Spectral fluorometric characterization of phytoplankton community composition and biomass, chromophoric dissolved organic matter and photosynthetic capacity using the algae online analyzer.

摘要

The composition of phytoplankton communities in estuaries can be highly variable in space and time. There is a general lack of information on how community composition varies on short time scales (hours to days). This stems, in part, from the fact that continuous monitoring of phytoplankton is laborious, time-consuming, and expensive. My thesis examined the performance of a commercially-available, fixed wavelength spectral fluorometer, the Algae Online Analyzer (AOA), which is designed and marketed for continuous monitoring purposes. Monospecific algal cultures and natural waters from Oyster Landing, North Inlet, were used to test the AOA.s ability to measure total chlorophyll a (chl a), phytoplankton community composition, chromophoric dissolved organic matter (CDOM), and phytoplankton group-specific photosynthetic capacity. In the field, I found that the AOA over-estimated total chl a (as compared to direct determinations by HPLC) by a factor of 2.2 +/- 0.6, but that the relationship between the total chl a by AOA versus chl a by HPLC was linear. Estimates of phytoplankton group-specific relative abundance by the AOA was never significantly different from those by HPLC-ChemTax for chromophytes from Oyster Landing in 2010, however cryptophytes were always significantly different. AOA estimates of green algal relative abundance at Oyster Landing had no significant difference between those by HPLC-ChemTax in May and December, while the same was true of cyanobacteria in July. In the lab, increasing amounts of background CDOM resulted in a progressive increase in overestimation of chromophyte chl a in a simulated mixed algal community. Comparisons of AOA measurements of CDOM to those by spectrophotometry showed a significant linear relationship. The AOA also accurately described trends in photosynthetic capacity for all phytoplankton groups as compared to DCMU measurements, except for the representative cryptophyte species.