TAYLOR. SALOMAN. and PREST: REGROWTH OF TURTLE GRASS 



LEAF GROWTH AND REGROWTH 

 AFTER HARVEST 



Growth of turtle grass foliage and ultimate 

 leaf length are largely controlled by water tem- 

 perature and depth (Phillips, 1960; Strawn, 

 1961 ) . In Tampa Bay, turtle grass normally ex- 

 hibits a seasonal growth cycle in which leaves 

 elongate rapidly from April to July and die back 

 to short stubble between October and March. 

 During the period of maximum leaf growth, 

 blades develop at a rate of 5 cm per month or 

 more and reach a total length of about 30 cm 

 (Figure 1). Leaves harvested in the growing 

 season had an equivalent or greater rate of 

 regrowth and reached the height of uncut plants 

 in about 2 months ( Figure 1 ) . Observed growth 

 rates of both cut and uncut leaves were compar- 

 able to figures previously reported from southern 

 Florida by Thomas et al. (1961) and Zieman 

 (1968). Furthermore, harvesting had no ap- 

 parent influence on production of new leaves. 

 For each month, the average number of shoots 

 produced by both cut and uncut plants was 

 nearly the same (Figure 2). 



Thus, from a comparison of leaf growth and 

 new leaf production among cut and uncut plants, 

 it seems likely that turtle grass in the Tampa Bay 



8> 

 i 



Figure 2. — Average monthly number of new shoots per 

 leaf cluster for cut and uncut turtle grass plants sam- 

 pled in Boca Ciega Bay (Tampa Bay), Fla., between 

 August 1968 and November 1969. 



area can be harvested twice each year without 

 adversely influencing plant vigor. 



DISCUSSION 



Our findings show that turtle grass beds can 

 sustain periodic cutting without apparent dam- 

 age at intervals of about 2 months in the growing 

 season. In deeper or warmer waters of the Gulf 

 and Caribbean where turtle grass has a longer 

 growing season, it may be practical to harvest 

 leaves more than twice per year. Inherent, tech- 

 nical problems presented by off"shore harvesting 

 would probably be offset by the fact that turtle 

 grass in deep water generally has longer leaves 

 and greater biomass than plants growing in shal- 

 low areas (Burkholder et al., 1959; Phillips, 

 1960). 



Offshore along the west coast of Florida esti- 

 mates show that turtle grass grows over about 

 4 million acres of the sea floor, and in the Car- 

 ibbean, turtle grass resources are even greater. 

 Thus, the tonnage of turtle grass available for 

 harvest is very large (Bauersfeld et al., 1969). 

 However, from the standpoint of resource man- 

 agement, there are a number of questions that 

 must be resolved before the harvest of turtle 

 grass can be seriously considered by commercial 

 enterprises. Principal queries include: (1) can 

 turtle grass leaves regrow normally after more 

 than two seasons of harvesting; (2) how are 

 other plant and animal members of the turtle 

 grass community influenced by harvesting op- 

 erations; (3) what would be the consequences 

 of removing vast amounts of primary production 

 from the food webs in coastal waters; (4) would 

 removal of foliage cause serious erosion of sed- 

 iments in and around turtle grass beds; and (5) 

 how would harvesting methods alter water clar- 

 ity, and thereby influence populations of phyto- 

 plankton and pelagic fishes, and water recre- 

 ation ? 



LITERATURE CITED 



Bauersfeld, P., R. R. Kifer, N. W. Durrant, and 

 J. E. Sykes. 



1969. Nutrient content of turtle grass {Thalassia 

 testudinum). Proc. Sixth Int. Seaweed Symp., 

 Madrid, p. 637-645. 



147 



