ABSTRACT
The freshwater Everglades and estuarine Florida Bay ecosystem are closely linked by marine and freshwater hydrologic cycles and by organisms that depend on both systems during different times of the year or periods of their life cycles. Impound ing of water in the Water Conservation Areas and diversion of water away from Shark River Slough and Taylor Slough for purposes of urban use and flood control have significantly reduced the volume of fresh water to Florida Bay. As a result, bay waters are now more saline in more locations and for longer periods of time than under premanaged conditions. The filling of passes and shallow banks between several of the Keys for construction of the Flagler Railroad in the early 1900s reduced circulation in Florida Bay, thereby exacerbating anthropogenically generated salinity anomalies. Delivery of fresh water to Florida Bay differs from premanaged conditions in both volume and timing. Numerous effects on biota and biotic processes in the bay and southern Everglades ecotone have been docu mented or implicated, including reduced recruitment of pink shrimp, snook, and redfish; lowered reproductive success of ospreys and great white herons; and shifts in distribution of West Indian manatees, American crocodiles, and many of the
wading birds that historically nested in the estuarine ecotonal area. One species, however, the gray snapper (.Lutjanus griseus), exhibits enhanced recruitment in years of higher salinity in Florida Bay. Reduced freshwater inflow is also implicated as one of a complex series of factors in the mass mortality of seagrasses in the bay that has occurred since 1987. Similarly, hypersalinity is likely a factor in dieback of mangroves in some Florida Bay localities. Excessive amounts and unnatural timing of freshwater delivery can also adversely affect biota. A sudden release of greatly elevated volumes of fresh water from the C - ll l canal resulted in the mortality of many estuarine organisms in Manatee Bay when salinities dropped from near marine to zero in a few hours and remained low for an 8-day period. These observations provide powerful evidence that productivity of Florida Bay is declining under current management practices.
