Microcystin-LR as an Emerging Aquatic Threat: A Literature Review of Ecotoxicological Effects in Fish and Remediation Methods.

Water pollution, intensified by anthropogenic activities, compromises aquatic ecosystems, especially through eutrophication, which favors the proliferation of microcystin-LR-producing cyanobacteria (MC-LR). We conducted a systematic and narrative literature review involving 72 studies on the effects of MC-LR on fish and 105 on remediation methods, aiming to understand the ecotoxicological impacts of this cyanotoxin and evaluate mitigation strategies. Our results show that most research is conducted under laboratory conditions, mainly with Danio rerio. MC-LR causes multiple adverse effects in fish, including liver, intestinal, and gill damage, alterations in the intestinal microbiota, reproductive, excretory, and neurological dysfunctions, as well as oxidative stress, the intensity of which varies according to the species, dose, and exposure time. We also assessed which of these studies evaluated the capacity of fish to recover or detoxify following MC-LR exposure, an aspect that remains comparatively understudied in the literature. Among the remediation techniques investigated, photocatalysis, adsorption, and biodegradation stand out, demonstrating potential but lacking validation in natural environments regarding efficacy, toxicity of byproducts, and practical viability. We conclude that in situ research with a greater diversity of species, especially native and economically relevant ones, is necessary, as well as rigorous testing of remediation methods in real environments.