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Contributed Talk

Session: : Climate Change 4

COS 254-1 - Biogeographic variation in organismal success: the influence of local physiology and thermal environment on the intertidal barnacle Balanus glandula.

Thursday, August 10, 2023
10:00 AM – 10:15 AM PDT
Location: B117
Abstract: Most species show intraspecific variation in thermal tolerances across their geographic range, but physiology is not always well-matched to location. Thermal mismatches increase vulnerability to warming temperatures under climate change. Marine intertidal species are unique in occupying a habitat with two distinct thermal environments. While extreme heat stress occurs primarily at low tide, most species are only active during high tide. Moreover, low and high tide temperatures are not spatially correlated along the west coast of the United States. We compared the growth rates of the intertidal barnacle Balanus glandula on naturally occurring rock walls at three locations spanning 1000 km: Los Angeles, California (LA, warm water/warm air), Bodega Bay, California (BB, cold water/cold air) and Friday Harbor, Washington USA(FH, cold water/warm air). Based on prior laboratory studies of each population's physiology we predicted that barnacles from the northernmost FH site would be the least well matched to local thermal conditions and show reduced survival and growth compared to the other two sites. We found that survival was greatest at the warmest of the three sites (LA) and lowest at the FH site. Surprisingly, survival rates increased at higher elevations within sites, suggesting that predation may play a larger role in B. glandula survival than emersion stress. Growth rates were higher at FH than LA, with BB intermediate, although the differences were not statistically significant. The higher growth at FH was unexpected and may reflect a dampening effect of colder water temperatures on overall energy demand. These results suggest that B. glandula’s success reflects a complex interplay between population-level differences in thermal response curves and local environmental conditions, with conflicting effects of air and water temperatures.