UW News

November 16, 2004

Ocean ecosystems at risk if plug pulled on Mother Nature’s ‘blenders’

News and Information

The loss of seemingly inconsequential animal species in the top 6 inches or so of mud and sediment on the floors of the world’s oceans is giving scientists a look ahead at the consequences of the steady decline of the Earth’s biodiversity.

Animals such as clams, brittlestars and marine worms churn up and fill the seafloor sediments with oxygen, making it possible for other forms of marine life to flourish, according to University of Washington assistant professor of biology Jennifer Ruesink, co-author of a paper in the Nov. 12 issue of the journal Science.

“Bottom-living marine species — usually out of sight, out of mind — have an essential role in determining the life-sustaining functions of the planet,” Ruesink says.

Considering the present trend in human activities in coastal waters — such as overfishing, habitat destruction and pollution — the researchers say the subsequent extinction of seafloor dwelling species is expected to reduce the amount of churning, or bioturbation, that occurs. The amount of change, they calculate, depends on the reasons species are going extinct and the order in which animals disappear.

“We know certain types of species are at greater risk of extinction than others,” says Bradley Cardinale, another co-author from the University of Wisconsin-Madison. “For example, large species often go extinct first, and that is important in the marine benthic environment because the bigger you are, the more sediment you are able to mix up.”

The new study rests on a comprehensive survey led by Martin Solan of the University of Aberdeen, Scotland, of 139 marine invertebrates that inhabit the sediment of Galway Bay, Ireland. By looking at how extensively the sediments are mixed there, and matching that with data on each species’ size, abundance and movement through the mud, it is possible to construct mathematical models to predict the ecological consequences of losing species.

Ruesink did most of the modeling for the group.

“It is important to consider the characteristics of particular species because they are not usually able to substitute for each other in what they contribute to the environment and, in this case, some have much higher impacts than others,” Ruesink says.

“Fortunately, it is not all random and we can makes some good guesses about which ones are ecologically important based on ecological principles.”

Other co-authors on the paper are Amy Downing of Ohio Wesleyan University, Katharina Engelhardt of the University of Maryland and Diane Srivastava of the University of British Columbia. The co-authors collaborated on the paper after a BioMERGE workshop funded by the National Science Foundation.

While the creatures that inhabit the mud at the bottom of the ocean may seem remote and unimportant, the oceans cover 70 percent of the Earth’s surface, and the productivity of the sea is intricately linked to sediments that generate nutrients and food for other organisms such as fish. Virtually all life has vanished in some places where human activities have disrupted marine sediments, such as the enormous “dead zone” in the Gulf of Mexico, the result, in part, of excess fertilizer flowing into it from the Mississippi River.


For more information:

Ruesink, (206) 543-7095, ruesink@u.washington.edu