Award: OCE-1041213

The material world of ocean acidifcation

            The survival of many of our favorite coastal organisms depends on the integrity of their structures.  Is their shell strong enough to deter predators?  Is their attachment to rock secure in the face of strong currents?  What happens to coastal marine communities when changing environmental conditions, such as ocean acidification (OA) or warming, alter how key biomaterials are manufactured and maintained? These questions guided our team of marine biomaterials experts based at the University of Washington’s Friday Harbor Laboratories (UW FHL). 

We targeted a suite of organisms (including mussels, seaweeds and other shellfish), each with a well-known biomaterial that serves a critical ecological function. Our research plan followed our unique ecomaterials approach; we use standard engineering techniques to detail how different combinations of environmental conditions affect the structural integrity of both calcified and non-calcified materials, then ask how such changes scale up to affect the performance of an organism under real-world challenges, such as crashing waves or crushing crab claws. Our ultimate goal is to provide insight into the range of possible biological responses to future changes in climate conditions.

 

A new  OAEL is bubbling with activity

One of our first activities was to contribute significantly to the build-out of one of FHL’s newest facilities, the Ocean Acidification Environmental Laboratory (OAEL).  Operating full swing in 2012, this state-of-the-art multi-user OA facility offers unique research and instructional opportunities for experimental manipulations with on-site monitoring of carbonate system parameters. The indoor mesocosms we developed were an essential tool for our work, allowing us to expose organisms to highly controlled environmental conditions. The mesocosms have been used widely by other researchers, from the University of Washington and several other institutions.     

 

Mussels lose their grip

While the oyster has become the “poster child” for the harmful effects OA on shellfish, there is growing concern that mussels are at risk as well. OA is well known to slow growth and erode shells, but our recent work shows OA targets a non-calcified structure that is literally a mussel’s lifeline, the byssal thread. 

A mussel uses its foot to mold each stretchy byssal thread one at a time to form a strong tether to culture ropes, neighboring mussels and whatever else it can reach. In fact, a challenge all mussel growers face is episodic “fall-off”, where water conditions cause mussels to produce weak byssus and up to 20-30% of the harvest slips off the ropes. We have observed similar mortality events in wild mussel populations as well.

What exactly triggers weak mussel attachment is unknown, but our recent work has identified two likely culprits: low pH and high temperature.  Using our highly controlled laboratory setting at the OAEL, we learned mussels produce weak, poor quality byssal threads if seawater pH is less than 7.6 or temperature is over 18°C.

Do mussels on the culture ropes or natural shores ever experience these conditions?  We are just beginning to find out, thanks to a new partnership with industry (Penn Cove Shellfish and Taylor Shellfish) and other federal and state agencies (NSF, NOAA, Washington DNR). We recently deployed in mussel rafts two sensor arrays that record temperature, pH, chl a, oxygen and salinity and post real-time to NANOOS (http://nvs.nanoos.org/Explorer, ...