Date of Award
Thesis: Open Access
MS Marine Science
Environmental and Ocean Sciences
Many marine ecosystems are facing the growing threat of biological invasions. These invasions can have a variety of different impacts on ecosystems and their inhabitants. The Pacific oyster, Crassostrea gigas, is currently in the relatively early stages of invasion in San Diego estuaries. Crassostrea gigas is a large, filter-feeding bivalve that forms dense oyster beds on hard substrate. These oysters are known to outcompete native counterparts and drastically alter habitats where they are present. Crassostrea gigas is an ecosystem engineer that, through shell creation and formation of a dense oyster matrix, impacts ecosystems in a variety of direct and indirect ways. However, the impacts of this ecosystem engineer at an early stage of invasion are not well-understood. To investigate the effects of C. gigas in a relatively recently-invaded site, this study examined the relationships between oyster beds and macrofaunal assemblages in Los Peñasquitos Lagoon, San Diego, California, USA. Mudflat areas with oyster beds had markedly higher total abundance, species richness, and biomass of resident macrofauna, with bivalves (not counting the oysters themselves), amphipods, and decapods tending to have higher densities and biomass in oyster beds. Interestingly, for the range of oyster beds examined here, there were minimal associations between the amount of actual shell material present and macrofaunal properties, suggesting that there may be a threshold associated with bed impacts. Overall, the findings of this study align with similar conclusions of other global studies in suggesting that C. gigas as invaders and ecosystem engineers have potentially large impacts on the biodiversity, and that this should be an important consideration in considering management of this non-native bivalve and coastal ecosystems.
Copyright held by the author
Digital USD Citation
Jansen-Yee, Noah, "Crassostrea gigas Invasion in Southern California: Macrofaunal Diversity and Local Community Impacts of Ecosystem Engineers on Estuarine Habitats" (2022). Theses. 53.