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

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 production. We present here the use of an autonomous underwater glider with an oxygen (O2) and a wet-chemical microfluidic total oxidised nitrogen (NOx-=NO3-+NO2-) sensor 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 O2: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.

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

10.5194/bg-2021-170 ◽

2021 ◽

Author(s):

Tom Hull ◽

Naomi Greenwood ◽

Antony Birchill ◽

Alexander Beaton ◽

Mathew Palmer ◽

...

Keyword(s):

Organic Matter ◽

Water Column ◽

Euphotic Zone ◽

Global Scale ◽

Net Community Production ◽

Wide Range ◽

Shelf Seas ◽

Shelf Sea ◽

Autonomous Underwater Glider ◽

Community Production

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.

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Carbon monoxide emissions by phytoplankton: evidence from laboratory experiments

Environmental Chemistry ◽

10.1071/en09020 ◽

2009 ◽

Vol 6 (5) ◽

pp. 369 ◽

Cited By ~ 12

Author(s):

Valérie Gros ◽

Ilka Peeken ◽

Katrin Bluhm ◽

Eckart Zöllner ◽

Roland Sarda-Esteve ◽

...

Keyword(s):

Carbon Monoxide ◽

Organic Matter ◽

Dissolved Organic Matter ◽

Atmospheric Chemistry ◽

Laboratory Experiments ◽

Euphotic Zone ◽

Global Scale ◽

Emission Rates ◽

Direct Production ◽

Diurnal Cycles

Environmental context. Carbon monoxide (CO) is a key component for atmospheric chemistry and its production in the ocean, although minor at the global scale, could play a significant role in the remote marine atmosphere. Up to now, CO production in the ocean was considered to mainly originate from the photo-production of dissolved organic matter (mainly under UV radiation). In this paper, we show evidence for direct production of CO by phytoplankton and we suggest it as a significant mechanism for CO production in the ocean. Abstract. In order to investigate carbon monoxide (CO) emissions by phytoplankton organisms, a series of laboratory experiments was conducted in Kiel (Germany). Nine monocultures, including diatoms, coccolithophorids, chlorophytes and cyanobacteria have been characterised. This was done by following the CO variations from monoculture aliquots exposed to photosynthetically active radiation during one or two complete diurnal cycles. All the studied cultures have shown significant CO production when illuminated. Emission rates have been estimated to range from 1.4 × 10–5 to 8.7 × 10–4 μg of CO μg chlorophyll–1 h–1 depending on the species. When considering the magnitude of the emission rates from the largest CO emitters (cyanobacteria and diatoms), this biotic source could represent up to 20% of the CO produced in oceanic waters. As global models currently mainly consider CO production from the photo-degradation of dissolved organic matter, this study suggests that biotic CO production should also be taken into account. Whether this biological production might also contribute to some degree to the previous observed non-zero CO production below the euphotic zone (dark CO production) cannot be deduced here and needs to be further investigated.

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Uncertainty and sensitivity in optode-based shelf-sea net community production estimates

Biogeosciences ◽

10.5194/bg-13-943-2016 ◽

2016 ◽

Vol 13 (4) ◽

pp. 943-959 ◽

Cited By ~ 4

Author(s):

Tom Hull ◽

Naomi Greenwood ◽

Jan Kaiser ◽

Martin Johnson

Keyword(s):

Open Source Software ◽

Accurate Estimation ◽

Net Community Production ◽

Open Source Software Package ◽

Shelf Sea ◽

Shallow Area ◽

Dynamic Regions ◽

Vulnerable Habitats ◽

Net Heterotrophy ◽

Community Production

Abstract. Coastal seas represent one of the most valuable and vulnerable habitats on Earth. Understanding biological productivity in these dynamic regions is vital to understanding how they may influence and be affected by climate change. A key metric to this end is net community production (NCP), the net effect of autotrophy and heterotrophy; however accurate estimation of NCP has proved to be a difficult task. Presented here is a thorough exploration and sensitivity analysis of an oxygen mass-balance-based NCP estimation technique applied to the Warp Anchorage monitoring station, which is a permanently well-mixed shallow area within the River Thames plume. We have developed an open-source software package for calculating NCP estimates and air–sea gas flux. Our study site is identified as a region of net heterotrophy with strong seasonal variability. The annual cumulative net community oxygen production is calculated as (−5 ± 2.5) mol m−2 a−1. Short-term daily variability in oxygen is demonstrated to make accurate individual daily estimates challenging. The effects of bubble-induced supersaturation is shown to have a large influence on cumulative annual estimates and is the source of much uncertainty.

