Seagrass resilience to marine heat waves
Climate change is increasing baseline sea surface temperatures and is also increasing the frequency and severity of marine heat waves - periods of 5 days or longer when the water temperatures exceed the 90th percentile of the long-term record. These heat waves can have devastating effects on coastal habitats, including seagrass meadows.
In coastal Virginia, marine heat waves in July 2012 and June 2015 caused large-scale die-backs of the eelgrass meadows. Using long-term monitoring data from the Virginia Coast Reserve LTER, I studied the resilience of the meadow to heatwave disturbance at the landscape scale (km2). Depth was a critical factor in the eelgrass recovery. Eelgrass growing at the shallow and deep ends of the habitable depth range was more vulnerable to the effects of the heat wave, due to interactions with light limitation at deeper depths and increased heat stress at shallow depths. This work is published in Estuaries and Coasts here.
Seagrass loss from marine heat wave disturbance can also affect the "blue" carbon stored in the sediments below the meadow. In our Virginia meadows, areas that were most exposed to high temperatures during a marine heat wave lost the most blue carbon, while less exposed areas of the meadows were more resilient. As climate change continues, seagrass blue carbon will be increasingly vulnerable to disturbance from marine heat waves. Our assessment of the impact of marine heat waves on seagrass blue carbon in the Virginia meadows is published in Frontiers in Marine Science here.