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Linking terrestrial and estuarine ecosystems: Organic matter sources supporting the high secondary production of a non-indigenous bivalve
Citation:
Dias, E., P. Morais, C. Antunes, AND J. Hoffman. Linking terrestrial and estuarine ecosystems: Organic matter sources supporting the high secondary production of a non-indigenous bivalve. Biological Invasions . Springer SBM, New York, NY, 16(10):2163-2179, (2014).
Impact/Purpose:
This study details the food web interactions of one of the most globally widespread aquatic invasive species, the Asian clam (Corbicula fluminea). The study revealed that the clam has the ability to switch nutritional sources based on the quality of food present. The result is important because it reveals a mechanism by which Asian clam can adapt to environments with low food quality. This demonstrates a potentially powerful competitive response in novel environments characterized by low food availability. The data also suggest that that Asian clam has the ability to couple both pelagic and benthic food webs in estuaries to the terrestrial ecosystem, thereby altering ecosystem-level energy flows.
Description:
The Asian clam Corbicula fluminea is one of the most pervasive species in freshwater ecosystems. Our objective was to characterize the trophic interactions of C. fluminea in the Minho river estuary (NW-Iberian Peninsula, Europe), an estuarine ecosystem in which C. fluminea presently dominates the benthic macrofauna biomass. We identified and quantified the contribution of different OM sources supporting the production of C. fluminea in the Minho River estuary using C and N stable isotope analysis. A pronounced shift in the quality of organic matter available for C. fluminea occurred along the estuarine mixing zone. Stable isotope analysis, C:N ratios, and phytoplankton contribution estimates based on C: Chl a revealed that POM was largely comprised of terrestrial derived organic matter (OM) in freshwater stations (TFW) and was increasingly comprised of phytoplankton, a more palatable food source, towards the polyhaline estuary. A similar shift in isotopic composition along the estuarine mixing zone was observed in C. fluminea, suggesting a shift in the food sources used in response to the change in food quality. Accordingly, the food web model attributed most C. fluminea biomass to terrestrial derived OM in the TFW (80%) decreasing downstream toward an increasing contribution of phytoplankton (50%). Although the majority of the food sources identified during this study were being filtered from the water column (70-90%), reliance on sediment OM and microphytobenthos provided evidence for deposit feeding by C. fluminea. Thus, data interpretation suggests that C. fluminea has the ability to adapt to environments with low food quality, which can be a competitive adaptation in systems with perennial low food quality such as the Minho River estuary. Moreover, its ability to couple benthic and pelagic environments and terrestrial ecosystems demonstrates a strong potential to alter food web flows in aquatic ecosystems.
