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Does warming enhance the effect of microzooplankton grazing on marine phytoplankton in the ocean?
Author(s) -
Chen Bingzhang,
Landry Michael R.,
Huang Bangqin,
Liu Hongbin
Publication year - 2012
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2012.57.2.0519
Subject(s) - phytoplankton , oceanography , environmental science , effects of global warming on oceans , grazing , global warming , climate change , ecology , biology , geology , nutrient
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 : μ . At low chlorophyll levels, m : μ decreases with increasing temperature, whereas at high chlorophyll levels, m : μ increases initially with temperature before reaching a peak and then declines. These complex responses of m : μ result from mixed effects of temperature and chlorophyll on microzooplankton biomass ( B z ), biomass‐specific microzooplankton grazing rate ( m : B z ), and phytoplankton growth rate ( μ ). B z decreases with rising temperature and increases with rising chlorophyll. m : B z increases with temperature and decreases with chlorophyll. Nutrient‐enriched growth rate of phytoplankton ( μ n ) and μ increase with increasing temperature and chlorophyll. Holding chlorophyll constant, the calculated activation energies of m : B z and μ n are 0.67 ± 0.05 and 0.36 ± 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.