Thorhaug, Anitra , Berlyn, Graeme .
A Comparison of Absorbance vs. Reflectance Measurements for Seagrasses at Two Salinities..
The question of measuring chlorophyll-related physiological responses of multicellular intact, whole living marine plants in a non-invasive, non-destructive tests has been attempted using three techniques from tree physiology: 2 photosynthetic absorbance and one spectral reflectance method. For tree physiology, one of US (G.B. & colleagues) demonstrated that spectral reflectance was a better indication of chlorophyll content than two types of absorbance meters tested.
To determine the differences between absorbance and spectral reflectance of seagrass, we use Thalassia testudinum. Thalassia spectral reflectance measurements responses had shown statistically significant differences between normal and low salinities (16 ppt) responses, incubated 24 hr. Specimens were simultaneously tested using spectral reflectance and two photosynthetic Absorbance measurements at 32 and 16 ppt for 24 hr. Three to 6 measurements per each of 2 blades per 12 specimens were measured sequentially for each technique using a UniSpec spectral reflectance analysis system, and SPAD-502 and CCCM-200 chl meter absorbance analysis systems. Previously, low salinity relations had been studied for Thalassia by us using reflectance spectral and also using long-term (24-72 hr) incubation visual analysis methods. 32 ppt was statistically significantly different from 16 ppt. The results of 3 test methods indicated that the reflectance indices were more sensitive indicators to physiological change than the absorbance meters.
1 - Yale University School of Forestry & Environmental Studies, 1359 SW 22 TER, Miami, Florida, 33145, USA
2 - Yale University, Greely Laboratories, 375 Prospect St, New Haven, Connecticut, 06511, USA
Presentation Type: Paper
Location: White Pine (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 11:45 AM