Dynamics of seagrass beds and land use–land cover characteristics in Vietnamese Marine protected areas

Seagrass beds are considered ecosystem engineers with important roles in the marine environment. Although the area of seagrass beds is declining in Marine Protected Areas (MPAs) of Vietnam, no study has compared the changes in the area of seagrass beds among MPAs using remote sensing technology and GIS for mapping temporal and spatial changes. This is the first study assessing the ecological characteristics of seagrass beds in Ly Son, Nha Trang and Phu Quoc MPAs. In this study, we characterized the current status and historical changes of seagrass beds in three MPAs between 2001 and 2018, but Ly Son MPA between 2001 and 2019. Field surveys, historical satellite remote sensing data and GIS technology were applied to interpret Landsat images and evaluate the relationship between the cover of terrestrial vegetation and seagrass bed ecosystems. The results indicated that the average coverage and shoot density were highest in Phu Quoc MPA (92.5 ± 6.6%, 6635 ± 5,111 shoot m−2, respectively), while the total dry biomass was dominant in Ly Son MPA with 2000.3 ± 949.8 g DW m−2. The Kappa coefficients and overall accuracies of the years 2001 and 2018 (2019) were generally higher than 87% and 0.83, respectively. Between 2001–2018 (2019), the loss of seagrass area was 307.3 ha in Ly Son MPA, 268.4 ha in Nha Trang MPA and 13,225.6 ha in Phu Quoc MPA. Besides the decline in seagrass area, the artificial land covers witnessed a significant increase during the study period. Thus, this study could contribute to basic information for the conservation and management of seagrass resources in MPA.