The death throes of a giant plankton bloom (the milky blue ribbon in the photograph) have been captured by Envisat, an earth-observation satellite operated by the European Space Agency. The algal bloom, snapped on 6 June, is among the largest recorded — at around 500 km long, it stretches the full length of Ireland.


The milky water, which would appear chalky-white to anyone on a boat sailing through it, forms as the plankton, having used up all the available nutrients in the sea around them, start to shed their calcite shells. The species involved in this particular display is likely to be Emiliania huxleyi (inset), which often forms blooms in the North Atlantic at this time of year.

Photosynthesizing plankton species such as E. huxleyi are at the root of almost all food webs in the ocean, being eaten by animal plankton. But despite their visual impact, little is known about how the blooms affect the local ecosystem.