MEPS 546:147-161 (2016)  -  DOI: https://doi.org/10.3354/meps11620

ABSTRACT: Climate warming may drive organismal body temperatures beyond important physiological thresholds, ultimately leading to detrimental effects on populations and communities. Much of what we currently know about species responses to warming has come from correlations with weather patterns or laboratory experiments, which can lack mechanism and realism, respectively. We incorporated both of these properties into warming experiments by manipulating substratum temperature in situ, using passively warmed black and white settlement plates. We monitored vital rates of coexisting barnacles over 1 yr at mid- and high shore levels of the rocky intertidal on Salt Spring Island (British Columbia, Canada), a ‘hot spot’ for intertidal thermal stress. Warming by ~2°C negatively affected the vital rates and population sizes of both barnacle species; however, survival of the competitive dominant, Balanus glandula, was more severely affected than that of Chthamalus dalli, leading to a temperature-induced change in relative space occupancy in the mid intertidal. Survival of B. glandula was reduced by 38–97%, leading to a 94–95% reduction in space occupancy, depending on shore level. C. dalli survival was also reduced by warming (10-44%), leading to a 63–73% reduction in space occupancy. Further, growth rates of both species were lower (16-50%) in warm treatments than in cool treatments, resulting in smaller adult body sizes, which can cause delays in reproductive maturity. Experiments like this one, which manipulate warming in the field on multiple species across ontogeny, will further enhance our understanding of the ecological effects of climate change.

KEY WORDS: Climate change · Temperature · barnacles · Growth rate · Survival · Population · Ontogeny