Underwater, oxygen is not as evenly distributed like it is here on land, and in some areas of the ocean or an estuary the oxygen level can fluctuate fairly rapidly. How does this happen? Here is a general overview of what causes the amount of oxygen to change before we get into the specifics of coastal and estuarine hypoxia.

What is unique to these water communities is that the processes that add oxygen are found primarily at the surface, and the processes that remove oxygen are deeper and near the bottom. Without wind and currents to mix the surface and deep water together, the ocean and estuaries naturally have less oxygen in the deep waters and more oxygen in the surface waters.

Explore what is happening to the oxygen in coastal Oregon and Washington waters:

• Coastal hypoxia case study: Oregon
• Estuarine hypoxia case study: Hood Canal, Washington