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Aquatic Microbial Ecology

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AME 32:1-10 (2003)  -  doi:10.3354/ame032001

Partitioning of microbial biomass in pelagic aquatic communities: maximum resiliency as a food web organizing construct

Edward A. Laws*

University of Hawaii, Department of Oceanography, 1000 Pope Road, Honolulu, Hawaii 96822, USA

ABSTRACT: Application of the principle of maximum resiliency to a pelagic food web model leads to the conclusion that the ratio of heterotrophic bacterial biomass to phytoplankton biomass is greatest under oligotrophic conditions. This prediction is in accord with the results of several field studies. Under eutrophic conditions, model results indicate that the same ratio is positively correlated with temperature, and that microbial biomass is dominated by phytoplankton at low temperatures and high production rates. Predictions of heterotrophic bacterial biomass based on the model and information on temperature and photosynthetic rates or phytoplankton biomass are in excellent agreement with field data from a wide variety of limnetic and marine habitats with depths ≥6 m. The model consistently underestimated heterotrophic bacterial biomass in systems impacted by riverine throughput and in hypereutrophic systems in which the euphotic zone was less than 3 m deep. In systems less than 3 to 4 the model was less successful in predicting heterotrophic bacterial biomass than in deeper systems, although there was no apparent bias in the results. Because of the short generation time of aquatic microbes, pelagic food web behavior that is determined primarily by the activity of these organisms may tend to display characteristics expected of the mature stages of ecological succession. Maximum resiliency, a characteristic expected of such mature stages, may therefore prove to be a useful construct in modeling the response of pelagic food webs to environmental change.

KEY WORDS: Bacteria · Model · Food web · Stability · Phytoplankton

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