Sea Grass as Possible Ocean Acidification Refugia for Shellfish in a High CO2 World (2014-16)

George Waldbusser
Oregon State University
College of Earth, Ocean, and Atmospheric Sciences
104 CEOAS Administration Building
Corvallis, Oregon 97331
Phone: 541-737-8964

Co-PI: Burke Hales, OSU

Concern is growing about the effects of ocean acidification on coastal species, particularly bivalves such as oysters and clams. Increased carbon dioxide (CO2) levels in acidified seawater changes how bivalve larvae form their shells. Prior laboratory studies showed that larvae perform better under pre-industrial CO2 concentrations, suggesting that these marine organisms may already be experiencing acidification stress. Indeed, larval failures at an Oregon shellfish hatchery have been linked to high CO2 water associated with coastal upwelling. Global increases in CO2 will result in more frequent, longer, and more intense high-CO2 events along the US West coast's California Current and associated estuaries.

Without a global carbon policy, adaptation and mitigation strategies are the only hope for coping with these conditions. One proposed strategy to improve conditions for acid-sensitive organisms is co-culture or restoration of photosynthesizing plant species in coastal zones. Aquatic plants such as sea grasses are known to absorb carbon in coastal and estuarine environments and are also associated with several species of bivalves. These associations appear strongest when conditions are most stressful. So, how can sea grasses help? 

The recent Washington State Blue Ribbon Panel on Ocean Acidification suggests that sea grasses are a likely candidate to help mediate the effects of acidification. However, the net sink of carbon by sea grasses can have significant day-to-night variability, and different sea grass species may differ in their influence on local carbon chemistry. Thus, more study is necessary before implementation of a widespread sea grass planting strategy.

Dr. Waldbusser’s research team hopes to build on their recent Sea Grant research on post-larval bivalves to better understand how acidification may affect oysters after they leave the hatchery. Researchers will determine whether sea grass meadows alter the local water chemistry, if different species affect water chemistry differently, and how oysters and clams perform in two different sea grass environments. Learning more about how acidification works in natural settings outside the lab is important to ecosystem-based management, maintaining the resilience of coastal habitats and keeping jobs and industry in our region.

Strategic Plan Focus Areas: Healthy Coastal Ecosystems and Habitats, Sustainable Fisheries and Aquaculture

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