The importance of our rivers in Middle Tennessee

By Ryan Jackwood on 22nd Jan 2020

Ryan Jackwood, Ph.D., Science Director for the Harpeth Conservancy and Meriweather Bean and Americorps member of the Harpeth Conservancy, looks at how natural resources are often overlooked and undervalued aspects of a geographic region. They argue if we don’t understand the importance and significance of our natural resources, then we may not make decisions that will lead to their protection.

Anyone that has kayaked, canoed, fished, or hiked in Middle Tennessee has witnessed the beauty of the rivers and streams in our region. Of course, it is not just beautiful, in fact, the southeastern U.S. has the third-highest aquatic biodiversity in the world – only behind the Amazon and Mekong Jungles. In other words, our rivers contain more species of fish, turtles, crayfish, and mussels than almost any other place on the planet. Approximately one-third of the world’s crayfish species1, 40% of the world’s freshwater mussel species2, and 79% of North America’s freshwater fish3 are found in the Southeast U.S. waterways. But why is having lots of different animal or plant species (a.k.a. high biodiversity) important?

In general, biodiverse ecosystems are very stable and resilient. A stable ecosystem will be able to more effectively provide our communities with ecosystem services, which is a fancy term for all of the services that our natural environments provide such as, flood mitigation, carbon sequestration (helps combat global climate change), pollution breakdown, groundwater recharge, oxygen production, etc. The air that we breathe, water that we drink, and many other aspects of our lives are improved by ecosystem services. Another important component of biodiverse ecosystems is that they provide biological resources such as food, medicine, wood products, ornamental plants, etc.

We are continuously making new medical discoveries from various plants and animals that have never been studied before. Scientists and engineers are even modelling everyday products that we buy after biological entities and processes found in nature – this process is called biomimicry. For example, the aerodynamic beak of a Kingfisher inspired Japan’s 500 Series Shinkansen bullet train. However, these critical organisms may go extinct before medical and scientific discoveries can be made if we do not protect our environments.

Threats to our rivers
When we talk about pollution, it is important to remember that virtually everything that is deposited on land will ultimately end up in our rivers and streams and eventually our oceans. For example, the plastic bag that falls out of your car will eventually wash into the closest stream, the fertilizer you put on your lawn will runoff into a river after a rain event, the oil that drips out of your car will flow through storm drains and eventually end up in the nearest waterway, and the list goes on. Three pollutants of concern in middle Tennessee are the excessive amounts of nutrients (specifically phosphorus and nitrogen), elevated levels of bacteria, and more recently the high concentrations of microplastics.

When we talk about pollution, it is important to remember that virtually everything that is deposited on land will ultimately end up in our rivers and streams and eventually our oceans.

Nutrients drive the excessive growth of algae in our waterways. These unnaturally large algal “blooms” (rapid growth of algae) can choke out local fish by removing oxygen from the water and limit plant growth by shading sunlight. Under certain circumstances, these algal blooms can also produce a toxin that threaten human and animal health. Algal blooms can have substantial impacts to water quality and our economy. The Dead Zone in the Gulf of Mexico is caused by a massive algal bloom (can be seen from space!) and cost the seafood and tourism industry roughly $82 million in 2017.

Bacteria also threaten our waterways and pose health risks to swimmers. Waterborne pathogens (bacteria capable of causing disease in humans) have been known to cause Salmonellosis, Legionnaires’ disease, Dysentery, and other stomach, respiratory, skin, and brain effects4. Bacteria sources may include sewage, urban runoff, agricultural runoff, or industrial waste. Across the U.S., 38% of all beaches must issue at least one beach advisory due to high levels of disease-causing bacteria. When these bacteria flow into our beaches and rivers they can pose serious health risks.

Microplastics are tiny pieces of plastic that break apart from larger plastic products such as bags or clothing. This pollutant only recently has been identified and its long-term effects are largely unknown. Microplastics are consumed by fish and other aquatic wildlife, which may result in health effects and degradation of water quality. The Tennessee River was recently found to have 18,000 microplastic particles per cubic meter of water, which is 90 times higher than the Rhine River in Europe. According to the World Wildlife Fund, humans are consuming about five grams of microplastics a week, which is equivalent to the weight of a credit card.

Pollution of our waterways can be scary, overwhelming and depressing. Organizations such as the Harpeth Conservancy located just outside of Nashville, TN are devoted to science-based conservation dedicated to clean water and healthy ecosystems for rivers in Tennessee.

Ways that Harpeth Conservancy is fighting for clean water
With the increase of these various forms of pollutants, it’s important to remember what we can do to combat them. One of Harpeth Conservancy’s priorities is to share tools and resources so to encourage individuals to take charge of the on-the-ground work that is vital to protecting the rivers that affect our daily lives. Water monitoring requires a network of efforts to be most effective and Harpeth Conservancy works with state and local organizations to implement science-based water quality monitoring programs. These programs range from intensive scientific studies to citizen science opportunities to community members in the form of our Water Reporter App.

The Water Reporter App has proven to be an innovative tool that allows individuals to observe and report the condition of the water systems they interact with daily. Through the app, members of Harpeth Conservancy’s group can send in photos of problematic areas on local rivers, etc. and, in turn, Harpeth Conservancy can more quickly address the issues. This program has progressed Harpeth Conservancy’s outreach tremendously by giving community members an opportunity to be involved in the work to keep the rivers healthy and clean.

Nutrients can enter our waterways through a variety of sources, one of which is through our own lawn fertilizers. Considering how unified efforts can be most impactful, monitoring what we put on our lawns can make a huge difference. Most lawns in our area already have more than enough phosphorus to support grass growth, so overfertilization is a common problem. Ultimately, reducing fertilizer use, or only using fertilizer with zero phosphorous, will have positive impacts on our river.

In the spirit of uniting efforts towards the goal of ensuring clean water and healthy streams in Nashville, Harpeth Conservancy was a founding member of The Nashville Waterways Consortium (NWC), which also consists of the Tennessee Environmental Council, Cumberland River Compact, The Nature Conservancy and Richland Creek Watershed Alliance. NWC’s mission emphasizes the point that, through a combined effort of small, measurable steps, everyone can do their part to make a difference.

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1. Richman, N. I. et al. Multiple drivers of decline in the global status of freshwater crayfish (Decapoda: Astacidea). Philosophical Transactions of the Royal Society B: Biological Sciences 370, 20140060 (2015).

2. Graf, D. L. & Cummings, K. S. Review of the systematics and global diversity of freshwater mussel species (Bivalvia: Unionoida). Journal of Molluscan Studies 73, 291–314 (2007).

3. Page, L. M. & Burr, B. M. Peterson field guide to freshwater fishes of North America north of Mexico. (Houghton Mifflin Harcourt, 2011).

4. Rodrigues, C. & Cunha, M. Â. Assessment of the microbiological quality of recreational waters: indicators and methods. Euro-Mediterranean Journal for Environmental Integration 2, 25 (2017).

5. Winjnand de Wit & Nathan Bigaud. No Plastic in Nature: Assessing Plastic Ingestion from Nature to People. (2019).

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