Río Negro, Amazon basin, Brazil

© Timothy Allen/Getty Image

Mirror, mirror, on the water. Río Negro, Amazon basin, Brazil

The Río Negro, originating in Colombia, is one of dozens of tributaries that flow into the massive Amazon River. Its name, which means black river, comes from its dark appearance when viewed from a distance. As a result, the water can reflect the colourful hues of the sky overhead, such as the vibrant blue and partial rainbow seen here. The colour of the river comes from the high concentration of humic acid, thanks to decomposing organic matter that seeps from nearby swamps. As one of the largest northern-bank tributaries of the Amazon River, the Río Negro plays a crucial role in the complex Amazon basin ecosystem. The river is home to many plants and animals, including the critically endangered Brazilian barefaced tamarin, the giant river otter and nearly 700 species of fish.