A large phytoplankton bloom in France’s Bay of Biscay brought bright swirls of light blue and turquoise to the surface across much of the bay. There are likely a variety of species of phytoplankton present. Dark green hues are possibly due to the green pigment chlorophyll, which phytoplankton use for photosynthesis (just like their land-based cousins). The green tint near the coastline could also be sediment emptying into the bay in the region’s rivers. This is likely as the green patterns near the shore correspond to the mouths of rivers. The sediment is tan in high concentrations, then appears blue and green as it becomes diluted.
In contrast, the much brighter, light blue swirls suggest the presence of coccolithophores, a species of phytoplankton that produce a calcite (basically limestone) shell around themselves somewhat resembling a hubcap. While each individual coccolithophore shell is tiny—only about three one-thousandths of a millimeter in diameter—a large bloom such as this can contain trillions of the organisms, giving the ocean an almost milky appearance at the surface.
Coccolithophores are not hazardous to their environment, and it is not at all unusual to see such a bloom in the Bay of Biscay this time of year. In addition to the role these organisms play in the marine food chain, scientists are interested in tracking coccolithophore blooms as indicators of the physical state of the ocean and how the ocean may be changing in response to shifting weather patterns and longer-term climate change. Moreover, scientists are working to revise their estimates of the “productivity” of these organisms on a global scale; i.e., how much carbon do they absorb during photosynthesis and how much calcite do they manufacture in their shells as a result? Currently, scientists estimate that coccolithophores produce more than 1.5 million tons (1.4 billion kilograms) of calcite per year, making them the ocean’s leading producer.
This image was captured by the MODIS on the Terra satellite on May 20, 2010.