Spectral definition of the macro-algae Ulva curvata in the back-barrier bays of the Eastern Shore of Virginia,USA |
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| Authors: | Elijah Ramsey III Amina Rangoonwala Mads Solgaard Thomsen Arthur Schwarzschild |
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| Affiliation: | 1. US Geological Survey, National Wetlands Research Center , Lafayette , LA , 70506 , USA elijah_ramsey@usgs.gov;3. IAP World Services, Inc., National Wetlands Research Center , Lafayette , LA , 70506 , USA;4. Centre for Ecosystem Management, Faculty of Computing, Health and Science, School of Natural Sciences, Edith Cowan University , Joondalup , WA , Australia;5. Department of Marine Ecology , National Environmental Research Institution , DK-4000 , Roskilde , Denmark;6. University of Virginia, Site Director Anheuser-Busch Coastal Research Center , Oyster , VA , USA |
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| Abstract: | We have developed methods to determine the visible (VIS) to near-infrared (NIR) spectral properties of thalli and epiphytes of bloom-forming and green macrophyte Ulva curvata in back-barrier lagoons in Virginia, USA. A 2% increase in NIR thalli reflectance from winter to summer (ca. 9.5%) matched the drop in summer NIR transmittance (ca. 90%). In contrast, summer and winter VIS reflectance (reaching 6%) were nearly identical while winter transmittance (ca. 85%) was 10–20% higher. NIR absorption remained at 5% but VIS absorption increased by 10–20% from winter to summer. Replicate consistency substantiated the high transmittance difference indicating thallus composition changed from summer to winter. Epiphytes increased thallus reflectance (<ca. 4%) and decreased transmittance (<ca. 10%) and exhibited broadband VIS and NIR absorptions in summer and selective peaks in winter. A simulation coupling water extinction with thallus reflectance and transmittance found seven submerged thalli maximized the surface reflectance enhancement (ca. 2.5%). |
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