Dueling Blooms

Dueling Blooms

As the seasons and years pass on Earth, different species tend to dominate the landscape at different times. Such is the case in summer in the surface waters of the Barents Sea, north of Scandinavia and Russia. NASA satellites recently captured a transitional moment between one form of microscopic, plant-like organisms (phytoplankton) and another as summer water conditions changed.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a natural-color image (above) of phytoplankton blooming in the waters off of Norway and Russia on July 10, 2014. Note the green swirls in the water on the center and left, while milky blue-white swirls color the upper right. Though it is impossible to know the types of phytoplankton without sampling the water directly, previous analyses of satellite images suggest that the green plankton were likely diatoms and the white ones were probably coccolithophores.

Previous research has suggested that diatoms, a microscopic form of algae with silica shells and plenty of chlorophyll, start to bloom in the well-mixed surface waters of spring and dominate the early summer. As the water warms and becomes more stratified, or layered, coccolithophores bloom more abundantly from late July into the autumn. Coccolithophores show up as milky white-green in satellite imagery due to their calcium carbonate shells.

The MODIS instrument on NASA’s Terra satellite acquired another image (below) of phytoplankton in the Barents Sea on August 3, 2014. Three weeks after the first shot, coccolithophores appear to have taken over control of the surface waters.

Both images are somewhat unusual because the Barents Sea is cloud-covered roughly 80 percent of the time in summer. The area in this image is located immediately north of the Scandinavian peninsula, a junction where several ocean current systems—including the Norwegian Atlantic, the Persey, and east Spitsbergen currents—merge and form a front known as the North Cape Current. The intersecting waters, plus stiff winds, promote mixing of waters and of nutrients from the deep.

NASA image by Norman Kuring, NASA’s Ocean Color web. Caption by Mike Carlowicz, with assistance from Norman Kuring and Sergio Signorini, NASA GSFC.

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