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February 22, 2016

Ecologists test stability of Maine ecosystem over two decades


Unprecedented field studies of alternative stable states play out in the rocky intertidal zones of Swan’s Island, Maine

Working on a lobster boat in Swan's Island, Maine, typically means an early wake-up call. The boats head out around 5:30 in the morning.

For University of Pennsylvania ecologist Peter Petraitis, California State Northridge biologist Steve Dudgeon and their team, it's not much later when they head out as well. But they're used to it. Petraitis and Dudgeon, along with Cheverus High School teacher Erika Rhile and her students, have been returning to this rocky intertidal zone every spring and summer for nearly two decades!

With support from the National Science Foundation (NSF), they survey a network of 60 experimental plots all around the island. The big question that brings them back year after year: Is an ecosystem like this a stable and permanent fixture, or, under harsh conditions, could it reach a tipping point? The idea is that changes in conditions could cause a switch from one community to another, such as from mussel beds to rockweed, and then back again.

In the Gulf of Maine, winter ice scour often removes mussels and rockweed, but it is not known if the species re-establishment is accidental (that is, ice scour can switch a rockweed stand into a mussel bed and vice versa) or deterministic (mussel beds always return to mussel beds). In ecology, the idea that disturbances such as fires, hurricanes, and even oil spills can abruptly switch one community type into another is known as the theory of alternative stable states.

Ecologists have watched such switches all over the country and sometimes, switches have undesirable consequences, such as when human activities impact coral reef communities or the loss of productive edible grasslands in the Southwest. The experimental approach of Petraitis and his colleagues has never been used to test for alternative states under natural conditions and the research has broad implications for studies of alternative states in other ecological communities.

The research in this episode was supported by NSF award #1020480, LTREB: Experimental tests of alternative states on rocky intertidal shores. LTERB stands for Long Term Research in Environmental Biology.

Miles O'Brien, Science Nation Correspondent
Kate Tobin, Science Nation Producer


Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.