Cyanobacteria Toxins: Diversity and Ecological Effects

Cyanobacteria are known to produce secondary metabolites which are toxic to mammals, commonly known as “toxins”. These have been described as having neurotoxic, hepatotoxic and dermatotoxic effects, being a hazard also to humans. Cyanobacteria blooms may represent a hazard to aquatic organisms, when cells collapse, releasing cyanotoxins to the water. Toxins, though, have a dramatic influence on many groups of other arganisms. Zooplankton species are affected by cyanotoxins Duphniu is used as a test organism for cyanobacteria toxicity evaluation. Rotifers and small cladocerans seem to be less sensitive to cyanobacteria toxicity. This partly explains the dominance of small zooplankton groups during cyanobacteria blooms. Molluscs such as mussels are also little affected by cyanobacteria toxins, being able to transfer them along food chains up to humans. Mussels purify microcystins from their body slowly, making them good toxin vectors. Larger crustaceans such as crayfish may be also considered as toxin vectors, having low toxin sensitivity even during early larval phases. The response of fish to toxins is quite diverse and is related to food habit. Carp seem to accumulate more toxins than mullet or barb and they are not much affected by oral toxicity. Many of these animals may act as vectors for toxins better than other more sensitive organisms, which may be badly affected by the toxins.