A storm in Africa's Sahara Desert brought a sandy fertilizer to the Atlantic Ocean on April 8, triggering plankton blooms that show up as blue-green swirls in this photo from the European Space Agency's Envisat satellite. The storm's plume covered parts of Ireland [top left], England [top right], France [below England] and the Iberian Peninsula [bottom right].

Saharan sand carries nitrogen, phosphorus and iron—delicious and essential treats for phytoplankton, which are microscopic ocean plants. The sand frequently hitches a ride on atmospheric convection currents and travels as far south as the tropical Atlantic and west to the Caribbean Sea.

Saharan dust in the ocean is a "mixed blessing," according to NASA's Earth Observatory. The plankton that feed on the dust's minerals can bloom significantly, providing food for other ocean creatures, but an overgrown bloom can consume much of the dissolved oxygen in an area and create an anoxic dead zone.

—Francie Diep