STUDY LOOKS AT TEMPERATURE CHANGES
A temperature change of only a few degrees can disrupt a community of animals, according to a researcher who studied how hot and cold affects the delicate balance of starfish and mussels in Oregon's tidal waters. Eric Sanford of Oregon State University said his study, published in the journal Science, suggests that if a key species in a community of animals is particularly sensitive to temperatures, a slight warming or cooling can start a whole cascade of rapid changes affecting every animal in an ecosystem.
Sanford found a 5-degree change in temperature is enough to change dramatically the feeding habits of the starfish, a five-armed creature that feeds mainly on mussels and is common along the Pacific coast of the United States. The finding, said Sanford, has important implications for understanding the effects of global warming.
"Many people have assumed that the effects of climate change would be gradual," the researcher said in an interview. "But this shows that if an important species in a community is highly sensitive to temperature, then the effects of a small temperature change can happen rapidly."
In his study, Sanford tracked the feeding patterns of starfish kept in the laboratory at different temperatures. He checked his results by manipulating the population of starfish and mussels in two areas along the Oregon coast.
Sanford found that a temperature drop of 5 degrees caused the starfish to virtually stop feeding on the mussels. This allows the mussels to rapidly expand in population. Conversely, when the water temperature was increased by 5 degrees, Sanford said starfish went on a feeding binge,quickly reducing the population of mussels. Either way, he said, there are dramatic changes in the tidal community of animals.
When mussels are not controlled by starfish, said Sanford, their population explodes. The mussels attach themselves to every surface in the near-shore tidal zone, crowding out barnacles, algae and other organisms. "If you take away the sea stars, then you go from an ecosystem with a diverse population of species to a system where there is essentially only one species," Sanford said.
When starfish eat too much, he said, the reef-like mussel communities quickly start falling apart. These reefs, Sanford said, are homes for crab, sea cucumbers and worms, all important parts of the ecosystem. Temperatures along the Oregon coast are affected by upwelling, cold deep waters surging to the surface. The frequency of upwellings, said Sanford, is determined by winds that, in turn, are affected by global temperatures. If cold upwellings become less frequent, starfish may eat more mussels, said Sanford; if the upwellings happen more often, thus cooling the tidal waters, starfish will eat less, allowing the mussel population to suddenly explode.