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Huge plankton bloom detected from space

Recent clear weather over the UK has allowed marine scientists to monitor a large plankton bloom developing on the sea surface between Cornwall and the French coast.

The most impressive satellite image - taken a few days ago - shows the bloom stretching 1000 square kilometres (400 square miles). Scientists at Plymouth Marine Laboratory (PML) have colour coded the satellite image, with red and orange indicating the densest patches of algae.

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 Millar from 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.'

Huge blooms are quite common in autumn. Indeed this year's bloom is a little later than usual, probably due to the prolonged cloudy weather.

It began life as a narrow ribbon but spread out. The late summer sun and nutrients released from deeper water have encouraged the plankton to reproduce.

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.

Millar says, 'We hope to reach a stage where we can identify blooms before they become a problem.'

This latest bloom marks the end of the season, and the end of the pilot scheme.

The first rough weather is already dispersing the current bloom. The next large blooms are due in spring.

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 equipment can distinguish between some species. Miller is working on ways to readily detect harmful blooms from space.

Plymouth Marine Laboratory is a Natural Environment Research Council collaborative centre.

Source: NERC PlanetEarth Online

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