MODIS Sees Phytoplankton Off Newfoundland
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MODIS Sees Phytoplankton Off Newfoundland

August 1, 2012
A swirling ribbon of milky blue colored the waters off Newfoundland in late July, 2012, marking the site of a continuing bloom of phytoplankton in the North Atlantic Ocean. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image on July 27 as it passed over the region.

The image is centered due east of Nova Scotia and southeast of St. John’s, Newfoundland, where the North American continental shelf forms the series of shallow underwater plateaus known as the Grand Banks of Newfoundland. In this area, the Gulf Stream carries warmer southern waters to mix with the cooler waters carried by the Labrador Current. The flowing and mixing of the waters stirs nutrients from the bottom. In the extended light of spring and summer, these nutrients help fuel large phytoplankton blooms in the region.

At the time this image was captured, a newly-outfitted research vessel, the R/V Falkor, was making a shakedown run in the same section of ocean as captured in the image. In the cruise log, located online at www.schmidtocean.org, the entry for July 23 notes that the crew observed a slightly rusty reddish hue to the water, a sharp contrast to the steel gray to deep blue waters seen up to that time during the voyage across the Atlantic from Newcastle, UK. The color was attributed to a bloom of a phytoplankton called Trichodesmium, a cyanobacteria (formerly called blue-green algae) whose favored home is the warm, salty water of the Gulf of Mexico and the Caribbean. The Falkor had entered a Gulf Stream warm-core ring -a large, northward meander of the Gulf Stream Current, where the water retained enough warmth and salinity to retain the more southerly phytoplankton population. This reddish bloom is not evident on the image, most likely because the warm-core ring was relatively small.

On July 24 and 25, the Falkor’s crew took samples of deep waters located about 200 miles east of Nova Scotia, and also likely within the phytoplankton bloom in this image. They observed indications of a dense population of oxygen generating phytoplankton at about 50 meters below the surface of the water. Below a few hundred meters, a sharp decrease in oxygen was observed, indicating the lack of such phytoplankton in the deeper layer of water, most likely because low light levels at this depth prohibited grown of oxygen-producing bacteria.

Credits: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC

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