Patterns in the Variation of CDOM Spectral Slopes in the Western Lake Erie Basin

<p>In recent decades, Western Basin of Lake Erie has been beset by various episodes of dense and sometimes harmful algal blooms. The federal government has mandated that jurisdictions have plans in place to predict and respond to harmful algal concentration explosions. In very large lakes like Lake Erie, satellite remote sensing can provide synoptic glimpses of the dynamics of algal growth along with wind and current mixing patterns. Colored dissolved organic matter (CDOM), which is a component of the water, absorbs light strongly in the ultraviolet to blue wavelengths, which overlaps a strong absorption area of the spectrum for the chlorophyll a in algae. Measurements in these wavelengths are essential for remote quantification of chlorophyll a aquatic concentrations. Since CDOM only absorbs electromagnetic energy and does not reflect a signal to the satellite, the purpose this study is to characterize the variation in the absorption spectrum of CDOM temporally and spatially in the Western Basin, detect terrestrial influences on the spectral slope of absorption, <i>S</i>, and determine the effect of <i>S</i> variations on satellite retrieval algorithms.</p><p>In 2011, absorption spectra for over 100 Western Basin water samples were measured with a spectrophotometer, and <i>S</i>, was calculated for each sample. The spectral slope values were tested for correlation with contemporaneous water physical factors and meteorological conditions. Changes in slope were compared to the timing of hydrograph peaks of four tributaries to the Western Basin. Using SeaDAS processed MERIS scenes from dates near the dates of the collections, slope values were examined as to their spatial relationships with algal blooms in the basin. To test the effect of the <i>S</i> variations on the results of satellite chlorophyll algorithms, the results of various values of CDOM and other optical components were modeled with HydroLight software. The remote sensing reflectances output by the model were applied to the OC3 algorithm to see what satellite retrievals would return compared to <i>in situ</i> chlorophyll concentrations.</p><p>No strong relationships between CDOM spectral slopes and the other parameters tested were verified during this study. The Western Basin is shallow, has a rapid rate of water column turnover, and steady currents moving the water masses. The results of large scale mixing may have made it difficult to track water masses with different CDOM absorption spectra. The slopes measured for the CDOM over the 2011 season ranged from 0.004 to 0.042 which is a broader variability than had been previously published for Lake Erie. The mean <i>S</i> was comparable to published data. CDOM <i>S</i> values of 16 and 11 produced the best performance of satellite-band retrieved values in the chlorophyll a algorithm, but often that meant errors of 30 or 40 percent.</p>

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Geology

Grantor dc:publisher

University of Toledo

Year dc:date

2012

Author dc:creator

• Traub, Janet

Contributors dc:contributor

• Becker, Richard

• Remote Sensing
• CDOM
• Lake Erie
• HydroLight
• case 2
• aquatic
• Great Lakes
• algae
• chlorophyll

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=toledo1352917941

OAI identifier oai:identifier

oai:etd.ohiolink.edu:toledo1352917941