Masters Thesis

Effects of Olympia Oyster (ostrea Lurida) Restoration Techniques on Invertebrate Community Composition

Ostrea lurida’s potential role as a foundation species has not been explored, so little is understood about ecosystem services produced by ongoing restoration efforts for the United States’ only native oyster species on the west coast. Further, the effectiveness of different techniques for restoring Olympia oyster beds has not been systematically evaluated. The most common technique is augmenting available habitat by adding dead shell onto mudflats and allowing remnant oysters to seed the shell with spat; shell has been added at varying thicknesses, either consolidated in bags or simply placed loose onto the mudflat. Here, I explored the effects of different combinations of Olympia oyster restoration techniques (varying the thickness of constructed shell beds using loose versus bagged oyster shell) on invertebrate abundance, diversity, and community composition. Twenty-five oyster beds were established in Newport Bay, Orange County, California in June 2010. Five beds were not augmented with any shell and were used as control plots. The other twenty beds were randomly assigned to be constructed using dead oyster shell at thicknesses of 12 cm or 4 cm using shell bagged in jute or loose shell (n= 5 replicates per treatment). Visual inspection of MDS plots and results from ANOSIM indicated after one year a significant shift in community composition of the oyster beds versus the control plots, with trends in differences of the thick beds and thin-bagged beds. However, the density of most invertebrate species changed over time and bagging of the shell in some cases also mattered. Amphipods, polychaetes and oligochaetes all declined significantly on some treatment plots over the study period, but not because of shell enhancements. Bivalves, gastropods and isopods all increased over the study period with trends towards increases on the thicker beds and thin-bagged beds, although insignificant. Results could inform future restoration efforts for this species and establish ecosystem services provided by O. lurida as a foundation species.

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