Mapping seagrasses on the basis of Sentinel-2 images under tidal change. (March 2023)

• Record Type: Journal Article
• Authors: Li, Yiqiong; Bai, Junwu; Chen, Shiquan; Chen, Bowei; Zhang, Li
• Is Part Of: Marine environmental research. Volume 185(2023)
• Publication Date: 2023-03
• Subjects: Seagrasses mapping -- Tides -- Sentinel-2 images -- Submerged Seagrasses Identification Index -- Coastal zone; Marine pollution -- Environmental aspects -- Periodicals; Marine ecology -- Periodicals; Mer -- Pollution -- Aspect de l'environnement -- Périodiques; Écologie marine -- Périodiques; Electronic journals; 577.705
• DOI: 10.1016/j.marenvres.2023.105880
• Languages: English
• ISSNs: 0141-1136

Abstract

Abstract: Tidal variations make the water bodies in satellite remote sensing images on different shooting dates have different inundation ranges and depths. Although the underwater substrates do not change, the spectral properties differ due to attenuation effects. These differences have an impact on the results when multi-temporal remote sensing images are used to analyze seagrasses. This paper proposes a remote sensing mapping method for seagrasses taking the tidal influence, using the seagrasses growth area in Xincun Bay, Hainan Province, China as a case study. a) The seagrasses growth area was determined from remote sensing images. The seagrasses were divided into two types: the seagrasses exposed to water surface or tidal flats (non-submerged seagrasses) and the seagrasses submerged in water (submerged seagrasses). b) The spectral features of seagrasses in Sentienl-2 image were analyzed. We found that the spectral characteristics of non-submerged seagrasses were similar to terrestrial vegetation and these seagrasses could be extracted by using NDVI. The submerged seagrasses spectral was different, forming a reflection peak at the first vegetation red edge band (i.e.705 nm) in Sentinel-2 images. This reflection peak was used to design the Submerged Seagrasses Identification Index (SSII) for extracting underwater seagrass. c) The extraction results of non-submerged seagrasses and submerged seagrasses were merged to map the seagrasses in the study area. The experimental results show that the mapping method proposed in this study can fully consider the influence of tidal changes in remote sensing images on seagrasses identification. The SSII constructed based on Sentinel-2 images extracted submerged seagrasses effectively. This study will provide references to remote sensing mapping of seagrasses and integrated ecological management in coastal zones. Graphical abstract: Image 1 Highlights: Tides can interfere with the extraction of information in the seagrasses remote sensing mapping process. A seagrasses remote sensing mapping process considering the tidal water change is proposed. The spectral of submerged seagrasses have a special reflection peak at 705 nm on Sentinel-2 images. A Submerged Seagrasses Identification Index based on Sentinel-2 images was constructed.