Mechanistic underpinnings of foraging variability in the common sea star, Asterias rubens, from Newfoundland, Canada

St-Pierre, Anne Provencher (2015) Mechanistic underpinnings of foraging variability in the common sea star, Asterias rubens, from Newfoundland, Canada. Masters thesis, Memorial University of Newfoundland.

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Abstract

The common sea star, Asterias rubens, is a major predator in rocky subtidal ecosystems in the northern Gulf of St. Lawrence and along the Atlantic coast of Newfoundland. Yet, knowledge about the mechanistic underpinnings of foraging variability in A. rubens in these highly seasonal systems is sparse. The present research tested effects of key biotic (body size, starvation, chemical cues from potential competitors) and abiotic (temperature, wave action) factors on: 1) displacement, microhabitat selection, and ability to contact blue mussel, Mytilus edulis, prey; and 2) mussel prey consumption and size selection in A. rubens from southeastern Newfoundland. Experiments in laboratory microcosms (wave tank and aquaria), as well as analysis of seabed imagery and sea temperature and wave data from one subtidal site, showed that wave action, and to a lesser extent starvation, are key modulators of the sea star’s inclination and ability to explore its environment and localize prey. In southeastern Newfoundland, the behavioral response of A. rubens to wave action and starvation is adaptable, being generally stronger in summer than winter, when sea temperature differs markedly. Starvation, body size, and their interaction strongly affect prey consumption and size selection. Consumption is relatively stable across the natural temperature range in late summer, significantly lower in winter than summer, and unaffected by the chemical presence of indigenous rock crab, Cancer irroratus, and invasive green crab, Carcinus maenas. Collectively, results speak to the importance of considering the interplay between organismal traits and ongoing changes in ocean climate to more accurately predict causes and consequences of alterations to northern reef communities.

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