Date of Award


Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)




Mary Jane Peny

Second Committee Member

Christopher V. Davis

Third Committee Member

Peter A. Jumars


An assessment of the spatial and temporal distribution of phytoplankton in the Damariscotta River Estuary, Maine, USA, as well as certain key environmental factors, was undertaken to better understand the variability of phytoplankton with regard to the carrying capacity of the estuary for shellfish aquaculture, an important economic resource in Maine. Chlorophyll α concentration and temperature had been measured for water samples collected mid-way up estuary at the Darling Marine Center since 2002. The present study, carried out in 2005, was an expansion of the original program and included additional sampling at stations at the head and mouth of the estuary. Three times a week, water samples were collected for chlorophyll α, nutrients, salinity, and temperature as well as less frequent collections for phytoplankton size and taxonomic composition. In 2005, the late winterlearly spring bloom occurred at approximately the same time throughout the estuary, but was later and lower in magnitude than previous years. The drawdown of nitrate and silicate began several weeks before accumulation of biomass in the 2005 bloom. At the middle station, large diatoms dominated in late winter and early spring, while flagellates dominated later in the year and dinoflagellates rarely dominated. At various times throughout the summer, in situ measurements of chlorophyll α fluorescence, salinity, and temperature were collected with towed, profiled, and moored instruments. Strong spatial gradients in temperature, salinity and chlorophyll a were observed in the estuary, with the largest phytoplankton biomass occurring in the upper section. Tidal oscillations were responsible for movement of the peak phytoplankton biomass up and downstream in the upper estuary. During the summer, maximal values of chlorophyll α occurred in the early evening and minimal values in early morning after sunrise. High pheopigments in the late spring and summer were suggestive of high rates of grazing.