Effects of Warming on Aquatic Snails and Periphyton in Freshwater Ecosystems with and without Predation by Common Carp

Abstract

Freshwater gastropods play key roles in shallow aquatic ecosystems, with a central position in the periphyton–gastropod–fish trophic pathway, as they feed on periphyton and are preyed on by animals of higher trophic levels. Thus, it is of great interest to explore how climate change impacts the gastropod community and the trophic cascading effects on periphyton. Here, we constructed a simplified, shallow lake food web in 24 large mesocosm tanks to simulate warming (+4.5 °C) on the population responses of two common snails (Bellamya aeruginosa and Radix swinhoei) in two different systems (without/with common carp Cyprinus carpio) over 200 days. We found that warming lowered the biomass and density of R. swinhoei by 16.8% and 41.6%, respectively, and accelerated the average time of density peak of R. swinhoei by 21.5 days in the common carp-absent system. The density of B. aeruginosa in the warming with common carp group was lowered by 79.8% more than in the warming group without common carp. The averaged biomass and density of R. swinhoei in the fish-present system significantly lowered by 64.4% and 92.5%, respectively, compared to the fish-absent system. Cascading effects were also observed, as the snail communities declined under warming, that is, the grazing pressure on periphyton was less, resulting in its higher biomass. In conclusion, in the fish-absent system, warming decreased the biomass and density of the R. swinhoei, and in both snail populations, the biomass and density were much higher than those in the fish-present system. Due to the different phenology of snail species and species-specific predation, future stronger predation in a continuous warming condition might undermine the diversity of the gastropods, thereby changing food web structures in shallow freshwater ecosystems.