Ocean invertebrates that live along the coasts seem to prefer living in the fast lane.
The speediest water is home to the widest variety of invertebrate species, according to new research.
Scientists had previously observed that the sponges, sea anemones, barnacles, soft corals and other invertebrates that dwell among the rocks below the breaking waves along coastlines seem to congregate in areas of swiftly flowing water.
Researchers at Brown University have now confirmed this suspicion with a series of experiments and observations in Alaska and Maine, where they manipulated water flow at several coastal spots.
Jon Witman, a professor of ecology and environmental biology, said the results were clear and consistent in both regions: areas with faster water had more diverse, more populous communities of sea creatures.
"It totally blew us away that we got almost identical results in two marine regions of the world separated by 4,000 miles with completely different regional diversities, and no species shared in common," Witman said. "It's a wake-up call saying that water flow is a really strong predictor of how many species are present in a particular area of the ocean."
James Palardy, a former Brown doctoral student and research team member, worked alongside Witman to develop a simple yet effective way to test the connection between water speed and biodiversity.
They built channels about 7 feet (2 meters) long and about 18 inches (46 centimeters) high, and lined the walls with plates where organisms could latch on and grow.
The test channels narrowed to about half their width in the middle, creating a bottleneck — forcing the water to move faster. (The control channels remained the same width throughout.)
The control and test channels were then placed in two sites in Maine and Alaskan coastal waters, and the scientists monitored their progress for over a year.
In every case they found that the number of different species on the plates in the test channels was much higher than on the plates in the control channels. Witman and Palardy also conducted extensive surveys of natural areas in the two test regions, and observed similar effects.
The correlation between fast-moving water and the increased variety in life it produces is somewhat akin to the phenomenon that occurs on land in areas where stiff breezes carry plant spores and seeds to new grounds, Witman said. The water serves as an expressway for the invertebrates' tiny larvae.
Witman said his hope is that the work will not just explain greater biodiversity, but may help ecosystems managers find and better protect vulnerable areas that are suffering the greatest losses.
"There's a global biodiversity crisis where we're losing species," Witman said. "Ecology is very much concerned with sustaining natural processes."
Witman and Palardy detailed their findings in the Nov. 15 issue of the journal Ecology Letters.