English: A winter phytoplankton bloom colored the waters of the North Atlantic Ocean off the Iberian Peninsula in late January 2023. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of the scene on January 23.

Phytoplankton are microscopic plant-like organisms that live in relatively small number in waters in this region year-round. Given adequate sunlight and nutrients, phytoplankton can reproduce explosively and create colorful blooms that are large enough to be visible from space.

There is some color in the open waters of the North Atlantic, but most appears near the coastline off of Portugal. It is likely that recent heavy rains and flooding swept sediment and nutrients from the coast into the ocean, spurring the growth of phytoplankton. Parts of the Iberian Peninsula experienced heavy rain in late December, and Porto, a city on the coast of Portugal, reported flooding as recently as January 8.