Abstract
Studies examining the impacts of introduced species on food webs often focus on the top-down effects of introduced predators. However, marine and estuarine systems have been invaded by plants that have the potential to alter carbon and nitrogen sources available to consumers. In San Francisco Bay, California, USA, hybridized cordgrass Spartina alterniflora × foliosa is adding C4 carbon biomass to this system. We used natural abundances of stable isotopes of carbon and nitrogen to examine whether infaunal and epifaunal food webs reflected the large detrital input from hybrid Spartina. We compared stable isotope signatures among macrofaunal invertebrate consumers collected in hybrid Spartina, native S. foliosa, or unvegetated mudflats. We found no additional shift towards hybrid Spartina in hybrid areas. Structural changes brought about by an invasive ecosystem engineer, specifically increased biomass and detrital inputs, do not necessarily result in its increased incorporation into the food web.
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Acknowledgments
Funding was provided by the Canon National Parks Science Scholars Program (E.B.), University of California Coastal Environmental Quality Initiative (E.B.), UC-Davis Public Service Research Group (E.B.), Bodega Marine Laboratory, Sigma Xi (E.B.), a Jastro Shields grant (E.B.), and the NSF Biocomplexity Program (DEB-0083583) (E.G.). We thank D. Ayres for cordgrass genetic analysis, and R. Blake, N. Rayl, S. Norton, and T. Dillon, for field and lab assistance. Point Reyes National Seashore (permit PORE-2001-SCI-0026), Gulf of the Farallones National Marine Sanctuary (permit GFNMS-2001–004), Cypress Grove Preserve, China Camp State Park, and East Bay Regional Parks provided access to study sites. We thank Grosholz lab staff, especially C. Tyler, as well as J. Stachowicz, D. Strong, and other reviewers for their comments and discussion.
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Brusati, E.D., Grosholz, E.D. Does invasion of hybrid cordgrass change estuarine food webs?. Biol Invasions 11, 917–926 (2009). https://doi.org/10.1007/s10530-008-9304-4
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DOI: https://doi.org/10.1007/s10530-008-9304-4