FISHERY BULLETIN: VOL. 71, NO. I 



Ecologists have shown that the turtle grass 

 community exhibits great biological diversity 

 and forms the basis of an extremely stable 

 and productive ecosystem (Margelef, 1962; 

 Odum, 1967). Its roots and rhizomes penetrate 

 the bottom down to 25 cm or more in a matlike 

 network that effectively binds and holds sedi- 

 ments and detritus against erosion, and provides 

 a unique habitat for many benthic invertebrates 

 (Bernatowicz, 1952; Voss and Voss, 1955 

 Ginsburg and Lowenstam, 1958; Phillips, 1960 

 Strawn, 1961; Thomas, Moore, and Work, 1961 

 O'Gower and Wacasey, 1967; Hartog, 1970). 

 The broad, elongate leaves of turtle grass have 

 a surface area of about 18 m^ for each square 

 meter of sediment they occupy, and usually rep- 

 resent a standing crop in excess of 1 metric ton 

 (dry weight) per acre (Phillips, 1960; Gessner, 

 1971 ) . Furthermore, leaves of turtle grass mod- 

 erate water movements, offer attachment sites 

 for various algae and sessile invertebrates, and 

 serve as a feeding ground, shelter, and nesting 

 area for many fishes and motile invertebrates 

 (Humm, 1964; Stephens, 1966). The rich mi- 

 crobial biota that reduces and recycles much of 

 the organic production from turtle grass beds 

 has been recently described by Fenchel (1970). 



PROCEDURE 



Turtle grass leaves were harvested in August 

 and October 1968 and in July and September 

 1969. The cutting was done within a 30 m^ ex- 

 perimental plot in lower Boca Ciega Bay (Tampa 

 Bay), Fla., where the standing crop of turtle 

 grass on a dry, whole weight basis was 1,198 

 g/m- (Taylor and Saloman, 1968) . The harvest- 

 ing machine was designed and constructed by 

 personnel at the Fisheries Service laboratory in 

 College Park, Md., and consisted of an adjustable, 

 motor-driven sickle bar mounted on a small, sty- 

 rofoam barge. The cutting head was set about 

 10 cm above the bay bottom, and the barge was 

 directed by hand as water depth was little more 

 than 1 m at high tide. 



Between harvests, weekly samples of at least 

 100 leaves were picked from plants dug by shovel 

 within the experimental plot and from uncut 

 plants that served as controls in the surrounding 

 area. The point of leaf removal was at the leaf 

 node. Leaf length was measured from both sam- 

 ple sets, and as an additional measurement of 

 plant vigor, the number of new shoots per leaf 

 cluster was also recorded from each set. 



1968 



1969 



Figure 1. — Average monthly length of turtle grass leaves from cut and uncut plants, and related 

 water temperatures in Boca Ciega Bay (Tampa Bay), Fla., between August 1968 and November 1969. 



146 



