Today’s story is the answer to the April 2024 puzzler.
On February 8, 2024, NASA’s PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite roared into space aboard a SpaceX Falcon 9 rocket. Less than two months later, NASA engineer Joseph Knuble compiled a gallery of 36 images from the satellite’s primary sensor. Among his favorites is this image of the Gulf of Oman.
PACE’s OCI (Ocean Color Instrument) acquired the data for this image on March 17, 2024. Knuble, the lead instrument systems engineer for OCI, composed this scene using red (630 nanometers), green (532 nanometers), and blue (465 nanometers) wavelengths of light. The image has been adjusted to draw out the fine details in the water. It is not a natural-color image in the traditional sense. Instead, it is more vibrant and detailed than what your eyes would see, but the features are all quite real.
Among the most notable features pictured here is a bloom of phytoplankton. When conditions are right, phytoplankton populations can grow explosively, forming a bloom large enough to be visible from space. On this day, turbulent eddies have drawn the bloom into thin, swirling bands. The image “highlights the beauty and complexity of that area,” said Jeremy Werdell, PACE project scientist at NASA’s Goddard Space Flight Center.
The swirls of green likely include Noctiluca scintillans—a type of marine dinoflagellate that has been found here in the past. Though Noctiluca blooms can be strikingly beautiful, their presence can have consequences for ocean life. Bacteria consume oxygen as they break down the dead phytoplankton, which can cause hypoxia and dead zones.
Across the wider Arabian Sea, waters have transitioned in recent decades from supporting abundant diatoms—a type of phytoplankton important for the marine food chain—to being dominated by Noctiluca. Unlike diatoms, Noctiluca can thrive in waters that are more stratified and contain fewer dissolved nutrients.
Determining which phytoplankton species is present within a bloom has only been possible with direct water samples. But with OCI’s ability to detect hundreds of wavelengths of light, scientists could soon be able to distinguish phytoplankton types from space.
NASA image by Joseph Knuble, using PACE data from NASA/GSFC. The image was made from an early, uncorrected version of PACE data not intended for scientific analysis. Story by Kathryn Hansen.
