Published Summer, 2009

by Cynthia Hansen

You might think that a mussel bed is home only to- well, mussels, of course! But the shells and filaments mussels use to anchor themselves to their rocky habitats can provide homes for hundreds of different species, offering protection from the harsh conditions of the intertidal zone. While mussel beds can withstand the changing tides, global climate change may cause damage to these diverse ecosystems. As the amount of CO2 in the air increases, so does the amount of CO2 dissolved in seawater. The resulting acidification changes the basic chemistry of the oceans and decreases the growth rate of organisms which rely on dissolved calcium carbonate to build their shells. If current CO2 emission trends continue, it is possible that mussels will remain smaller for longer periods of time and be less able to protect associated epifauna (organisms which live on and among the mussels) from temperature extremes, which may also increase due to global climate change.

Rebecca Gooding, a graduate student working towards her PhD at the University of British Columbia in Vancouver and the recipient of a 2008 Padilla Bay Research Assistanceship, is studying how mussel size and mussel bed temperature impact epifaunal communities. Her research is being conducted on the rocky shores of Saddlebag Island, located just east of Guemes Island in Padilla Bay.

Becca used two techniques to create mussel beds on Saddlebag Island. First, she cleared small plots of algae, added mesh cages to keep out predators, and allowed mussels to settle in both the shaded (cool) and unshaded (warm) plots. Second, she transplanted mussels of various sizes from dock pilings to Saddlebag Island. Mussels of small (10-30 mm) and large (35+ mm) shell lengths were painted black or white to increase or decrease temperature. By sampling the epifauna among the mussels and identifying individual species in the lab, Becca will be able to observe how mussel size and mussel bed temperature combine to impact the hundreds of other organisms that call mussel beds home. Becca's research will provide insight into how intertidal communities in and around Padilla Bay might react to changes in the Earth's climate. It will also provide a framework for future research into climate change's impact on whole communities rather than individual species. As atmospheric CO2 levels rise, it's important to keep looking among the mussels.