Meeting Abstract
Nearshore eelgrass habitats along the Pacific coast of North America play an important role in erosion control, fish and invertebrate development, and local biogeochemical processes. A key grazer in these ecosystems is Phyllaplysia taylori, a sea hare living on the Zostera marina eelgrass blades that cleans blades of epiphytic algae, diatoms, and bryozoans, allowing for increased photosynthesis and growth. P. taylori has direct development, evident in ecological surveys indicating limited dispersal potential. Isolated populations from Grays Harbor, WA to Morro Bay, CA were tested for local adaptation in thermal tolerance plasticity, calculated as acclimation response ratios of upper thermal limits (CTmax ARR); upper limits were recorded as high as 35°C. Sea hares were subject to a 4°C/hour ramp and monitored for muscle failure, when they are unable to perform their ecological function. Populations from Humboldt Bay, CA and San Francisco Bay, CA had the highest ARRs over the range of 13°C-21°C (ARR=0.46, 0.38). Differences in the ARR between sites were most parsimoniously explained by a linear model with ecological factors of eelgrass length and frequency, epiphytic coverage, and location found (ΔAIC=0). Evidence of local adaptation in thermal plasticity is strong, as the ARR was best explained by differences in ecological factors, not latitude. Our results suggest that mid-range populations have the greatest potential for thermal acclimation and therefore a greater chance of persistence under future climate scenarios. Since P. taylori plays a key role in eelgrass health, understanding local differences in thermal plasticity will have significant implications for eelgrass restoration efforts under future ocean warming.
