The ecological consequences of nonindigenous corbicula fluminea establishment on a benthic macroinvertebrate community

Abstract

The frequently high abundances achieved by the nonindigenous Asian clam, Corbicula fluminea, has caused concern regarding the potential negative ecological impact the clams may have on native benthic macroinvertebrate communities. This study examined the ecological consequences of C. fluminea establishment on the benthic macroinvertebrate community in a New Hampshire, USA, river by comparing the benthic community before and after establishment and comparing sites with and those without C. fluminea. The nonmolluscan benthic communities were sampled using a ponar grab and compared using community metrics of macroinvertebrate densities, taxa richness, Shannon diversity, Hilsenhoff Biotic Index, and Bray-Curtis similarities cluster analysis and MSD ordination. Native bivalves were sampled by divers excavating 0.25 m2 quadrats and compared using abundance and size-frequency distributions. No consistent significant difference was seen when comparing macroinvertebrate metrics before vs. after C. fluminea establishment or when comparing sites with and without C. fluminea for any of the metrics used. Metrics were often similar or improved at sites with C. fluminea relative to years before establishment or when compared to reference sites lacking C. fluminea. Bray-Curtis cluster analysis and MDS ordination failed to separate sites with vs. those without C. fluminea. Similarly, native bivalve abundances, namely Elliptio complanata and Sphaeriidae, were similar at sites with vs. sites without C. fluminea. Elliptio complanata size-frequency distributions did not differ significantly when compared across sites with and without C. fluminea. Rather than having negative consequences on the benthic macroinvertebrate community as many have proposed, it appears that C. fluminea may either have no effect or positive effects on the macrobenthos.