Wasson, K., T. Fenn, and J.S. Pearse, 2003. Habitat Bias in Marine Invasions of Central California, Elkhorn Slough National Estuarine Research Reserve.

Proceedings of the Third International Conference on Marine Bioinvasions, La Jolla, California, March 16-19, 2003, p. 127.

Habitat Bias in Marine Invasions of Central California

We carried out a two-part investigation that revealed habitat bias in marine invasions. First, we compared invasibility of hard vs. soft substrate habitats in Elkhorn Slough, an estuary in central California, by comparing abundance and richness of native vs. non-native species in quantitative samples from each habitat type. Our results reveal that the hard substrates are much more heavily invaded than the soft substrates; the infaunal mudflat community is dominated by native species, while the fouling community on rocks and shells is dominated by non-native species. Nearly all the hard substrates in Elkhorn Slough, as in most estuaries along the Pacific coast of North America, are artificial (jetties, rip-rap, docks, etc.). The absence of an extensive native fouling community adapted to hard substrates may facilitate invasions of this habitat type. Moreover, two major vectors responsible for marine introductions, oyster culturing and ship-hull fouling, are much more likely to transport fouling species than mudflat infauna.

The second component of our investigation consisted of a comparison of estuarine and open coast invasion rates. We
examined native vs. non-native species richness in Elkhorn Slough and adjacent rocky intertidal habitats along the central California coast from Carmel to Pigeon Point. The absolute number of non-native species in the estuary was about an order of magnitude higher than along the open coast. Moreover, non-natives accounted for over 10% of the richness of the estuarine fauna, while they comprised less than 1% of the richness of the open coast fauna. The strikingly higher invasion rate of estuaries vs. open coasts may be the result of multiple factors, including greater human alteration of estuaries, less rich native estuarine communities to provide biotic resistance, and greater influence of transport vectors bringing invasive propagules to estuaries.

Contact: Kerstin Wasson, Elkhorn Slough National Estuarine Research Reserve, 1700 Elkhorn Road, Watsonville, CA 95076, USA
Key Words: Nonindigenous, Colonization, Population_dynamics
Product Type: Publication, Proceedings
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