Regional Assessment of the Invasive Macrobenthos in the Small West Coast
Estuaries

Henry Lee II 1, Walter Nelson 1, Janet Lamberson 1, and Deborah A. Reusser 2

1. U.S. Environmental Protection Agency (USEPA), ORD, WED, Pacific Coastal Ecology Branch, Newport, OR
2. U.S. Geological Survey (USGS), National Mapping Division, WGSC, Seal Rock, OR

In 1999, U.S. EPA's EMAP program surveyed the soft-bottom benthic communities in the estuaries of California, Oregon, and Washington exclusive of the large systems (Puget Sound, Columbia River, and San Francisco Bay which were sampled in 2000). Out of a total of 677 benthic species, 43 were nonindigenous and 88 were cryptogenic. The polychaetes Pseudopolydora paucibranchiata and Hobsonia florida and the amphipods Grandidierella japonica and Corophium acherusicum were the most abundant nonindigenous species. The polychaetes Streblospio benedicti and Pygospio elegans were the most abundant cryptogenic species. In contrast to the importance of polychaetes among the nonindigenous and cryptogenic species, amphipods were the numerical dominants among the native species, in particular two species of Corophium. The EMAP probabilistic survey design allowed statistically unbiased estimates of the area invaded as measured by different metrics. Approximately 25% of the estuarine area contain no nonindigenous species. In contrast, nonindigenous species constituted >=50% of the individuals in 2.5% of the area. As measured by the percentage of the species per sample, nonindigenous species were the major component of species richness in 7.5% of the area of these estuaries. Using proposed invasion criteria, approximately 15% of the area of the small West Coast estuaries would be classified as invaded or highly invaded. These results provide the first regional-scale evaluation of the nature and extent of invasion of the estuaries on the West coast.

Keywords: Invasive species, macrobenthos, West Coast, estuaries, EMAP