Low dissolved oxygen (DO) levels and hypoxia pose a significant risk to fish and bottom-dwelling species. Every year during the late summer, several of Puget Sound’s inlets become hypoxic (DO < 2 mg/L), which have previously resulted in mass fish kills. Many other estuarine and coastal systems around the globe attribute low DO to anthropogenic nutrient pollution, which acts as a fertilizer for algal blooms that eventually use up oxygen as they are broken down at depth. However, Puget Sound is distinct from other systems because of its deep basins, its many branching channels, and its large nutrient input from natural oceanic exchange. Thus, much more investigation is needed to understand oxygen dynamics in Puget Sound.
Our goals are to:
- Understand the long-term change in oxygen in Puget Sound, and the mechanisms driving this change
- Identify the main drivers of hypoxia that explain the spatial variability of DO across Puget Sound
- Characterize the impact of anthropogenic nutrient pollution to Puget Sound, and quantify the extent to which anthropogenic loads influence DO relative to other natural processes
- Explain the physical mechanisms that influence DO in hypoxic inlets
We are answering these questions using both historical observational records as well as numerical models.
The figure below shows results from the LiveOcean model. On average, between 2014-2019, the model predicts hypoxia in six inlets across Puget Sound.
