Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Correlations between fluorescence, beam attenuation, photosynthetically active radiation, and chlorophyll in phytoplankton
Student Author(s): Cronin, Alex
Faculty Advisor(s): Chavez, Francisco
Pages: 36
Location: Final Papers Biology 175H
Date: June 1992
Abstract: In situ instruments report a daily periodicity in fluorescence (f) and beam attenuation (c) in the ocean. The daily changes are hypothesized to result from changes in phytoplankton physiology. To determine the relation between f, c, chlorophyll (chl), and photosynthetically active radiation (PAR), time series measurements were made on cultures of phytoplankton which were exposed to different light conditions. F normalized to chl (f*) varied inversely to PAR. c* displayed daily changes that did not correlate to PAR. The f* response is well above experimental noise and its amplitude is two times as strong as the in situ signal. The c* response is not significantly outside of the experimental error, and its amplitude is within the range of the in situ signal. Absorption (a) was also measured. A* did not correlate to PAR or time, but steadily decreased as cultures grew older. I conclude c* varies due to b* (scattering per chl.) with a circadian rhythm, and f* varies in response to PAR. This is consistent with in situ data. Further, I present what is believed to be the first reported empirical method to measure chl from both f and PAR.