Submarine groundwater discharge and associated nutrient fluxes to Discovery Bay, Jamaica

Abstract

Submarine groundwater discharge (SGD) and associated fluxes of nutrients were investigated in Discovery Bay, Jamaica during the early 2000's. The flow of water discharging from submerged springs was measured using hand-held flow meters while diffuse seepage was evaluated using Lee-type seepage meters. Concentrations of ammonium, nitrate+nitrite, soluble reactive phosphorus (SRP) and total dissolved nitrogen and phosphorus were measured in bay waters as well as waters emerging from submarine springs and as diffuse seepage. The dominant nitrogen and phosphorus species in the SGD and bay waters were dissolved inorganic nitrogen (DIN = NH4+ + NO3− + NO2−) and SRP, but varying levels of organic nitrogen and phosphorus were detected. Significant amounts of SGD were detected in Discovery Bay which was enriched in nitrogen relative to phosphorus with N:P ratios typically greater than 100. SGD, via flow from 63 submarine springs, was estimated at between 9 and 19 × 103 m3 d−1 with associated nutrient fluxes of 160–780 mol N d−1 and 0.4–7.0 mol P d−1. Diffuse seepage rates were highly variable across the bay and ranged from 0 to 1.2 m d−1 leading to seepage nutrient fluxes of up to 17.7 mmol N d−1 m−2 and 0.25 mmol P d−1 m−2. Seasonal variations and the implications of these fluxes on the nearshore coral reef system are discussed. This study provides the first reported estimates of SGD nitrogen and phosphorus fluxes to a karst-dominated small island developing state in the Caribbean.