USING IN SITU CHLOROPHYLL METHODS FOR DETECTION OF PHYTOPLANKTON BIOMASS

Because all plankton have chlorophyll it is the most dependable proxy used for measuring phytoplankton biomass. In this project we used multiple sources of chlorophyll data from profiles and morred in vivo chlorophyll fluorometers (YSI, Inc. WETLabs, Inc. respectfully) in order to investigate a variety of in situ sensors. We used extracted chlorophyll concentrations as the true values for both laboratory calibration using a known culture, and in situ validation with water samples that were collected over the past two years (spring/summer 2008 - 2009) in Harpswell Sound, Casco Bay, Maine.

We were able to deduce that color dissolved organic matter (CDOM) fluorescence contaminated the in situ chlorophyll fluorometer’s signal requiring a separate calibration (Proctor and Roesler submitted). In situ validation showed that the moored and profiling chlorophyll fluorometer’s data were well correlated with the extracted data with the exception of a few outliers, the majority of which had underlying causes (i.e. non-photo chemical quenching). By comparing the extracted chlorophyll to the in vivo absorption chlorophyll data (absorption line height at 676 nm), we were able to discern distinct phytoplankton communities, whose populations are separated by time and cell size. While there are many different methods to measure phytoplankton biomass from remote observations, all data must be validated first. Uncertainties about the measurements must be explored before accurate conclusions can be made.