Testing hypotheses on the calcification in scleractinian corals using a spatio-temporal model that shows a high degree of robustness

Calcification in photosynthetic scleractinian corals is a complicated process that involves many different biological, chemical, and physical sub-processes that happen within and around the coral tissue. Identifying and quantifying the role of separate processes in vivo or in vitro is difficult or not possible. A computational model can facilitate this research by simulating the sub-processes independently. This study presents a spatio-temporal model of the calcification physiology, which is based on processes that are considered essential for calcification: respiration, photosynthesis, Ca²⁺-ATPase, carbonic anhydrase. The model is used to test different hypotheses considering ion transport across the calicoblastic cells and Light Enhanced Calcification (LEC). It is also used to quantify the effect of ocean acidification (OA) on the Extracellular Calcifying Medium (ECM) and ATP-consumption of Ca²⁺-ATPase. It was able to reproduce the experimental data of three separate studies and finds that paracellular transport plays a minor role compared to transcellular transport. In the model, LEC results from increased Ca^2＋-ATPase activity in combination with increased metabolism. Implementing OA increases the concentration of CO₂ throughout the entire tissue, thereby increasing the availability of CO^-₃ in the ECM. As a result, the model finds that calcification becomes more energy-demanding and the calcification rate increases.