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major changes in phases and particle size-spectra: POM (particulate) -- > polymers (dissolved
and colloidal) -- > monomers (dissolved) -- > attached bacteria (particulate) and free-living
bacteria (colloidal and fine particulate). These transitions could greatly increase the surface area
of the particulate phases and decrease the sinking rate of particles, with implications for vertical
flux of organic matter and surface-reactive materials in the ocean. It is therefore important to
elucidate the magnitude and the mechanisms in the flow of carbon from POM to free-living and
attached bacteria, particularly in the ocean's interior.
CONCLUDING REMARKS
We have presented the notion that variability in ecosystem roles of bacteria reflects the varied
adaptive strategies of bacteria for survival and persistence in the ocean's pelagial. Heterogeneity
in the organic matter field imposes variations in metabolism of bacteria (e.g. whether or not
metabolic products such as ammonium are secreted) and hence leads to reversals of the
ecosystem roles of bacteria. Interactions among bacteria, phytoplankton detritus and protozoa
can critically influence nutrient cycling, primary productivity, and sinking flux. In keeping with
the theme of this NATO ASI, we emphasize that global ocean-scale biogeochemical dynamics
are regulated at the level of individual cell and particle at micro scale of space. In order to build
mechanistic models of biogeochemical dynamics, then, we need to understand microbial
metabolism and interactions at the micrometer scale. This is an exciting challenge and will
require the development of methods to study microorganisms as components of intact consortia
in their natural setting. Only then will we have a mechanistic basis for incorporating the roles
of bacteria into models to understand the variability in the ocean's biogeochemical state.
ACKNOWLEDGEMENTS
The preparation of this manuscript was supported by NSF and ONR grants to F. Azam.
major changes in phases and particle size-spectra: POM (particulate) -- > polymers (dissolved
and colloidal) -- > monomers (dissolved) -- > attached bacteria (particulate) and free-living
bacteria (colloidal and fine particulate). These transitions could greatly increase the surface area
of the particulate phases and decrease the sinking rate of particles, with implications for vertical
flux of organic matter and surface-reactive materials in the ocean. It is therefore important to
elucidate the magnitude and the mechanisms in the flow of carbon from POM to free-living and
attached bacteria, particularly in the ocean's interior.
CONCLUDING REMARKS
We have presented the notion that variability in ecosystem roles of bacteria reflects the varied
adaptive strategies of bacteria for survival and persistence in the ocean's pelagial. Heterogeneity
in the organic matter field imposes variations in metabolism of bacteria (e.g. whether or not
metabolic products such as ammonium are secreted) and hence leads to reversals of the
ecosystem roles of bacteria. Interactions among bacteria, phytoplankton detritus and protozoa
can critically influence nutrient cycling, primary productivity, and sinking flux. In keeping with
the theme of this NATO ASI, we emphasize that global ocean-scale biogeochemical dynamics
are regulated at the level of individual cell and particle at micro scale of space. In order to build
mechanistic models of biogeochemical dynamics, then, we need to understand microbial
metabolism and interactions at the micrometer scale. This is an exciting challenge and will
require the development of methods to study microorganisms as components of intact consortia
in their natural setting. Only then will we have a mechanistic basis for incorporating the roles
of bacteria into models to understand the variability in the ocean's biogeochemical state.
ACKNOWLEDGEMENTS
The preparation of this manuscript was supported by NSF and ONR grants to F. Azam.