>Across all aquatic ecosystems, from streams and rivers, lakes, reservoirs, and ponds to estuaries, coasts, and the open ocean, dissolved oxygen (DO) concentrations have rapidly and substantially declined in recent decades. Lakes and reservoirs have experienced oxygen losses of 5.5% and 18.6% respectively since 1980. The oceans have experienced oxygen losses of around 2% since 1960 and, although that number is smaller, it represents a more geographically and volumetrically extensive mass.

>For example, the midwaters off of Central California have lost 40% of their oxygen in the last few decades.

As the oxygen carrying capacity of water is very low, an increase in temperature, that increases the overall consumption rates of organisms near the surface, could cause large magnitude changes in DO concentrations.