Award: OCE-1131038

Increases in average temperature due to global warming have been implicated in changes in population dynamics, species interactions, and community structure in many ecosystems. Predicted increases in temperature variability are likely to drive additional biological disturbance, placing new demands on organismsÆ physiology and increasing the risk that species will exceed their tolerance limits. Resulting shifts in biodiversity may significantly alter important ecosystem properties such as productivity, nutrient cycling, and resistance to disturbance or invasion. While there is widespread recognition that climate change and loss of biodiversity can both dramatically alter ecosystem processes, we lack a well-developed framework for understanding the relative magnitudes of these effects or their interactions. Using a novel experimental manipulation of species diversity and temperature variability in the rocky intertidal zone, researchers Allen and Denny have demonstrated that with respect to transfer of energy up the food chain, high intertidal limpets (marine snails) are physiologically resistant to moderate increases in thermal variation. More surprisingly, diverse mixtures of grazing species respond to increased temperature variability in a complementary fashion that increases their overall productivity, due perhaps to better partitioning of their microalgal food. Based on their experimental data, they developed a graphical model to predict how local thermal regime and food availability interact to determine when sublethal negative effects of temperature stress will be large relative to the risk of mortality, and under what environmental conditions constitutive (permanent) versus inducible (plastic) forms of thermal defense should be favored. An important aspect of their model is its explicit recognition that physiological and ecological consequences of increasing environmental variability are determined by complex relationships between temperature and food. As the frequency and intensity of high temperature stress increase, the overall importance of sublethal effects will depend upon the level of food available to individuals. By simultaneously measuring the productivity, nutrient composition, and diversity of the microalgae that are the base of this food web, they were also able to explore how the composition of the algal community changes in response to different levels of limpet diversity, grazing pressure and temperature stress. Measuring interacting effects of consumer diversity and temperature variability allows them to better predict how natural communities will respond to a complex set of changing conditions, advancing our knowledge of the relative magnitudes of these drivers and the potential for interactions among them. Their results, concerning the impacts of thermal variation, can then be compared to predictions in the literature about the impacts of solely changing average temperature on biodiversity and ecosystem functioning. Broader impacts of this project were focused on increasing participation of women and underrepresented minorities in science by continuing an existing successful collaboration between California State University, Long Beach (CSULB), a High Hispanic Enrollment (HHE) Primarily Undergraduate Institution (PUI), and Stanford University. CSULB students spent 10 weeks each summer living and working at Hopkins Marine Station, gaining intensive hands-on research experience that will greatly enhance their preparation for graduate school and future careers in science. This award supported the research of 17 undergraduates; to date, seven have gone on to graduate school (one is an NSF Graduate Research Fellow) and several others are currently working in science professions; many of them are co-authors on peer-reviewed publications or manuscripts currently in preparation for submission. The postdoctoral researcher associated with the project, Dr. Luke Miller, received training and mentoring experience...