From satellite to microscope


Guinardia delicatula - a marine diatom

Guinardia delicatula - a marine diatom, a microscopic plant that can form blooms so large that they can be seen from space. The April bloom formed close to the Cornish coast (arrowed above, left) and spread to the south west.

The chains of ‘cells’ average about 50μm (5/100ths of a millimetre) in length, and have been ‘blooming’ off the coast of south Devon and Cornwall over the last few weeks, reaching densities of almost 100,000 cells/litre of seawater.  

Guinardia is one of the first phytoplankton species to bloom in spring as the recent combination of calm sunny weather and high levels of nutrients following the winter recharge provide ideal conditions for its growth.  As the plankton uses nitrates in the water as food to proliferate, the nutrients are rapidly used up and the bloom fades. But not before tiny animals, zooplankton, feast on the plant bounty, themselves providing food for larger animals such as fish; dead cells eventually sink through the water column to provide food for the organisms living on the seabed. Guinardia is thus a key link in coastal food chains at this time of year.

Not only have scientists at PML collected samples for investigation through powerful microscopes they have obtained images of the same bloom using the Visible Infra-red Imaging Radiometer Suite (VIIRS) on board the Suomi-NPP satellite. Operated by the US National Oceanographic and Atmospheric Administration (NOAA) the satellite beams signals from an orbit 824 km (512 miles) above the Earth to a ground station, and then on to PML for analysis. Simultaneous measurements taken at the Western Channel Observatory L4 autonomous data buoy, stationed 13km (8 miles) off Plymouth, were able to track the decline in nitrate as it was consumed by the expanding bloom.

The ability for us to look at the same ocean phenomena from satellites sweeping the globe, microscopic examination of samples from the bloom and chemical sensors within it, at high resolution, allows us to piece together how the seas and the life they contain function, in ways that were previously not possible. While this particular bloom poses no threat to humans or wildlife, these techniques are able to spot and identify algal blooms that may prove harmful.

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