ENVIRONMENTAL AND OPTICAL SIGNATURES OF COCHLODINIUM POLYKRIKOIDES IN NARRAGANSETT BAY, RHODE ISLAND

Abstract

In the summer of 2018, a dinoflagellate bloomed in the open waters of Narragansett Bay, Rhode Island. The dinoflagellate, Cochlodinium polykrikoides, is a potentially toxic phytoplankton that has appeared in the Bay sporadically over the past few decades. It was first recorded in the Narragansett Bay Time Series in 1979, but its appearance was infrequent. In the summers of 2016 and 2018 C. polykrikoides bloomed in the bay at densities high enough to form rust colored patches on the surface due to the dark pigmentation of the cells, which was distinct enough to be seen from shore, and from small boats. The 2018 bloom was captured by an Imaging FlowCytobot deployed or from the URI GSO Pier, which recorded a sample approximately every 20 minutes continuously throughout August. This provided a unique opportunity to study the bloom at fine-scale temporal resolution. The goals of this thesis were to assess the relationship between C. polykrikoides and surrounding environmental parameters, assess the community composition before, prior to, and after the bloom period, and measure the inherent optical properties of this dinoflagellate. Two environmental parameters, salinity and dissolved oxygen, were found to have significant relationships with the number of images containing C. polykrikoides in the Imaging FlowCytobot. A time series of additional community data from the Imaging FlowCytobot allowed for a community composition analysis that resulted in a significant difference between four periods within the time series. C. polykrikoides was among the top contributors to the dissimilarity within these periods. Lastly, absorption and scattering of C. polykrikoides cultures revealed double peaks in absorption in the blue wavelengths and a single peak in the red wavelength.