title: Development and evaluation of a genetic algorithm-based ocean color inversion model for simultaneously retrieving optical properties and bottom types in coral reef regions.
abstract: This work presents a novel approach that integrates a shallow water semi-analytical (SSA) model and a genetic algorithm (GA) to retrieve water column inherent optical properties (IOPs) and identify bottom types simultaneously from measurement of subsurface remote sensing reflectance. This GA-SSA approach is designed based on the assumption that each pixel is homogeneous with regard to the bottom type when viewed at small (centimeter) scales, and it is validated against a synthetic data set (N=11,250) that consists of five types of bottom, three levels of bottom depth, 15 concentrations of chlorophyll-a (Chl-a), and a wide range of modeled IOP variations in clear and optically complex waters representing the coral reef environment. The results indicate that the GA-SSA approach is accurate and robust in the retrieval of IOPs and its success rate in identifying the real bottom type is limited by the level of Chl-a and bottom depth. When a pixel is homogeneous at a small scale, the maximum allowable concentrations for GA-SSA to perfectly identify all the five bottom types are 0.7  mg/m3 at 5 m bottom depth, 0.2  mg/m3 at 10 m, and 0.07  mg/m3 at 15 m. A promising 80% recognition rate of the benthic community is possible with GA-SSA when an underwater hyperspectral imager is deployed to examine the health status of coral reefs in a clean (Chl-a<1  mg/m3) and shallow (bottom depth<10  m) environment. Further study that collects field data for direct validation is required to ensure that the GA-SSA approach is also applicable in real coral reef regions.
authors: Chih-Hua
authors: CH
authors: Chang
authors: Cheng-Chien
authors: CC
authors: Liu
authors: Hsiao-Wei
authors: HW
authors: Chung
authors: Long-Jeng
authors: LJ
authors: Lee
authors: Wen-Chang
authors: WC
authors: Yang
mesh_terms: D000465:Algorithms; D002734:Chlorophyll / Q000737:chemistry*; D000077194:Chlorophyll A; D003116:Color; D003124:Colorimetry / Q000379:methods*; D003198:Computer Simulation; D057894:Coral Reefs; D004784:Environmental Monitoring / Q000379:methods*; D008027:Light; D008956:Models, Chemical; D008957:Models, Genetic; D009792:Oceans and Seas; D012031:Refractometry / Q000379:methods*; D058998:Remote Sensing Technology / Q000379:methods; D012542:Scattering, Radiation; D012623:Seawater / Q000032:analysis / Q000737:chemistry*
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A