Starry stonewort (Nitellopsis obtusa) is a macroalgae causing ecological and economic impacts as it spreads in the US Northeast and Midwest. Monitoring the species’ distribution is essential for understanding and controlling its spread. Starry stonewort is established within the Great Lakes basin and was first recorded in Chicago’s Lake Michigan harbors in August 2023. Because boats are a known vector for the species and often travel among Chicago’s harbors, we suspected the species was present in additional harbors. Prior work showed that SCUBA surveys are substantially more effective for detecting starry stonewort than standard rake toss methods. We performed SCUBA surveys in six of Chicago’s harbors to establish a baseline of starry stonewort presence and growth form. SCUBA surveys consisted of two divers searching for five minutes at 10 sites within each harbor. We identified starry stonewort in multiple forms in every harbor and at 75% of all sites surveyed. There were areas where we could not perform SCUBA surveys due to lack of access, low visibility, or heavy boat traffic. To address these shortcomings, we are developing a species-specific environmental DNA (eDNA) assay for starry stonewort. We capture eDNA present in the harbor by pumping water through a filter, extract DNA from the filter, and perform qPCR using primers that amplify starry stonewort DNA. We are able to detect starry stonewort from harbor samples using low annealing temperatures and we can prevent amplification of closely related species using high annealing temperatures. We are testing adjusted extraction and qPCR protocols to increase the sensitivity of the assay while maintaining the specificity. Once the assay is optimized, we will test filters from nine of Chicago’s harbors. Our distribution and growth form data from the SCUBA surveys will aid in the validation of our eDNA results. SCUBA surveys offered high resolution monitoring but required extensive time and trained divers, in addition to having limits associated with access and conditions. Ultimately, we aim to produce a reliable and deployable methodology for detecting starry stonewort eDNA so that more frequent and widespread monitoring for the species will be possible.