Classification of Seagrass Beds by Coupling Airborne LiDAR Bathymetry Data and Digital Aerial Photographs
Evaluation of the spatial distribution pattern of patchy and fragmental seagrass beds, as hotspots of faunal biodiversity and of high primary productivity, is key to the robust understanding of the ecological state and of the effects of environmental chan
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Classification of Seagrass Beds by Coupling Airborne LiDAR Bathymetry Data and Digital Aerial Photographs Satoshi Ishiguro, Katsumasa Yamada, Takehisa Yamakita, Hiroya Yamano, Hiroyuki Oguma, and Tsuneo Matsunaga
Abstract Evaluation of the spatial distribution pattern of patchy and fragmental seagrass beds, as hotspots of faunal biodiversity and of high primary productivity, is key to the robust understanding of the ecological state and of the effects of environmental changes on biota in coastal areas. Supervised classification of aerial photographs and satellite imagery is used for assessing the state of shallow-water bottom features (i.e., substrata), such as rock and seagrass patches. For accurate classification, it is important to measure the topography of the seabed extensively and at high resolution, because the color of aerial photographs must be corrected for depth. This is difficult, however, because the shallowness of the water restricts the movements of survey vessels. We generated a digital surface model (DSM) of shallow-water bottom features via airborne LiDAR bathymetry and then used the DSM and digital aerial photographs to classify the bottom features. We conducted simultaneous bathymetry and aerial photography of a bay on the east coast of Tohoku, Japan, using a Fugro LADS Mk 3 system for bathymetry (at 5-m resolution) and a RedLake image sensor for aerial photography (at 0.4-m resolution). After using the topographic data to correct for absorption, we classified the imagery
S. Ishiguro (*) • H. Yamano • H. Oguma • T. Matsunaga National Institute for Environmental Studies, Onogawa 16-2, Tsukuba 305-8506, Japan e-mail: [email protected] K. Yamada Research Center for Fisheries and Environment in the Ariake and Yatsushiro Bay, Seikai National Fisheries Research Institute, Fisheries Research Agency, Taira-machi, Nagasaki 851-2213, Japan T. Yamakita Japan Agency for Marine Earth, Science and Technology, Institute of Biogeosciences, Natsushimacho 2-15, Yokosuka 237-0061, Japan © Springer Science+Business Media Singapore 2016 S.-i. Nakano et al. (eds.), Aquatic Biodiversity Conservation and Ecosystem Services, Ecological Research Monographs, DOI 10.1007/978-981-10-0780-4_5
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to reveal the distribution of seagrass beds. The estimated distribution corresponded with empirical observations. Keywords Airborne LiDAR • Supervised classification • Shallow-water bottom features • Absorption correction • Seagrass
Introduction Seagrass generally enhances faunal diversity by increasing habitat complexity, providing living space and shelter for a great variety of animal species. This is because seagrass leaves provide habitats and a wide range of food sources (e.g., epiphytic microalgae, phytoplankton, and seagrass detritus) for a variety of species. As a result, seagrass beds in coastal areas are regarded as hotspots of faunal biodiversity (e.g., Hemminga and Duarte 2000; Larkum et al. 2006; Yamada et al. 2007, 2011; Yamakita and Miyashita 2014). Therefore, the evaluation of t
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