Eutrophication and pathogen abatement in the San Juan Bay Estuary

The San Juan Bay Estuary is a tropical lagoon system severely impacted by eutrophication and by elevated pathogen concentrations. This investigation examined alternatives for pollution abatement primarily through physical modifications to the system. The investigation included field surveys, computation of pollutant loads, and application of hydrodynamic and eutrophication models. A eutrophication model developed for temperate estuaries was successfully transferred to San Juan Bay Estuary. Results indicate two primary modifications reduce eutrophication. The first clears a constricted channel to the interior of the system and promotes flushing. The second fills deep holes in which anoxic conditions promote sediment nutrient release to the water column. Major reductions in pathogen concentration require regional controls on sources.