Date of Award

Spring 2023

Project Type


Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Elizabeth Harvey

Second Advisor

Easton White

Third Advisor

Brittany Jellison


Globally, harmful algal blooms are a severe issue for marine ecosystems, animals, and humans both ecologically and economically. The Gulf of Maine is no stranger to harmful algal blooms, specifically the dinoflagellate, Alexandrium catenella, that has routinely been forming toxic blooms since the early 1970s. In 2016, a new species, the diatom Pseudo-nitzschia spp. formed a massive bloom and has had annual blooms since. Anecdotally, these two species do not bloom concurrently, suggesting there may be specific environmental conditions that promote bloom formation for each species. The intent of this research is to uncover potential parameters that are affecting bloom formation in each species. Analysis of a dataset of harmful algal bloom observations from coastal NH during 2017 to 2022 suggests that neither species has significantly increased in abundance over this time period. While Pseudo-nitzschia spp. is present in greater abundance than Alexandrium spp. its presence has not prevented Alexandrium spp. from blooming. Additionally, Pseudo-nitzschia spp. was present in the water column for a longer period relative to Alexandrium spp., suggesting environmental factors may play a role in mediating the population abundances of these two HAB alga. In an analysis that included nutrient concentration, temperature, and salinity, phosphorus was found to be an important factor in driving the cell abundance of each species. A correlation analysis indicated a negative and significant correlation between Alexandrium spp. and phosphorus, whereas a positive and significant trend between large sized Pseudo-nitzschia spp. and phosphorus was observed. These findings will provide an enhanced understanding into how the environment influences the abundance of these two species allowing for better predictions of the future trajectory of these species in a warming Gulf of Maine.