Johnson received her B.S. in 1993 in marine science from Texas A&M University-Galveston, where she became the very first African American student body president. She received her Ph.D. in oceanography from Texas A&M University in 1999. Her areas of research include environmental aquatic radio geochemistry, 2) professional development of students and early-career scientists, and 3) STEM diversity-focused initiatives. Her radio geochemistry research activities utilize various biogeochemical indicators to interpret past events impacting marine, estuarine, and freshwater environments.