Eutrophication of water bodies occurs when high levels of nutrients fuel high rates of primary production and accumulation of algal biomass, either as macroalgae or phytoplankton. Some ecosystems are naturally eutrophic, but in others human activity causes ecosystems to undergo transformations into a eutrophic state. This is termed cultural eutrophication, and is the primary concern in evaluating the status of marine waters of Puget Sound.
Source: Puget Sound Science Review
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.
Nitrogen is a chemical element that is essential for the growth of all life on earth. But too much nitrogen can lead to low dissolved oxygen and other problems such as toxic algal blooms that can harm or kill aquatic organisms.
The search goes on for a set of definitions and thresholds to represent low-oxygen concentrations that threaten various aquatic creatures. Over the years, ecologists have relocated, reshaped and revised the word “hypoxia” to describe these conditions. In part four of our series "Oxygen for life" we look at how scientists determine whether oxygen levels are low enough to be considered harmful to sea life.
