Coral Growth Rate Calculator

This calculator projects coral colony growth by scaling a species' baseline linear extension rate (cm/yr) with three independent environmental multipliers, then multiplying them together rather than averaging them — so a colony can only grow as fast as its worst-limiting factor allows. Temperature uses a Gaussian penalty centered on 27°C with a 3°C spread, meaning growth falls off symmetrically as water drifts from that optimum in either direction, not just when it gets too warm. Light follows a Michaelis-Menten saturating curve with a half-saturation point at 200 µmol photons/m²/s, capturing how zooxanthellae photosynthesis ramps up quickly at low light but plateaus rather than climbing without limit at high light. Calcification capacity is modeled as roughly proportional to how far aragonite saturation state (Ω) sits above 1.0, reflecting the real chemistry threshold below which corals struggle to build skeleton at all.

The effective annual rate is then applied linearly over the projection period to estimate future colony diameter, and colony volume is approximated with a simple hemisphere formula — a reasonable stand-in for massive coral forms but a poor fit for branching or plate corals. A separate bleaching-risk estimate kicks in only above 30°C and scales linearly with degrees exceeded; it is a coarse heuristic, not a Degree Heating Weeks calculation, so treat it as a rough warning flag rather than a precise thermal-stress metric. Real-world growth also depends on nutrient loading, disease, predation, and sedimentation that this model does not capture.