Heavy metal concentrations (Pb, 

 Hg, Cr, Co, and Zn) to the seaward 

 side of the upper Keys follow the 

 same pattern as described for the 

 upper Keys lagoonal (bayward) en- 

 vironment (Manker 1975). Metal 

 concentrations are similar in both 

 suspended particulates and the four- 

 micron fraction of the bottom sedi- 

 ments. Concentrations in both frac- 

 tions greatly exceed the concentra- 

 tions in the bulk sediment. Areas 

 of higher heavy metal concentration 

 correlate with high population den- 

 sity, automotive and boat traffic, 

 and improperly monitored and main- 

 tained sewage disposal systems 

 (Manker 1975). In all cases, a boat 

 basin/marina located in the John 

 Pennekamp State Park exhibited the 

 highest heavy metal concentration 

 observed in bulk sediment. Manker 

 (1975) attributes this to gas com- 

 bustion by-products, improper waste 

 disposal (boats), and stormwater 

 runoff. For the bulk sediment 

 samples taken from the seaward side 

 of the upper Keys (excluding the 

 boat basin/marina), chromium (Cr), 

 cobalt (Co), and zinc (Zn) did not 

 exceed background levels except for 



a small nearshore area adjacent 

 to where U.S. Highway 1 joins the 

 Florida Keys. 



Lead (Pb) and mercury (Hg) ex- 

 hibit high concentrations (exceeding 

 background levels of 19 ppm and 0.2 

 ppm, respectively) at four general 

 areas: (1) nearshore of Plantation 

 and Tavernier Keys; (2) BiscayneBay 

 to the reef tract; (3) where U.S. 

 Highway 1 joins the Keys; and (4) in 

 the John Pennekamp boat basin/mari- 

 na. Concentration of all heavy 

 metals in the marina are three to 

 seven times the observed background 

 levels. Table 21 shows heavy metal 

 concentrations in live and dead 

 corals from several reefs (Hen and 

 Chickens Reef) along the upper reef 

 tract. Based on this data, Manker 

 (1975) speculates that: (1) reef 

 damage in the upper Florida Keys and 

 Biscayne Bay area is caused by the 

 influx of chilled waters associated 

 with cold frontal passage, and sec- 

 ondarily to toxic metals; and (2) 

 depauperate macrophytic communities 

 in the John Pennekamp State Park 

 boat basin/marina "may" be a result 

 of toxic metal contamination. 



Location (North to South) 



Fowey Rocks 



Triumph Reef 



Pacific Reef 



Carysfort Reef 



Elbow Reef 



Molasses Reef 



Hen & Chickens (Live Corals) 



Hen & Chickens (Dead Corals) 



Ha 



Cr 



Co 



Zn 



Table 21. Concentration (ppb) of heavy metals mercury, chromium, cobalt, 

 and zinc in corals from the upper Keys reef tract (adapted from 

 Manker 1975). 



105 



