Managing the White Zone: An Interview with Yale’s Assistant Professor Sparkle on the Impact of Water Management in the Everglades

In this conversation, Assistant Professor Sparkle Malone from the Yale School of the Environment delves into her research on the carbon dynamics of subtropical coastlines and their ability to capture and store carbon. Using the latest technology, such as the Spectrevue leaf Spectrometer, her team studies wetlands in the Everglades to understand how much carbon is absorbed or released. The research aims to improve water management strategies and predict future wetland carbon storage.

One area of focus is the “white zone” in the Everglades. This zone is not a particularly friendly environment for either freshwater or saltwater species of plants and is causing problems with soil formation and keeping pace with sea level rise. How exactly does the white zone impact carbon sequestration and soil formation? How can the information gathered from this research help manage the coastal ecosystems? What are the other benefits of this research? The conversation provides an in-depth look into the research and its applications. It raises many essential questions to understand human activities impact on the natural world.

Our Interview with Sparkle Malone:

Scott: Sparkle, thank you for taking the time to speak with me today. To begin, can you introduce yourself and explain what you do?

Sparkle: Of course. My name is Sparkle Malone, and I am an assistant professor at the Yale School of the Environment. I am currently using the CID Bio-Science SPECTRAVUE leaf spectrometer for a research project funded by the National Science Foundation. The project examines how carbon dynamics change across subtropical coastlines and their ability to capture and store carbon.

The project involves measuring carbon fluxes using the eddy covariance method to understand how much carbon is absorbed or released from different wetlands in the Everglades. This information will enable us to predict future carbon storage better and improve water management strategies to create more resilient systems that can hold onto their carbon. This is particularly important in Florida, where carbon storage is critical for soil formation and keeping the state above water.

One area of particular interest to us is a low productivity zone in the Everglades, known as the “white zone.” This zone, visible in satellite imagery as a white band along the coastline, is influenced by freshwater and saltwater and is not a particularly friendly environment to either freshwater or saltwater species of plants. As a result, it has low productivity and can be problematic for soil formation and keeping pace with sea level rise. We are monitoring this zone to understand how it changes and inform water management strategies to keep it from expanding.

We are using the CI-710s SPECTRAVUE to detect when vegetation is under stress and to measure the degree of that stress. We study mangrove and sawgrass species in variable and experimental conditions where we subject them to stress and measure their spectral signatures. This provides a baseline measurement and helps us identify the bands most useful for detecting stress in coastal environments.

Scott: How does carbon sequestration relate to soil formation?

Sparkle: Two main processes can influence soil formation. The first is through vegetation capturing carbon from the atmosphere, growing biomass, and that biomass eventually breaking down and entering the soil. The second is through large storms stirring up sand from the ocean floor and depositing it on coastal environments, which can rapidly grow the soil. Of these two methods, the most consistent is through vegetation growth.

Scott: So, in simple terms, healthier vegetation means more biomass, more soil formation, and a greater ability for Florida to stay above water?

Sparkle: Yes, that’s correct. But with wetland ecosystems, how the site remains inundated can also influence how long it can hold onto its soil carbon. If a wetland is drained or exposed, the carbon stored in the soil will be released back into the atmosphere, resulting in a loss of carbon rather than a gain. So we also have to consider the water conditions of the environment.

Scott: How will this research ultimately benefit the Everglades and Florida at large?

Sparkle: This research can inform water management strategies to create more resilient coastal ecosystems that can better withstand sea level rise and extreme weather events. Additionally, understanding how carbon is stored in these ecosystems can inform policies and practices to mitigate climate change.

Scott: How can this research be applied to ensure proper biomass production, drainage, and other factors?

Sparkle: The South Florida Water Management District is responsible for allocating water to the Everglades and nearby ecosystems. We can provide information on the optimal water management strategy for carbon sequestration. In addition, we have a comprehensive Everglades restoration plan, a multi-billion dollar plan aiming to redistribute water across these ecosystems.

It is essential to manage these systems for the people living in South Florida. If we don’t properly allocate water, we could face similar issues to what California is currently experiencing, with large wildfires occurring more frequently than they should. We must maintain the hydrological dynamics that are required for different systems to be healthy, and now, we also need to manage for sea level rise. If we don’t keep these systems healthy, they won’t be able to form soil and as the oceans rise, the land won’t and it will make an already bad situation much worse.

Scott: That makes sense. Can you discuss the tools you are using for your study? You previously mentioned the SPECTRAVUE leaf spectrometer, what other instruments are you using?

Sparkle: We measure carbon fluxes at these sites using eddy covariance towers and take leaf-level measurements using the Licor LI-6800. We also make chamber measurements of fluxes of both CO2 and methane from the same wetland ecosystems.

Scott: Can you explain your methodology and processes for collecting and analyzing measurements using the SPECTRAVUE leaf spectrometer?

Sparkle: Sure. We conduct experiments on campus, manipulating the salinity levels in test environments to create intentionally stressful conditions. This helps us understand what certain bands or indices will look like for each plant species under stress. We then take seasonal measurements in the field across different wetland ecosystem types to understand the spectral signature and how it relates to the hydrological conditions the plants are experiencing at the time of measurement. Combining these experiments helps us understand what the data is telling us and what is happening in the field.

