INVESTIGATING NUTRIENT CONTAMINATION FROM SURFACE AND GROUNDWATER INPUTS IN KINGSTON HARBOUR, JAMAICA

Urban and industrial development have adversely affected the water quality of Kingston Harbour over the past six decades. Increased nutrient and organic pollution due to inflows of untreated domestic and industrial wastewater, fertilizer run-off and solid waste, have led to increased primary production, ecosystem diversity shifts and the destruction of important marine habitats, including coral reefs and mangrove forests. Efforts have been made to decrease contaminant inputs and improve the water quality in the harbor, however, the impact of these efforts is largely unknown as no comprehensive study of the water quality of the harbor has since been conducted and the relative contributions of point and non-point sources of pollution are still unknown. Thus, in this study, we examine the impact of surface and groundwater inputs on the water quality of the harbor over a 13-month period, from May 2022 to May 2023. Salinity-temperature-depth profiles were obtained at 44 sites on seven occasions spanning wet and dry seasons. Lower salinities were obtained at the water surface near surface water inflows (river and gullies). However, salinity decreased at water depths below 8 meters in the eastern section of the harbor, indicating possible submarine groundwater discharge. Total oxidized nitrogen (NO3¯ + NO2¯, TOxN), soluble reactive phosphorus (SRP) and total dissolved nitrogen and phosphorus (TDN, TDP) concentrations were measured during the same period, at 36 sites where surface flows and suspected groundwater discharge were identified. Elevated nitrogen concentrations were observed near gullies and suspected groundwater sites (maxima: 16.79 μM TOxN, 49.45 μM TDN) while the maximum phosphorus concentrations were detected where the largest surface inflows to the harbor occurred (via Hunt’s Bay) and in the vicinity of a mangrove site (Refuge Key) (1.69 μM SRP, 5.67 μM TDP). Seasonal variations in the nutrient concentrations were also detected, with increases in concentrations observed following heavy rainfall in the basin. The results are indicative of the ongoing impact of urban pollution on the water quality of Kingston Harbour and have implications for the continued management of this important harbour.