Florida has a long history of water management and control. The initial plan to drain the Everglades for development and agriculture originates in 1881, and in 1907 the Everglades Drainage District was created. This diversion of water flow, in some instances through the use of locks and dams, has had observable impacts on many Florida estuaries including the Saint Lucie, Loxahatchee, and Caloosahatchee Rivers and all of the Everglades drainage basins. One species of concern that lives in these estuaries that is directly affected by this water control is the eastern oyster (Crassostrea virginica). Attempts to restore the natural water flow to Florida and also reduce impacts on C. virginica were initiated with the Water Resources Development Act in 1996 and finalized with the Comprehensive Everglades Restoration Plan (CERP) in 2000.
This diversion of water flow has had impacts on oyster reefs that can be observed over both short-term and long-term periods. One estuary being monitored as part of CERP is the Loxahatchee River Estuary. Monitoring includes reef survey counts and monthly recordings of water salinity. The North and South Forks of this estuary are areas of focus and have two drastically different freshwater inputs and saltwater tidal influence. The North Fork has more natural water input and the South Fork has more controlled input through the S-46 lock on the C-18 canal. When water control locks are open for short periods the freshwater release may result in distress to eastern oysters that may ultimately result in death of oysters on that reef, however oysters typically recover in less than a year. In contrast, withholding freshwater over long periods may result in elevated estuarine salinity over oyster reefs leading to chronic disease and increased densities of reef pests, ultimately deteriorating the reef structure, which is leading to permanent loss of reef habitat. A better understanding and awareness of when reefs are showing signs of decline due to chronic hyper-salinity can be red flags used to notify water control managers when water releases may be necessary to save these reefs.