two water bodies would result in an 

 overall benefit. 



Davis (1977) stated that there 

 have been changes in the salinity of the 

 estuarine areas of the Everglades frorr 

 to 12 ppt prior to 1940, up to 25 to 

 40 ppt presently. This has probably 

 changed the nursery ground function of 

 affected areas, but the nature of the 

 changes is not know n. 



Numerous years of data show that 

 the year-class strength of redfish in 

 Florida Bay proper is positively corre- 

 lated to high salinities in the spring, 

 whereas the year-class strength of sea 

 trout is positively correlated to low sa- 

 linities in the spring. Alterations in 

 springtime salinity might constitute a 

 tradeoff between the population levels 

 of these two fishes. 



Pink shrimp and spiny lobster pro- 

 vide the two largest commercial catches 

 in Florida. They are both highly de- 

 pendent upon Florida Bay as a nursery. 

 Recreational species, such as bonefish 

 and tarpon, are also wery dependent 

 upon Florida Eay as a nursery. The 

 effect of salinity changes in the produc- 

 tion of these important commercial and 

 recreational organisms is not known 

 (Davis 1977). 



It has been observed by Davis 

 (1977) that the best coral reefs along 

 the Florida Keys occur at the northern 

 extremity where exchange of water with 

 Florida Eay has always been minimal. 

 John Pennecamp National Underwater 

 Preserve is known worldwide and is lo- 

 cated in this area. Coral is known to 

 be very sensitive to altered salinities, 

 temperature fluctuations, and turbidity 

 and siltation. Waters flowing from Flor- 

 ida Bay to the Atlantic Ocean through 

 the Keys' channels are high in salinity, 

 have large temperature fluctuations and 

 are relatively turbid and silty due to 

 wave action in shallow areas. If water 

 circulation was increased between Flor- 

 ida Bay and the Atlantic Ocean, there 

 might be resultant impacts upon coral 

 reef communities. 



The FDOT has agreed to conduct a 

 two-phase study of the possible causes 



of a potential remedial action for the 

 hypersalinity problem in Florida Bay. 

 The first phase will include studies to 

 determine the relative contribution tc 

 the hypersalinity of the causeway area, 

 natural physical processes, channeliza- 

 tion of the Everglades, and other fac- 

 tors. It will also determine the possible 

 results of various measures to alleviate 

 the problem. The second phase of the 

 study will be to project the biological 

 consequences of possible remedial 

 actions, such as increasing the flow be- 

 tween the Keys. 



Another major concern regarding 

 the project is that valuable turtle grass 

 beds will be directly and indirectly (sil- 

 tation) affected by dredging. After 

 several meetings it was agreed that 

 FDCT would mitigate turtle grass losses 

 acre for acre (Bailey 1977, Hall 1977). 

 The FDOT has conducted a study to de- 

 lineate the turtle grass beds as they 

 presently exist. A comparable study 

 after construction will define the acres 

 of turtle grass that will be mitigated. 



Most of the shoals bordering the 

 Keys contain flat limestone bottoms 

 which do not have unconsolidated sedi- 

 ments and are, therefore, not suitable 

 for turtle grass growth. During an in- 

 terview with F. Bingham of the Florida 

 Department of Transporation, it was 

 pointed out that some of the best turtle 

 grass beds in the Keys are in the old 

 borrow pits which resulted from the 

 construction of the railroad and original 

 causeway (Figure 55). The depth of the 

 borrow pits fosters sedimentation of or- 

 ganic material which serves as an excel- 

 lent turtle grass substrate. It is not 

 known, however, how long it takes for 

 the turtle crass to establish itself in 

 borrow pits" (Hall 1977). The depth of 

 the borrow pit probably affects its suit- 

 ability for turtle grass growth and the 

 time period necessary for turtle grass 

 establishment. The acre-for-acre mitiga- 

 tion of turtle grass beds might possibly 

 be accomplished by dredging a flat lime- 

 stone bottom and allowing sedimentation 

 and turtle grass establishment. 



Environmental concerns surround- 

 ing the bridge replacement are many. 

 Nearfield effects are somewhat classical 



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