Ms Robin Fales1,2, Helen Berry3, Danielle Claar3, Emily Carrington1,2
1University of Washington, Department of Biology, Seattle, USA, 2Friday Harbor Laboratories , Friday Harbor, USA, 3Washington Department of Natural Resources, Nearshore Habitat Program, Olympia, USA
Increased global temperatures have negatively impacted a variety of marine ecosystems. One strategy to mitigate these impacts is to focus conservation and restoration efforts on populations already capable of dealing with higher temperatures. There are a broad range of abiotic conditions in the Salish Sea of western USA & CAN, with colder waters near the open coast and warmer waters in inlets. While there is a large diversity of cold-water kelp species in the Northeastern Pacific, Nereocystis luetkeana (bull kelp) plays an important role as the only large canopy forming species within the inland Salish Sea and is experiencing declines at sites associated with elevated temperatures. Therefore, we utilized this natural gradient of temperatures to test whether thermotolerance of adult sporophyte blades differed across populations at eight sites. We measured kelp condition including pneumatocyst size, blade thickness, C:N ratios, and we collected blade tissue plugs for laboratory experiments. We incubated tissue plugs for 36 hours in constant temperatures ranging 9-27°C and measured growth, photosynthesis, respiration, and dark adapted yield (Fv/Fm) to estimate thermal performance curves. We found higher optimal temperatures (Topt) at warmer sites but a similar critical thermal maximum (CTmax) of 21°C across all sites. Our findings indicate that conservation and restoration should be targeted in waters below 21°C and that warmer populations, potentially due to their poor condition as evidenced by thin blades, may not be more thermotolerant.
Biography:
Robin Fales is a PhD candidate at the University of Washington, Department of Biology and Friday Harbor Laboratories in the US. Her dissertation focuses on kelp physiological responses to climate change to inform conservation.