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Swept under the carpet: the effect of organic matter burial in global biogeochemical ocean models

Biogeosciences Discussions ◽

10.5194/bgd-10-10859-2013 ◽

2013 ◽

Vol 10 (7) ◽

pp. 10859-10911 ◽

Cited By ~ 2

Author(s):

I. Kriest ◽

A. Oschlies

Keyword(s):

Organic Matter ◽

Numerical Models ◽

Global Scale ◽

Benthic Fluxes ◽

Biogeochemical Fluxes ◽

Biogeochemical Models ◽

Wide Range ◽

Potential Impact ◽

Bathypelagic Zone ◽

Global Carbon

Abstract. Although of substantial importance for marine tracer distributions and eventually global carbon, oxygen, and nitrogen fluxes, the interaction between sinking and remineralization of organic matter, benthic fluxes and burial is not always represented consistently in global biogeochemical models. We here aim to investigate the relationships between these processes with a suite of global biogeochemical models, each simulated over millennia, and compared against observed distributions of pelagic tracers and benthic and pelagic fluxes. We concentrate on the representation of sediment-water interactions in common numerical models, and investigate their potential impact on simulated global sediment-water fluxes and nutrient and oxygen distributions. We find that model configurations with benthic burial simulate global oxygen well over a wide range of possible sinking flux parameterizations, making the model more robust with regard to uncertainties about the remineralization length scale. On a global scale, burial mostly affects oxygen in the meso- to bathypelagic zone. While all model types show an almost identical fit to observed pelagic particle flux, and the same sensitivity to particle sinking speed, comparison to observational estimates of benthic fluxes reveals a more complex pattern and may be influenced by the data distribution and methodology. Still, evaluating model results against observed pelagic and benthic fluxes of organic matter can complement model assessments based on more traditional tracers such as nutrients or oxygen. Based on a combined metric of dissolved tracers and biogeochemical fluxes, we here identify two model descriptions of burial as suitable candidates for further experiments and eventual model refinements.

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Spring–summer net community production, new production, particle export and related water column biogeochemical processes in the marginal sea ice zone of the Western Antarctic Peninsula 2012–2014

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2017.0177 ◽

2018 ◽

Vol 376 (2122) ◽

pp. 20170177 ◽

Cited By ~ 12

Author(s):

Hugh W. Ducklow ◽

Michael R. Stukel ◽

Rachel Eveleth ◽

Scott C. Doney ◽

Tim Jickells ◽

...

Keyword(s):

Sea Ice ◽

Primary Production ◽

Water Column ◽

Antarctic Peninsula ◽

Net Primary Production ◽

Western Antarctic Peninsula ◽

New Production ◽

Net Community Production ◽

Particle Export ◽

Community Production

New production (New P, the rate of net primary production (NPP) supported by exogenously supplied limiting nutrients) and net community production (NCP, gross primary production not consumed by community respiration) are closely related but mechanistically distinct processes. They set the carbon balance in the upper ocean and define an upper limit for export from the system. The relationships, relative magnitudes and variability of New P (from 15 NO 3 – uptake), O 2 : argon-based NCP and sinking particle export (based on the 238 U : 234 Th disequilibrium) are increasingly well documented but still not clearly understood. This is especially true in remote regions such as polar marginal ice zones. Here we present a 3-year dataset of simultaneous measurements made at approximately 50 stations along the Western Antarctic Peninsula (WAP) continental shelf in midsummer (January) 2012–2014. Net seasonal-scale changes in water column inventories (0–150 m) of nitrate and iodide were also estimated at the same stations. The average daily rates based on inventory changes exceeded the shorter-term rate measurements. A major uncertainty in the relative magnitude of the inventory estimates is specifying the start of the growing season following sea-ice retreat. New P and NCP(O 2 ) did not differ significantly. New P and NCP(O 2 ) were significantly greater than sinking particle export from thorium-234. We suggest this is a persistent and systematic imbalance and that other processes such as vertical mixing and advection of suspended particles are important export pathways. This article is part of the theme issue ‘The marine system of the west Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

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Swept under the carpet: organic matter burial decreases global ocean biogeochemical model sensitivity to remineralization length scale

Biogeosciences ◽

10.5194/bg-10-8401-2013 ◽

2013 ◽

Vol 10 (12) ◽

pp. 8401-8422 ◽

Cited By ~ 20

Author(s):

I. Kriest ◽

A. Oschlies

Keyword(s):

