Patterns of groundwater discharge into Florida Bay

Natural chemical tracers of groundwater discharge (Rn-222 and CH4) were sur veyed to evaluate possible patterns of groundwater interactions with surfac e water in Florida Bay. Radon and methane concentrations in water samples c ollected from wells, solution holes, canals, and Florida Bay showed a signi ficant correlation, despite the fact that these two trace gases have indepe ndent sources. Groundwater flux was also measured directly via seepage mete rs in several Florida Bay locations. Natural abundance of nitrogen isotopes measured on attached algae and seagrass showed the greatest N-15 enrichmen t near the Keys. Collectively, our results suggested greater groundwater fl ow along the bay side of the Florida Keys. Nutrient flux estimates, based o n interstitial nutrient concentrations and groundwater flux measurements, s uggested that groundwater in the eastern part of Florida Bay may provide as much nitrogen (110 +/- 60 mmol N m(-2) yr(-1)) and phosphate (0.21 +/- 0.1 1 mmol PO43- m(-2) yr(-1)) as surface freshwater sources from the Everglade s (i.e., Taylor Slough and C-111). However, the inputs are clearly not unif orm, and areas near solution holes or tidal springs may have a substantiall y greater nutrient flux into surface waters then these estimates.