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Levin, L.A., Scripps Institution of Oceanography, La Jolla, USA, llevin@ucsd.edu
Neira, C., Scripps Institution of Oceanography, La Jolla, USA, cneira@coast.ucsd.edu

TROPHIC PATHWAYS OF INVASIVE SPARTINA REVEALED THROUGH 15N ENRICHMENTS

To understand the community-level consequences of Spartina foliosa-alterniflora hybrid invasion of the San Francisco tidal flats it is desirable to identify the species that consume the invasive as detritus. In separate experiments we enriched both the native, S. foliosa and the Spartina hybrid with 15N and introduced labeled detritus into surface and subsurface sediments. We observed rapid, strong 15N-label uptake by those infaunal species that survive well in Spartina-invaded sediments, primarily subsurface-deposit feeding annelids. Species that survive poorly in invaded sediments (surface feeding polychaetes, crustaceans and bivalves) ingested little 15N-labeled Spartina detritus, but some took up 13C-labeled surface algae. Among detritivorous macrofauna we observed similar food preferences for the native and invasive Spartina, with some evidence that blades and culms are preferred over roots and standing dead material. Isotope enrichment experiments can elucidate food chains in invaded ecosystems, in this case revealing bottom-up controls on faunal succession following invasion.

Presented at Estuarine Research Federation Conf. Seattle, WA Sept. 2003

Levin, L. A., IOD, Scripps Inst. Ocean., La Jolla, CA, USA, llevin@ucsd.edu
Currin, C., Nat. Ocean Service, NOAA, Beaufort, NC, Carolyn.Currin@noaa.gov
Neira, C. IOD, Scripps Inst. Ocean., La Jolla, CA, USA, cneira@coast.ucsd.edu
McMillan, P., IOD, Scripps Inst. Ocean., La Jolla, CA, USA, pmcmillan@ucsd.edu
Mendoza, G., IOD, Scripps Inst. Ocean., La Jolla, CA, USA, guillmendoza@hotmail.com
Whitcraft, C., IOD, Scripps Inst. Ocean., La Jolla, CA, USA, cwhitcra@ucsd.edu
Gonzalez, J., IOD, Scripps Inst. Ocean., La Jolla, CA, USA, jpgonzal@ucsd.edu
Carman, K., Dept. of Biol. Sci, LSU, Baton Rouge, LA, USA, zocarm@lsu.edu

IMPROVED UNDERSTANDING OF LARGE-SCALE TROPHIC SUCCESSION THROUGH SMALL-SCALE ISOTOPIC ENRICHMENT EXPERIMENTS

Of the many factors regulating succession in benthic marine communities, food has commanded relatively little attention. In California tidal wetlands, disturbance, restoration and plant invasions induce shifts from microalgal-dominated to plant-covered sediments. By enriching algae or bacteria with C-13 and Spartina or cyanobacteria with N-15, we are able to identify those infaunal taxa that preferentially feed on each food source, or C and N derived from these. Experimental results combined with time-series community data reveal that large-scale shifts in community structure in restored salt marshes (from insect to annelid-dominated assemblages) and Spartina-invaded tidal wetlands (from surface to subsurface feeders) are likely to be caused by changes in food availability.

2003 Am. Society of Limnology and Oceanography Meeting

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