Ruesink, 2010, Scale-dependent and indirect effects of filter feeders on eelgrass:  Understanding complex ecological interactions to improve environmental impacts of aquaculture

Summary 

In the Pacific Northwest, eelgrass (Zostera marina) and native oysters (Ostrea conchaphila) have historically provided valuable bioengineered habitats for varied species, like juvenile salmonids transitioning from freshwater to the ocean. Recently, endangered listing of some salmon stocks has raised questions about the impact of aquaculture farms on these species and their habitats, particularly eelgrass. To address these concerns, this project aims to understand the ecological ramifications of cultivating two filter-feeding bivalves—Pacific oysters (Crassostrea gigas) in Willapa Bay and geoducks (Panopea abrupta) in Puget Sound—regions that also harbor native eelgrass populations.

Our focus here is twofold: we aim to assess how increased bivalve populations ("press perturbations") and planting and harvest disturbances ("pulse perturbations") affect eelgrass' resilience and resistance respectively. This understanding will facilitate scientific decision-making on aquaculture practices that balance commercial interests with ecological sustainability, aiding managers in conservation efforts. The proposed research will provide insights into the interplay between aquaculture practices and habitats crucial for community ecostasis.

Objectives

1. Test the ability of benthic filter feeders to remove particulates from marine waters, and the response of eelgrass in distribution or growth rate.
2. Test the ability of benthic marine filter feeders to increase the nutrient and organic content of sediments through production of feces and pseudofeces, and the response of eelgrass in distribution, growth rate, and tissue quality.
3. Test the response of eelgrass to filter feeders in terms of eelgrass seed recruitment, germination, and seedling success.