Primary Investigators: Jeff Davidson, Maya Groner Co-Primary Investigators: John Bucci, Colleen Burge, Carolyn Friedman, Sandy Wyllie-Echeverria

Climate change has been associated with declines of coastal organisms and this is impacting wild and farmed fisheries. In the case of organisms with calcifying shells, ocean acidification (OA) is a particular threat and has led to closures of oyster aquaculture sites and production losses. This is not only an economic loss, but an ecological one as well, as oysters provide numerous ecosystem functions, including water filtration and formation of reef habitats. One possible mitigation strategy for OA in soft sediment coastal habitats is by transplanting seagrass species to affected sites. Seagrasses grow faster in high CO2 environments and fauna associated with healthy seagrass meadows can benefit from OA environments, in part because seagrasses remove CO2 and HCO- from the water column for photosynthesis. This photosynthetic activity can create an OA buffer that extends beyond the seagrass canopy, such that these beds can provide a refuge for pH-sensitive organisms that reside in and close to these systems.

We propose to use field and mesocosm experiments to quantify the effects of co-culturing eelgrass (Zostera marina) and oysters in current and projected ocean chemistry profiles. We will assess growth, survival, health and population size of eelgrass, and of larval and juvenile Pacific oysters (Crassostrea gigas). The proposed research fills the goals of CERC by providing evidence-based research central to sustainability of aquatic food and animals.

We will test the following hypotheses: 1) Eelgrass presence increases seawater pH, alkalinity and the aragonite saturation state; 2) Eelgrass presence improves oyster survival and growth rates; 3) Eelgrass health increases with decreasing ocean pH.