During late spring and early summer, every year, the North Sea is flooded with massive algal blooms, which bring about a visible change in the color of the water. This curious phenomenon is caused due to the proliferation of microscopic, plant-like organisms, called phytoplankton. Photosynthetic in nature, the algae’s blue-green tint actually alters the color of the ocean. Recently NASA released a series of images, captured by its satellites, that show the phytoplankton blooms in striking detail.
Increasing sunlight and the abundance of nutrients in the water, towards the end of spring and the beginning of summer, are two of the main reasons that cause algal blooms in the North Atlantic Ocean. Some researchers, however, believe that the annual plankton growth starts in the middle of winter. This is because the intense winds and storms, usually associated with the season, induce a vigorous churning of the deep ocean waters, making it harder for the predators to actually spot the organism.
The first image, dated June 6, was captured by the Terra satellite’s Moderate Resolution Imaging Spectroradiometer (MODIS) technology. It clearly shows a mass of thriving plankton, encompassing a huge area between the UK, Germany and Denmark. According to NASA, the lighter hues, in the picture, could be caused by coccolithophores, a type of phytoplankton. The greener areas, on the other hand, indicate a dense population of diatoms or even dinoflagellates, both microscopic organisms inhabiting the marine ecosystem.
The following images show the algal blooms, at different stages of the cycle. In the second picture, taken by the Aqua satellite, the green patches have become visibly smaller in area, thus indicating a decreasing phytoplankton population. At the same time, it shows a significant coccolithophore bloom, as noted from the increase in the lightly-colored areas. Speaking about the phenomenon, the spokesperson of NASA elaborates:
The change could be due to the short life span of phytoplankton—two to six days—and differences between the species. Some outlast others because of their ability to survive at lower nutrient levels… The third image, taken on July 1, 2015, by MODIS on Terra, shows an area slightly north of the earlier bloom. It could be a new burst of coccolithophores, or it could be a continuation and migration of the same bloom from earlier in June.