Field cyanobacterial blooms producing retinoid compounds cause teratogenicity in zebrafish embryos

Abstract Cyanobacteria routinely release potentially harmful bioactive compounds into the aquatic environment. Several recent studies suggested a potential link between the teratogenicity of effects caused by cyanobacteria and production of retinoids. To investigate this relationship, we analysed the teratogenicity of field-collected cyanobacterial bloomsamples by means of an in vivo zebrafish embryo test, an in vitro reporter gene bioassay and by the chemical analysis of retinoids. Extracts of biomass from cyanobacterial bloomswith the dominance of Microcystis aeruginosaand Aphanizomenon klebahnii were collected from water bodies in the Czech Republic and showed significant retinoid-like activity in vitro, as well as high degrees of teratogenicity in vivo. Chemical analysis was then used to identify a set of retinoidsin ng per gram of dry weight concentration range. Subsequent fractionation and bioassay-based characterization identified two fractions with significant in vitro retinoid-like activity. Moreover, in most of the retinoidseluted from these fractions, teratogenicity with malformations typical for retinoidsignalling disruption was observed in zebrafish embryos after exposure to the total extracts and these in vitro effective fractions. The zebrafish embryo test proved to be a sensitive toxicity indicator of the biomass extracts, as the teratogenic effects occurred at even lower concentrations than those expected from the activity detected in vitro. In fact, teratogenicity with retinoid-like activity was detected at concentrations that are commonly found in biomasses and even in bulk water surrounding cyanobacterial blooms. Overall, these results provide evidence of a link between retinoid-like activity, teratogenicity and the retinoidsproduced by cyanobacterial water bloomsin the surrounding environment.