Northeastern University researchers at the Marine Science Center have shown that the behavior of the "middle child" in the predator-prey food chain plays a strong role in determining how the reef as a whole will fare. The new research from the team was published online on Tuesday in the journal Ecology Letters.
Northeastern ecologist David Kimbro, who claims to have watched a lot of TV growing up, particularly The Brady Bunch, compares the "middle child" behavior of oyster reefs to the show: "You could kind of get a flavor for how an episode was going to turn out based on how Jan or Peter were faringyou know, the middle kids," said Kimbro, an assistant professor in the Department of Marine and Environmental Sciences.
The work complicates the evolution of a paradigm that has pervaded ecology since the 1960s, namely that the species at the top of the food web dictate the welfare of the entire system simply by eating.
For instance, observations in the Aleutian Islands in the 1970s showed that when sea otters were doing well, the nearby kelp forests below the ocean's surface also thrived. This was due, theory said, to the fact that the otters' feeding patterns naturally managed the sea urchin population, which feeds on kelp.
Fast-forward four decades and one sees a large body of evidence indicating that predators do more than eat; they frighten too. In the early 2000s, Grabowski showed that having a predatory fish scare the middle child has the same effect as predation itself. Likewise with the sea ottersjust swimming around scares the urchins enough to send them into hiding and stop eating kelp.
These observations have led researchers to assume that the mere presence of a top predator is always beneficial for habitats like oysters and kelp, Kimbro said. "But," he added, "we had a hunch that the lynch-pin of behavior is fickle. I mean, I can turn on a dime. Just ask my family when I mi
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