Investigation of the Deep Chlorophyll Maximum in Lake Louise, Georgia
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Authors
Ward, Danielle Marie
Issue Date
2020-04
Type
Thesis
Language
en_US
Keywords
Academic theses , Chlorophyll , Georgia--Stephens County , Phytoplankton , Thermal analysis
Alternative Title
Abstract
Lake Louise, a temperate lake in south-central Georgia, USA, is 6.5 meters deep at its deepest point and approximately 6 hectares in area. Despite being relatively shallow, the lake stratifies each year, typically stabilizing from mid-March until mid-November, with a thermocline located at a depth of 2.0 – 2.5 meters. During the summer, high tannin concentrations in the water also cause a sharp decrease in light levels with less than 0.1% of incident light reaching a depth of 2.5 m. However, spectrophotometric pigment analysis indicates that a distinct deep chlorophyll maximum (DCM) develops at an approximate depth of 3.0 m, well below the photic zone, and contains higher apparent chlorophyll b concentrations than the surface waters. Photosynthetic activity at this depth suggests organisms which are capable of compensating for extremely low-light. Preliminary data at 3.0 m indicate an abundance of filamentous, photosynthetic organisms that are visually consistent with cyanobacteria. Chlorophyll spectra from sampling events suggested bacteriochlorophyll d as the primary photosynthetic pigment in the DCM, while initial imaging of filters and sequencing of 16s RNA PCR amplicons further indicated the presence of eubacteria in the phyla Chlorobi and Chloroflexi. A Chloronema-type trichome has been identified through light micrographs that may be indicative of a novel morphospecies.
Keywords: Chlorophyll; Phytoplankton; Chloronema; Thermal stratification;
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This dissertation is protected by the Copyright Laws of the United States (Public Law 94-553, revised in 1976). Consistent with fair use as defined in the Copyright Laws, brief quotations from this material are allowed with proper acknowledgement. Use of the materials for financial gain with the author's expressed written permissions is not allowed.