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Dwarf eelgrass, Zostera japonica: a malevolent, benevolent, or benign invasive ecosystem engineer?
Citation:
COLE, F. A. AND S. P. FERRARO. Dwarf eelgrass, Zostera japonica: a malevolent, benevolent, or benign invasive ecosystem engineer? Presented at 20th Biennial Meeting of the Coastal and Estuarine Research Federation, Portland, OR, November 01 - 05, 2009.
Impact/Purpose:
Dwarf eelgrass, Zostera japonica, is an introduced ecosystem engineering species first reported on the US west coast in 1957.
Description:
Dwarf eelgrass, Zostera japonica, is an introduced ecosystem engineering species first reported on the US west coast in 1957. In some US Pacific Northwest estuaries its areal coverage now exceeds that of the native eelgrass species, Zostera marina. Natural resource management’s response to Z. japonica’s invasion has varied. In Washington State, it is a protected species. In California, there are programs for its eradication. Oregon has no management policy on Z. japonica. Benthic macrofauna are an important component of the estuarine food web providing food for ecologically and economically important fish, crabs, birds and other wildlife. The spread of Z. japonica could alter estuarine foods via its effect on benthic macrofaunal communities. In this study, we compare benthic macrofaunal communities in Z. japonica, Z. marina, and unvegetated intertidal habitats in three US Pacific Northwest estuaries: Tillamook Bay and Yaquina Bay, Oregon, and Grays Harbor, Washington. In all three estuaries the proportion of non-indigenous benthic macrofaunal species and individuals was much higher in Z. japonica than in Z. marina or unvegetated habitat. In across-habitat comparisons, the mean (gm-2) total benthic macrofaunal biomass was greatest in Z. japonica habitat in Tillamook Bay and Grays Harbor and lowest in Yaquina Bay. Estuary-wide benthic macrofaunal species richness was lower in Z. japonica habitat than in Z. marina habitat in all three estuaries and lower than unvegetated in two of the three estuaries. Our results indicate that, with respect to benthic macrofauna, the primary deleterious effects of Z. japonica’s expansion in US Pacific Northwest estuaries are the facilitation of non-indigenous benthic macrofaunal species and the possible reduction of benthic macrofaunal species richness at the landscape scale.