Mark Julian Wetzel (1950-2025)
With deep sorrow, we announce the passing of Mark Julian Wetzel, a beloved member of the Society for Freshwater Science and a research scientist at the Illinois Natural History Survey, who departed this world on June 6, 2025, in Urbana, Illinois. He was 75.
Mark devoted his life to the study and stewardship of freshwater ecosystems and was a passionate NABS/SFS member. Trained in zoology at Eastern Illinois University and the University of Illinois, he became known for his unparalleled expertise in aquatic annelids—especially freshwater oligochaetes, earthworms, leeches, branchiobdellidans, and related groups. His seminal 1992 review of Illinois aquatic annelids and his authoritative classification of freshwater oligochaetes of North America continue to serve as cornerstones for taxonomic work. Through decades of collaboration with the International Taxonomic Information System and landmark publications in Megadrilogica and Zoosymposia, Mark’s scientific reach was global. His wide network of friends across the globe is a testament both to his warm and collegial personality as well as his deep expertise of Annelid worms. Anyone who had the experience of going in the field with Mark would appreciate his broad knowledge of aquatic invertebrates, as well as his passion for “field food”. He was a walking encyclopedia of off-the-beaten-path places to find good food, especially in the Midwestern US.
Mark was truly one of the unsung heroes of SFS; he joined NABS as a young scientist and contributed to the Society in innumerable ways. In 2022, he was honored for his uninterrupted attendance at 50 annual meetings. Mark also served on the Technical Issues Committee and the Literature Review Committee (since 1978). He became chair of the latter upon the death of Donald Webb in 2012, continuing in that capacity until the last 2015-2016 issue of “Current and Selected Bibliographies on Benthic Biology” was released in 2017. True to his taxonomic interests and expertise, he compiled an annual list of citations on Oligochaeta for inclusion in the Bibliography for over 40 years. As a founding member of the SFS Taxonomic Certification Committee, Mark had an enormous impact; he was an enthusiastic and active member of that committee for the past 20+ years and was still weighing in on committee business shortly before his passing. Mark was always the first to volunteer at the SFS Taxonomy Fairs at the annual meetings. The level of his personal expertise and knowledge regarding the taxonomy and ecology of freshwater species of segmented worms (Phylum Annelida) is beyond reproach and irreplaceable. He exhibited the true passion for the taxonomy of the Annelida in a science so often overlooked in recent times. Mark is probably best known for his ubiquitous presence at the annual meeting- camera in hand at every Society function, and could always be found at the Jam Session.
Mark will be deeply missed. His contributions have enriched our understanding of freshwater life and strengthened our commitment to conservation. Above all, his friendly demeanor and ever-present smile will be missed by all who knew him. Rest in peace, Mark.
- AJ Reisinger