Currently, thanks to the development of sensitive analytical techniques, the presence of different emerging pollutants in aquatic ecosystems has been evidenced; however, most of them have not been submitted to any regulation so far. Among emerging contaminants, antimicrobials have received particular attention in recent decades, mainly due to the concerning development of antibiotic resistance observed in bacteria, but little is known about the toxicological and ecological impact that antimicrobials can have on aquatic ecosystems. Their high consumption in human and veterinary medicine, food-producing animals and aquaculture, as well as persistence and poor absorption have caused antimicrobials to be discharged into receiving waters, with or without prior treatment, where they have been detected at ng-mg L−1 levels with the potential to cause effects on the various organisms living within aquatic systems. This review presents the current knowledge on the occurrence of antimicrobials in aquatic ecosystems, emphasizing their occurrence in different environmental matrixes and the effects on aquatic organisms (cyanobacteria, microalgae, invertebrates and vertebrates).

Genus Vibrio is involved in common pathologies of aquaculture fish species, being responsible for significant economic losses for that industrial activity. Microalgae and cyanobacteria have demonstrated to count on bioactive compounds able to diminish mortality and morbidity by their use as functional food supply or by addition of those bioactive compounds previously purified. The main goal of this work has been to evaluate the anti-microbian effect (growth of bacterial population measured as changes in optical density) of 25 microalgae extracts on the bacterial strain Vibrio anguillarum CECT 522T. Stock microalgae extracts were obtained from lyophilized biomass treated with methanol 99.9%. A total of thirteen extracts exhibited antibacterial activity. The highest activity corresponded to Monochrysis lutheri, followed by Hemiselmis cyclopea, Porphyridium cruentum, Tetraselmis rubens, Cryptomonas sp, Navicula sp. The anti-bacterial activity was not related to a taxonomic group, indicating species-specific or even strain-specific activity.

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