Temperature and Dissolved Oxygen in Water Quality

Temperature:

We often think of temperature as how hot or cold something is, and that’s exactly how scientists think about it. Various water temperatures support different ecosystems. Temperature affects an animal’s metabolism, rate of reproduction, and survival rate. Because different animals thrive at different temperatures, dramatically fluctuating temperatures jeopardize the survival of indigenous animals.

There are many different factors affecting the temperature of Crystal River. For example, Three Sisters Springs feeds the river with a consistent water temperature of 68-75 degrees Fahrenheit, while the Gulf of Mexico either brings hot or cold water depending on the season. While a significant change in temperature does not necessarily indicate degrading water quality, a deviation from the norm of recorded temperatures can signal the presence of a contaminant. More contamination means lower water quality.

Measuring temperature helps quantify the amount of pollution caused by greenhouse gas emissions. For example, take the Crystal River nuclear power plant. Nuclear plants use water to cool their reactors. This makes the nearby water warmer. Consequently a few years ago, hundreds of manatees found refugee around nearby nuclear plants because of the warm water. (See link for more information: https://www.winknews.com/2020/01/22/manatees-gather-near-the-power-plant-in-fort-myers-to-keep-warm/)

Temperature is just one of the many factors scientists study when determining water quality. However, studying it alone is not enough to determine a convincing water quality measurement. Even a body of water with expected temperatures can have pollution.

Dissolved Oxygen:

Interestingly, temperature directly relates to dissolved oxygen (DO), our next topic. The warmer the water, the less DO the water can hold, and the colder the water, the more DO it retains. Aquatic animals and plants require oxygen in the water to survive. If dissolved oxygen levels decrease from something like an algae bloom, these surface blooms will suffocate underwater life.

Algae blooms happen when there is an excessive amount of nutrients in the water generated from phosphorus and nitrogen. (These elements are often found in fertilizers.) Therefore, cyanobacteria and algae can grow and reproduce at an incredibly fast rate. (We call this process biomagnification.) In order to grow, these organisms require oxygen, and they use up all of the DO from the water, making it impossible for any other life to survive.

Additionally, a severe enough algae bloom can lead to a phenomena called red tide. Have you heard of a beach being closed due to red tide? Have you ever smelled a beach with red tide? The smell often comes from the dead fish that didn’t have enough oxygen to survive in the bloom. Sometimes, too much DO can be harmful. Thus, the ideal amount of dissolved oxygen for marine life ranges from 6.5-8 mg/L (80-120% DO concentration). See the chart above for a visual.

Save Crystal River’s efforts to plant eelgrass has been a major component in maintaining a healthy DO concentration in the water. Eelgrass is known for producing large amounts of oxygen. As a result, you can see oxygen released from the eelgrass blades and bubbling to the surface. In other words, since Save Crystal River is planting eelgrass, it raises the DO concentration and allows for a healthier ecosystem.

I’ll see you on the water,

Walker A. Willis