Something is invading the ocean waters off the northeastern U.S. coast, as revealed in recent satellite imagery.
For several weeks now, eerie green plumes have been swirling in the shallow waters of the Mid-Atlantic Bight, the region that spans the coastlines from Massachusetts to North Carolina.
Beginning in April, blue-green swirling patterns have appeared in NASA satellite imagery, resembling colored smoke billowing into the waters of Delaware Bay, Chesapeake Bay, and other shallow areas along the northeastern coast.
Such regions are known for their discoloration, which scientists specializing in remote sensing describe as “noisy” environments, due to sediments and other materials that flow from inland, carried by rivers that empty into the ocean and deposit microscopic particles.
According to NASA, the blending of organic matter into ocean water, driven by warmer weather, can help feed periodic blooms of phytoplankton, which create the stunning swirls of deep green and blue seen in satellite images of Earth.
“This mix creates optical complexity that has long made it harder for scientists to distinguish and categorize phytoplankton blooms in shallow coastal zones compared to the deeper, darker, more uniform waters of the open ocean,” said Adam Voiland in a recent update for NASA’s Earth Observatory.
For the last two years, the American space agency has been managing several missions to help it better characterize such conditions, including the Plankton, Aerosol, Cloud, Ocean Ecosystem (PACE). Initiated in 2024, PACE collects information on the chemistry and ecology of our oceans using satellite imagery that observes ocean color worldwide. The information PACE satellites gather can provide crucial insights into our planet’s carbon cycle and a range of other factors that often influence the size and duration of phytoplankton blooms.
The “optical complexity” Voiland describes is a particular challenge for scientists observing these phenomena in coastal regions such as the Mid-Atlantic Bight. Fortunately, NASA’s PACE mission data is complemented by data from other satellite missions, such as Aqua and Terra, all of which have contributed to the iridescent phytoplankton blooms that began appearing in early April.
Specifically, scientists point to diatoms, a variety of phytoplankton that undergo sudden surges in growth in the spring, as river runoff, often driven by meltwater that is carried downstream from higher elevations, is combined with increased seasonal daylight and a range of other environmental factors.
“Diatoms typically dominate blooms early in the spring, but we are seeing some signs of coccolithophores mixed in as well,” according to Anna Windle, a research scientist currently at Goddard Space Flight Center. Windle says that, based on data collected by PACE, some of the recent greens and blues have now been confirmed as the result of phytoplankton blooms, as shown in chlorophyll mapping of PACE satellite data.
While sometimes appearing brown or even indiscernible from sea level, diatoms in ocean water this time of year often appear in vibrant hues of green and blue in satellite imagery.
Certain varieties of phytoplankton blooms, such as those involving coccolithophores, are more likely to produce the turquoise coloration seen in imagery collected in recent weeks. These microscopic plant-like organisms inhabit the uppermost ocean layers and possess thick, scaly exteriors that are highly reflective, resulting in an iridescent greenish coloration often visible even at sea level.
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Coccolithophores also play a significant role in the biogeochemical cycles in our seas, and scientists attribute as much as half of the calcium carbonate precipitation in our oceans to these organisms.
Over the next few weeks, the waters off the eastern seaboard will likely resume their normal coloration, unless these microscopic organisms are nourished by additional influxes of nutrients resulting from storms or other environmental events, which periodically carry organic materials into the “noisy” northeastern ocean waters.
You can learn more about phytoplankton blooms at NASA’s Earthdata page.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.