An Alternative Framework to Assess Marine Ecosystem Functioning in Shelf Seas (AlterEco)

Lead Research Organisation: Plymouth Marine Laboratory
Department Name: Plymouth Marine Lab


Continental shelf seas are typically less than 200m deep and can be described by the shallow ocean surrounding continental land masses. Due to their accessibility, shelf seas are commercially and economically important, with oil and gas extraction alone in UK shelf seas valued at £37B pa. Despite occupying only 7% of the surface ocean, shelf seas also play a major role in the global carbon cycle and marine ecosystem. Shelf seas are 3-4 times more productive than open-ocean, are estimated to support more than 40% of carbon sequestration and support 90% of global fish catches providing a critical food source for growing coastal populations. However, shelf seas are also exposed to climate driven and anthropogenic stress that could have a profound impact on their biological productivity, oxygen dynamics and ecosystem function. Many processes contributing to this threat are related to regions that undergo vertical stratification. This process occurs when the bottom layer of shelf seas becomes detached from the atmospherically ventilated near surface layer. In temperate shelf seas stratification predominantly occurs as solar heating outcompetes the tide and wind-driven mixing to produce a warm surface layer, resulting in seasonal stratification over large areas of the NW European shelf seas. A combination of physical detachment from the surface and increased biological oxygen consumption in the bottom layer, accentuated by the enhanced productivity that stratification also supports in the upper ocean, can result in a drastically reduced bottom layer oxygen concentration. When oxygen levels get so low, they are classified as being oxygen deficient and this can be problematic for benthic and pelagic marine organisms and have a detrimental effect on ecosystem function.

Evidence of increasing seasonal oxygen deficiency in the regions of North Sea by members of the AlterEco team and a recognised global increase in the extent of shelf sea and coastal oxygen deficiency calls for an urgent need to increase the spatial and temporal measurement of oxygen and a better understanding of the processes that lead to oxygen deficiency in shelf sea bottom waters. This need is severely impeded by the natural complexity of ecosystem functioning, the impact of a changing climate, connectivity between different regions of our shelf seas and large-scale external forcing from ocean and atmosphere. Current methods are severely restricted in resolving this complexity, due to the poor resolution in observational coverage, which calls for a new strategy for observing and monitoring marine ecosystem and environmental status.

AlterEco seeks to address this challenge within the framework of the given call by the development of a novel monitoring framework to deliver improved understanding of key shelf sea ecosystem drivers. We will capitalise on recent UK investments in marine autonomous vehicles and planning capability to investigate an area of the North Sea known to undergo variable physical, chemical and biological conditions throughout an entire seasonal cycle, including areas identified to experience low bottom layer oxygen levels during summer months. Ocean gliders will be used to undertake repeat transects over a distance of ~150km, sufficient to capture important shelf sea features; such as fronts and eddies. The AlterEco strategy will employ small fleets of vehicles to capture these meso-scale features (typically ~100km in scale) but will also resolve sub-mesoscale variability (~100m). We will benefit from successes and lessons learnt from recent, pioneering deployments of underwater gliders and use a suite of sensors that permit high-resolution coincident measurements of key ecosystem indicators. Combining the expertise within the AlterEco team we will not only provide a new framework for marine observations that has global transferability, but also the diagnostic capability to improve understanding of shelf sea ecosystem health and function.

Planned Impact

In the UK alone, marine data collection costs approximately £80 million per year, but there is increasing pressure across sectors to reduce these costs. Coupled with public demand for open access, verifiability and the need for sharing data across different stakeholders and users, has led to the creation of the UK Integrated Marine Observing Network (UK-IMON). AlterEco will help achieve the aim of UK-IMON to provide the evidence base for future assessments of environmental status.

The UK government singled out "Robotics and autonomous systems" as one of "eight great technologies" with large economic growth potential ( In the marine community alone, RCUK, Higher Education Institutions and industry have recently invested over £100 million in Smart and Autonomous Observing Systems. AlterEco will capitalise on this investment by using novel platforms and sensors to provide high-quality observations of shelf-sea dynamics, nutrient and carbon cycling. In turn, this will demonstrate how these new capabilities can be used together with existing techniques to help fulfill the UK's statutory requirements for monitoring water quality and Good Environmental Status, as mandated by the Marine Strategy Framework Directive (MSFD), the Convention on Biological Diversity and the OSPAR Convention. AlterEco will thus be of interest to stakeholders such as agencies with marine monitoring obligations (Defra, Cefas, Marine Scotland and AFBI) as well as the community of glider and sensor manufacturers and users as a whole. It will allow them to optimise target locations of their monitoring programme, make it more efficient and feed into future policy requirements.

Under the umbrella of the UK Marine Science Coordination Committee (MSCC), the UK Marine Assessment and Reporting Group oversees and coordinates the activities of the four UK Marine Monitoring and Assessment Strategy (UKMMAS) evidence groups (Clean and Safe Seas Evidence Group, Healthy and Biologically Diverse Seas Evidence Group, Productive Seas Evidence Group, Ocean Processes Evidence Group). AlterEco will provide part of the evidence required by these groups, in particular the latter three.

