Story
Monitoring water quality in Plymouth Sound and beyond
17 October 2024
Initial fieldwork results are shared from a project aiming to transform water quality monitoring around the globe.

The EO4AgroClimate project, VISualisation and Assessment of water quality using an Open Data Cube FOR the weStern English channel (Vis4Sea), is set to revolutionise water quality monitoring in Plymouth Sound and further afield.
Through the use of cutting-edge water monitoring technologies and an international collaboration of leading research organisations, the project is focusing on the environmental challenges relating to reduced water quality, due to periodic flooding, faced by dynamic marine environments like Plymouth Sound.
Issues surrounding local flooding, agricultural run-off, sewage effluent and heavy metal contamination all have an impact on water quality, and are affecting the fragile marine ecosystems in the area. These include seagrass beds and mud flats, which are important for local biodiversity and carbon capture habitats.
To help address these issues, the team are combining traditional and innovative water monitoring techniques to help understand the full extent of the impacts and developing recommendations for improving water quality.
The project builds upon PML’s ongoing work with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) AquaWatch program, an initiative focused on monitoring water quality using satellite and autonomous sensor networks.
Initial results from fieldwork activities
To date, PML has conducted extensive direct sampling transects along the Tamar and Plym Rivers that feed into Plymouth Sound, collecting data on Escherichia coli (E. coli), nutrients (especially nitrate, ammonia and phosphate), heavy metals, total suspended matter (TSM), inorganic suspended matter (ISM) and organic suspended matter (OSM) during both flooding and non-flooding conditions. Novel low-cost optical ‘Hydraspectra’ instruments have also been deployed on Tamar Bridge, near Laira Bridge and on research vessels to monitor the changes in water colour related to these factors, in real time.

One finding from the direct sampling showed that in some areas of the Tamar and Plym catchment, E.coli levels were 10 times higher following heavy rainfall than after a dry spell. At the sampling site near Laira Bridge, E.coli concentrations rose from 74.6 cells per 100 millilitre in the June sampling to a staggering 736.67 in the April samples, which followed a bout of intense rainfall. Similarly E coli numbers rose sharply in July after a period of high rainfall.

The direct sampling of ISM showed that it reached a peak in winter when Total Nitrogen (TN) concentrations were also high, suggesting that it is coupled with run-off from agricultural land.

Regarding heavy metals in the sediment, likely from former and/or current mining operations, Blaxton Creek showed high levels of iron and copper, Weir Quay was high in aluminium, magnesium and zinc, Cotehele was high in lead and Tory Brook was high in manganese.

In tandem with the direct sampling, drone flights are capturing aerial data over intertidal areas like Wilcove mud flats, while Sentinel-1 and Sentinel-2 satellite data are being processed over the Plymouth Sound and the Tamar and Plym rivers to detect flooding events and track the spread of contaminants. These approaches will help identify periods of heightened vulnerability, such as when bare soils are more prone to runoff after rainfall.
To make the processing of all of this data more efficient, the team are employing an Open Data Cube (ODC) system that integrates data from the variety of sources as well as applying advanced optical, machine- and deep-learning algorithms to satellite data to generate actionable water quality information, such as maps of TSM, E. coli and TN. These in combination with particle tracking models, based on measured physical parameters, are being used to track where these substances end up after flowing out of the local rivers.

Dr Gavin Tilstone, lead on this project and Bio-Optical Oceanographer at Plymouth Marine Laboratory (PML), said:
“Flooding events are becoming more common and can result in potentially damaging run-off from land and the discharge of sewage effluent to the coast, both of which can have a negative effect on the important marine habitats and tourist beaches around Plymouth Sound.”
“We are keen to gain a better understanding of how these water inputs affect coastal waters to help protect marine life and the people who use these waters”.
The project’s findings are being disseminated through various stakeholder forums, including discussions with policy makers, environmental agencies, local authorities and legal entities. As the project progresses, the aim is to provide insights that will help influence future environmental policies related to river and coastal water quality in the western English Channel. The data and models developed could be key in managing agricultural and urban runoff, mitigating the impacts of climate change and protecting delicate marine ecosystems.
With its cutting-edge technology and global collaboration, Vis4Sea is positioned to play a vital role in safeguarding water quality and ensuring the health of coastal ecosystems both in the UK and beyond. While the core focus remains on Plymouth Sound, the project has a broader reach, extending its monitoring efforts to Australia’s Fitzroy River and Great Barrier Reef and creating a unique transnational collaboration on water quality.
The PML-hosted Western Channel Observatory, in partnership with the Marine Biological Association, is already benefiting from the collaboration with the AquaWatch program through the provision of high-resolution data on the downstream effects of flooding. PML is further expanding this by establishing a comprehensive data network that combines direct sampling, autonomous sensors and satellite data for Plymouth Sound.
Vis4Sea, running until March 2025, is a partnership between PML, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Pixalytics Ltd., and Specto-Natura Ltd., and funded by the UK Research and Innovation (UKRI)’s Science and Technology Facilities Council (STFC).