Distribution Pattern of Sargassum spp. on the South Coast of Gunungkidul Regency, Special Region of Yogyakarta, Indonesia Using Satellite Imagery

Sargassum spp. is one of the most abundant types of macroalgae on Gunungkidul coast, Yogyakarta, Indonesia. Its ability to adapt to the characteristics of the Gunungkidul coast causes this macroalgae to thrive. The highly varied biochemical composition of this macroalga species makes it a promising natural resource. However, efforts to develop it optimally have not been made until now. Therefore, an initial study is needed to determine the distribution pattern of Sargassum in the waters of Gunungkidul for sustainable management. The present study utilized secondary data acquired from BMKG and Satellite Imagery (Sentinel-2 L2A). Measurements of normalized difference vegetative index (NDVI), Sargassum index (SI), and sea surface temperature (SST) were collected over three years (2020-2022) using the ESA SNAP and QGis software. The classification of the Sargassum area was carried out using Random forest. Data analysis used univariate and Posthoc Tukey with a 95% confidence level and bivariate correlation between environmental parameters and vegetation index and area. Satellite imagery data indicated that Sargassum is present year-round in Gunungkidul waters. The average results of humidity and SST in Gunungkidul waters during 2020-2022 significantly affect the growth of Sargassum. The largest Sargassum growth area was found in January-May and August-October at Ngunggah Beach and its surroundings, the Central part, namely Ngrenehan Beach, Kukup, Sepanjang, Watu Kodok, Drini, Betueng, Krakal, Sadranan, Trenggole, and Dadapan Beach. The mean Sargassum biomass in Gunungkidul waters exhibited a greater wet weight in comparison with other regions in Indonesia and Asia, particularly during the months of January-April and September-November.