According to Natural Environmental Research Council, a satellite image showed the bloom stretching 1000 square kilometres (400 square miles). Blooms, which are made up of billions of microscopic marine plants, can harm fisheries but the current one is not thought to be a threat - it is already dispersing.
Dr Peter Miller from Plymouth Marine Laboratory (PML) says, 'It's only when you get the really dense blooms coinciding with onshore winds that push the algae towards the beaches that there can be a problem.'
Plankton blooms are an important part of the marine food chain. Tiny animals called zooplankton eat these microscopic plants, and larger fish then feed on the zooplankton.
So the timing of blooms can be quite crucial to fish larvae and so to fish stocks. But some can harm fish, as well as humans bathing on beaches. In April, marine researchers set up a pilot scheme called AlgaRisk with the Environment Agency and the Met Office.
Miller says, 'We hope to reach a stage where we can identify blooms before they become a problem.'
The bloom was detected using the NASA satellite Aqua. An instrument onboard can measure the density of chlorophyll from its orbit 440 miles above the Earth - the chlorophyll indicates the presence of plankton.
The Plankton Forecast: Huge Bloom off Cornwall
UK - Marine scientists recently monitored a large plankton bloom developing on the sea surface between Cornwall and the French coast. As a threat to fisheries scientists hope to identify blooms before they become problematic. Sea.
