Meeting Abstract
Climate change is expected to cause organisms to shift their distributions and there is great interest in understanding when and where they will move. The porcelain crab Petrolisthes cinctipes is found under rocks in the mid-intertidal zone on North America’s Pacific coast where temperatures reach the crabs’ thermal limit. The low intertidal zone is a cooler habitat but moving there would likely result in their increased density. We hypothesized that elevated temperatures will cause P. cinctipes to move, increasing their density and aggressive interactions. We tested this with experimental mesocosms that replicate an elevation gradient with automated temperatures and tides. Temperatures used were recorded under a rock at the collection site and modified to not exceed the critical thermal limit of the crabs. Tides were programmed to mimic the tides experienced during that same week. There were 3 treatments: tidal water variation with low tide warming, tidal water variation with no low tide warming, and constant immersion. Experiments lasted one week after which crabs were surveyed for location and injury/mortality. We found that crabs in enclosures with warming experienced more injuries (proportion of crabs injured = 0.17 ± 0.02 vs 0.08 ± 0.02, p=0.003) but there was no difference for crab locations (proportion of crabs in high intertidal zone = 0.18 ± 0.05 vs 0.11 ± 0.04, p=0.32). Increased injury under heat stress suggests that there may be indirect negative effects of temperature stress that result from altered behavioral interactions. Understanding indirect effects such as these may help predict how and when species distributions will shift in the future.
