Seasonal Salinity Trends in Central and Southern Biscayne Bay, Florida

Abstract

Salinity in estuaries varies naturally due to tides, weather, geomorphology, freshwater flow, climate, and sea level. Before the 1950s, water management in southern Florida focused on diverting freshwater to the ocean to make historic wetlands more amenable to development and to protect human life. However, current water management activities aim to restore wetlands and estuaries while maintaining flood control and drinking water for the human population. Due to anthropogenic alteration, the spatiotemporal variability in salinity within Biscayne Bay, Florida, is a significant concern for ecosystem restoration under the Comprehensive Everglades Restoration Plan (CERP). This study aims to analyze daily seasonal salinity trends within the Bay and quantify the change in salinity per year (salinity slope). Salinity data, collected at 30 stations within the central and southern regions of Biscayne Bay over 16 years (2005–2020), were examined for trends. The nonparametric seasonal Kendall trend test, at a 0.05 significance level, was used for the analysis. Results of the trend analysis show that salinity slopes were consistently positive (indicating increasing salinity over time) in the southern portion of the study area and negative (indicating decreasing salinity over time) in the northern portion of the study area. Throughout the study region, most salinity slopes were positive in the wet season and negative in the dry season. The study results show trends in seasonal salinity, which helps in understanding changes in this region. This study will aid future management efforts within Biscayne Bay.