Chen BZ, MR Landry, BQ Huang, HB Liu.Limnol. Oceanogr., 2012. 57: 519-526.

We evaluated a hypothesis derived from the metabolic theory of ecology (MTE) that the ratio of microzooplankton herbivory (m) to phytoplankton growth (µ) will arise in a warming ocean because of the different temperature dependencies of autotrophic and heterotrophic organisms. Using community-level growth and grazing data from dilution experiments, generalized additive models (GAMs) were constructed to describe the effects of temperature and chlorophyll on m: m. At low chlorophyll levels,m:µdecreases with increasing temperature, whereas at high chlorophyll levels,m:µincreases initially with temperature before reaching a peak and then declines. These complex responses ofm:µresult from mixed effects of temperature and chlorophyll on microzooplankton biomass (Bz), biomass-specific microzooplankton grazing rate (m:Bz), and phytoplankton growth rate (µ).Bzdecreases with rising temperature and increases with rising chlorophyll.m:Bzincreases with temperature and decreases with chlorophyll. Nutrient-enriched growth rate of phytoplankton (µn) and m increase with increasing temperature and chlorophyll. Holding chlorophyll constant, the calculated activation energies ofm:Bzandµnare 0.67 6 0.05 and 0.36 6 0.05 eV, respectively, both consistent with previous MTE estimates for heterotrophs and autotrophs. Our study indicates that warming may enhance phytoplankton losses to microzooplankton herbivory in eutrophic but not in oligotrophic waters. The GAM analysis also provides important insights into underlying system relationships and reasons why community-level responses in natural systems may depart from theory based on laboratory data and individual species.