[3][4] Paerl attended Aragon High School in California and received an AA in biological sciences from the College of San Mateo in 1967.

[2][6] Paerl's collaborative research addresses microbially-mediated nutrient cycling and primary production dynamics, including environmental controls and management of harmful algal blooms and their toxins.

[20][21] He is also well known in the scientific community for having written foundational synthesis and review pieces on harmful algal blooms.

[22][23][24] Since 2018 Paerl has been one of the lead investigators in the Great Lakes Center for Fresh Waters and Human Health.

The center is under the direction of Professor George Bullerjahn, an American microbiologist and collaborator with Paerl on several studies.