SEA 



SCIENCE 



Brant Touchette examines eelgrass growing in controlled 

 environments. 



"Eelgrass doesn't follow that model. 

 Just why it has not evolved a mechanism to 

 shut down at night is a question for another 

 day," he muses. 



Contributing factors 



A widespread eelgrass die-off stunned 

 scientists in the early 1930s. The so-called 

 "Wasting Disease" decimated about 90 

 percent of all eelgrass in northern Atlantic 

 waters. On the east coast, the eelgrass 

 growing range extends from the Arctic Circle 

 to North Carolina. 



Scientists have proposed many theories 

 as to the cause — bacteria, fungus, and mold. 

 But the literature records several previous 

 eelgrass declines, and some suggest that 

 periodic sunspots might be to blame. Others 

 have correlated periods of above average 

 precipitation with the decline, while still 



others have suggested 

 the decline could be 

 drought-related. 



Another theory 

 points to increased 

 water temperatures as 

 a contributing culprit 

 — something that 

 Touchette also 

 considered in his 

 recent research. 



His lab experi- 

 ments show that an 

 increased temperature 

 can reduce eelgrass 

 shoot density by about 

 40 percent. Tempera- 

 ture also may decrease 

 leaf and root develop- 

 ment, and may alter 

 internal carbon and 

 nitrogen compositions. 



But Touchette is 

 not ready to draw any 

 correlation between 

 global warming and 

 the current decline of 

 eelgrass. "The jury is 

 still out on that," he 

 says. 



However, he is willing to stick his neck 

 out and name names when it comes to 

 contributing factors to nutrient loading and 

 eelgrass loss. 



"There is an obvious need to control 

 point and nonpoint pollution. Better 

 stormwater management is a big step, since 

 historically storms mean high concentrations 

 of nitrogen in runoff," Touchette says. Also, 

 sediments, which begin as ammonia 

 compounds, may oxidize into nitrate in the 

 water column. 



A National Research Council report 

 states that more than 60 percent of U.S. 

 coastal rivers, estuaries and bays are 

 moderately to severely degraded by nutrient 

 overenrichment, says Burkholder, co- 

 investigator of Touchette' s eelgrass research. 



She says that Touchette' s findings are 

 important in helping scientists, coastal 



managers and concerned citizens understand 

 that eelgrass, a valuable seagrass on the U.S. 

 Atlantic coast, is extremely sensitive to 

 nitrate pollution. 



"From bypasses of raw sewage into 

 coastal waters during moderate rainstorms, 

 to poorly treated animal wastes that spill into 

 waterways, to urban runoff from our 

 sprawling and densely populated coastal 

 cities, water pollution control should be a 

 much higher priority," Burkholder says. 



"Some may say it's impossible to 

 eliminate all sources of pollution," Touchette 

 observes. "It's true that pollution is not easily 

 managed. But one of the many consequences 

 of not trying to do more could be the 

 disappearance of eelgrass beds, along with 

 many of the economically important fisheries 

 they host." 



Eelgrass evolved long ago before 

 modern levels of pollution existed, explains 

 Burkholder. Eelgrass forms underwater 

 meadows where young fish can hide from 

 predators and find a wealth of food to eat. 



"The enormous surface area provided by 

 these plants also acts as a highly efficient 

 biological filter that removes harmful 

 pollutants from the water, helping to protect 

 fish health. Whether we live along the coast 

 or inland, we all depend on eelgrass meadows 

 to produce many of the marine fish that we 

 use for food," says Burkholder. 



Essential habitat 



There's a growing body of data to show 

 the importance of eelgrass and other 

 submerged aquatic vegetation in the lifecycle 

 of commercial and recreational fish, says 

 Carrie Selberg, a habitat specialist with the 

 Atlantic States Marine Fisheries Commission 

 in Washington, D.C. 



"Essential fish habitat is more than a 

 buzz phrase," she says. "Many fish spend part 

 of their lives in seagrass habitat. For some it's 

 a place of refuge where they can find cover 

 from prey. Others dine on the organisms 

 trapped on waves of grass. Some species 

 spawn in the quiet waters." 



Selberg, who earned her master's degree 

 in 1999 from Duke University's Nicholas 



24 HOLIDAY 2002 



