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MEPS 292:111-126 (2005)
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Abstract
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Benthic macrofaunal communities of three sites in San Francisco Bay invaded by hybrid Spartina,with comparison to uninvaded habitats
Carlos Neira1,*, Lisa A. Levin1, Edwin D. Grosholz2
1Integrative Oceanography Division, Scripps Institution of Oceanography, La Jolla, California 92093-0218, USA
2Department of Environmental Science and Policy, One Shields Avenue, University of California, Davis, California 95616,
USA
*Email: cneira@coast.ucsd.edu
ABSTRACT: A hybrid cordgrass, formed from a cross between Spartina alterniflora (Atlantic cordgrass) and S. foliosa (Pacific cordgrass), has recently spread within the intertidal zone of south San Francisco Bay. Sediment properties and
macroinfaunal community structure were compared in patches invaded by Spartina hybrid and adjacent uninvaded patches at 3 sites in San Francisco Bay (2 tidal flats and 1 Salicornia marsh). We hypothesized that (1) sediments vegetated by
Spartina hybrid would have reduced sediment grain size, higher organic matter content, lower redox potential, lower salinity and reduced microalgal biomass relative to adjacent unvegetated tidal flat sediments, and (2) that differences in the
sediment environment would correspond to changes in the infaunal invertebrate community structure and feeding modes. We observed 75% lower total macrofaunal density and lower species richness in Spartina-vegetated sediments at Elsie Roemer (30 yr
old invasion) than in an adjacent unvegetated tidal flat. This was due to lower densities of surface-feeding amphipods, bivalves, cirratulid and spionid polychaetes. The proportional representation of subsurface-deposit feeders was greater in Spartina
patches than in unvegetated sediments. At a more recently invaded site (Roberts Landing; 15 yr invasion), Spartina patches differed from tidal flat sediments in composition, but not in abundance. Native (Salicornia) and Spartina
patches exhibited similar sediment properties at San Mateo, where the Spartina hybrid invaded 8 to 10 yr earlier. No differences were detected in densities or proportions of surface- or subsurface-deposit feeders, but the proportion of
carnivores/omnivores and grazers increased in the hybrid-invaded patches. These studies suggest that the invasive Spartina hybrid in south San Francisco Bay can have differing effects on sediment ecosystems, possibly depending on the location, age,
or type of habitats involved.
KEY WORDS: Benthos · Biodiversity · Cordgrass · Deposit feeding · Infauna · Macrobenthos · Plant invasion · Salt marsh · Redox potential
Full text in pdf format
Published in MEPS Vol.
292
(2005) on May 12
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2005
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