Organic Matter ◽

Numerical Models ◽

Global Scale ◽

Heterogeneous Data ◽

Global Ocean ◽

Biogeochemical Model ◽

Length Scale ◽

Benthic Fluxes ◽

Biogeochemical Models ◽

Wide Range

Abstract. Although of substantial importance for marine tracer distributions and eventually global carbon, oxygen, and nitrogen fluxes, the interaction between sinking and remineralization of organic matter, benthic fluxes and burial is not always represented consistently in global biogeochemical models. We here aim to investigate the relationships between these processes with a suite of global biogeochemical models, each simulated over millennia, and compared against observed distributions of pelagic tracers and benthic and pelagic fluxes. We concentrate on the representation of sediment–water interactions in common numerical models, and investigate their potential impact on simulated global sediment–water fluxes and nutrient and oxygen distributions. We find that model configurations with benthic burial simulate global oxygen well over a wide range of possible sinking flux parameterizations, making the model more robust with regard to uncertainties about the remineralization length scale. On a global scale, burial mostly affects oxygen in the meso- to bathypelagic zone. While all model types show an almost identical fit to observed pelagic particle flux, and the same sensitivity to particle sinking speed, comparison to observational estimates of benthic fluxes reveals a more complex pattern, but definite interpretation is not straightforward because of heterogeneous data distribution and methodology. Still, evaluating model results against observed pelagic and benthic fluxes of organic matter can complement model assessments based on more traditional tracers such as nutrients or oxygen. Based on a combined metric of dissolved tracers and biogeochemical fluxes, we here identify two model descriptions of burial as suitable candidates for further experiments and eventual model refinements.

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Nanomolar phosphate supply and its recycling drive net community production in the subtropical North Pacific

Nature Communications ◽

10.1038/s41467-021-23837-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Fuminori Hashihama ◽

Ichiro Yasuda ◽

Aki Kumabe ◽

Mitsuhide Sato ◽

Hiroshi Sasaoka ◽

...

Keyword(s):

North Pacific ◽

Dissolved Inorganic Carbon ◽

Euphotic Zone ◽

Vital Role ◽

Net Community Production ◽

Molar Ratios ◽

C And N ◽

N 93 ◽

20 Nm ◽

Community Production

AbstractSeasonal drawdown of dissolved inorganic carbon (DIC) in the subtropical upper ocean makes a significant contribution to net community production (NCP) globally. Although NCP requires macronutrient supply, surface macronutrients are chronically depleted, and their supply has been unable to balance the NCP demand. Here, we report nanomolar increases in surface nitrate plus nitrite (N+N, ~20 nM) and phosphate (PO4, ~15 nM) from summer to winter in the western subtropical North Pacific. Molar ratios of upward fluxes of DIC:N+N:PO4 to the euphotic zone (< 100 m) were in near-stoichiometric balance with microbial C:N:P ratios (107~243:16~35:1). Comparison of these upward influxes with other atmospheric and marine sources demonstrated that total supply is largely driven by the other sources for C and N (93~96%), but not for P (10%), suggesting that nanomolar upward supply of P and its preferential recycling play a vital role in sustaining the NCP.

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Uncertainty and sensitivity in optode-based shelf-sea net community production estimates

Biogeosciences Discussions ◽

10.5194/bgd-12-15611-2015 ◽

2015 ◽

Vol 12 (18) ◽

pp. 15611-15654

Author(s):

T. Hull ◽

N. Greenwood ◽

J. Kaiser ◽

M. Johnson

Keyword(s):

Open Source Software ◽

Accurate Estimation ◽

Net Community Production ◽

Open Source Software Package ◽

Shelf Sea ◽

Shallow Area ◽

Dynamic Regions ◽

Vulnerable Habitats ◽

Thames River ◽

Community Production

Abstract. Coastal seas represent one of the most valuable and vulnerable habitats on Earth. Understanding biological productivity in these dynamic regions is vital to understanding how they may influence and be affected by climate change. A key metric to this end is net community production (NCP), the net effect of autotrophy and hetrotrophy, however accurate estimation of NCP has proved to be a difficult task. Presented here is a thorough exploration and sensitivity analysis of an oxygen mass-balance based NCP estimation technique applied to the Warp Anchorage monitoring station which is a permanently well mixed shallow area within the Thames river plume. We have developed an open source software package for calculating NCP estimates and air-sea gas flux. Our study site is identified as a region of net heteotrophy with strong seasonal variability. The annual cumulative net community oxygen production is calculated as (−5 ± 2.5) mol m−2 a−1. Short term daily variability in oxygen is demonstrated to make accurate individual daily estimates challenging. The effects of bubble induced supersaturation is shown to have a large influence on cumulative annual estimates, and is the source of much uncertainty.

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