Citation:

Specht, D T., P J. Clinton, AND D R. Young. MAPPING NON-INDIGENOUS EELGRASS ZOSTERA JAPONICA, ASSOCIATED MACROALGAE AND EMERGENT AQUATIC VEGETARIAN HABITATS IN A PACIFIC NORTHWEST ESTUARY USING NEAR-INFRARED COLOR AERIAL PHOTOGRAPHY AND A HYBRID IMAGE CLASSIFICATION TECHNIQUE. Presented at 2nd National EPA Non-indigenous Species Workshop, Research Triangle Park, NC, February 2-4, 2004.

Description:

We conducted aerial photographic surveys of Oregon's Yaquina Bay estuary during consecutive summers from 1997 through 2001. Imagery was obtained during low tide exposures of intertidal mudflats, allowing use of near-infrared color film to detect and discriminate plant communities. Approximately 90 percent of submerged aquatic vegetation occurs in the intertidal zone at this latitude. Color diapositives were digitized and orthorectified for image analysis. A hybrid image classification algorithm was developed to allow discrimination of intertidal habitats dominated by the non-indigenous eelgrass species Zostera japonica, the green macroalgae Ulva spp.and Enteromorpha spp., the brown alga Fucus sp., unvegetated (bare sediment) areas and various emergent upper-intertidal reeds, grasses and sedges. Application of this algorithm has promise of allowing habitat delineation and change analysis mapping at the sub-meter level over time in Pacific NW estuaries characterized by significant tidally-exposed habitats. Such changes are of interest in the assessment of environmental stresses such as land use management practices (as a typical source of anthropogenic stress), non-indigenous plant species invasions, episodic weather events, and long-term (decadal) weather cycles on the resiliency of these plant communities. The method should find utility in assessment of relative changes over time in the distribution of non-indigenous vs native submerged aquatic vegetation in estuarine habitats.

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