The coastal zone, where fresh and saltwater meet, hosts some of the most dynamic, diverse and productive ecosystems on Earth. Ecological and hydrological land-ocean connectivity are important drivers of these ecosystems. This study will advance the understanding of hydrological-ecological coupling and connectivity, by studying relationships of key fauna with coastal groundwater hydrology in the tropical realm on the Yucatan Peninsula in Mexico. The use of groundwater proxies embedded in shells of fast-growing molluscs as bio-indicators for hydrological-ecological coupling in the coastal zone will be explored, and the usage pattern of a groundwater-fed coastal inlet by the iconic Queen Conch Strombus gigas will be documented. High-resolution sclerochronology in a sessile hydrological sentinel, the bivalve Isognomon alatus together with traditional hydrological investigations will be used to document variability of groundwater exposure to resident biota, and shell sclerochronology of the roaming Strombus gigas and concurrent acoustic telemetry will explain habitat usage of this endangered and socio-economically important species in the Caribbean Sea on whole-of-life scale.