Meeting Abstract

36.2  Tuesday, Jan. 5  Climate change and species interactions: predicting indirect effects GILMAN, Sarah; Friday Harbor Laboratories, University of Washington sgilman@jsd.claremont.edu

Average global temperatures are expected to warm by 1.4-5.8C over the next century. Although the direct effects of temperature on individual performance are well-documents for many species, less well understood is how these direct effects of temperature will influence interactions among species within a community. The barnacle Balanus glandula is one of the major space occupying organisms in rocky intertidal habitats in the San Juan Islands region of Washington, and is preyed upon by the intertidal whelk Nucella ostrina. Temperature is predicted to alter both the growth rate of B. glandula and the foraging activity of N. ostrina. To examine the cumulative effect of these changes, I separately manipulated body temperature and prey size distribution of N. ostrina and observed changes in growth rate and foraging behavior. Experiments were conducted in an outdoor tidal mesocosm system that allowed for two high tides and two low tides each day. Snails were assigned to one of three temperature treatments and one of two prey size treatments. Snails ate more barnacles when presented with smaller prey, but energy consumption (calories) declined. Warm temperatures reduced both snail growth and survival, particularly for the smallest snails in the experiment. When larger snails, were fed on the larger prey treatment, their growth and survival under the warmest temperature treatment was not reduced relative to controls. These results present a complex picture of the effect of temperature: changes in the prey size distribution altered the predator’s performance under thermal stress.