Effects of microcystins on fish

Area of Science:

• Environmental toxicology
• Aquatic ecology
• Fish biology

Background:

• Microcystins (MCs) are toxic compounds produced by cyanobacteria.
• Cyanobacterial blooms are increasing globally, leading to widespread MC contamination in aquatic ecosystems.
• Fish are primary targets for MC exposure and accumulation in food webs.

Purpose of the Study:

• To review the effects of microcystins on fish across different life stages.
• To discuss the potential consequences of MCs in aquatic food webs.
• To highlight knowledge gaps regarding MCs' sublethal effects and ecological fate.

Main Methods:

• Literature review of field and experimental studies on MCs and fish.
• Analysis of MCs' impact on fish embryonic development, survival, growth, physiology, and behavior.
• Examination of MCs' accumulation, detoxification, and trophic transfer in fish.

Main Results:

• MCs cause dose-dependent adverse effects in fish early life stages, including reduced hatching success, survival, and growth, along with histopathological damage.
• Adult and juvenile fish accumulate MCs primarily in the liver, affecting growth, osmoregulation, enzyme activity, and behavior, with varying effects based on exposure route.
• Fish detoxify MCs via glutathione conjugation, a conserved pathway across diverse organisms.

Conclusions:

• Naturally occurring MC concentrations can significantly impact multiple trophic levels in aquatic ecosystems.
• MCs pose a substantial threat to fish populations, particularly sensitive early life stages, and can biomagnify in food chains.
• Further quantitative research is essential to understand the sublethal effects, accumulation, and long-term fate of MCs in aquatic food webs.