Author(s): K. H. Cheng; S. N. Chan; Joseph H. W. Lee
Keywords: No Keywords
Abstract: The explosive growth of phytoplankton (algal blooms) in subtropical coastal waters can lead to water discoloration and severe dissolved oxygen depletion–resulting in fish kills and other environmental problems. Traditional algal bloom monitoring relies on field sampling and laboratory analysis of chlorophyll-a (Chl-a) concentration, which is resources intensive and time consuming. Because of the prevalence of cloudy weather throughout the year and the limited spatial and temporal resolution of satellite images, remote sensing has not been successful for algal bloom monitoring in Hong Kong. Based on Unmanned Aerial Vehicle (UAV) technology we have recently developed a robust method for the remote monitoring of coastal algal blooms from lower altitudes unaffected by cloud coverage. With the use of a commercially available UAV fitted with a digital camera, the surface irradiation reflectance in three visible wavelength bands is mapped along a planned flight route (at 70 m height) and calibrated against direct Chl-a measurements in a marine fish culture zone. For the first time the feasibility of using a light-weight UAV to map surface Chl-a concentration distribution is demonstrated. The method can be used to complement field surveys and water quality modelling, and support emergency response.