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Eye in the Sky: How satellite data on algal blooms is supporting the marine economy

27 October 2022

Algae may be tiny but many in maritime industries know all too well the large-scale negative impacts some of these microscopic plants can have on businesses and activities that rely on safe, clean and productive marine and coastal waters.
Harmful algal bloom detected off the Cornish coast
Harmful algal bloom detected off the Cornish coast

Under certain environmental conditions with suitable levels of sunlight, warm temperatures, rainfall, and increases in nutrients due to human activities such as agricultural or general land run-off, naturally-occurring algae can experience a period of rapid growth and ‘bloom’.

The blooms can occur in fresh or salt water across the globe, can last for weeks and some are sufficiently large that they are visible from space.

Many algal blooms pass unnoticed but blooms made up of certain species of algae may:
  • produce toxins damaging to fish, shellfish and humans;
  • deplete the oxygen supply in the water;
  • smother habitats and/or,
  • reduce sunlight that penetrates through the water column, which can prevent some marine organisms from growing, such as seaweeds and sea grasses.
These Harmful Algal Blooms (HABs) can have a significant economic and social cost and are expected to increase in frequency due to climate change. In the EU, the annual cost of HABs to related industries is estimated to be in excess of £800 million and current methods of tracking HABs in the English Channel are expensive, costing nearly £2 million annually to monitor just 6% of the Channel.

Combining data from four respondent shellfish farms in the south-west of England, the potential weekly loss in sales due to HABs could range between £26,350 and £100,000. These cost were based on the selling price of mussels and the weekly quantity produced during summer time in the UK but does not include the cost of recalling the mussels if they have already been dispatched. Recalling 1 tonne of mussels in the UK can cost around £160.

As such, there is much research being undertaken around the world to help mitigate the extensive financial, social and environmental impacts of HABs. One such collaborative research project is the INTERREG-VA project S-3 EUROHAB, which is a collaboration between France and England to investigate how satellite imagery can complement the monitoring of HABs and increasingly high levels of nutrients (eutrophication) to support marine management.

Project graphical overview

Over the last five years, the project team have used data from the European Space Agency’s (ESA) Copernicus Sentinel 3 satellite and other sources to track HABs and examine water quality to feed into the development of a cost-effective, rapid and user-friendly web-based alert system; a first-of-its-kind tool to help monitor the growth and spread of HABs.

The running cost of the alert system is estimated to be only £37k per year to cover the entire English Channel and will determine the risk of some HAB species based on their abundance in the surface waters.

The system currently covers the species Karenia mikimotoi (can reduce oxygen in the water column), Phaeocystis globosa (produces foam and can smother the seabed and clog fish gills) and Pseudo-nitzschia (responsible for Amnesic Shellfish Poisoning). The project also conducted research into detecting Dinophysis sp. (produces diarrhetic shellfish toxins) and Lepidodinium chlorophorum (associated with mass mortalities of fish and cultured bivalves) from space.

Another significant part of this collaborative project was to bring together in situ, mooring, and satellite data from multiple sources on both sides of the English Channel, to enable the assessment of the environmental factors that lead to HABs and validate the HAB risk map within the web-based alert system. The data collated included temperature, salinity, nutrients, chlorophyll-a (Chl-a), phytoplankton counts (including HAB species), dissolved oxygen, turbidity, surface solar irradiance and wind speed.

Stakeholder meetingThe S-3 EUROHAB team worked closely with over 70 end-users, decision-makers and other interest-holders to help ensure the developed alert system is a meaningful step forward in HAB monitoring. Interest-holders helped inform aspects such as alert frequency, seasonality and ground sample size through a series of ‘Stakeholder Workshops’ as well as highlight other factors that would be helpful, such as air temperature, water transparency, currents and river plume modelling. 10 alert system demos were also conducted with end-users and these will continue to be available on request.

The research from this project was well received at last year’s COP26 climate change event in Glasgow, Scotland, and the team are currently exploring the efficacy of the water quality algorithms under extreme conditions as well as completing research into its transferability to other regions.

Lead scientist on the project, Dr Gavin Tilstone of Plymouth Marine Laboratory, said: “It was great working on a collaborative project with French partners with such a wealth of expertise. The web alert system has assembled an array of products to aid marine managers, monitoring organisations and shellfish farmers to help track harmful algal blooms and water quality in the English Channel.”

A project partner commented: “Good use of satellite technology to help track blooms that is a real benefit to monitoring organisations.”

An end-user fed back: “The Research & Development on new HAB algorithms will benefit both shellfish organisations and marine management in being able to track the blooms at high resolution.”

The final version of the S-3 EUROHAB web alert system was officially launched in September 2022 and can be found at A demo using the web alert system can be found at

Web alert system
S-3 EUROHAB web alert system

Feedback from new users would be very welcome so if you have any comments then please contact Dr Gavin Tilstone on and for more information about the INTERREG-VA project S-3 EUROHAB then please visit the S3 EUROHAB website.

Related information

The INTERREG-VA project S-3 EUROHAB, which ran from November 2017 until October 2021, was partially funded by the Interreg France (Channel) England programme and the European Regional Development Fund. The project was made up of nine organisations; five from France (IREMER-Brest, IFREMER-Port-en-Bessin, IFREMER-Boulogne-sur-Mer, Comité Régional des Pêches de Basse Normandie Universite de Brest) and three from the UK (Plymouth Marine Laboratory, Environment Agency, University of Southampton).