Harmless Bloom of Plankton Visible from Space

ESA BloomBoth the European Space Agency (ESA) and NASA in the USA have recently released dramatic photographs of a giant “bloom” of harmless microscopic plants, known to marine scientists as ‘phytoplankton’, off the West Coast of Ireland.  

Satellite image from the European Space Agency (ESA) showing the swirls of phytoplankton blooms south of a cloud bank off the coast of Ireland (photo: courtesy ESA)



“Blooms of phytoplankton are important events in the sea and occur mainly during the summer months,” said Marine Institute scientist Joe Silke. “Phytoplankton are freely drifting, microscopic plants that convert sunlight and chemicals into plant material, just as plants do on land. They form the base of the marine food chain and are important contributors of atmospheric oxygen and essential components of a healthy oceanic biodiversity.”  

picture of coccolith

In recent weeks and in response to the fine weather, there have been reports of several blooms around the Irish coasts. The most dramatic of these - shown in the ESA photo of an algal bloom to the west of Ireland – was taken on the 23 May. The large swirls of turquoise water, south of the large cloud mass, are due to the presence of a species of phytoplankton known as Emiliania huxleyi.  


These phytoplankton are members of a group called the ‘coccolithophorids’ and are covered with an ‘armour plating’ of chalk plates. Each microscopic cell measure approximately four one thousandths of a millimetre in diameter and is therefore invisible to the naked eye. However, in response to warm surface waters and sunlight these tiny plants form blooms where billions of these cells can accumulate and cause the sea to turn a  milky white colour.  

NASA satellite image

NASA satellite image showing the bloom extending down along the west coasts of Ireland, France and Spain. (photo: Courtesy of the North American Space Administration - NASA)

“This is clearly visible in the satellite images,” says Joe Silke. “The colour due to tiny calcium carbonate platelets that cover the cell and act as tiny mirrors reflecting light that strikes them, resulting in chalky white water. This resemblance to chalk is not incidental as the same coccoliths form chalk deposits including the famous White Cliffs of Dover and many other calcium carbonate coastal formations".  


Coccolithophores including Emiliania huxleyi could be susceptible to ocean acidification over the next 50 or so years as carbon dioxide diffuses across the sea-surface making the surface ocean more acidic, resulting in a detrimental impact on the occurrence of this beautiful natural phenomenon.  

“The presence of this bloom is a good sign that the waters to the west of Ireland are currently in a healthy state," says Silke. "Blooms such as these are important producers at the bottom of the food  chain and generate oxygen both in the sea and the atmosphere." 

The Marine Institute National Phytoplankton Monitoring Programme is carried out year round to monitor the presence and impact of harmful species but also to identify occurrences of widespread  blooms of  public interest and to study trends in water quality.    

Picture credits:

ESA Image courtesy of the European Space Agency.

NASA Image by Jeff Schmaltz, MODIS Rapid Response Team. 
Instrument: Terra - Modis.