Date of Award

10-2026

Rights

© 2026 Jhana LoRe

Document Type

Thesis

Degree Name

Master of Science in Marine Sciences

Department

Marine Science

First Advisor

Markus Frederich

Second Advisor

Patricia Thibodeau

Third Advisor

Alicia Williams

Abstract

Jellyfish were once hypothesized to be successful survivors in the face of climate change. While it was thought that jellyfish were increasing in abundance worldwide in a process called “jellification”, recent evidence suggests that increases are regional. The Gulf of Maine is an area of concern for ecological change due to its recent period of severe and rapid warming, as well as other anthropogenic impacts, such as overfishing, eutrophication, and ocean acidification. These impacts eliminate the natural predators and competitors of jellyfish. Additionally, heightened temperatures increase reproduction and speed somatic jellyfish growth. Despite these concerns, the Gulf of Maine has not been recently assessed for regional changes in jellyfish populations. Jellyfish are ecologically important predators and prey, yet their fragile morphology, patchy distribution, and episodic blooms complicate conventional monitoring. This study characterized the temporal distribution of cnidarian and ctenophore jellyfish and evaluated environmental DNA (eDNA) as a monitoring tool by integrating citizen-science observations from 2015 to 2025, field eDNA sampling conducted from 2021 to 2025, species-specific quantitative PCR assay development, and controlled eDNA shedding experiments with the lion’s mane jellyfish, Cyanea capillata. Citizen scientists submitted 1,068 reports representing ten genera. Cyanea capillata comprised 53% of observations, followed by Aurelia aurita at 19%, and Staurostoma mertensii at 12%. Sightings ranged from Cape Cod to the Gulf of Saint Lawrence, with higher reporting densities along midcoast Maine and Canadian waters. Total jellyfish abundance varied significantly among years, peaking in 2015, and showed strong seasonal variation, with the most reports taking place in July, with 64% of bloom reports taking place during this month. However, there was no evidence for a sustained increase in jellyfish abundance across the time series. Of five primer-probe sets evaluated, only a newly designed C. capillata 16S assay with a probe produced reliable amplification and a strong standard curve. Assays targeting A. aurita were unsuccessful. Field eDNA concentrations did not differ significantly by month, date, or location and did not correspond with visual observations. Only three of 32 additional water samples collected from 2021 to 2023 amplified C. capillata eDNA. Laboratory incubations containing one or five C. capillata showed no relationship between number of individuals and eDNA concentration These findings demonstrate that citizen science can establish regional patterns in jellyfish occurrence and seasonality, whereas eDNA concentration is not yet a reliable proxy for C. capillata abundance. Improved genomic references, more in-lab and in-field experiments to better understand shedding constraints, and species-specific estimates of shedding, transport, and degradation under changing environmental and oceanographic conditions are required before eDNA can be used as a suitable technique for monitoring jellyfish in the Gulf of Maine.

Comments

Master's Thesis

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