MAPPING SPATIAL/TEMPORAL DISTRIBUTIONS OF GREEN MACROALGAE IN A PACIFIC NORTHWEST COASTAL ESTUARY VIA SMALL FORMAT COLOR INFRARED AERIAL PHOTOGRAPHY

摘要

A small format 35 mm hand-held camera with color infrared slide film was used to map blooms of benthic green macroalgae upon mudflats of Yaquina Bay estuary on the central Oregon coast, U.S.A. Oblique photographs were taken during a series of low tide events, when the intertidal mudflats along the drowned-river were exposed. The resulting images were digitally scanned and georeferenced to commercially produced digital orthophotographs. Benthic surveys of two transects (～ 3500 m~2) oriented perpendicular to the estuary's channel were conducted within about two weeks of each aerial survey. Distributions of the perennial seagrass Zostera marina along the upper edge of the channel were delineated from the aerial photographs taken in late spring before extensive development of the green macroalgae beds. Summer expansion and fall contraction of these algal beds (comprised principally of Ulva spp. and Enteromorpha spp.) was documented via a series of four aerial and ground surveys conducted between May and December. The study demonstrated the usefulness of this approach in mapping blooms of green macroalgae in Pacific Northwest estuaries.