Long-term Passive Acoustic Monitoring is the foundation of the entire program and it is achieved through the use of non-invasive underwater recorders. We are currently focused on the northernmost portion of the MesoAmerican Reef, continuously monitoring at The Listener sculpture site in Punta Nizuc, and intermittently at two other sites located at Isla Mujeres and Isla Contoy. We have also incorporated sensors for temperature and light along with the acoustic sensors.