more difficult to take Redfish Bay 

 plants and place them in the highly 

 saline Laguna Madre than to place Laguna 

 Madre plants in Redfish Bay, but the 

 conclusion is that Halodule is an adapt- 

 able plant. 



Little is known about light re- 

 quirements of Halodule . The species 

 seems to be principally an intertidal 

 plant, extending perhaps to 1.5 to 2.0 m 

 (5.0 to 6.5 ft) deep, although I have 

 seen some plants growing in deeper wa- 

 ter. In the northeast Gulf of Mexico 

 off Apalachicola in Florida, I have ob- 

 served Halodule from 5 to 6 m (16 to 20 

 ft) deep. Halodule appears to tolerate 

 a more sandy substrate than will Thalas- 

 sia . 



The optimum temperatures for eel- 

 grass seem to lie between 10°C to 20°C 

 (50°F to 68°F). In Puget Sound, eelgrass 

 grows in a range of water temperatures 

 from 6°C (43°F) in winter to 18°C (64°F) 

 in summer in some shallow bays. In Rhode 

 Island, strains of eelgrass tolerate 

 25°C (77°F to 82°F) in summer. Eelgrass 

 dies at 18°C to 20°C (64°F to 68°F) in 

 Puget Sound and at 25°C to 28°C (47°F to 

 82°F) in Rhode Island. Eelgrass probably 

 forms different temperature races in 

 different areas; if that is correct, it 

 could influence survival when plants are 

 transplanted over too great a distance. 

 Salinity optima for eelgrass seem to 

 range from 20 °/oo to 35 °/oo, even 

 though in the Baltic Sea the salinity 

 can be as low as 6 °/oo. Again, it is 

 possible that Baltic Sea eelgrass is a 

 different strain from eelgrass else- 

 where. The best eelgrass growths in Pu- 

 get Sound are found from 7 to 10 m (23 

 to 33 ft) deep; reports of eelgrass ex- 

 tending to 30 m (98 ft) deep exist for 

 the Mediterranean Sea and off San Diego 

 in the San Diego Trench. Eelgrass pre- 

 fers a substrate of silty sand, but I 

 have not seen eelgrass, nor any other 

 seagrass, growing in pure sand. Eelgrass 

 will tolerate some sedimentation, but I 

 am not aware of studies defining sedi- 

 ment tolerances for the species. 



The range of Thalassia and Halodule 

 begins in Venezuela or perhaps as far 

 south as Brazil, and extends northward 

 around the Gulf of Mexico to Cape Canav- 

 eral, Florida. There is a disjunct pop- 

 ulation of Halodule at Beaufort, North 

 Carolina. 



Eelgrass grows from Cape Hatteras, 

 North Carolina, northward to the south- 

 ern tip of Greenland, with the best 

 growths extending from New Jersey to 

 Nova Scotia. On the west coast there 

 are eelgrass populations in the Gulf of 

 California, but better growths begin 

 near the middle of Baja, California, and 

 extend northward to the Bering Sea in 

 the Arctic Circle. 



TRANSPLANTATION WORK 



Background 



Seagrass transplantation programs 

 to date have been concerned with three 

 seagrass species, Halodule wrightii and 

 Thalassia testudinum in the Gulf of Mex- 

 ico and southern Florida, and eelgrass 

 in the north temperate zone on both 

 coasts. Van Breedveld (1975) reported 

 several transplant experiments using 

 manateegrass ( Syrinqodium filiforme ) 

 near St. Petersburg, Florida. Previous 

 field observations and experimental work 

 indicate that in the tropical system 

 Halodule is a pioneer plant and Thalas- 

 sia is a climax plant. In the temperate 

 zone eelgrass is both a colonizing and a 

 climax species. 



My studies on transplanting sea- 

 grass had two overall objectives. The 

 first was to investigate basic biologi- 

 cal problems in seagrasses, such as in- 

 traspecific variation, phenotypic plas- 

 ticity, adaptations to the environment, 

 and physiology. The second objective 

 was to develop transplanting techniques 

 which will allow an accelerated recovery 

 of damaged meadows such as occurred on a 

 massive scale from 1931 to 1933, when 

 90% to 99% of all the eelgrass in the 

 North Atlantic disappeared. The malady 

 was called the wasting disease and was 

 attributed to a small mycetozoan organ- 

 ism. Scientists now believe that this 

 die-off was caused by a slightly upward 

 shift in water temperatures during that 

 period, during which the plants were 

 secondarily weakened. Plants unable to 

 adjust to the temperature change died. 

 In toth Europe and the United States 

 research showed that it took 30 yr for 

 full natural recovery of the meadows. 

 Managers are trying to speed up the 

 normal recovery time by using trans- 

 plants. 



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