Laguna de la Cruz, a karstic meromictic lake located in the Serrania de Cuenca (East Spain) before and after a massive calcium carbonate precipitation event known as a lake whiting. The precipitation of CaCO3 (marl) occurs each summer when high photosynthesis and temperature shifts the equilibria between carbon dioxide, bicarbonate and carbonates. Photos taken in late July (above) and early August (below) by Eduardo Vicente and Antonio Camacho (University of Valencia).