M 15 



Figure 8. Depth distribution of four seagrasses on the northwest coast of Cuba. 1 = 

 Thalassia testudinuin , 2 = Syringodiun f i1 i forme , 3 = Halophila dec i pi ens , 4 = h[. engel- 

 manni (from Busea 1975). Although Syringodium is quite abundant in certain localities, 

 note the preponderance of Thalassia biomass and the absence of Halodule on the Cuban 

 coast. 



bays of south Florida, the turbidity and 

 therefore the maximum depth for rooted 

 plants can vary over short distances. 

 Phillips (1960) recorded turtle grass 

 ranging from 10 to 13 m (33 to 43 ft) in 

 depth. In the relatively clear waters of 

 the back reef areas behind the Florida 

 Keys, turtle grass is common to 6 or 7 m 

 (20 or 23 ft) and occurs down to 10 m (33 

 ft); by contrast, in the relatively turbid 

 portion of the "lakes" of Florida Bay, 

 maximum depths of only 2 m (7 ft) are 

 common. 



2.10 EXPOSURE 



The seagrasses of south Florida are 

 all subtidal plants that do not tolerate 



exposure well. Exposed leaf surfaces will 

 lose water constantly until dry, and there 

 is no constraint to water loss that would 

 limit drying (Gessner 1968). Although 

 exposure to the air definitely occurs at 

 certain low tides on shallow turtle grass 

 or shoal grass flats, unless it is 

 extremely brief, the exposed leaf surfaces 

 will be killed. 



Following exposure, the dead leaves 

 are commonly lost from the plant. Rafts 

 of dead seagrass leaves may be carried 

 from the shallow flats following the 

 spring low tides. Normally the rhizomes 

 are not damaged and the plants continue to 

 produce new leaves. 



19 



