Research Article

Satellite image analysis reveals changes in seagrass beds at Van Phong Bay, Vietnam during the last 30 years

¹ Nha Trang Institute of Technology Research and Application, Viet Nam Academy of Science and Technology, 02 Hung Vuong, Nha Trang City, Viet Nam
² Institute of Oceanography, Viet Nam Academy of Science and Technology, 01 Cau Da, Nha Trang City, Viet Nam
³ Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima City, Hiroshima 739-8528, Japan
⁴ Graduate University of Science and Technology. 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam

^* Corresponding author: nguyenxuanvi@gmail.com

Handling Editor: David Kaplan

Received: 4 November 2019
Accepted: 22 March 2020

Abstract

Seagrass meadows are fragile ecosystems in the coastal zone. Natural disasters, land reclamation and various human activities seem to exert negative impacts on the distribution and biological performance of seagrass beds in Vietnam. In this present study, satellite Landsat TM/OLI image analysis was applied to determine changes in seagrass distribution at Van Phong Bay, Vietnam in the last 30 years. The maximum likelihood decision rule was used to extract seagrass bed distribution data. The error matrix using the in situ reference data for HLM image classification was 81–95% accurate, and Kappa coefficients were between 0.72 and 0.91. The results indicated that 186.2 ha (or 35.8%) of the original seagrass beds were lost in the last three decades at Van Phong Bay, and decline in each specific site may have been due to different causes. Typhoons may have caused the loss of seagrass beds at open-sea sites whereas aquaculture activities, excavation and terrigenous obliteration may have caused such losses in protected sites.