements and needs exceeding the natural global production, man developed aquaculture in order to regulate the imbalance between nutritional requirements and natural production. Under natural conditions, there are several and wide ranging varieties of mussels, with multiple sea habitats: sandy, rocky and stratified bottoms in the water column in rocky strata. This allows them to assimilate a varied diet of micronutrients consisting mostly of phytoplankton. Although, depending on their habitat, mussels can filter waste from other species such as feces, pseudofeces, microcellular debris or compounds from anthropogenic input. From the many species of phytoplankton, about 80 of them are known for producing phycotoxins through blooms, Dinophysis sp. being the species of dinoflagellates associated with the production of toxins in the Austral Pacific fjords. These dinoflagellates are filtered and accumulated by hydrobiological organisms, such as mussels, that accumulate toxins in the digestive glands. Here they are subjected to numerous reactions of biotransformation mediated by enzymatic pathways, nonenzymatic pathways or by bacteria present in bivalves, which extends the toxic spectrum of the assimilated toxins, an event that is magnified by the interaction of vector organisms that expand the toxic forms through the trophic chain. Lipophilic marine biotoxins (OA-, AZA-, PTX- and YTX-group), constitute the group of toxins that affect mussels from natural origin and aquaculture the most. These kind of toxins are accumulated in the tissues of mussels where they are retained according to their chemical affinity and/or modified into more toxic forms (AZA-1→AZA-3) and/or thermodynamically more stable forms (PTX-2-SA→7-epi-PTX-2-SA), in some cases allowing accumulated toxins by mussels to become harmless (DTX-1→DTX-3; YTX→carboxy-YTX). Since blooms associated with lipophilic marine biotoxins may occur simultaneously, different species of mussels and those species related to their habitat can accumulate and/or transform the wide spectrum of toxins. This generates a toxin profile and variable toxicity in their tissues, which lasts according to the exposure time to the bloom and the purification pathway of toxins from mussels. In this chapter, the main events associated with lipophilic marine biotoxins (OA-, AZA-, PTX- and YTX-group), as well as their interaction in the habitat of Mussels sp. in the Austral Pacific fjords are presented.