Biomagnification or biodilution of microcystins in aquatic foodwebs? Meta-analyses of laboratory and field studies

• Published in: Harmful algae 2012-06, Vol.18, p.47-55
• Main Authors: Kozlowsky-Suzuki, Betina, Wilson, Alan E., Ferrão-Filho, Aloysio da Silva
• Format: Article
• Language: English
• Subjects: Algae; Anabaena; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; Blue-green algae; Cyanobacteria; Fundamental and applied biological sciences. Psychology; Meta-analysis; Microcystins; Microcystis; Mollusca; Plant cytology, morphology, systematics, chorology and evolution; Plants and fungi; Thallophyta; Trophic transfer
• ISSN: 1568-9883; 1878-1470
• DOI: 10.1016/j.hal.2012.04.002

► We synthesized data from 42 studies on the concentration of microcystins in consumers. ► Meta-analyses indicated biodilution of microcystins as prevailing in aquatic foodwebs. ► Zooplankton and zooplanktivorous fishes showed potential for biomagnification. ► Study design and sampling technique may influence the magnitude of biodilution. ► Prolonged exposure to toxic food resulted in higher accumulation in aquatic consumers. Cyanobacteria, conspicuous photoprokaryotes in aquatic ecosystems, may produce secondary metabolites such as the hepatotoxins, microcystins (MC). While MC have been quantified in numerous aquatic consumers across a variety of ecosystems, there is still debate whether biomagnification or biodilution of MC generally occurs in aquatic foodwebs. Given the threat that MC pose to aquatic foodwebs, livestock, and humans, we synthesized data from 42 studies on the concentration of MC in consumers, such as zooplankton, decapods, molluscs, fishes, turtles and birds, to determine the dominant process. To compare results across studies, we calculated the biomagnification factor (BMF) as the ratio between the MC concentration measured in consumers and their diet. Biomagnification is indicated when BMF mean and associated 95% confidence intervals (CI) >1. Biodilution is shown if a BMF mean and 95% CI 1). Plausible, but largely unexplored, possibilities for the relatively higher MC accumulation by these consumers are low detoxification efficiency by zooplankton, MC trophic transfer via the microbial foodweb, contamination of zooplankton net samples with large cyanobacterial colonies and filaments, or the release of both free and bound MC in zooplankton during digestion by fish. Factors related to study design may have influenced the magnitude of MC biodilution. For example, consumers fed diets consisting of highly toxic cyanobacterial lab cultures and large, potentially inedible net phytoplankton showed greater biodilution when compared to seston. Given their hepa