Document: DAN-3-80-7

Alteration of microbial community composition and decomposition by an invasive intertidal eelgrass, Zostera japonica, in a Washington estuary.

HAHN, D.R.*

University of Washington Seattle WA 98195 USA ¹

Abstract:
Biological invasions clearly alter the composition and community dynamics of invaded areas and can potentially alter ecosystem processes including productivity, decomposition, nutrient cycling and hydrology. Quantitative data demonstrating such effects, however, are scarce, especially in marine environments. I have conducted research at Padilla Bay, Washington to examine the effect that an introduced intertidal eelgrass, Zostera japonica, has on microbial processes, rates of decomposition, and associated ecosystem properties in this estuarine environment. A series of observational and experimental studies examined sole source carbon usage (SSCU) by microbial assemblages, enumerated bacterial abundance, and assessed rates of decomposition in beds of Z. japonica and in beds of its native congener, Z. marina. Differences in SSCU by microbial assemblages and differences in bacterial enumeration indicate that microbial assemblages differ between beds of the invasive and native species. Decomposition of eelgrass in the field differed between Z. japonica and Z. marina with each eelgrass species decomposing more slowly when placed in beds of its own vegetation type than the vegetation of its congener. These results indicate that this abundant invasive species can alter rates of decomposition and does so mainly by altering the associative decomposer assemblage.

Keywords: invasive species, estuarine, decomposition

This abstract is being presented at: 2:45 PM in session:
Oral Session #65: Wetlands, Estuaries and Salt Marshes.