II-D-6 



Zieman, J.C. 1975. Quantitative and dynamic aspects of the ecology of 



turtle grass, Thalassia testudinum . Pages 541-562 jin_ L.E. Cronin, ed., 



Estuarine research, Vol. 1. Academic Press, New York. 



In recent years the vast beds of sea grasses bordering the temperate 

 and tropical coastlines have been recognized as a valuable resource. 

 Techniques were developed to measure the production and seasonal dynamics 

 of Thalassia testudinum , the dominant marine grass of the Caribbean. 

 Conventional productivity measures are subject to error from gas 

 storage within the leaves. Production of leaf material varied from 

 0.3 to 10.0 g dry wt m"^ day"^ in the south Florida area, with mean 

 values of 2.3-4.0 g m~^ day"'. Leaf growth rates averaged 2-5 mm 

 day"^ with maximum values exceeding 10 mm day"^ . The rhizomes of 

 Thalassia were found 5-25 cm in the sediment, and roots penetrate 

 to 4-5 m. Leaves constituted 15-22 percent of the total plant biomass, 

 and leaf standing crops were found from 30-650 g dry wt m"^, with average 

 values of 126 and 280 in inshore and offshore waters, respectively. 

 Leaf densities averaged 3460-4300 blades per m^. Standing crop varied 

 by about 50 percent throughout the year, with leaf decreases during 

 flower and fruit production and again in the fall. Thalassia produced 

 about 6.8 crops of leaves per year. Few were directly grazed. The 

 leaves decayed rapidly, losing 65 percent of their original weight 

 in seven weeks. Drying and agitation greatly accelerated decomposition. 

 Turtle grass contributes to the maintenance of the high production of 

 ■ estuaries in many other ways also. (A. A.) 



Keywords: turtle grass, Thalassia testudinum , seagrasses, primary 

 productivity, Florida 



E. Growth Factors, Nutritive Value, and Weight 



II-E-1 



Joanen, T., and L.L. Glasgow. 1965. Factors influencing the establishment 

 of wigeongrass stands in Louisiana. Pages 78-92 ui^ Proceedings of the 

 nineteenth annual conference of the Southeastern Association of Game 

 and Fish Commissioners. 



A study of the factors that influence the establishment of natural 

 and artificial stands of wigeongrass ( Ruppia maritima ) was conducted 

 on Rockefeller Refuge during 1962-63. Physical, chemical and biotic 

 factors were investigated; growth was measured monthly and germination 

 tests of wigeongrass seed were carried out. 



Physical factors such as turbidity, fluctuating water levels, and 

 water depth were found to be controlling factors in the establishment 



80 



