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MAPPING SEAGRASS AND GREEN MACROALGAE DISTRIBUTIONS IN AN OREGON ESTUARY USING COLOR-INFRARED AERIAL PHOTOGRAPHY: 1997 & 1998
Citation:
Young, D R., D T. Specht, AND P J. Clinton. MAPPING SEAGRASS AND GREEN MACROALGAE DISTRIBUTIONS IN AN OREGON ESTUARY USING COLOR-INFRARED AERIAL PHOTOGRAPHY: 1997 & 1998. Presented at 7th International Conference on Remote Sensing for Marine and Coastal Environments, Miami, FL, May 20-22, 2002.
Description:
Aerial photograph surveys of Oregon's Yaquina Bay estuary were conducted during the summers of 1997 and 1998. Advantage was taken of daylight low tide conditions when most of the intertidal mudflats in the estuary were exposed. The absence of overlying water permitted the use of color infrared film, which has proved much more useful than full color film for resolving meadows of the seagrass Zostera marina from beds of green macroalgae (mostly Ulva spp. and Enteromorpha spp.). The photographs were digitized and orthorectified for image analysis. As part of the ground verification program, during 1997 intertidal vegetative cover was measured at more than 200 stations throughout the estuary, most within about one week of the aerial photography. This provided a strong base for assessing the accuracy of the distributions of seagrass and green macroalgae obtained from analysis of the digital orthophotographs. In general, the accuracy assessment results validated image analysis results. The 1998 aerial survey revealed a distinct increase in the extent of algal cover on the mudflats. This remote sensing approach has promise for monitoring temporal changes in distributions of intertidal macroalgae and seagrass, and should be useful in addressing concerns about eutrophication of Pacific Northwest estuaries.