Flushing rates and hydrodynamical characteristics of Mosquito Lagoon (Florida, USA)

A hydrodynamic model is applied to a domain encompassing Mosquito Lagoon and a segment of north Indian River Lagoon on the east coast of Florida with the goals of (1) describing the hydrodynamic regime of the area according to existing conditions and (2) to determine the flushing rates of the system after introducing a hypothetical pollutant (numerical dye tracer). Results from the 1-year simulation agree with observations and show that the Mosquito Lagoon (ML) and North Indian River Lagoon (NIRL) are dominated by the nontidal (low frequency) water level oscillations except at the northernmost part of the ML where the influence of tidal renewal dominates. The global tracer application results reveal that only the two northernmost segments of Mosquito Lagoon (ML-ac and ML-df) reach 50% of tracer concentrations (R50) within the year of simulation (day 19 and day 176 respectively). The five (discrete) segments tracer study resulted in lower R50 values and the hypothetical pollutant is removed (flushed) from each of the segments within the year and with an averaged renewal time value for the Mosquito Lagoon basin of 98 days. Observed throughout the simulation period is the interaction across the different segments and a predominantly two-layered water mass exchange through the Haulover Canal. Most significant is that the resulting renewal times (R50) indicate the existence of three dynamically distinct sections within Mosquito Lagoon. These findings aid in the identification of poorly flushed zones and serve as a baseline for the duration and possible propagation of detrimental conditions such as a harmful algal bloom (HAB) event or a contaminant spill.