Seagrasses in Dire Straits

By Heath, David

Seagrasses, an ecologically important group of flowering plants that have adapted to life submerged in seawater, are in dire need of a targeted global conservation effort to protect them and lhc services they provide, according to an international team of scientists. In the December issue of BioScience, the researchers note the critical roles seagrasses play in coastal systems and how a set of anthropogenic perturbations have contributed to large-scale losses of the plants worldwide.

Existing along at least one coastline of every continent except Antarctica, seagrasses and the meadows they form serve as important food sources and habitat for many animals, protect coastlines by stabilizing sediments, and sequester a large amount of carbon. (An acre of seagrass sequesters the equivalent in carbon dioxide emissions of a car driving 3.860 miles.)

A seagrass die-out can be a harbinger of larger problems, providing “resource managers advance signs of deteriorating ecological conditions caused by poor water quality and pollution,” says coauthor William Dennison, a vice president of and professor at the University of Maryland Center for Environmental Science.

Although seagrass populations have naturally fluctuated over their 70 million to 100 million-year existence, “the very gradual changes in environmental conditions over the history of seagrass evolution are overshadowed by current changes to the coastal zone resulting from increased human pressures,” including increased nutrient and sediment runoff, hydrological alterations, and commercial fishing practices, the authors write.

Many beachgoers have likely seen the remnants of seagrasses on the sand and may have mistaken the plants-which have roots, stems, and leaves-with seaweed, all species of which are algaes. Television viewers may have caught a glimpse of them in undersea educational programs as endangered animals such as manatees or green sea turtles eat them or as fish swim among them-but for the most part, they are given short shrift in the media in terms of marine ecosystem importance, and, according to the researchers, this is part of the problem.

“Translating scientific understanding of the value of seagrass ecosystems into public awareness, and thus effective seagrass management, has not been as effective as for other coastal ecosystems, such as salt marshes, mangroves, or coral reefs,” says coauthor Robert Orth, a professor at the Virginia Institute of Marine Science. “Elevating public awareness about this impending crisis is critical to averting it,” Orth adds.

-BioScience, December; and University of Maryland Center for Environmental Science press release and fact sheet, 1 December. (D.H.)

Copyright Heldref Publications Jan/Feb 2007

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