OLI Funded Grant: Making a Living in the Deep Sea: Enhanced Cycling of Dissolved Organic Carbon and Nitrogen by Marine Piezophiles
Grant Funded: 2005
Enormous amounts of carbon and essential nutrients (nitrogen and
phosphorus) are sequestered in the ocean in dissolved organic matter.
In many areas of the ocean, particularly in nutrient limited regions or
mid ocean gyres, > 95-98% of dissolved N and P are sequestered as
organic nutrients. The high concentrations of dissolved organic
nutrients in N and P limited regions of the ocean are particularly
enigmatic, in view of a large body of recent evidence that shows many
marine plankton and bacteria are capable of metabolizing N and P
containing organic compounds.
Dissolved organic matter concentrations decrease rapidly below the
euphotic zone due to consumption by deep sea bacteria. However, when
surface seawater is incubated for long periods of time (up to 2 years)
in the laboratory, very little degradation of DOC is observed. As a
result, we have been unable to study the bacteria that degrade most of
the organic carbon in the ocean, or the metabolic pathways that return
a large fraction of N and P to phytoplankton. If a large fraction of
DOC is cycled so rapidly in the environment, why is DOC so recalcitrant
in laboratory bottle experiments? One variable that has not been
studied experimentally is pressure. Recent research on the genetic
apparatus of deep-sea bacteria (piezophiles) shows these microbes are
particularly well suited to degrade the types of compounds found in
DOC. With this in mind, we propose to conduct a suite of controlled
experiments to study the degradation of DOC at high pressures. In our
experiments, we will couple the degradation of DOC to gene expression
in piezophilic bacteria. Our goal is to identify the microbes
responsible for DOC degradation and to use the metabolic pathways
employed by bacteria to better understand DOC composition and cycling.
Originally published: February 1, 2005