[4][5] She is known for her work on applying molecular tools to the study of phytoplankton, and she was the first to develop primers for polymerase chain reaction that targeted eukaryotic organisms,[6] She applied this tool to taxonomic studies of multiple species of phytoplankton cultured in the laboratory.
[7][8][9] Her work extended into the ocean where she examined the diversity of phytoplankton in different regions including the Pacific Ocean,[10] Antarctica,[11] and the time series from the German research station at Heligoland.
[12] Through the application of molecular tools, Medlin was able to define species differences in coccolithophores[13] and examine the evolution of diatoms.
[17][18][19] Medlin was elected foreign member of Norwegian Academy of Science and Letters in 1998.
[24] Medlin received the Yasumoto Lifetime Achievement Award from the International Society for the Study of Harmful Algae in 2021.