NASA's PACE Mission Tracks Spring Phytoplankton Blooms in Mid-Atlantic Waters
In early April, orbital observatories began detecting vivid swirls of green, turquoise, and brown staining the waters off the U.S. Mid-Atlantic coast. The discoloration, most intense in the Mid-Atlantic Bight—where the Chesapeake Bay and other estuaries meet the open ocean—has drawn the attention of NASA scientists, who are using the agency's latest satellite to decipher its cause.
According to a NASA update, the colorful plumes likely stem from a mix of sediment, organic matter, and phytoplankton blooms. Unlike the relatively uniform open ocean, these coastal waters are considered "noisy" and "dirty," making it difficult to pinpoint the exact source. However, the PACE satellite—short for Plankton, Aerosol, Cloud, Ocean Ecosystem—has given researchers unprecedented clarity.
Anna Windle, a NASA research scientist supporting the PACE science team, noted in an agency statement that while some color may come from river outflows and storm-churned sediment, "there are likely phytoplankton blooms happening." She added that diatoms, a type of single-celled algae, typically dominate early spring blooms, but signs of coccolithophores are also present.
Diatom blooms appear greenish in natural-color imagery and are common in spring, while coccolithophores—phytoplankton with limestone-like armor—produce a milkier, turquoise hue and usually peak in late spring or summer. The ability to distinguish between these types is a significant step forward for oceanography.
Why Scientists Track These Blooms
These colorful plumes are more than a visual curiosity. Phytoplankton are the ocean's primary carbon recyclers, produce at least half of Earth's oxygen, and serve as a foundational food source for marine life. Fluctuations in their populations can alter ocean color and affect how deeply light penetrates the surface, which has broader implications for marine ecosystems.
Phytoplankton blooms often fade as quickly as they appear, typically as part of a healthy cycle. They thrive on nutrients brought to the surface by cold winter winds, but as spring blooms expand, they deplete those nutrients. Oscar Schofield, an oceanographer at Rutgers University, explained in the NASA release that unless major river outflows or storms replenish the nutrients, the bloom is likely to decline in the coming weeks.
The observations come as NASA continues to leverage PACE's advanced sensors to monitor ocean health. While the current bloom is not unusual, the detailed data gathered will help scientists better understand the dynamics of coastal ecosystems and their response to environmental changes.
