This is the 2D counterpart to the 3D single-polyp coral simulation. Instead of orbiting one polyp, it solves the same Platt photosynthesis-irradiance physiology as a function of depth: sunlight is absorbed exponentially as it travels down through seawater (the Beer-Lambert law), so every polyp in the water column sees a different local light dose, and therefore sits at a different point on the same P-I curve.
I(z) = I₀·exp(−k·z) (Beer-Lambert attenuation)
P(I) = Ps·[1 − exp(−αI/Ps)]·exp(−βI/Ps) (Platt et al. 1980, same as 3D model)
Ps = Pmax(T) = Pmax₀·exp(−(T−Topt)²/2w²)
Near the surface, irradiance can be high enough to sit past the curve's peak — photoinhibited. Moving down, light falls exponentially and P(z) can actually rise for a stretch as the polyp moves off the photoinhibited shoulder, before falling again into light limitation and eventually below the compensation threshold (Zc) where photosynthesis can no longer keep the tissue net-productive — the same "subsurface production maximum" seen in real reef and phytoplankton light profiles.
- Surface irradiance — PAR arriving at the water surface, same range as a shallow midday reef.
- Water clarity (k) — the attenuation coefficient; clear oceanic water is ~0.04/m, turbid coastal reef water can exceed 0.2/m. Higher k compresses the whole photic profile into a shallower band.
- Water temperature / Symbiont density — shift the intrinsic P-I curve exactly as in the 3D model (thermal-performance ceiling and photoinhibition steepness; total flux per unit tissue).
- Probe depth — drag the marker on the water-column view (or this slider) to sample local irradiance, O₂ production, CZAR and light-enhanced calcification at any depth.
- Auto day cycle — sweeps surface irradiance through a sinusoidal daylight curve; watch the whole depth profile brighten and dim together.