Effects of macroconsumers on benthic communities across a gradient of vegetation loss in tropical karst streams

Abstract

Though many studies have demonstrated top-down control by macroconsumers on benthic communities and ecosystem processes in tropical streams, few have simultaneously addressed such effects across a gradient of riparian vegetation loss. Here, we investigated if potential top-down effects induced by macroconsumers interact with native vegetation changes of tropical karst streams in Brazil. We experimentally excluded macroconsumers (e.g., fish and shrimp) from benthic habitats of seven streams with a range of forest cover from 20% to 100% and examined the effects on benthic invertebrate and periphyton communities. Across sites, the absence of macroconsumers had no effects on mean chlorophyll-a concentrations, total dry mass or abundance of benthic invertebrates. However, the periphyton community significantly differed between control and treatment replicates. Overall, experimental exclusion of macroconsumers resulted in weak or negligible effect on benthic communities, which contrasts a significant proportion of related literature conducted elsewhere. Such top-down effects have been poorly studied in tropical karstic streams to date.