The data gathered by AlterEco will be archived at the British Oceanographic Data Centre (BODC), to make them available for historic analyses, model validation and testing. BODC, as well as NERC, Cefas, Marine Scotland and SAMS are partners of the Marine Environmental Data and Information Network (MEDIN), which provides a contractual framework and single-point of access portal and software tools to retrieve data from the network of specialist data archive centres contributing to it. Project results will also feed into international data infrastructures provided by the International Council for the Exploration of the Sea (ICES) and the European Marine Observation and Data Network (EMODNet).

The UK Met Office (UKMO) will be providing output to AlterEco from their coupled physical-biogeochemical NEMO-ERSEM model. In turn, real-time data from our project will be used for operational trialing of the assimilation of glider data into UKMO models, starting with temperature and salinity in September 2017 (from historical collated datasets), but then rapidly moving on to include biogeochemical variables (September 2018: chlorophyll a fluorescence; September 2019: oxygen concentrations), entraining real-time AlterEco data from our planned North Sea mission.

Other members of the ERSEM modelling community in the UK (NOC, PML, Cefas, UEA) and beyond will also greatly benefit from long-endurance, high-frequency physical and biogeochemical measurements delivered by AlterEco. This includes the consortium addressing Challenge 2 of the Autonomous Observations programme and will provide improved estimates and forecasts of oxygen deficiency in UK shelf seas.


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Description We have developed a real-time system for processing glider data into fields of primary production. This has been implemented on gliders during the mission phase of this project (November 2017 - May 2019) and is modified to use data inputs for non-optimal conditions (e.g. sensor failure or necessary sensors not available)

We have expanded the methodology to use a multi-platform approach - and reprocessed all of the data from the gliders which weren't necessarily optimised for determining primary production.
Exploitation Route By implementing our scheme on their data. We are investigating through other ODA projects the possibilities of doing this.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Environment

Title Primary productivity estimates derived from ocean glider in situ sensors and photosynthetically available radiation estimates from in situ and satellite data between November 2017 and May 2019 in the North Sea. 
Description As part of the Alternative Framework to Assess Marine Ecosystem Functioning in Shelf Seas (AlterECO) project (NERC grant reference NE/P013902/1), Seagliders and Slocum gliders were deployed in a physically dynamic region of the North Sea, known to undergo seasonal oxygen depletion, between November 2017 and May 2019. These deployments are part of an 18 month observational programme using marine autonomous vehicles. During each deployment the gliders tracked repeat North-South or East-West transects close to Dogger Bank. Each glider carried a standard CTD package measuring temperature and water conductivity (salinity) and an oxygen optode sensor with additional sensors such as downwelling PAR and optical sensors for chlorophyll fluorescence and backscatter deployed for some missions. In this dataset, estimates of primary productivity are calculated from glider deployments carrying optical sensors for chlorophyll fluorescence, using the method described in Loveday et al. (2021), a modification of that presented in Hemsley et al. (2015). For glider deployments carrying an in situ downwelling PAR sensor, primary productivity is calculated. Primary productivity is also calculated for all glider deployments using Earth observation-based PAR derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) daily product. The variables in each file consist of; corrected in situ PAR, quenching corrected chlorophyll, mixed layer depth, euphotic depth, depth resolved estimates of primary productivity and depth integrated primary productivity. The chlorophyll fluorescence and PAR data are recorded at a lower sampling frequency when compared to the CTD sensor. Therefore, chlorophyll and PAR data values have been linearly interpolated onto the depth record time base. During the 3-year programme, and by developing and implementing a novel monitoring framework, AlterEco aims to deliver an improved spatio-temporal understanding of shelf sea function and provide measurements of critical indicators of marine ecosystem health over seasonal timescales. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact First annual quantification of Primary Production in the North Sea using a fleet of autonomous gliders 
Description Development of real-time glider primary production data 
Organisation University of East Anglia
Country United Kingdom 
Sector Academic/University 
PI Contribution Using the data provided by UEA we have prototyped an operational system, with real-time and delayed-mode capabilities, for processing glider data into a primary production product.
Collaborator Contribution Provision of data
Impact Prototype primary production data
Start Year 2017
Title Operational system for processing glider data into primary production product. 
Description Processing chain, implementing new and existing techniques (published), to determine primary production from real-time glider data 
Type Of Technology Software 
Year Produced 2018 
Impact This should be highly transferrable to other glider theatres of operation - e.g. ODA work. 
Title Waveglider net calibration data 
Description Spreadsheets of plankton abundance data provided by flowCam and microscopic analysis. These are based on about 80 net samples used to calibrate the waveglider (Lyra) acoustics during May and August cruises to the North Sea 
Type Of Technology New Material/Compound 
Year Produced 2020 
Impact none yet