ABSTRACT: Reductions in body size are hypothesized to be a universal response to climate warming, yet the proximate causes of change remain unresolved. In this study, we combined field evidence and demographic models to explore mechanisms relevant to temperature-related declines in the body size of an ectotherm exhibiting indeterminate growth. Our field data demonstrate that the body size of cup corals Balanophyllia elegans has decreased by ~35% over nearly 4 decades (1969-2007), during which seawater temperatures have increased by 0.6°C in the San Juan Islands, Washington State, USA. We developed a modeling framework, based on the Arrhenius equation and temperature-size theory, to explore the thermal dependence of maximum body size. Our models identified the growth rate of corals as a key demographic leverage point for changes in maximum body size, but temperature alone was likely insufficient to cause the observed magnitude of change. Our case study provides a simple template for integrating detailed demographic data with predictions derived from the temperature-size theory, in order to evaluate empirically the magnitude of body size decline in the context of climate warming. 

Author Info: 

Robin Elahi1,*, Kenneth P. Sebens2, Giulio A. De Leo1 

1Hopkins Marine Station, Stanford University, Pacific Grove, CA 93940, USA (*Biology PhD, '12)
2Department of Biology and Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA

Read full paper in the Marine Ecology Progress Series.