David Lewis – Associate Professor (CV)

I am interested in understanding controls on the flux and storage of nutrients and energy in ecosystems, human-environment interactions, and their implications for ecosystem structure and function. My research presently focuses on freshwater wetlands and intertidal habitats in mixed-use landscapes. I also study soil biogeochemistry in managed landscapes ranging from urban yards to farms and forests. I collaborate with natural and social scientists and environmental managers to better understand the dynamics of coupled natural-human socioecosystems. My teaching program includes graduate and undergraduate courses on various areas of ecology and environmental science.

Bert Anderson – Ph.D.. candidate
The distribution and biogeochemistry of algal mats of the coastal salt pans of west central Florida

My research focuses on describing the spatial arrangements of coastal salt pans within their landscape. Scattered throughout these rare and understudied unvegetated patches are mats of algae and microbes. Where these microbial mats occur and the nature of their biogeochemical consequences are also central to my research.

Jessica Balerna – M.S. student
Just getting started! Thesis topic under development, in area of human-environment interactions around issues of water redistribution and wetland condition

Dawei Tang – M.S. student
Decades-long land use changes and their effects on the biogeochemical characteristics of urban streams

I hope to gain a better understanding of how land cover/ land use changes could affect urban stream biogeochemistry. Long-term (>30 years) stream biogeochemistry data gathered by Environmental Protection Commission of Hillsborough County are paired with the corresponding land use GIS map to illustrate the effects of land use changes on stream nutrient parameters throughout decades. In addition, I hope to investigate the effects of different land use on urban stream nutrient compositions with finer details (e.g. chemical constituents of nitrogen and phosphorus, rather than total nitrogen and phosphorus), using monthly gathered water and sediment samples at two local urban streams.

Andres Santini Laabes – Undergraduate & Post-Bacc researcher
Andres’ research examines longitudinal and temporal variation in a nutrient and organic carbon concentrations in a stream as it moves through a variety of urban and riparian forest land use types and past potential point sources of pollution.

Annie Majette – Undergraduate Honors student
Annie’s undergraduate honors research examines the possible adjustment of soil microbial function to long-term exposure to elevated temperatures. Working in intertidal sediments, Annie is interested in thermal effects on nutrient storage and mineralization along temperature gradients.


Sandra Voors – M.S. 2018 (also a lab B.S. Honor’s thesis alum!! See her Honor’s poster)
Masters thesis: Linking Ecosystem Function and Phenotypic Variation in Spartina Alterniflora Salt Marshes

My thesis research investigates the relationship between plant functional traits and nutrient cycling dynamics in tidal salt marshes. I am interested in exploring the feedbacks that drive the cycling and storage of carbon and nitrogen in marsh soils, and the corresponding phenotypic variation in smooth cordgrass, Spartina alterniflora.

Kristen and something other than a red mangrove seedling

Kristen Langanke – M.S. 2017
Master’s thesis: “Response to nitrogen and salinity conditions in Rhizophora mangle seedlings varies by site of origin”

Using a common garden experiment, Kristen investigated differences among sites (plausibly, populations) and maternal lineages in the growth responses and survivorship of red mangrove (R. mangle) seedlings to manipulations of salinity and nutrient (specifically, nitrogen) supply. The research sheds light the scope for plasticity and the importance of within-species diversity in coping with expected coastal environmental change such as sea level rise and eutrophication. Kristen was primarily advised by Dr. Christina Richards, while also being a member of the Lewis Lab.

Kirsti Martinez – B.S. 2014, Honors, Goldwater Scholar
Undergraduate honors thesis: “Lateral and vertical components of leaf litter inputs to mesic flatwood and floodplain swamp ecosystems on a subtropical toposequence”

Soil properties are strongly shaped by plants, as plants are the principal source of organic matter to soil, and shape the physical and chemical environment through shading, root growth, and a host of other mechanisms. Yet, soils do not always “match” the plants they are found beneath. Kirsti explored a possible mechanism for this mismatch to investigating the magnitude and lateral redistribution of plant leaf litter across an quintessential Florida landscape.

Viviana Penuela – M.S. 2014
Master’s thesis: “Influences of yard management intensity on urban soil biogeochemistry”

Viviana investigated how lawn management practices give rise to soil biogeochemical differences among lawns that are located on the same soil types. She was particularly interested in examining the practice of irrigating lawns with reclaimed water, and investigating whether the chemistry of reclaimed water rendered it a stressor or a nutrient subsidy for soil microbial communities. Viviana is now an Environmental Specialist for the FL Dept of Environmental Protection

Sharon Feit – M.S. 2012
Masters thesis: “Variability in hydrology and ecosystem properties and their role in regulating soil organic matter stability in wetlands of west-central Florida.”

Sharon now works for Barr, an engineering and environmental consulting firm in Minnesota, where she works on endangered species, habitat assessments, wetland/waterbody surveys, and regulatory permitting.

Kristine JimenezKristine Jimenez
Lab Manager and Research Technician, 2011-13
Kristine spearheaded a project using the rare stable isotope  of nitrogen (15N) to investigate rapid storage of N into stable organic forms in coastal wetland soils, focusing on salt marsh and mangrove forest habitats. She also managed our lab, from coordinating schedules and budgets to maintaining highly specialized instrumentation. Finally, while here at USF, she participated in outreach by using soils to explore sustainability themes with Native American students at the College of Menominee Nation, in Wisconsin. After departing from the lab, Kristine was first a technician and manager in the Univ. of Cincinnati Stable Isotope Biogeochemistry facility, and then moved on to a technician/scientist position at Cincinnati Children’s Hospital.

Jewel Brown – B.S. 2012, Honors
Undergraduate honors thesis: Interactive effects of simulated sea-level rise and warming on microbial carbon and nitrogen cycling in mangrove and salt marsh soils. Selected for presentation at the USF Undergraduate Research and Arts Colloquium. Jewel went on from the lab to medical school at the Univ. of South Florida, from which she graduated in 2017.