Thorhaug, Anitra , Berlyn, Graeme .
The comparison of light and salinity changes on four seagrasses:spectral reflectance and partial absorption measurements and indices. Halodule wrightii,Thalassia testudinum,Syringodium filiforme & Zostera marina.
The usefulness of spectral responses are two fold: Remote sensing for mapping and monitoring of resources, and stress studies of plants. The indices of the spectral reflectance and its various derivatives are useful for both. The responses seen in spectral reflectance measurements to diminishing light in these seagrasses shows differing patterns in various species. The Thalassia, Syringodium and Halodule have qualitative accessory pigment differences in their responses, while Zostera has only quantitative differences with less response to less light. The differences in light responses between varying light levels from 10% and 100% and among these former species at a given light level is shown sharply in the 1st and 2nd derivatives of reflectance and partial absorbance in 400-620 nm, and in the green edge. The responses of these same four seagrasses to varying salinity changes tended to be quantitative within the reversible range of salinities (seawater down to about 20 to 24 ppt). With increasing dilution to 16 ppt, there were quantitative changes in the first and second derivatives and statistically significant changes in the 510-530 nm, 650-670 nm, and above 900 nm range. The response differences between light and salinity sets of responses appear to be seen clearly in the green edge, and in the blue and green ranges. Comparison of quantitative levels at various wavelengths were also useful. The responses again showed Zostera to have a difference in response to salinity changes than the other three species, demonstrating less response. The Syringodium responses were to the most extreme to lowered salinity, followed by Thalassia and then Halodule. The quantitative differences did not occur within the normal oceanic seawater range, but at the lower salinities, clearly evident in the partial absorption, and first and second derivatives.
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1 - Yale University, School of Forestry and Environmental Sciences, Greeley Laboratories 359 Prospect St., New Haven, Connecticut, 06901, USA
2 - Yale University, School of Forestry and Environmental Sciences, Greeley Laboratories 375 Prospect St., New Haven, Connecticut, 06901, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 9:15 AM