Date of Award


Document Type

Open Access Thesis


Marine Science

First Advisor

James Pinckney


Bioluminescent bays resulting from dense concentrations of bioluminescent dinoflagellates are rare, with only 14 documented systems worldwide. One of these bays, Mangrove Lagoon, is located in Salt River Bay National Park in St. Croix, USVI. Very little is known about the environmental factors responsible for maintaining the high dinoflagellate densities in this lagoon. In order to assess the dynamics of the dinoflagellates, in situ nutrient addition bioassays were conducted to determine which nutrients regulate the phytoplankton community, which includes the bioluminescent dinoflagellate Pyrodinium bahamense. Bioassays were conducted in two different seasons, (January 2013 and May 2013) to examine seasonal responses to nutrient additions. The three hypotheses that were addressed in this project are (1) is the phytoplankton community is phosphorus-limited and (2) does mangrove leachate stimulates the growth of dinoflagellates relative to the other phytoplankton, and (3) does vitamin B12 will stimulate the growth of the dinoflagellate Pyrodinium bahamense var. bahamense in comparison to the other phytoplankton present. Photopigment biomarkers were used to assess community composition and biomass in the bioassays as well as ambient waters. The phytoplankton communities, except the dinoflagellates were co-limited in nitrogen and phosphorus. The ANOVAs indicated nutrient addition effects on each individual group except dinoflagellates and non-peridinin dinoflagellates (p < 0.01). A posteriori multiple comparisons indicated a significant positive effect of N+P for diatoms and green algae and significantly higher responses to B12 for cyanobacteria and haptophytes. There was a significant negative effect of leaf additions for all groups except dinoflagellates, which showed a significant positive response to the 6 yellow and 3 orange leaf treatments (p < 0.05). Responses to mangrove leaf color and number did not show a discernible trend for the other algal groups other than the general negative response to all leaf additions. Dinoflagellates seem to be best suited for Mangrove Lagoon, as they are not nutrient limited, possibly because they are able to vertically migrate and the not significantly inhibited by mangrove organic matter.