Springtime blooms on land in North America are usually obvious: green vegetation sprouts and flower buds open in ways that bring bright color to the landscape. Springtime changes in the North Atlantic Ocean are less obvious to the human eye, as not all of the action takes place at the surface and much of the color is camouflaged by the dark greens, blues, and blacks of the deep sea.
Satellite sensors give us other ways to see blooms of phytoplankton, the plant-like primary producers of the ocean. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite observes Earth in 36 different visible, infrared, and near-infrared wavelengths. Over the past three decades, scientists have tuned the sensors and the processing of those spectral data to identify areas with high concentrations of chlorophyll-a, the primary pigment used by phytoplankton to harvest sunlight for energy.
Data for the images above were collected by Aqua MODIS on March 30, 2021. The top left image shows concentrations of chlorophyll-a in the North Atlantic Ocean from New Jersey to Nova Scotia; the darkest shades of green show areas with the greatest chlorophyll concentrations. The right image shows the same scene in natural color, as the human eye might see it. It is unusual at almost any time of year to have a clear view of such a wide area of the cloudy North Atlantic.
Note how the phytoplankton wrap into swirls and rings in some places. They often trace the edges and fronts of ocean eddies and warm core rings that spin off from currents like the Gulf Stream. Some of the chlorophyll abundance also shows up around the region’s shoals and underwater banks—such the Le Have and Emerald banks off the south coast of Nova Scotia—where upwelling and nutrient mixing promotes phytoplankton growth. The most famous patch is Georges Bank, where currents meet the relatively shallow water and promote an abundant crop of phytoplankton that fuels other marine species. The Gulf of Maine and Georges Bank have historically been among the most productive fishing grounds on the planet.
Phytoplankton account for nearly half of Earth’s primary production, turning carbon dioxide, sunlight, and nutrients into organic matter and providing the fundamental nourishment that fuels almost everything in the sea. The amount and location of phytoplankton affects the abundance and diversity of everything from finfish to shellfish and zooplankton to whales. Phytoplankton also affect the chemistry and climate of the planet. They produce about half of Earth’s oxygen and they draw carbon out of the atmosphere—locking it up for a time in their cells, in the animals that consume them, and in pellets of waste that drop to the seafloor.
NASA Earth Observatory images by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Michael Carlowicz.