Thorhaug, Anitra , Berlyn, Graeme .
Light relations of 4 seagrasses: spectral reflectance and partial absorbance. Light relations of 4 seagrasses: spectral reflectance and partial absorbance. Light Relations of Four Seagrasses:Spectral Reflectance and Partial Absorbance Measurements.
The light available to plants growing in the marine environment rapidly diminishes from a full to only blue-green spectral light as depth increases from 0 to 10 meters in clear seas. The tidal level, sea state, water particles (plankton, dissolved organic and particulate matter) acutely effect which wavelengths of spectral light are experienced by marine plants as a function of depth. These wavelengths fluctuate hourly, rather than remaining at a steady state. Our experiments measured the spectral reflectance of both intertidal temperate Zostera marina and tropical Halodule wrightii, and subtidal tropical/subtropical Thalassia testudinum and Syringodium filiforme incubated for 6 hr at various light levels from 100% to 10% of full surface light with no color change. A PP Instrumentsí Unispec measured both reflectance and partial absorbance. Results showed the spectral reflectance diminished as light intensity diminished, some species exhibiting greater reflectance diminution than others. The partial absorbance defined as the portion of absorbance which is the inverse of the reflectance showed highly-defined absorbance in the chlorophyll and accessory pigment ranges vs light diminution, which differed at a light level among the 4 seagrasses. The Thalassia specimens were simultaneously tested at various temperatures and light intensities. Thalassia testudinum at 30C vs. 25C developed a change in major spectral reflectance peaks with a zeaxanthin-violazanthin pigment shift when subjected to the higher temperature, then reincubated at a lower temperature. The xanthin-changed blades, after incubation above 31C, appeared red to the naked eye. When subjected to 25C on consecutive days, the spectral response of the blades switched back to the normal pigments. Thalassia specimens found in nature in extremely shallow water in the warm fall weather with blades red to the naked eye had a different spectral profile than green-bladed specimens of the same age found in deeper water.
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1 - Yale University School of Forestry & Environmental Studies, 1359 SW 22 TER, Miami, Florida, 33145, 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
Location: Stevens 1/Hilton
Date: Wednesday, July 11th, 2007
Time: 1:45 PM