Effects of the invasive Asian clam Corbicula fluminea on benthic macroinvertebrate taxa in laboratory experiments

Abstract

: The invasive burrowing bivalve Corbicula fluminea has an impact on ecosystem processes and on ortter dynamics in sediments. However, little is known about its effect on benthic communities especially ganic matter dynamics in sediments. However, little is known about its effect on benthic communities, especially on macroinvertebrates. In laboratory experiments, we determined the effect of naturally occurring densities of C. fluminea (1012 ind. m -2 ) on ten macroinvertebrate taxa typical for the littoral zone of Lake Constance: two species of leeches, three species of gastropods, two amphipod species, one isopod, and two taxa of insect larvae (a stonefly and chironomids). We hypothesized that these benthic organisms might prefer C. fluminea over sand in pairwise habitat-choice experiments because of structural and biotic effects of the bivalves. We distinguished between biotic effects of living infaunal C. fluminea that were either starved (only bioturbation) or fed with algae (biodeposition, bioturbation and nutrient reallocation), and we tested the importance of their structural role using C. fluminea valves lying on sand. No benthic taxa avoided areas with live C. fluminea or their valves. The detritivorous gastropod Lymnaea stagnalis and the amphipod Gammarus roeselii were found in higher numbers in areas with fed C. fluminea than in areas with sand. Starved clams were only preferred over sand by the amphipod Dikerogammarus villosus. The epifaunal taxa Erpobdella octoculata, Glossiphonia complanata (Hirudinea), D. villosus, G. roeselii (Amphipoda), Asellus aquaticus (Isopoda), and Centroptilum luteolum (Ephemeroptera) preferred areas with C. fluminea valves to areas with sand. The crustacean species and the leeches preferred valves over sand more than they preferred fed or starved living clams over sand. C. luteolum was the only taxon that responded differently to C. fluminea in the three experiments, whereas gastropods and chironomids did not show differences. We conclude that on poorly structured sediments, valves of C. fluminea, which increase the surface area and substrate diversity, could lead to an increase of most epifaunal benthic invertebrates.