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On the ground floor of Williamson Hall, a cold room holds the layered remnants of Florida’s past. Behind a refrigerator door, precisely labeled tubes of lake sediment are stacked and ready for study. Researchers with the Land Use and Environmental Change Institute (LUECI) analyze these samples to trace the impacts of storms, droughts and development, revealing how both nature and people have shaped the state’s waterways over time.

Established in 2000 as a collaboration between the departments of Geological Sciences, Geography, Anthropology and the Center for Latin American Studies, LUECI provides a support network and resources to researchers who investigate how human activities and natural phenomena shape our environments.

LUECI’s research spans multiple disciplines but is perhaps best recognized for the study of lake sediment cores. To collect these samples, researchers use a specialized coring device with a transparent barrel that they insert into the lakebed. This enables them to extract an intact column of sediment, which they section and store in labeled containers for analysis. Examining these layers helps scientists reconstruct how a lake has changed over time. For more than three decades, Professor of Geological Sciences and LUECI Director Mark Brenner and Associate in Biogeochemistry William Kenney have led such investigations, retrieving sediment cores from lakes across Florida, which is home to over 8,000 bodies of water.

Because of the importance of tourism and recreation in Florida, the health of the state’s freshwater resources is of utmost importance. Florida’s waters are shaped by human impact, and core sampling and analysis tell us a lot about a waterbody’s health and provide a history of changes in the ecosystem over time.

For example, a study conducted on lakes near Tampa that receive pumped groundwater revealed high concentrations of radium in recent sediments. Alarming levels of the radionuclide were also found in the tissues of local mussels, posing a cancer risk if consumed on a regular basis, but LUECI’s findings led health experts to warn against allowing the lakes to drain. “They determined that if the groundwater pumps were turned off and sediments at the bottom of the lake were exposed to the air, inhalation of wind-blown sediment dust would also constitute a serious health risk,” Brenner explained.

Brenner and Kenney’s research can also provide valuable insights into a lake’s past productivity. Productivity is a measure of the rate at which biomass, or the total amount of organic matter, is produced in a lake and reflects how nourished it is with essential nutrients like phosphorus and nitrogen. Well-nourished, or eutrophic, lakes are more productive and are often characterized by green water with dense algae and cyanobacteria blooms. They also typically support large populations of fish and other aquatic organisms. Poorly nourished, or oligotrophic lakes, are less productive and tend to have clear water. They are often preferred for recreational activities like swimming and water skiing.

A lake’s nutrient concentrations and productivity are one way to describe its condition. Florida waterbodies span the full range, from oligotrophic to eutrophic systems. Some have become more nutrient-rich recently due to fertilizer runoff or leaking septic systems, whereas some are naturally very productive and green in appearance because they sit atop phosphate-rich geologic deposits. Such eutrophic systems are not necessarily unhealthy, as they serve as excellent wildlife habitats, can be good fishing spots and serve as carbon sinks by removing carbon dioxide from the atmosphere and accumulating organic matter in their sediments. Determining how a lake’s productivity has changed over time can help local communities make wiser decisions in managing their bodies of water.

“We sometimes get asked by management agencies to help them figure out if lake restoration is feasible,” Brenner said. “Our analysis can reveal what the baseline, pre-disturbance condition of the lake was. With that information in hand, the agency can evaluate whether it might be possible to restore the lake to a more natural state that approximates the pre-existing condition.”

Recently, Brenner and Kenney conducted a small study on an 84-cm-long sediment core from Lake Alice. The core contained abundant algae and cyanobacteria in the upper sediment sections, but organic matter content declined in deeper sediment layers. Concentrations of potentially dangerous elements such as cadmium, lead and arsenic were relatively low; however, mercury content was sufficiently high to raise concerns, especially if dredging of the lake were ever contemplated.

“Our studies on other lakes near Gainesville, for example, Lake Wauburg and Newnans Lake, showed that both waterbodies have long histories of having been very productive and will likely remain that way,” Brenner said.

Through its interdisciplinary research, LUECI provides vital insights into how Florida’s environment responds to human and natural forces. Each sediment core contributes to a better understanding of how the state’s aquatic ecosystems function and how best to sustain them.