EFFECTS OF LOW TIDE TEMPERATURE ON INTERACTIONS BETWEEN A PREDATOR AND ITS MOBILE PREY

Understanding how environmental conditions influence predator-prey interactions is crucial for assessing the effects of stress on rocky intertidal systems. I investigated the short- and long-term effects of ecologically relevant low tide conditions on interactions between sea star predators, Leptasterias, and mobile prey, the limpet, Lottia scutum, in Washington State. I observed short-term effects of low tide after a single exposure to one of three treatments: No Low Tide (underwater, 12 °C), Cool Low Tide (13 °C), or Warm Low Tide (21 °C). Low tide exposure and temperature affected the movement of Leptasterias: 100% of sea stars from the No Low Tide treatment moved during predation trials, compared to a maximum of 73% of individuals from the Warm Low Tide treatment. In contrast, low tide exposure and temperature had minimal effects on Lottia scutum. I quantified long-term effects of low tide on consumption rates of sea stars over a 32-day experiment that mimicked natural tidal cycles. Leptasterias from the No Low Tide treatment consumed 97 limpets in total, significantly more than those from the low tide treatments, which consumed only 41 limpets in total. Leptasterias in No Low Tide treatment gained an average of 22% of their starting body weight, while those in the low tide treatments lost weight. Differences in Leptasterias consumption rates between treatments emerged during periods of simulated spring tides with daily low tide exposure and at first diminished during periods of simulated neap tides with constant immersion, but differences grew over time. While we did not see evidence that these temperature conditions were stressful for this predator, low tide itself was a stressor. Our findings emphasize the importance of considering the cumulative effects of environmental stressors on intertidal organisms and the potential long-term consequences on ecosystem dynamics.