Date Approved

2026

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department or School

Biology

Committee Member

Cara Shilllington, Ph.D.

Committee Member

Kristin Judd, Ph.D.

Committee Member

Maria Goodrich, M.S.

Abstract

The peach blossom jellyfish (Craspedacusta sowerbii) is the only freshwater medusa found in the United States, yet its distribution, abundance, and mechanisms of dispersal remain poorly understood. Given its uncertain status, understanding the ecology of this species is a priority. To characterize population dynamics during the medusa season, surface water temperature and medusa abundance were surveyed at six inland lakes in Michigan. Occurrence records of C. sowerbii in Michigan were then used to compare co-occurrence patterns with nine aquatic invasives as a window into potential dispersal mechanisms and to create a regional ecological niche model. Medusae were observed in one lake during the field season, where abundance followed a significant quadratic seasonal curve peaking in mid-September, a thermal optimum near 25 ℃, and marginally nonsignificant increases during moderately bright lunar periods. Aquatic invasives were disproportionately reported at sites with reports of C. sowerbii, particularly zebra mussel, purple loosestrife, and Eurasian watermilfoil, suggesting overlapping dispersal pathways or habitat preference. The ecological niche model showed fair predictive ability and identified high habitat suitability in the southern lower peninsula, with winter climate exerting the greatest influence on predicted distribution. The unpredictable nature of C. sowerbii blooms highlights the difficulty in tracking this species. Understanding its dispersal pathways and climatic constraints provides a framework for future monitoring efforts and broader public awareness. Keywords: Craspedacusta sowerbii, freshwater jellyfish, ecological niche model, nonnative species

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