Spatiotemporal hydrological dynamics in the Caribbean Anthropocene: the case of a Puerto Rican coastal urban wetland

The present study aimed to understand how the combined interactions of local weather variability, marine-terrestrial connectivity and/or anthropic modifications influence spatiotemporal hydrological dynamics and ionic concentrations of anthropically impacted urban coastal wetlands. Sampling was carried out in Ciénaga Las Cucharillas Nature Reserve, a palustrine-estuarine wetland located in the northeastern of Puerto Rico with historical hydrological modifications. We conducted monthly sampling from 2018 to 2022 from ten monitoring wells at phreatic level and at 2.5 m depth. Water salinity, and ionic concentrations (Na, Mg, Ca, and K) were measured. Local climate regulated temporal variations in salinity and freshwater inputs, as well as phreatic levels. Extreme rainfall associated with atmospheric disturbances elevated phreatic levels above surface and homogenized salinities throughout the sampling site. A tridimensional hydrological mosaic was observed throughout the study area that stemmed from the deep sub-surface terrestrial-marine connectivity and the presence of natural subsurface channels connecting areas to the coastline. The wetland’s geomorphology, substrate composition, and water flow also contributed to the hydrological dynamics of the wetland as reflected in Mg/Ca and Na/K ratios. The present study provides a valuable framework for modeling impacted urban coastal wetlands. Future monitoring and management strategies should include groundwater salinity measurements, as the results indicate that is equally as important as phreatic salinity and may even obscure evidence of deep-subsurface marine intrusion.