139. ZIEMAN, J.C., "Quantitative and Dynamic Aspects of the Ecology of Turtle 

 Grass, Thalassia testudinxm," Eetuavine Researahy Vol. 1, Oct. 1973, 

 pp. 541-562. 



Seagrasses bordering the temperate and tropical coastlines are a valuable 

 resource. Techniques were developed to measure the production and seasonal 

 dynamics of Thalassia testudinum. Production of leaf material varied from 0.3 

 to 10.0 grams dry weight per square meter per day in south Florida. Mean 

 values were 2.3 to 5.0 grams dry weight per square meter per day. Leaf growth 

 rates averaged 2 to 5 millimeters per day; maximum values exceeded 10 milli- 

 meters per day. The rhizomes of Thalassia were found 5 to 25 centimeters in 

 the sediment, and roots penetrated 4 to 5 meters. Leaves constituted 15 to 22 

 percent of the total plant biomass, and leaf standing crops were found from 30 

 to 650 grams weight per square meter, with average values of 126 and 280 grams 

 weight per square meter in inshore and offshore waters, respectively. Leaf 

 densities averaged 3,460 to 4,300 blades per square meter. Thalassia was 

 found to have an optimum temperature near 30° Celsius and an optimum salinity 

 near 30 parts per thousand. Standing crop varied by about 50 percent through- 

 out the year. 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 7 weeks. 



140. ZIEMAN, J.C, "Methods for the Study of the Growth and Production of 

 Turtle Grass, Thalassia testudinum Konig," Aquaaultuve, Vol. 4, No. 2, 

 Oct. 1974, pp. 139-143. 



Measurement of the productivity of vascular hydrophytes by gas exchange 

 methods is inaccurate due to the storage of gases within the leaves. A method 

 was developed for the study of turtlegrass (Thalassia testudinum), which 

 allows (a) the monitoring of the blade populations without disturbing the 

 plant, and (b) the determination of leaf growth and net production of the 

 blades, in addition to other biotic variables associated with the growth and 

 development of the plant. The technique involves the marking of individual 

 blades with a modified stapler, and the retrieval of the marked blades after a 

 2- to 3-week interval. The production measured is that which is readily 

 available as a nutrient source to the consumers of the Thalassia community. 



141. ZIEMAN, J.C., "Tropical Seagrass Ecosystems and Pollution," Tropical 

 Marine Pollution, E.J.F. Wood and R.C. Johannes, eds., Elsevier 

 Scientific Publishing Co., New York, 1975, pp. 63-74. 



This article provides a general discussion of seagrasses, their value to 

 the coastal ecosystem, and the effect that pollutants and stresses have on 

 seagrass beds. Halodule, Syringodium, Cymodocea, and Halophila are discussed; 

 Thalassia testudinum is emphasized as the species on which most information 

 has been collected. The adverse effects of dredging and filling, sewage, 

 changing temperature, and salinity on seagrasses are discussed. 



142. ZIEMAN, J.C, "Seasonal Variation of Turtle Grass, Thalassia testudinum 

 Konig, with Reference to Temperature and Salinity Effects," Aquatic 

 Botany, Vol. 1, June 1975, pp. 107-124. 



Although turtlegrass {Thalassia testudinum) is a tropical marine plant, 

 studies show it undergoes seasonal fluctuations. Maximum values of pro- 

 ductivity, standing crop, leaf length, blade density, and other biotic vari- 

 ables are reached in the warmer summer months. Thalassia has a temperature 



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