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Study Highlights Oceans’ Steadily Vanishing Seagrass

Posted on: Saturday, 4 July 2009, 08:30 CDT

A new study has shed light on the extent and causes behind the oceans’ quickly vanishing seagrass meadows, a vital resource for thousands of species of marine life.

In the study published this week in the Proceedings of the National Academy of Sciences, researchers reported that 58 percent of the world’s seagrass meadows have been shrinking at a rate of about 7 percent a year since 1990.  Scientists based their conclusions on data from over 200 surveys and some 1,800 observations dating as far back as 1879, which show seagrass meadows disappearing at a pace similar to that of rainforests and coral reefs.

“Seagrasses are disappearing because they live in the same kind of environments that attract people,” explained co-author of the report James Fourqurean of Florida International University.

“They live in shallow areas protected from large storm waves, and they are especially prevalent in bays and around river mouths.”

Marine biologists say that seagrass plays a vital role in marine ecosystems.  Breaking-down and processing waste, stabilizing sediment on the seabed, and providing food and shelter to countless species of marine life are just a few of the functions of seagrass, which fills a niche in the aquatic world comparable to that occupied by plants and fungus in terrestrial biomes.

Scientists are blaming global climate change as one of the critical factors contributing to the decline of seagrass, which they say is sensitive to the rising ocean levels and warming water temperature caused by greenhouse gases. 

But researchers are also pointing to another man-made problem that may be having a more immediate effect on seagrass’ ability to thrive.  Ocean water made cloudy by pollution from coastal industry is able to transmit less sunlight to the photosynthetic plants, ultimately restricting the depth at which they are able to grow .

Not Just An Environmental Concern

Conservationists are not the only people who have cause for concern over vanishing seagrass meadows.  The marine vegetation is also home to a number of commercially valuable fish like the tarpon, permit and bonefish.  One recent study estimated that every 2.5 acres of seagrass has an annual economic value of roughly $3,500.

“Seagrass beds are at least as economically and ecologically important as tropical forests or coral reefs,” explained Fourqurean.

The transnational study estimated that nearly 20,000 square miles of seagrass have been eradicated in the last 130 years—more than 25 percent of the global total of roughly 68,350 square.

“Globally, we lose a seagrass meadow the size of a soccer field every thirty minutes,” said co-author William Dennison of the University of Maryland.

Experts say that the industrial revolution of the late 19th century led to rapid development of coastal regions and, in turn, the large-scale destruction of seagrass meadows throughout much of North America and Europe.

In modern times, explosive population growth and industrial expansion in regions like Southeast Asia are mirroring the heavy loss of seagrass seen in Europe and America at the turn of the 20th century.

Fourqurean explained that experimental efforts to restore seagrass meadows have shown promising signs of success.  One municipality in Florida, for example, simply changed their methods for treating wastewater and within years surrounding seagrass meadows had rebounded measurably.


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National Academy of Sciences

University of Maryland

Florida International University

Source: redOrbit staff

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