Temperature - Food Web projects
1. Warming strengthens herbivore-plant interactions. Metabolic effects of warming suggest declines in herbivore abundance with warming, and either no change in plant abundance, or declines. We reached this conclusion by combining metabolic models with classic consumer-prey models.
O’Connor, M. I., B. Gilbert, and C. J. Brown. 2011. Theoretical predictions for how temperature affects the dynamics of interacting herbivores and plants. The American Naturalist. 178(5): (or email for copy).
O’Connor, M.I. 2009. Warming strengthens an herbivore-plant interaction. Ecology. 90(2) 388-398.
2. Warming Shifts Food Web Structure and Metabolism. Small amounts of ocean warming may have dramatic effects for ocean food web processes, and these effects may be quite predictable. Consistent with predictions based on universal metabolic responses to temperature, we found that warming strengthened consumer control of primary production, shifted food web structure and reduced total biomass despite increases in primary productivity in a marine food web. Synopsis.
3. Testing the temperature dependence of stocks and fluxes in an aquatic food web
Increasing evidence suggests a fundamentally weaker response to warming for primary production relative to heterotrophic metabolism. For food webs dominated by ectotherms, environmental temperature should therefore change the flux of energy and materials in food webs, and potentially lead to changes in food web structure in a predictable way. Theory predicts that fluxes through the food web increase with warming but standing stocks at higher trophic levels decline as metabolic rates increase. Important questions remain: Does this prediction apply to food webs with three trophic levels? Can the functional responses of flux or standing stocks can be modified by changes in body size? We tested these questions by warming planktonic freshwater food webs for 11 weeks in summer 2011 at an outdoor facility at the University of British Columbia. In a regression design, 30 cylindrical 300-L mesocosms spanned a temperature range of about 10 C. In early June, clean water was inoculated with identical planktonic assemblages (phytoplankton, zooplankton and notonectids). [Mary O’Connor and James Stegen, 2011. Presented at ESA 2012.]
4. Integrating body size and thermal scaling to understand the effects of temperature on food webs. Hamish Greig and Mary O’Connor led a working group funded by CIEE to synthesize theory and predictions for how warming affects food webs. The group includes top theorists and empiricists, and we plan two meetings and several products.
5. What are the indirect effects of warming on prey food quality and size structure? Jessica Garzke from IMF-GEOMAR is leading Tank Experiment 2012!
6. Effects of ocean temperature on marine larval dispersal. Life cycles of marine animals are influenced by ocean temperature. At warmer temperatures, young marine animals develop faster than they would in colder water. For many fish, shellfish and other species, the development period is a time of dispersal in ocean currents to habitats where young animals can grow to adulthood. Warmer temperatures shorten the period of dispersal, and therefore may have major implications for the distance the larvae disperse. So ocean temperature can be linked to population connectivity, species ranges, and possibly the effectiveness of conservation and management efforts.
Using a statistical analysis, we tested the generality of the effect of temperature on larval development. We found that for a diverse set of marine animals (nearly all we tested) a single quantitative model describes the effect of temperature on larval development (O’Connor et al PNAS 2007). This effect implies potentially severe and predictable effects of small changes in ocean temperature for the dispersal distance and survival of marine larvae.