not only vary on a short-term tempo- 

 ral level but spatially as well- 

 Lloyd (1964) observes temperatures 

 on the same day as much as 2°C 

 (3.6°F) higher over shallow calcare- 

 ous mud-bank shoals or 2°C (3.6°F) 

 lower in nearby "lakes" as compared 

 to the mean water temperature. This 

 spatial quality is also reflected in 

 the annual temperature range. Gins- 

 burg (1956) reports water tempera- 

 tures of shallower areas ranging 

 from 19° to 38°C (66° to 100°F) 

 annually while deeper waters around 

 mud banks ranged from 20° to 30° 

 (68° to 90°F). 



Variation of pH and Eh is tied 

 to organic activity and temperature, 

 and therefore varies in a similar 

 pattern as described for temperature 

 (Lynts 1966, Multer and Hoffmeister 

 1968). Diurnal pH changes in the 

 Key's littoral marine environment 

 range from a pH of 7.4 to 9.2, and 

 in the freshwater environment from a 

 pH of 6.5 to 10.0. This daily fluc- 

 tuation is related to photosynthesis 

 and respiration (P/R) processes 

 which control the uptake (photosyn- 

 thesis) and release (respiration) 

 of C02. These processes attenuate 

 the CaC03 (calcium carbonate) 

 equilibrium which modifies the wa- 

 ter's alkalinity and therefore its 

 pH. 



Turbidity varies a great deal 

 in the nearshore bay environment of 

 the upper Keys. Important variables 

 controlling the level of turbidity 

 include: (1) water body axis and 

 orientation; (2) bottom morphology 

 (depth); (3) sediment type; and (4) 

 wind direction, duration, and speed 

 (Chesher 1974, Griffin 1974, Manker 

 1975). Manker (1975), monitoring 

 turbidity at several nearshore loca- 

 tions on the bay side of Plantation 

 Key and Key Largo, found suspended 

 particulate concentration (turbid- 

 ity) to be 2 to 3 times greater in 



lagoonal environments than in the 

 reef tract areas. Within the bay 

 side environment, stations sheltered 

 from the prevailing winds by man- 

 grove capped mud banks exhibit tur- 

 bidities ranging from 0.38 mg/l to 

 1.95 mg/l. Exposed or open stations 

 monitored on the same day with simi- 

 lar wind direction and speed exhibit 

 turbidities ranging from 2.95 mg/l 

 to 7.30 mg/l. 



The only study reviewed that 

 examines water quality bayward of 

 the Florida Keys, outside the realm 

 of the basic physiochemical para- 

 meters previously discussed, is 

 Manker's (1975) examination of heavy 

 metals in the suspended particulates 

 and bottom sediments. In general, 

 the heavy metals lead (Pb), mercury 

 (Hg), chromium (Cr), cobalt (Co), 

 and zinc (Zn) are found to be equal- 

 ly concentrated in the fine suspend- 

 ed particulates and the fine (four 

 micron) fraction of the bottom sedi- 

 ments, and much less concentrated in 

 bulk sediment. Manker (1975) notes 

 that the fines are very susceptable 

 to resuspension and, because of the 

 greater concentration of heavy met- 

 als, provide a potential mechanism 

 for conveying these substances out 

 of the area and onto the reef tract. 

 The greatest values reported corre- 

 late with areas of increased human 

 activity (boating and vehicular) and 

 population density. In additon to 

 the routine sampling program, an 

 additional bottom sediment sample 

 was taken from the bay side of 

 Tavierner Key from a stormwater 

 pipe providing drainage for U.S. 

 Highway 1. This sample exhibited 

 extremely high levels of metal 

 contamination; concentrations of 

 chromium and cobalt were 1.5 to 2.0 

 times concentrations reported at all 

 other stations, 5 times greater for 

 mercury, 10 times greater for lead, 

 and 50 times greater for zinc. 



98 



