How the reef “bathtub” model works

Open the model →sliders, long runs, data

This page builds up a simple model of the Reef Flat, one process at a time. Each figure shows output from a real simulation, and each number quoted in the text comes from the simulation. If you want to see the equations as you go, switch them on at the top of the figure.

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photosynthesis takes CO₂ out respiration and the atmosphere put it in
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skeleton dissolvingcorals building
total alkalinity (µmol/kg)
DIC (µmol/kg)
the two thick arrows on the moving point are three hours of change at the rate holding right now; the thin black arrow is their sum
water tint ·

What the model leaves out

It is a single well-mixed box. There is no spatial structure across the reef flat, no waves or wind, no distinction between corals, algae and sediment, no nutrients and no seasonal cycle. Photosynthesis, respiration, calcification and dissolution are prescribed rates rather than a community that grows and changes. The purpose is to show how the processes compete, not to reproduce a particular reef.