File:Bloom in the Bass Strait (MODIS 2021-06-01).jpg

English: A large stain of milky-blue colored the waters of the Bass Strait north of Tasmania and south of Australia in late May 2021. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite acquired a true-color image of the scene on May 22.

The colorful water was caused by a large bloom of phytoplankton—microscopic plant-like organisms that live in these waters year-round in relatively small numbers. When conditions are right (enough nutrients, sunlight, and adequate water temperature), phytoplankton begin to reproduce explosively, sometimes creating a large floating mass that can be seen from space.

There are many species of phytoplankton, each containing chlorophyll which is used in the presence of sunlight to convert water and carbon dioxide into energy. Some species also contain other pigments or features that may create characteristic colors when massed into a floating bloom. The milky color of this particular bloom suggests that it is created by coccolithophores, which are a type of phytoplankton that surround themselves with calcite scales. Each tiny chalk-colored scale is only three one-thousandths of a millimeter in diameter, yet the milky bloom stretches at least 117 km (73 miles) wide and 160 km (100 mi) long.