LTREB: Experimental tests of alternative states on rocky intertidal shores

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This research investigates the ecological factors that drive the patchwork pattern of algal stands and mussel beds common in the rocky intertidal zone along ocean coasts. In the Gulf of Maine, winter ice scour often removes mussels and macroalgae, which are known as rockweeds, 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 theory of alternative stable states. Petraitis and Dudgeon are testing this theory using large experimental clearings they created in 1996-1997 and followed through 2008. In 2010, half of the experimental plots will be re-cleared, re-set to initial conditions, and followed for at least five more years. Plots that are not re-cleared serve as controls. If rockweed stands and mussel beds are truly alternative states, then re-setting experimental plots to initial conditions should produce different outcomes than previously observed. If succession is deterministic, then the past should predict the future. This approach 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 project includes plans for online management and dissemination of data, involvement of K-12 students and teachers, and outreach efforts to the local community in Maine where the research is being done. High school students and teachers are involved in data collection. Datasets from this study represent one of the most comprehensive collections of data on intertidal systems world-wide and are invaluable for establishing long-term baselines, data mining and retrospective analyses unrelated to this specific project. Data files and results will be made accessible to high school students and K-12 teachers through the development of a separate web page.