Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Environmental Studies Program


Denise Bruesewitz


Gloeotrichia echinulata is a cyanobacteria species that has been increasingly forming blooms in oligotrophic lakes in the Northeastern United States. The Belgrade Lakes in central Maine have experienced increasing blooms over the past decades. Long Pond and Great Pond in the Belgrade Lakes region are popular locations for summer tourism and year-round residents. Research into G. echinulata is important to the Belgrade community because of potential effects to water quality, public health, and recreation. Studying G. echinulata bloom density throughout the summer and how it may affect the phosphorous cycle, the nitrogen cycle, and the plankton community will help scientists inform policy makers on water quality initiatives.

G. echinulata can serve as a warning sign for lake eutrophication and blooms can mark tipping points between eutrophication stable states. Further research should focus on luxury phosphorus uptake from the sediment during recruitment because it could mitigate the positive effects alum treatment.

The use of 15-nitrogen (N) stable isotope tracers is a valuable tool for understanding nitrogen cycling in aquatic ecosystems. Traditionally, analytical measurements of 14N:15N ratios involves a time consuming process of incubations to concentrate N onto filters for analysis by isotope-ratio mass spectrometry. The process also requires large sample volumes, which is a challenge for microcosm experiments. Here, we present a technique for measuring 14N:15N in ammonium using ESI-TOF mass spectrometry, to better characterize nitrogen cycling in lake and estuarine systems.

The G. echinulata blooms are linked to chlorophyll-a concentrations, pheophytin concentrations, and total phosphorus concentrations. G. echinulata is possibly a driver of eutrophication and it is an important organism to study, especially in low nutrient lakes.


Gloeotrichia, Maine, cyanobacteria, Limnology, Chlorophyll-a, phosphorus