|
Marine aquaculture has developed very rapidly in China and at present, China has become the largest producer of marine aquaculture in the world. While bringing huge economic benefits to China, aquaculture has caused serious damage to the coastal ecological environment, such as eutrophication of seawater and a series of water pollution problems. How to effectively monitor the pollution of offshore aquaculture to guide fishery production and prevent red tide is an urgent problem to be studied and solved. Remote sensing, with its advantages of wide coverage, periodicity and low cost, can effectively monitor the spatial and temporal changes of offshore polluted water bodies, which is conducive to the comprehensive analysis of Marine phenomena. In recent years, the eutrophication of waters of Zhelin Bay has intensified, which has become a red tide area, bringing serious economic losses to fishery. It is of great significance to study the distribution of chlorophyll a concentration and its spatiotemporal variation. Take the Zhelin Bay culture area in eastern Guangdong as an example, it is an important aquaculture base in China. Based on the measured hyperspectral data and the concentration of water quality parameters, the spectral characteristics of water body analyzed in Zhelin Bay .Remote sensing inversion model established by the optical classification theory. The accuracy of the inversion model verified by using multi-temporal Sentinel-2 satellite remote sensing images. The distribution characteristics and the temporal and spatial variation of Chlorophyll-a concentration were studied. The results show the reflectivity ratio at the wavelength of 705 nm has a good correlation with the chlorophyll a concentration, and the correlation coefficient is 0.7. For the sentinel-2 data, the model constructed with (Rrs(705)-Rrs(665))/(Rrs(705)+Rrs(665)) as the inversion factor has the best fitting effect, the determination coefficient R2 is 0.891, and the average relative error is 13.25%. Spatial distribution pattern of chlorophyll a concentration: chlorophyll a concentration is higher in the western and northern coastal aquaculture areas of Zhelin Bay, followed by the central net box culture area in the bay, and the shellfish culture area is lower. Spatial and temporal variation characteristics of chlorophyll a concentration: higher concentration of chlorophyll a found in the late stage of breeding, followed by the middle stage and the early stage. It provides scientific basis for the protection of offshore ecological environment, marine pollution monitoring and the coordinated development of fisheries.
|
