CELLULAR AND MOLECULAR BIOMARKERS FOR ASSESSING THE HARMFUL EFFECTS OF MARINE TOXINS IN BIVALVE MOLLUSKS.

The worldwide ongoing increase in the frequency, severity and geographic distribution of harmful algal blooms (HABs), together with the huge economic losses they cause, represent a significant problem in many coastal regions. The consumption of shellfish contaminated with marine toxins can trigger serious and potentially fatal intoxications in human populations; most of them can be prevented through the forced prolonged closure of large harvesting areas to allow shellfish decontamination. To reduce the impact produced on the aquaculture sector, new methods for detecting toxic blooms are constantly being reported, and their effects on their principal vectors, bivalve mollusks, are examined. These organisms seem to be insensitive somehow to harmful effects of these toxins since their viability rates after toxic blooms are in general maintained. Nevertheless, some recent biomonitoring studies proved that they can indeed show a cellular and molecular response against toxin exposure. In the last decade, there has been an increase in the use of biomarkers of effect to estimate the negative impact of marine toxins on bivalve mollusks. Certain cellular and molecular parameters are considered as suitable biomarkers, since they reflect the biological response of these organisms to marine toxins. Thus, cellular biomarkers such as DNA breaks, chromosome alterations or cell viability rates are used to evaluate genotoxic and cytotoxic effects; whereas, molecular biomarkers such as gene expression levels, protein levels and enzyme activities of heat-shock proteins, multi-xenobioticresistance proteins or antioxidant enzymes have been studied to assess the response to these toxins. The aim of this chapter is to provide an overview of the current status of biomarker use in the assessment of the effects of marine toxins on bivalve mollusks. In a general way, this work reviews the studies dealing with the application of cellular and molecular biomarkers for monitoring and assessing the different effects induced by exposure of bivalve mollusks to marine toxins. [ABSTRACT FROM AUTHOR]