Meeting Abstract

52.6  Thursday, Jan. 6  Foraging activity of the whelk Nucella ostrina in manipulated tidal regimes CARRINGTON, E*; KULL, K; UW Friday Harbor Laboratories ecarring@uw.edu

An important first step in developing a biophysical model to predict body temperature is to characterize the microhabitat in which the organism lives. This can be difficult for mobile organisms in complex landscapes with substantial thermal variability. In the case of the intertidal predatory whelk Nucella ostrina, foraging on its barnacle prey generally requires movement higher on the shore, which potentially increases the risk of thermal stress. How do snails balance the reward of food acquisition with the risk of temperature stress? We used outdoor tidal mesocosms to examine foraging patterns of snails over 16 weeks in Friday Harbor, WA. Treatments varied in the timing of aerial exposure, while total emersion time was constant. Snails exposed to daytime low tides followed a biweekly pattern, leaving refuges to feed for 2-4 days, then retreating for approximately ten days. The peaks in foraging activity coincided with the onset of spring tides, when aerial exposure was confined to early morning hours; snails acquired prey during times of reduced thermal risk. Foraging patterns of snails experiencing nighttime tides were aperiodic and elevated relative to those exposed to daytime low tides. These results underscore the importance of understanding the temporal patterns of microhabitat use when assessing the thermal exposure of mobile organisms.