A risky business? Mussel farming in the face of ocean acidification and warming

As you walk past the Kings Market seafood aisle in Friday Harbor or browse at Costco, chances are that you will see fresh mussels harvested locally from Penn Cove Shellfish on Whidbey Island, WA. These mussels have been cleaned and washed to look enticing to buy, cook, and eat. What you do not see when you look at these mussels is one of the most important parts: the byssal threads that attached the mussels to the lines they grew on (Figure 1), enabling them to then progress from the ocean to your plate. (…)

The problem arises when the mussels fall off, leaving the lines bare. Mussel fall-off due to seasonally weak attachment and increased storm action is a process mussels encounter on rocky shores (Paine and Levin, 1981). A mussel becomes weakly attached when it produces fewer or poor quality individual byssal threads, making the animal more likely to dislodge under waves and currents. Mussel fall-off cuts into a grower’s yield at harvest and is a problem for the industry worldwide.

With funding support from Washington Sea Grant and the National Science Foundation, a team led by Dr. Emily Carrington and including Dr. Carolyn Friedman, Dr. Michael (Moose) O’Donnell, Penn Cove Shellfish General Manager Ian Jefferds, Biology graduate students Matt George, Molly Roberts, and Laura Newcomb have set out to address this problem. Our work seeks to identify what environmental factors may trigger weakened mussel attachment in farmed mussels. We started in the laboratory by identifying two potential culprits to test, ocean acidification and ocean warming. Using controlled experimental mesocosms (aka fancy Igloo coolers) in Friday Harbor Laboratories’ Ocean Acidification Environmental Laboratory (FHL OAEL), we exposed mussels to a range of conditions to identify the threshold values for weakening: pH below 7.6 (O’Donnell et al. 2013) and temperature above 19˚C (66˚F). We also learned that elevated temperature reduces the number of threads a mussel makes, further weakening whole mussel attachment.

With the lab experiments identifying pH and temperature as possible weakening agents, we moved out to a mussel farm to ask if mussels ever encounter these threshold conditions and if so, do these events coincide with weak mussel attachment?

Partnering with Penn Cove Shellfish (the oldest and largest mussel farm in the nation), we installed multi-parameter instruments in Penn Cove on Whidbey Island to log hourly measurements of seawater temperature and pH, as well as salinity, dissolved oxygen, and chlorophyll. These data are uploaded onto the internet in real time (http://nvs.nanoos.org/Explorer) so that we (and anyone else) can check in to see what the conditions are like at any time (Figure 4). (…)

Moving our research from the lab to the field has allowed us to extend our results to an industry that stands to be affected by changing ocean conditions. By installing sensors that monitor the water in real time, we hope to give mussel farmers an early warning system for conditions that could threaten their mussels. Recently we have expanded our studies to include Penn Cove Shellfish’s farm in Quilcene Bay, WA, made possible by our partnership with Washington State Department of Natural Resources. We are excited our collaborative research can contribute to sustaining a culturally and economically important resource for Washington State – and keep this popular seafood in grocery stores for years to come (Figure 5).

Laura Newcomb, San Juan Islander, June 2015. Article.


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