This is an image of a phytoplankton bloom that occurred in April 2023 off the east coast of the United States. Phytoplankton are microscopic organisms that live in both fresh and saltwater, and can be bacteria, protists, or single-cell plants. In this area, blooms occur in the spring due to the increase in sunlight and the high availability of nutrients brought to the ocean surface by the winter turbulence. Additional color in this image comes from sediment and colored dissolved organic matter (CDOM), likely sourced from runoff in the Delaware River watershed. This runoff also contains nutrients from farms, wastewater treatment plants, and other sources that can contribute to the growth of phytoplankton. I find it interesting how large amounts of such tiny organisms can make ocean current and eddies more visible, especially with such vibrant colors.
Image credit: L. Dauphin; via NASA Earth Observatory.