Bright jewel tones lit up the dark waters of the Celtic Sea and the Atlantic Ocean lying south and west of Ireland in early June, 2013. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard the Terra satellite captured this true-color image at 1:17 p.m. local time (12:15 UTC) on June 4.
These dazzling colors are the result of a vigorous bloom of phytoplankton, microscopic organisms that grow in the surface waters when sunlight, temperatures and nutrient levels are favorable. Phytoplankton form the base of the marine food chain, becoming food for grazer and predatory planktonic animals (zooplankton), which then feed fish, squid and, in turn, higher predators such as tuna, shark, turtles and seabirds. Phytoplankton is also an important component of the carbon cycle, taking up carbon dioxide and, through photosynthesis, releasing oxygen.
The waters off Ireland often host huge, colorful blooms of phytoplankton. Two warm-water ocean currents in the region play roles in creating favorable conditions for growth. The first is the North Atlantic Current (the northern arm of the Gulf Stream) which warms the western waters. The other is a current that flows northwards along the European continental shelf edge, and which brings not only warm water but additional plankton to the region from the Mediterranean Sea. Just off Irelandís continental shelf lies a deep trough, and upwelling currents bring cold water and nutrients to the surface. The mixing of waters and nutrients, along with strong spring and summer sunshine, creates perfect conditions for abundant bloom.