California has wildfire season. The southeastern states have a rainy season. Now, Oregon has a hypoxia season … and it’s killing fish in their lakes.
What is hypoxia in lakes, and what causes it?
Lake hypoxia occurs when the dissolved oxygen content in the water is too low to sustain marine life. The microorganism phytoplankton is at the base of the mechanism creating regions of hypoxic water. The number of nutrients in the water and water temperature are the main factors affecting the growth of these microorganisms.
They will continue to grow until either of these factors limits them. Increasing water temperature or the number of nutrients in the water can trigger massive phytoplankton blooms.
Though the growing phytoplankton population causes other problems in the marine microenvironment, it isn’t the root cause of lake hypoxia. The trouble begins when once these massive populations of the microorganisms die off. They sink to the bottom of the body of water, where bacteria decompose them.
This step of the food chain underlays the depletion of oxygen. Bacteria use up much of the oxygen in this deepest part of the water when digesting the dead phytoplankton. The more phytoplankton there are to decompose, the more oxygen the bacteria will use. Increased use of oxygen by the bacteria does not significantly change the natural rate at which dissolved oxygen is added to the body of water. Thus, oxygen concentration at this depth decreases, and other organisms in this habitat can die.
Regions where hypoxia is prevalent
Hypoxia is not a new environmental condition. Runoff from farms contain fertilizers and high concentrations of nutrients. Wastewater from cities piped into rivers can combine with this. And when drained into lakes or oceans, it accumulates to create a great environment for microorganism growth. The Gulf of Mexico has low oxygen levels, especially where the Mississippi River drains into it, due to these factors.
In Oregon, however, the main cause of hypoxic water conditions is an increase in the water temperature. This is due to increased overall temperatures, ultimately attributable to climate change. Summers are especially bad times for phytoplankton growth, and because of this, summers have become Oregon’s “hypoxia season”.
With decreased water oxygen content, many of the native fish species in Oregon are struggling. This is an even larger problem for marine life that is place-bound. In other words, in such scenarios, marine life cannot move to another place fast enough to get more oxygen.
A temporary solution to help marine life?
Professor Mason Terry’s research group at the Oregon Institute of Technology is working to help increase oxygen concentration in Oregon rivers where endangered species live. Earlier this month, the group finished designs for and deployed a solar-powered aeration system in the state’s Upper Klamath Lake.
The system is on a raft and obtains power from four 310-watt solar panels. The system is also equipped with a battery that can run the device for up to 32 hours. Hence, it can add oxygen to the lake even when the sun isn’t shining.
Terry’s aeration system is essentially a much larger version of the smaller air pumps used in fish tanks. Two compressors take power from the solar panels and push air from the environment down into the lake. A hose helps ensure that the air is deposited at the bottom of the lake, where it is needed the most.
While this will only help small portions of the lake, the raft has been placed at a spot the endangered species can gather at.
While it is not possible to know the effectiveness of this system until the next fish counts, it is a step forward in helping sustain the diversity of animal life.
Scalability of this solution
As climate change continues, rising air temperatures will lead to increased water surface temperatures and correspondingly lower levels of dissolved oxygen. It is possible that hypoxia in bodies of water could become an increasingly big problem in the future.
If this project from the Oregon Institute of Technology is successful, it will be a victory because it will show that humans can aid in helping marine life suffering from not having enough oxygen in the water.
However, we will also need to consider how to make this a more scalable device. This solution is still low-impact, but with increased research, there is a possibility of maintaining marine diversity.
Maddie is a Writer at The Rising and a Bioengineering, Materials Science and Engineering, and Behavioral Neuroscience student at the University of Illinois at Urbana-Champaign.