Cyanobacteria as a Food Source for Invertebrates: Results of a Model Experiment

Abstract

Abstract Cyanobacterial blooms are regarded as a global environmental problem. The role of cyanobacteria in the food web of water bodies is still unclear. We have carried out an experimental study of invertebrate trophic relationships during the bloom of the cyanobacterium Aphanizomenon flos-aquae . The key links of the food web—plankton, microperiphyton, detritus, and benthic invertebrates—were collected for stable isotope analysis of carbon (δ 13 C) and nitrogen (δ 15 N) after 20-day exposure in mesocosms simulating the conditions of the near-shore biotope of the Rybinsk Reservoir without cyanobacteria (variant I) and with high abundance of cyanobacteria (variant II). Statistically significant differences in the δ 15 N values for crustaceans (Cladocera, Copepoda, Asellus aquaticus and Gmelinoides fasciatus ), and mayfly larvae have been revealed between the variants: these values were 1–4‰ lower in the variant with cyanobacteria than in the variant without them. The cyanobacteria-induced shifts in the δ 15 N value for consumers indicate an assimilation of diazotrophic nitrogen and incorporation of cyanobacterial nutrients into their food chains.