BROWN, A.C.; WEBER, K.L.*; University of New England, Biddeford, ME; University of New England, Biddeford, ME: Effect of Seasonal Temperature on Prey Size Selection, Consumption Rates, and Energetic Cost of Attack by Asterias vulgaris on Mytilus edulis
The intertidal habitat on the coast of Maine has large seasonal fluctuations in temperature and there is very little known about how these variations affect the predator-prey relationship between Asterias vulgaris and Mytilus edulis. Seastars in the fall (water temperature ~ 13oC) consumed the same sized mussels as in the winter (water temperature ~ 3-5oC). The consumption rate by seastars at fall temperatures (5.33 � 4.21 mussels per seastar per 2 weeks) was not statistically different than that of seastars at the winter temperatures (5.89 � 3.33 mussels per seastar per 2 weeks). The seastars in the fall had a �resting� metabolic rate of 1.57 � 0.39 kJ per 2 weeks per animal, which increased to 1.65 � 0.36 kJ per 2 weeks per animal when they attacked M. edulis. This was a 4.6% increase in the metabolic rate due to cost of attacking prey. The seastars in the winter had a �resting� metabolic rate of 0.98 � 0.47 kJ per 2 weeks per animal, which increased to 1.33 � 0.68 kJ per 2 weeks per animal while feeding. This was a 34.7% increase in the metabolic rate as the seastar attacked the mussels. The seastars in the fall consumed on average 24.4 kJ per 2 weeks while they only needed 1.57 kJ per 2 weeks to survive. The seastars in the winter consumed on average 25.5 kJ per 2 weeks yet only needed to consume 0.98 kJ per 2 weeks to survive. Despite the apparent increase in the cost of attack at winter temperatures, there is a slightly lower �scope for growth� at higher fall temperatures due to temperature effects on metabolic rate and no concomitant change in consumption rate.
