Eutrophication

Scientists at the Washington Department of Ecology along with many other researchers have spent years studying and debating the problem of low oxygen in Puget Sound. Now, many new developments — technical, scientific and legal — are reaching a critical stage and setting up a framework to make some major decisions. This four-part series was originally published in the Puget Sound Institute blog and looks back on how we have reached our present condition, including a consideration of possible solutions. Subsequent parts of the series are available through a link at the conclusion of this article.

About 83% of the water in Puget Sound comes from the ocean. That brings with it all kinds of benefits, including an ocean-size amount of life-giving nutrients that feed the creatures that live here. But it has one potential drawback. That ocean water is notoriously low in oxygen. Why is that and what does it mean for the future of Puget Sound?

Low dissolved oxygen levels put aquatic life in Puget Sound at risk – but not everywhere. A combination of careful monitoring efforts and powerful computer models are now enabling scientists to identify which areas of our regional waters are most prone to low oxygen levels, when, and why. This article is part of a series of reports funded by King County about the quest to define healthy oxygen levels in Puget Sound.

Oxygen is indisputably essential to aquatic life, but conflicts are brewing over water quality standards mandated in state regulations. This article is part of a series of reports funded by King County about the quest to define healthy oxygen levels in Puget Sound. By some estimates, those definitions could affect billions of dollars in state and local spending. [Editor's note: King County is currently in litigation with the Washington State Department of Ecology over the issue of dissolved oxygen water quality standards.]

In June we observed a widespread Noctiluca bloom in Central Puget Sound, evident by bright orange streaks in the water. Noctiluca blooms in Puget Sound have lasted much longer and occurred on a much larger scale than in previous years.

Chronic stress from lack of oxygen can make aquatic organisms more vulnerable to disease, pollution, or predation. Low oxygen can also result in reduced habitat for some species. Aquatic species may escape, acclimate, adapt, or die with exposure.