NASA MODIS Image of the Day: April 13, 2011 – Phytoplankton bloom in the Bay of Biscay
In early April 2011, a flowing ribbon of the bright jewel tones of a spring phytoplankton bloom graced the Bay of Biscay, off the coast of France.
The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image on April 6 at 11:15 UTC as it passed over the region.
Near the coast, particularly in the plumes of the many rivers and estuaries which drain the continent, the waters are tinted with tans and dull greens, which are typical colors of sediment. In the spring, runoff from the Loire River, on the northern coast, and the Gironde Estuary further south, are major contributors of sediment to the Bay, as can be clearly seen in this image. The large volume of freshwater flow from these waterways also induces buoyant plumes, which drive significant northward currents over the inner continental shelf. The strong currents mix low-salinity fresh water and nutrient-rich sediments with Bay water rising from spring upwelling, creating ideal conditions for a rich nursery for phytoplankton. Where conditions are favorable, phytoplankton blooms in bands of turquoise blue mixed with bright green swirls. In some areas, the blue is distinctly milky in color, suggesting the presence of coccolithophores, a species of phytoplankton that produce a calcite shell around themselves. This shell is lightly colored, and when trillions of the microscopic organisms are concentrated together, the near-white coloration of the shells lends a milky sheen to the water. Phytoplankton forms the base of the marine ecosystem, as it is the bottom element of the marine food chain. It is also the first biological element which responds to the varying hydrodynamic and climatic conditions, including the variation of the nutrient input by coastal upwelling and continental input by the river systems. As conditions change, phytoplankton begins to bloom. Shortly afterwards, zooplankton begin to graze on the phytoplankton and they bloom as well, serving as food for hatchling anchovy and other species. In this way, spring phytoplankton blooms begin a cycle of growth that ends in the growth and reproduction of important elements of the marine ecosystem, and also nurtures healthy fisheries.
