Blue Tides Off the Emerald Isle

The waters of Ireland are normally black, but on June 2, 2006 NASA's Aqua satellite captured this image of swirling clouds of blue and green off the island's west coast. The colorful swirls were a large bloom of phytoplankton--microscopic plants that grow on the sunny ocean surface.

While phytoplankton create a beautiful Van Gogh-esque image when viewed from above, they also play an important role in sustaining ocean ecosystems and influence global climate. The tiny plants sit at the base of the marine food chain, and regions with frequent blooms tend to support a thriving marine population.

The plants need nutrients such as iron to grow, so fertile waters are often located near a continental shelf where cool water from the ocean's depths pushes to the surface. This upwelling carries nutrients that had settled on the ocean floor to the surface and sustain large phytoplankton blooms.

Like all plants, phytoplankton influence global climate by regulating gases in the atmosphere by absorbing carbon dioxide and releasing oxygen as they grow. When the plants die, they sink to the ocean floor, carrying the absorbed carbon with them. Since carbon dioxide is a greenhouse gas--it traps heat at the planet's surface--the Earth would be much warmer without phytoplankton. Over the course of Earth's history, the oceans have become the primary sink for atmospheric carbon dioxide.

--Bjorn Carey

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Credit: NASA GSFC