Preprints
https://doi.org/10.5194/bg-2021-170
https://doi.org/10.5194/bg-2021-170

  30 Jul 2021

30 Jul 2021

Review status: this preprint is currently under review for the journal BG.

Simultaneous assessment of oxygen and nitrate-based net community production in a temperate shelf sea from a single ocean glider

Tom Hull1,2, Naomi Greenwood1,2, Antony Birchill3,4, Alexander Beaton4, Mathew Palmer4, and Jan Kaiser1 Tom Hull et al.
  • 1Centre for Ocean and Atmospheric Sciences, University of East Anglia, Norwich, UK
  • 2Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, UK
  • 3School of Geography, Earth and Environmental Sciences, University of Plymouth, Plymouth, UK
  • 4National Oceanography Centre, Southampton, UK

Abstract. The continental shelf seas are important at a global scale for ecosystem services. These highly dynamic regions are under a wide range of stresses and as such future management requires appropriate monitoring measures. A key metric to understanding and predicting future change are the rates of biological productivity. We present here the use of a single autonomous underwater glider with oxygen (O2) and total oxidised nitrogen (NOx = NO3 + NO2) sensors during a spring bloom as part of a 2019 pilot autonomous shelf sea monitoring study. We find exceptionally high rates of net community production using both O2 and NOx water column inventory changes, corrected for air-sea gas exchange in case of O2. We compare these rates with 2007 and 2008 mooring observations finding similar rates of NOx consumption. With these complementary methods we determine the O:N amount ratio of the newly produced organic matter (7.8±0.4) and the overall O2:N ratio for the total water column (5.7±0.4). The former is close to the canonical Redfield O2:N ratio of 8.6±1.0, whereas the latter may be explained by a combination of new organic matter production and preferential remineralisation of more reduced organic matter at a higher O2:N ratio below the euphotic zone.

Tom Hull et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-170', Anonymous Referee #1, 15 Aug 2021
  • RC2: 'Comment on bg-2021-170', Anonymous Referee #2, 07 Sep 2021

Tom Hull et al.

Tom Hull et al.

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Short summary
The shallow shelf seas play a large role in the global cycling of CO2, they also support large fisheries. We use an low-cost autonomous underwater vehicle in the Central North Sea to measuring the rates of change of oxygen and nutrients. Using these data we determine the amount of CO2 taken out of the atmosphere by the sea and measure how productive the region is. These observations will be useful for improving our predictive models and help us predict and adapt to a changing ocean.
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