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Roles of food web and heterotrophic microbial processes in upper ocean biogeochemistry: Global patterns and processes
Author(s) -
Rivkin Richard B.,
Legendre Louis
Publication year - 2002
Publication title -
ecological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.628
H-Index - 68
eISSN - 1440-1703
pISSN - 0912-3814
DOI - 10.1046/j.1440-1703.2002.00475.x
Subject(s) - carbon cycle , environmental science , microbial food web , food web , biomass (ecology) , plankton , biogeochemistry , zooplankton , ecosystem , southern hemisphere , ecology , phytoplankton , equator , global change , oceanography , climate change , atmospheric sciences , biology , nutrient , latitude , geography , geology , geodesy
The growth and dynamics of plankton in the ocean vary with natural cycles, global climate change and the long‐term evolution of ecosystems. The ocean is a large reservoir for CO 2 and the food webs in the upper ocean play critical roles in regulating the global carbon cycle, changes in atmospheric CO 2 and associated global warming. Microheterotrophs are a key component of the upper ocean food webs. Here, we report on the results of an analysis of the distribution of bacteria and related properties in the World Ocean. We found that, for the data set as a whole, there is a significant latitudinal gradient in all field‐measured and computed bacterial properties, except growth rate. Gradients were, for the most part, driven by an equator‐ward increase in the Southern Hemisphere. The biomass, rates of production and respiration and dissolved organic carbon concentrations were significantly higher in the Northern than the Southern hemispheres. In contrast, growth rates were the same in the two hemispheres. We conclude that the lower biomass and production in the Southern Hemisphere reflects greater top‐down control by microbial grazers, which would be due to a lower abundance or activity of omnivorous zooplankton in the Southern than Northern Hemispheres. These large spatial differences in dynamics, structure and activity of the bacterial community and the microbial food web will be reflected in different patterns of carbon cycling, export and air–sea exchange of CO 2 and the potential ability of the ocean to sequester carbon.