Tuesday 16th June was a gloriously beautiful, calm, Scilly day; the kind that Scilly-fans dream of.  The postcard picture perfect blues and greens, with highly saturated colours that, when posted on Social Media, are often accompanied with #NoFilter and #NoFilterNeeded. 

Due to the country being in Lockdown many locals had taken to Facebook, Twitter and Instagram to share images of the Islands with family and friends who were unable to be here.  

The images may look eerily fake or photoshopped but we can assure you they are all as "nature-intended". 

We speculated at the time that the colours must have been as a result of some kind of natural phenomenon; in all probability an algal bloom of some description, given the very distinct lines and tones we were seeing. 

But speculation led us on the hunt for an answer, which we've now got thanks to our friends and colleagues at the Centre for Environment Fisheries and Aquaculture Science (Cefas) and Plymouth Marine Laboratory (PML).

When the North Atlantic Blooms in June

What we were witnessing was a Coccolithophore bloom (bit of a mouthful, but we'll come back to exactly what it is in a minute).  Not only that, according to NEODAAS (NERC Earth Observation Data Acquisition and Analysis Service) researchers based at PML, it may have been the largest ever Coccolithophore bloom recorded in the Channel! 

It was big enough to be spotted from space, as you can see below in the "Enhanced colour image using Copernicus Sentinel 3A data (composite 16th - 22nd June 2020)" processed by PML.

But what is a Coccolithophore bloom?

Adam Lewis (Research Phycologist/Team leader, Cefas) explains what Coccolithophores are.  "Coccolithophores are a type of phytoplankton (microscopic algae) which live in all of the oceans of the world. They are some of the most common organisms on the planet and are also very important in marine ecosystems.

Although they are tiny they are covered in very complex ‘scales’ called coccoliths. These scales cover their surface and are made from calcium carbonate, which is also what limestone is made from.  Each species of Coccolithophore has a unique pattern of coccoliths and these can change throughout the organisms life cycle (a selection can be seen to the right - "The Diversity of Coccolithophores" taken from Wikimedia).

Coccolithophores are important in the oceans because they photosynthesise, fixing energy from sunlight and making it available to other animals. As a result of their coccoliths, they are also important in fixing carbon dioxide from the air and removing it from the atmosphere.

Coccolithophores can cause enormous blooms, covering large areas and turning the seawater a light blue or milky colour (like witnessed in Scilly).  Coccolithophore blooms also make the surface of the sea more reflective, this is because of the calcite crystals in the scales that cover the cells.

When these blooms finish the Coccolithophores sink to the bottom of the ocean taking the carbon and calcium they fixed at the surface with them."

So what we were seeing was millions, if not billions, of these tiny planktonic creatures all smooshed together in one place (albeit a very big place) and the explosion of colour was amplified by the sun hitting those tiny particles whilst on the surface!  They vanished almost as quickly as they appeared, sinking back down to the bottom of the ocean with their newly acquired loads of carbon and calcium with them. 

Blooming Science...

This particular Coccolithophore bloom was followed closely by many scientists and researchers across the South-West and as we've already said it may have been the largest ever Coccolithophore bloom recorded in the Channel!  The NEODAAS researchers, based at PML, use a variety of methods to monitor and track events like the one back in June, including in this case satellite data and imagery.

Bridie Kennerley (Communications Officer, PML) shared with us, "The team process data from some of the many satellites circling the Earth to find out key information.  Some of these satellites provide frequent (daily) images at lower resolution, while others provide images less frequently (every 3 – 4 days) but with a much higher resolution.  In the case of this bloom, using multiple satellites meant the team could create spectacular images that showed exactly where the bloom was.

One set of data came from Sentinel-2B (image below), one of a pair of a European Space Agency satellites operated as part of the Copernicus program. 

The image produced from it is so detailed that, on the full size image (above), you can zoom in close enough to see individual ships out at sea (as shown below).

Bridie continued, "When the researchers make images from satellite data like this, they can also enhance the colours to show certain things more clearly and apply algorithms to extract more information. So, in this case, they could highlight where the Coccolithophores were, but they can also use this to show things like phytoplankton (microscopic marine organisms that, like plants on land, use chlorophyll to capture sunlight and convert it to energy).

These are important as they can give researchers a lot of information about the health of the ocean in general, but can also cause harmful algal blooms, which need to be monitored closely.

The images can also be made up of composite data recorded over a longer period of time, from 24 hours to a whole week. This helps to avoid images being obscured by cloud cover, something very common around the coast of the UK!"

Scilly's Living Seas...

In the run up to this recognised Coccolithophore bloom the sea was full of life; those out boating around the islands will no doubt have noticed the various tell tale signs that something was occurring.  The sea, although beautifully clear, looked almost "dusty" as the sun shone through the water column and you could see multitudes of living creatures of varying sizes; some as small as dust particles, eggs and "seeds", salps, right up to and including large Jellyfish. 

Indeed in the last week of May we had a lot of Sea Foam (aka Spume or Ocean Foam) around the Islands too (as pictured here above off of Annet). 

Sea Foam is caused by the agitation of sea water, generally out deeper, particularly when it contains high concentrations of organic matter, i.e. the break down of Algal Blooms or masses of planktonic type creatures, and is just another wonder of the natural world for us to marvel at.

Coccolithophore Update (December 2020):

Since writing about the Coccolithophore Bloom in June we have also received further information from both PML and NEODAAS. 

Dr Daniel Clewley (NEODAAS Manager) has reviewed the data and made a good estimate on the size of the bloom stating, "Based on the satellite date it was estimated that the bloom off the South West coast was 170km long, 60km wide and covered an area of over 9,000km2." 

Additionally, Professor Steve Widdicombe (Director of Science, PML) shared in a news article from PML, "The ‘bloom’ made up of tiny single-celled Emiliania huxleyii wasn’t just large in extent, it was also very dense with up to 11 million cells per litre of seawater, so dense that the water was white with their calcite liths, we haven’t seen anything approaching this for the last 30 years”.


With thanks to Dr Andrew Turner and Adam Lewis, of Cefas, Bridie Kennerley, of PML, and Dr Daniel Clewley of the NEODAAS Team for their help and contributions.  

Dr Andrew Turner and Adam Lewis are scientists working in the Natural Aquatic Toxins Team within the Food Safety Group at the Cefas laboratory in Weymouth, Dorset. As part of their remit, they are part of a team focussed on the delivery of routine monitoring of shellfish such as mussels, clams and oysters for the presence of harmful algal toxins which can cause human poisonings. They also conduct a range of research projects assessing new testing methods, new and emerging toxin threats, impacts of climate change and other long term changes, as well as work to help other countries develop their technologies to better mitigate against the impacts of harmful algae.

They are founders of the “ScillyHAB” project, an initiative focussed on looking for HABs (Harmful Algal Blooms) in the Isles of Scilly, where they have been working with school children and teachers from the Five Islands Academy, as well as local citizen scientists. It is hoped their work in the islands will help develop a better understanding of the presence of certain species of algae and any potential impacts on human, animal and ecosystem health.

If you like to more about the work of either Cefas (Centre for Environment Fisheries & Aquaculture Science) or NEODAAS (NERC Earth Observation Data Acquisition and Analysis Service) please head on over to their respective websites. 

Cefas (Centre for Environment Fisheries & Aquaculture Science)

NEODAAS (NERC Earth Observation Data Acquisition and Analysis Service)