Ecological theory and experiments indicate that warming can increase the relative strength of top-down eVects via alterations to metabolic rates in several diVerent systems, thereby resulting in decreased plant biomass at higher temperatures. However,
the general influence of increased environmental temperature on top-down eVects is not well understood in systems where organisms experience relatively large variation in temperature. Rapid ocean temperature changes are pervasive throughout the Galapagos Islands due to upwelling and downwelling of internal waves, ENSO events and seasonality. We measured the eVect of large, but not uncommon, wáter temperature variation on the metabolism and grazing rate of a common subtidal herbivore and on photosynthesis of their algal prey in the Galapagos Islands in July 2012. We found that green urchin consumption and metabolism were greater at the higher temperature treatment (28° C), resulting in significantly less algal biomass. Our result that warming increased green urchin metabolic rates, even in a highly dynamic system, provides further support for a mechanistic link between environmental temperature and feeding rates. And further, our findings suggest individual response to temperature results in changes in top-down eVects. And if this response is maintained over longer-time scales of days to weeks, this could translate to alterations of larger-scale ecological patterns, such as primary producer community composition and structure.

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