Why Are the Eastern Margins of Ocean Basins Full of Fish?

At the eastern side of the Atlantic and Pacific Oceans, Earth’s rotation combined with winds blowing toward the equator push water away from the coasts. Deep ocean water rises to replace what was pushed away, in a process called upwelling. The colder, deep water that rises to the surface is rich in nutrients and oxygen, and it supports healthy ecosystems. That is, upwelling in coastal oceans equals lots of fish! There are four coastlines where upwelling is crucial, known as eastern boundary upwelling systems (EBUS for short). These regions cover <3% of the world’s ocean area, but they are responsible for 20% of the global fish catch. EBUS change constantly along with Earth’s changing climate. Given their extraordinary biological productivity, it is very important to understand how global warming may impact EBUS. In this article, we describe what EBUS are and discuss how climate change may affect them and the fish populations in their ecosystems.