Oceanic communities are sources or sinks of CO2, depending on the balance between primary production and community respiration. The prediction of how global climate change will modify this metabolic balance of the oceans is limited by the lack of a comprehensive underlying theory. Here, we show that the balance between production and respiration is profoundly affected by environmental temperature. We extend the general metabolic theory of ecology to the production and respiration of oceanic communities and show that ecosystem rates can be reliably scaled from theoretical knowledge of organism physiology and measurement of population abundance. Our theory predicts that the differential temperature-dependence of respiration and photosynthesis at the organism level determines the response of the metabolic balance of the epipelagic ocean to changes in ambient temperature, a prediction that we support with empirical data over the global ocean. Furthermore, our model predicts that there will be a negative feedback of ocean communities to climate warming because they will capture less CO 2 with a future increase in ocean temperature. This feedback of marine biota will further aggravate the anthropogenic effects on global warming.global change ͉ metabolic theory ͉ oceanic carbon cycle T he role of the oceans in the CO 2 budget of the biosphere depends largely on the balance between the uptake of carbon by phytoplankton photosynthesis and its remineralization by the respiration of the whole planktonic community (1). For large areas of the epipelagic ocean, planktonic community respiration (CR) exceeds gross primary production (GPP), resulting in net heterotrophy and a source of CO 2 (2-4). The solution of the contentious debate over the extent of such heterotrophic areas (5-7) is hindered by the limited spatiotemporal coverage achievable by traditional incubation methods (8, 9). Here, we tackle this question from a different perspective based on the metabolic theory of ecology (MTE) (10). The flux rates within an ecosystem are the result of the sum of the individual rates of all its constituent organisms (11,12), which, in turn, are governed by the combined effects of body size and temperature (13-15). Although MTE suggests a universal scaling of metabolic rate as the 3͞4 power of body size, it predicts a differential temperaturedependence of heterotrophic processes (driven by ATP synthesis) and autotrophic rates (controlled by Rubisco carboxylation) (12). Following the MTE, the respiration of a heterotrophic planktonic organism B i can be estimated if we know its body size M i and the ambient absolute temperature T:where b 0 is a normalization constant independent of body size and temperature, e ϪEh͞kT is Boltzmann's factor, where E h is the average activation energy for heterotroph respiration (13), and k is Boltzmann's constant (8.62⅐10 Ϫ5 ⅐eV⅐K Ϫ1 ), and ␣ h is the allometric scaling exponent for body size (14,15). For the metabolic rates of marine autotrophs, things are complicated by the dependence of photosyntheti...

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Although the oceans cover 70% of the Earth's surface, our knowledge of biodiversity patterns in marine phytoplankton and zooplankton is very limited compared to that of the biodiversity of plants and herbivores in the terrestrial world. Here, we present biodiversity data for marine plankton assemblages from different areas of the world ocean. Similar to terrestrial vegetation, marine phytoplankton diversity is a unimodal function of phytoplankton biomass, with maximum diversity at intermediate levels of phytoplankton biomass and minimum diversity during massive blooms. Contrary to expectation, we did not find a relation between phytoplankton diversity and zooplankton diversity. Zooplankton diversity is a unimodal function of zooplankton biomass. Most strikingly, these marine biodiversity patterns show a worldwide consistency, despite obvious differences in environmental conditions of the various oceanographic regions. These findings may serve as a new benchmark in the search for global biodiversity patterns of plants and herbivores.

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