Spectacular phytoplankton in the dynamic yet fragile waters of the Gulf of OmanWith the rhythm of the seasonsIn full bloom, it can even be seen from space. Driven by upwellings caused by monsoons, these algal blooms dye the ocean green. But behind the beauty lies a threat: the rise of noctiluca, a type of plankton that disrupts marine ecosystems by depleting oxygen and reshaping food webs. along withNASA satellites track these dramatic changes, and scientists have uncovered the mystery of ocean changes and their far-reaching impacts.

Phytoplankton blooms in the Gulf of Oman are not only a stunning seasonal spectacle, but also a sign of a changing marine ecosystem in which oxygen-consuming noctiluca takes on an increasingly important role.

The Gulf of Oman is a funnel-shaped body of water between Oman and Iran. It connects the Arabian Sea to the west, the Strait of Hormuz and the Persian Gulf to the east. This strategic waterway is not only a major route for international shipping, but also supports active artisanal fisheries that are vital to the economies of several countries in the region.

One of the most striking features of the Gulf of Mexico is the frequent blooms of phytoplankton—sudden surges in the populations of tiny plant-like organisms that form the basis of aquatic food webs. These blooms tend to follow seasonal patterns, occurring when conditions such as temperature, sunlight and nutrients are most favorable for phytoplankton growth.

The largest algal blooms usually occur in winter and early spring (January to March) and summer (June to August). During winter and early spring, monsoons play a key role in pushing surface water away from the coast. This triggers upwelling, a process that brings cooler, nutrient-rich water to the surface, encouraging the growth of phytoplankton.

These algal blooms are so large that they can even be seen from space. In February and March, NASA satellites captured footage of massive algae blooms drifting across the Gulf of Oman and into the Arabian Sea, a natural phenomenon visible from above.

The above image was captured by the OLI (Ocean Land Imager) on Landsat 8 on March 8, 2025, when eddies and ocean currents swept the phytoplankton into a narrow vortex. The OCI (Ocean Color Instrument) on board the PACE (Plankton, Aerosols, Clouds, Marine Ecosystems) satellite captured similar images on March 8 and March 24, while also measuring chlorophyll concentrations in surface waters.

Like plants on land, phytoplankton use chlorophyll and other light-harvesting pigments for photosynthesis, absorbing carbon dioxide and producing sugars for fuel. Chlorophyll in water changes the way it reflects and absorbs sunlight, allowing scientists to map the abundance and location of phytoplankton.

Green swirls may contain Noctiluca, a type of marine dinoflagellate that has been found here in the past. While noctiluca blooms are beautiful, their presence can have serious consequences for marine life. Bacteria consume oxygen as they break down dead phytoplankton, which can lead to hypoxia, sometimes with oxygen levels low enough to kill fish and other marine life.

In recent decades, the waters of the Arabian Sea have shifted from abundant growth of diatoms, a type of phytoplankton vital to the marine food web, to being dominated by Noctiluca. Unlike diatoms, Noctiluca can thrive in waters that are more stratified and have fewer dissolved nutrients. The shift had knock-on effects, including increases in jellyfish and seaweed algae and decreases in copepod and fish populations.

The NASA Earth Observatory image was taken by Wanmei Liang, using Landsat data from the U.S. Geological Survey.

Compiled from /ScitechDaily