Understanding controls on oxygen deficits in UK waters using a community ecosystem model and isotopic tools

Lead Research Organisation: University of East Anglia
Department Name: Environmental Sciences

Abstract

In UK waters, ongoing assessments have identified significant downward trends in c(O2) in the northern and southern North Sea and the English Channel. However, the assessments also identified significant gaps in the data and monitoring practices, as well as a lack of understanding of how the interactions between physical, biological and climatological processes control c(O2). This project aims at narrowing these gaps in understanding using a combination of i) data for c(O2) on the UK Shelf; ii) model data generated in the NERC-Defra Shelf Seas Biogeochemistry (SSB) Programme (PML Grant Number NE/K001876/1); and iii) a novel combination of oxygen isotope data and model simulations.

In Phase 1 of the project, the student will validate relevant model runs with existing data using basic univariate and multivariate statistical techniques. They will then analyse the model results for historic and future trends in c(O2) under different management scenarios, and identify the dominant driving mechanisms behind changes in c(O2). Working closely with Cefas, the student will develop analysis software that will be easily adaptable for other OSPAR/MSFD indicators. This will lead to the identification of risk areas that could be targeted for improved monitoring and/or management. During this phase of the project the student will participate in a research cruise aboard the RV Cefas Endeavour. The choice of cruise will be guided by early results from the study, and samples for c(O2) and O2 isotopologues taken.

In Phase 2, the student will implement an oxygen isotope fractionation scheme in the model, which will allow results to be compared with the new and archived O2 isotopologue data. The student will spend three months at UEA analysing the isotope data. The student will then run 1D model simulations and assess the use of oxygen isotopes for diagnosing the relative contribution of different biological populations to overall O2 consumption. During the project the student will write high impact scientific papers and a PhD thesis.

As a member of the EnvEast DTP, the student will attend compulsory residential and in-house events (e.g. the EnvEast Summer School), which include specific Personal and Professional Development (PPD) modules tailored to the student's background, research and employment aspirations. The progressive training program is designed to develop advanced scientific skills for the next generation of research leaders as well as generic management and communication skills to increase employability across a range of professions. PPD modules include Project management; Time management; Critical thinking; Latex; Scientific writing; Effective scientific presentations; Thesis writing; Viva preparation; and Interview skills.

The student will attend advanced taught modules and training events to develop specific skills. Courses will be selected from the list of NERC Advanced Training Short Courses, where previous courses include "Environmental Statistics and Data analytics training", "Numerical Earth Science Modelling", and "Understanding and Communicating Environmental Risk and Uncertainty".

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
NE/P010628/1 01/10/2017 30/09/2021
1947414 Studentship NE/P010628/1 01/10/2017 31/03/2022 Francesco Pallottino
NE/W503034/1 01/04/2021 31/03/2022
1947414 Studentship NE/W503034/1 01/10/2017 31/03/2022 Francesco Pallottino
 
Title Determine the viability of NOP_? (O2/Ar) method in continental shelf sea environments adopting an observing system simulation experiment 
Description A new tracer model representing the argon cycle was written within the European Regional Seas Ecosystem Model (ERSEM) model (Butenschön et al., 2016). The ERSEM model coupled to the water column model GOTM (Umlauf, Burchard and Bolding, 2012), was used to run 1D simulations and assess NOP_? (O2/Ar) bias caused by dynamic physical processes found at L4. To do so, NOP was considered as a known entity (prognostic model) and calculated with the ERSEM model (NOP_ERSEM). NOP_? (O2/Ar), was calculated as diagnostic box model and assessed using simulation results from the prognostic model. The difference between NOP_? (O2/Ar) and NOP_ERSEM terms, determined the viability of discrete sampling oxygen to argon ratios across the water column to assess net community production. To perfect matching between NOP_? (O2/Ar) and NOP_ERSEM, diagnostic calculations were initially simplified by integrating the mass balance of the full water column in a fully mixed box model thus ruling out possible complications caused by vertical transport. Complexity in the diagnostic model was increased by including hydrodynamic processes such as turbulent mixing. The mass balance of biological oxygen was then calculated for the mixed layer, the euphotic zone and the bottom waters, including vertical fluxes across the three reservoirs of the water column (following Haskell II et al., 2016). Consecutively adding new physical and biogeochemical terms violated the major assumptions for NOP_? (O2/Ar), namely: 1) NOP at steady state, 2) constant mixed layer depth (MLD) and no oxygen exchange across MLD. In this way systematic error would have been measured and quantified (c.f. Nicholson et al., 2012; Jonsson et al., 2013, 2015). Oxygen/argon data collected at L4 in the past by the past PhD student Dr. Johanna Gloel was used to validate the novel ERSEM-Argon model and how this interacts with pre-existing ERSEM-oxygen model. 
Type Of Material Computer model/algorithm 
Year Produced 2018 
Provided To Others? No  
Impact This is the first time that Argon gas was added to ERSEM as new state variable. Argon gas has very similar solubility to oxygen gas nut is inert to biology. It's use can help scrutinising physical oxygen fluxes from the biological. 
 
Title The North Sea inventory of dissolved oxygen, triple oxygen isotopes and oxygen/argon, August 2019. 
Description This is the first dataset showing triple oxygen isotope inventory and oxygen-to-argon ratios in the North Sea. A total of 48 stations were sampled by CTD casts across the North Sea during the RV CEFAS Endeavour CEND12/19 (Lowestoft, UK, 7th of August to 5th of September 2019) covering the southern and northern North Sea approximately 2 months before the end of the stratification period north of Dogger Bank and near the end of the stratified period in the Oyster Grounds (Greenwood et al. 2010; Queste et al., 2015). CTD stations were assigned day after day considering the cruise ground fish survey schedule, and weather conditions (usually around 3:00 am and 18:00 pm depending on the ground fish survey plan). Discrete samples were collected at each CTD station at surface, bottom and mid depth at deep chlorophyll maxima (when this was detected by the CTD's fluorometer). This yield 123 samples for triple oxygen isotopes and O2/Ar and 189 samples for Winkler titrations. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? No  
Impact This dataset will allow direct comparisons for triple oxygen isotope and oxygen-to-argon future estimates. These applications will provide cost-effective means for monitoring gross and net community production in the North Sea.