Alexis Johnson

 Alexis Johnson
Mentor: Dr. David Kaplan
College of Engineering
"I enjoy looking at the big picture of things and hope that research will allow me to contribute to our understanding of how small anthropogenic changes translate to complex interactions on the full ecosystem scale. I am especially looking forward to working in some of Florida’s beautiful natural areas and addressing environmental issues that are prevalent locally."


Environmental Engineering



Research Interests

  • Water Resources Management
  • Ecosystem Education
  • Environmental Education

Academic Awards

  • UF University Scholars Program
  • Gator Nation Scholarship
  • CALS Scholarship


  • Society of Environmental Engineers
  • Student Honors Organization


  • UF English Language Institute
  • Florida Trail Association

Hobbies and Interests

  • Tennis
  • Skiing
  • Being Outdoors
  • Drinking Coffee

Research Description

The Effect of Variable Hyporheic Exchange on Nitrate Removal in Florida Springs: A Smart Tracer Approach
One of the most pressing issues facing the waterways of Florida is anthropogenic nitrate (NO3-) pollution. Due to more than 50 years of rapid population growth and increased agricultural activity, NO3- concentrations in groundwater, springs, and other bodies of water have increased dramatically. The presence of excess NO3- and other nutrients can cause eutrophication and destructive algal blooms that reduce biodiversity and make water unfit for human use both in terms of aesthetics and potability. Nitrate removal through denitrification is thought to be positively correlated with hyporheic exchange; however this phenomenon is not fully understood as direct measurements of water-sediment interaction are difficult. The goal of this research is to identify the connection between flow velocity and nitrate removal rate using a biologically reactive tracer to measure hyporheic exchange in a tidally influenced springshed. Tracer studies will be performed under varying velocity gradients and the breakthrough curves of the reactive tracer and a nonreactive tracer will be used to model the streamflow. This data will then be compared to measured nitrate levels to determine the contributions of residence time and hyporheic exchange to nitrate removal. Identifying the driving hydraulic force in denitrification could aid in ecosystem restoration and water treatment decisions as well as predictions of how aquatic ecosystems would respond to changing hydrologic conditions including flooding, drought, and groundwater recharge and depletion.