Factors affecting algal toxicity

Toxic microalgae belong to a variety of taxa, and the bioactive molecules that they produce highly differ in chemical structure, molecular weight and biological activity. It is believed that toxins should confer some ecological advantages to their producer, although in many cases their real function is difficult to identify; the role against predators and/or competitors is among those mostly hypothesized, although different functions are considered. Regardless of their function, toxins are considered stress molecules whose amounts increase in response to environmental drivers, mainly as a consequence of metabolism diversions and, due to their different structure, it can be expected that the various stressors differently affect the metabolic pathways responsible for the production of the different toxin groups. This chapter deals with studies performed on the effect of environmental factors on the toxin content of microalgae. It summarizes information that could point out interactions between environmental factors and phytoplankton secondary metabolism in order to identify possible common triggering patterns for the production of toxins having similar structure. For this reason toxins of known chemical structure and papers based on quantitative chemical analyses were mainly considered.