Reef-Flat Bleaching Front 2D: Bathymetry-Coupled ROS Diffusion

This 2D companion to the per-polyp coral-bleaching model swaps 520 independent point-polyps for a continuous field view of a reef flat from above. Reactive-oxygen buildup and symbiont density are solved as coupled reaction-diffusion PDEs on a grid, so bleaching spreads outward as a real propagating front through the shared tissue and boundary-layer water between coral heads. The field is coupled to an actual reef-flat bathymetry map through the Beer-Lambert light-attenuation law and a depth-dependent thermal-stratification cooling term, so shallow lagoon patches and deeper channels experience very different local stress from the same sea-temperature reading — producing a patchy bleaching pattern driven by real seafloor topography rather than per-polyp genetic variance alone. Raise sea temperature and irradiance to trigger a heatwave and watch the front spread, switch to the bathymetry view to see the depth map underneath it, or cool the water back down to test recovery.