Scott: How many measurements are you ultimately collecting?

Sparkle: We measure each research site three or four times per season and we run about 10 transects for each ecosystem type.

Scott: Why did you choose to study sawgrass and mangrove species?

Sparkle: Sawgrass is a dominant species in freshwater sites in the Everglades and the marl prairies, so it gives us a good indication of what would happen to freshwater species. Plus, it’s the most prominent freshwater species there. For example, at one of our sites, the sawgrass can’t handle the salinity conditions, so it’s dying back. Understanding the differences in the spectral signature of sawgrass under extreme stress versus more favorable conditions can be helpful because the low productivity zone changes and moves. We have to understand what those thresholds are, so when we make measurements in the field, we can better understand what that change or difference in the spectral signature means.

Scott: In your experience, is greater salinity directly caused by human activity such as building roads and cutting off fresh water? Or is it more due to storm activity bringing saline water inland?

Sparkle: Actually, it’s a combination of both. Depending on where you are in the landscape, you will see a dominant pattern. If you’re along the coast and experiencing extreme salinity conditions, it’s likely the area is not getting enough fresh water to dilute the salt water that’s coming in. In these areas, we know that part of the reason for the low productivity zone is salt that is introduced by a storm surge across a road. The road causes the salt to get “stuck”. Whenever the water levels at these locations get low because of a lack of freshwater flows, their salinity spikes because of the salt that was trapped when that storm initially introduced it. On the other hand, in other areas, human activities such as building roads and cutting off fresh water flows can also lead to increased salinity levels. Overall, a combination of both natural and human factors can contribute to the salinity levels in these ecosystems.

Scott: How long have you been working on this project and have you seen anything that really surprised you?

Sparkle: We started in 2020 and, yes, the site where we started working has almost completely converted into a mangrove scrub. Right now, the conversion is so strong that we’re questioning whether or not it will stop at being a scrub. It might become a forest, which is unusual. In the Everglades, something is happening where in one part of the landscape, the same species will grow into very tall trees and become a mangrove forest. But, if you go to the east side, something stops the mangrove at the scrub stage and they never become trees. They stay scrubbed and short. But at this specific site location, the mangroves are getting taller than the scrub, which is just to the west of them. Now we’re wondering if we’re going to see a mangrove forest in a location that we would have never predicted. But, we don’t actually have hard facts on why mangroves in this part of the landscape normally stay scrub and don’t become tall forest.

Scott: Do you have any hypotheses as to why this might be happening?

Sparkle: Well, I know that it has something to do with the water. The Everglades are very unique. They call it the upside-down wetland. Usually, a wetland has more nutrients further inland and will be nutrient-poor closer to the ocean. However, the Everglades is a eutrophic system. It has fewer nutrients available in the freshwater sections, while the ocean brings in additional nutrients that can supplement the low-nutrient conditions. So it is believed, but not proven, that the tall mangrove forest has a constant renewal and refresh of salt water and also has enough fresh water flowing in to help offset the negative impacts of salt.

In the short stature scrub areas, it’s believed that there is salt that comes in but it does not get enough fresh water to flush the salt. Being a scrub might be a cost to having to deal with high salinity conditions.

Scott: How much have sea levels risen in the Everglades?

Sparkle: Enough to be a big problem. We have several kilometers of changes and wetlands have migrated to different locations because of salinity. Salinity has been an active issue in the Everglades for some time and, because Florida is actually able to do something about it, there’s a lot of research going into finding out where these changes are occurring and what can be done to slow them down.

Scott: Outside of water management, are there other methods for controlling salinity?

Sparkle: It’s mostly some form of water management.

Scott: How has the SPECTRAVUE leaf spectrometer worked for you in the field?

Sparkle: We usually assign the 710 to our new researchers because it’s so easy to use. It’s really nice that you can edit your readings and see everything while you’re taking measurements. With a lot of equipment, I can’t throw out a measurement while I’m in the field. I have to wait till I get back and connect to a computer, which isn’t helpful because I have to remember which measurement needs to be thrown out. With the 710, you can throw it out in the moment if it was a mistake. In addition, figuring out how to use it, how to reset the time, and things like that is very straightforward. This is one piece of equipment that we don’t have to take the manual into the field with us because anything that goes wrong, we can fix it ourselves.

Scott: Perfect! Thank you so much for spending time talking with me today. It’s been a real pleasure.

Sparkle: You too. Thank you.

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Assistant Professor Sparkle Malone’s research on the carbon dynamics of subtropical coastlines and their ability to capture and store carbon provides valuable insights into the functioning of wetlands in the Everglades. The focus on the “white zone” in the Everglades highlights the importance of proper water management in ensuring the resilience and health of these ecosystems. The research not only informs water management strategies, but it can also inform policies and practices to mitigate climate change. These findings are crucial to understanding the impact of human activities on the natural world and how we can best manage and protect our coastal ecosystems for future generations.