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Project proposed to understand the respiration of bacteria in the ocean

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Project proposed to understand the respiration of bacteria in the ocean

Dr Carol Robinson and Dr Elena Garcia Martin at the University of East Anglia are developing a NERC grant proposal to investigate bacterial respiration (CO2 production) rates in marine environments using a variety of methods. They are interested to hear from anyone who might be interested in this work, in particular non-academic end users who might benefit and who could contribute to the development of the project to ensure its broadest impact and usefulness. For more information please contact

In most of the world’s oceans, the concentrations of inorganic nutrients such as nitrate and phosphate and organic matter such as carbohydrates and amino acids are very low. These regions can therefore support only very low levels of biological activity, and small sized cells such as bacteria with low energy requirements tend to predominate. Larger organisms such as phytoplankton (which are able to photosynthesise) and zooplankton (the food of small fish) need abundant nutrients, and so occur in only reduced numbers in these waters.

Bacteria respire in a similar way to humans, consuming oxygen and producing carbon dioxide. The bacterial production of CO2 in these regions is a relevant contribution to the global carbon cycle and their activity influences the capacity of the ocean to mediate climate. The proportion of CO2 produced by bacteria in relation to the proportion produced by phytoplankton and zooplankton appears to vary between 20 and 80%. However, these data were derived from a method which relies on separating the bacteria from the rest of the plankton community before measuring their respiration, which is prone to error. Recent data, derived from a new enzymatic method based on the respiratory reduction of a tetrazolium salt, which does not require pre-separation of the bacterial community, suggest that bacteria and cyanobacteria (cells sized between 0.2 and 0.8 micrometers) produce only 40% of the CO2 produced by the microbial plankton. This is surprising since bacteria and cyanobacteria make up the majority of cells in these regions. In addition, this proportion did not vary between low productivity open ocean regions and high productivity coastal regions which are dominated by larger phytoplankton and zooplankton. This raises a number of questions – which organisms are responsible for the 60% of the respiration not accounted for by bacteria and why does the bacterial fraction not vary between high and low productivity regions.

In order to address these questions, a group of chemists, molecular biologists and ecologists from the University of East Anglia are proposing to work with a team of international enzyme kineticists and microscopists to determine the proportion of CO2 produced by bacteria in a range of ecosystems in the Atlantic Ocean. The study will also include culture work to assess the uptake and reduction of the tetrazolium salt by a representative range of plankton cells, including bacteria, cyanobacteria, phytoplankton and microzooplankton. We are interested in hearing from anyone whose work might benefit from this multidisciplinary project.

Posted by Martin Johnson on Mon, 30 Oct 2017

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