CHAPTER THREE AFFECTED ENVIRONMENT 



I. MARINE ENVIRONMENT 



A. LOCATION 



Looe Key Reef is a submerged section of the Florida Reef Tract located 

 12.4km (6.7 nm ) southwest of Big Pine Key in the lower Florida Keys at 

 latitude 24°, 33' north and longitude 81°, 24' west. It is bounded on the 

 south by the Straits of Florida and on the north by Hawk Channel. (See 

 Figure 1) 



The Florida Reef Tract extends from the Miami area southwesterly, paral- 

 leling the Florida Keys and terminating in the Dry Tortugas. The most seaward 

 portion, or Outer Reef Tract, lies to the east and south of the emergent 

 Keys at a distance of from 4.8 to 11.3 km (2.6 to 6.1 nm). Beyond the 

 outer reef, the bottom slopes gradually for a few miles and then drops sharply 

 to about 900 meters in the trough of Florida Straits. 



Although the reef tract extends for a linear distance of approximately 

 370 km (200 nm) , it is actually composed of a chain of individual living 

 reefs separated from each other by considerable areas which do not contain 

 living coral formations. According to Marszalek, et al (1977), approximately 

 96 km of outer bank reefs occur between Fowey Rocks Lighthouse near Miami 

 and the Marquesas Keys west of Key West, a distance of 270 km. The existence 

 of these living reefs in this latitude is, to a great extent, a result of 

 the proximity of the Florida Current, which carries warm, clear water of 

 normal salinity northward along the seaward edge of the outer reef. 



The most extensive living reef areas occur in the northern portion of 

 the tract, while in the southern sector, well developed reefs are generally 

 smaller and are separated from each other by greater distances than those of 

 the northern tract. Between the outer reef and the emergent Florida Keys, 

 there exists a broad, shallow platform with an average water depth less than 

 ten meters. This area is known as Hawk Channel and contains more than 6,000 

 patch reefs (Marzalek et aT_, 1977). 



B. ENVIRONMENTAL SETTING 



Coral reefs occur in clear, tropical waters, and tolerate only minor 

 fluctuations of physical and chemical oceanographic parameters. Kissling 

 (1975) has measured some of these parameters over a four year period for the 

 Looe Key Reef area. 



Maximum and minimum amplitudes for the mixed, semidiurnal tides are 80 

 cm and 20 cm, respectively. Dissolved oxygen content of surface water varies 



45. 



