It is a common misconception that all rivers are freshwater. In actual fact, many rivers can possess an intricate blend of freshwater and saltwater, with the Mississippi River being no exception. Depending on its geographical location, salinity levels within the river can vary greatly and even exceed those of the ocean at so-called “salt cones,” which form in the river’s deeper reaches. This is because the densely populated Mississippi basin is host to a vast arrangement of tributaries, which gradually mix and often bring with them saltwater from the Gulf of Mexico. How can we better understand this curious phenomenon?
According to Jason Burgeson, a researcher at the University of Texas at Tyler, the salinity levels within the Mississippi River are determined by the “amount of water discharged from the Atchafalaya River delta and from other streams that feed into the area.” Significant changes in the river’s salinity result from this process, with freshening occurring during low-flow cycles when the Atchafalaya River is not able to flood enough of its water into the Mississippi.
Recent studies have shown that during high-flow cycles, the salinity of the Mississippi River tends to reach up to 7.2 parts per thousand (ppt). While this might sound low, it is worth noting that a salinity of 5ppt or more sharply increases the morphological complexities of the river, a detail which has been causing concern to authorities in recent years.
The brackish water produced by the Mississippi River, however, can pose potential benefits to those living nearby. It is believed that the river’s unique blend of salty and fresh water provides an ideal habitat for certain types of fish, increasing the abundance and diversity of the natural food resources in the area. It seems then that the mix of fresh and saltwater in the Mississippi River can work harmoniously to produce a unique and vibrant ecosystem flourishing with life.
Vegetation Changes
As salinity levels of the Mississippi River increase, there can also be a change in the vegetation present in the area. With the presence of saltwater, vegetation cannot as easily flourish in these areas due to the elevated levels of salt in the soil profile, leading to the death of grasses and causing weaker root growth of trees.
In the last decade, experts have been working to help counter the effects of increased salinity levels, particularly those that have appeared within Louisiana’s Atchafalaya Delta. By introducing flood water barriers and floodplain restoration efforts, conservationists have been able to mitigate the damage that has been caused and to help ensure that the vital ecosystems of the Delta region can still remain healthy for generations to come.
In addition to this, the US Geological Survey has been examining the Mississippi River Delta in order to learn more about the relationship between the river’s water management and its long-term ecological health. Through this they hope to gain a greater understanding of the delta’s ecology and how the ever-shifting mix of saltwater and freshwater affects the area’s quickly-changing environmental and biological processes.
Impact on Aquaculture
The Mississippi river delta and the brackish waters that it produces are of great value to the nearby fishing and aquaculture industries. Brackish water often provides ideal conditions for shrimping, oystering and other types of fishing activity, yet with climate change, salinity levels are rapidly increasing and causing problems for nearby fisheries.
In 1986, for example, Mississippi saw a significant reduction in oyster production due to the continued increase of salinity in the Delta area. As the salinity becomes too high for oyster larvae to survive, the industry was forced to rethink its approach and consider other sources of fresh and brackish water. This is a phenomenon that is being replicated all over the world, with salty water gradually infiltrating both the ecology and the economy of those who live and work in the area.
In order to protect the livelihoods of those in the fishing and aquaculture industries it is therefore essential that the complex and fast growing issue of accelerating salinity levels is addressed. Without rapid intervention, the Mississippi Delta and its many tributaries may not be able to survive the ever-growing pressure of such high saline levels.
Researchers Take Action
To help prevent this, research into the Mississippi River’s salinity levels is taking place across the world. This research aims to provide a more thorough understanding of the Delta’s intricate ecology and to identify any areas that need more attention. According to Mark Shafer, an ecosystem ecologist from the University of Chicago, “Our research is examining the distribution and abundance of these critical resources in order to inform management and protection efforts of aquatic ecosystems.”
By gathering more data on the various causes and effects of accelerated salinity levels, it is hoped that initiatives can be put in place to help reduce its damaging impacts. For example, initiatives could help to improve coastal resiliency in the area, restore habitats, and prevent the spread of ever-increasing saltwater levels.
The Mississippi River has been providing a vital resource to those living in the area for hundreds of years, yet many still do not truly understand the complex dynamics of its freshwater and saltwater blend. It is up to us, then, to continue researching and understanding the intricacies of the Delta region and its mix of aquatic environments.
Unique Benefits of Mixing
Overall, the unique blend of freshwater and saltwater and the profound impact it can have on the environment and livelihoods of those living in the area should not be overlooked. As well as the potential negative effects that elevated salinity levels can bring, it is also important to recognise the unique benefits that arise from this phenomenon.
Not only can the brackish water of the Mississippi River offer an ideal habitat for certain species of fish, but it can also provide a unique, beneficial ecosystem to those who live nearby. Through understanding the mix of fresh and saltwater within the Mississippi and its many tributaries, authorities can work to create a more resilient and sustainable environment that can exist in harmony with the river.
Conclusion of Human Activity
At the same time, humans need to recognise and be aware of the potential risks faced by this unprecedented mix of freshwater and saltwater. The Mississippi River is one of the most heavily populated river basins in the world and the impacts of human activity can have a detrimental effect on its delicate, ever-changing balance of aquatic environments.
Ultimately, this is a complex and ever-shifting phenomenon, yet by investing in research, understanding the effects of climate change, and protecting the Delta’s vital ecosystems, we can work to ensure the long-term health of the Mississippi and its many priceless resources.
