In a paper published in the current issue of Progress in Oceanography, Dr. Jeremy Collie, University of Rhode Island Graduate School of Oceanography, Dr. Katherine Richardson, University of Arhus, Denmark, and Dr. John Steele, Woods Hole Oceanographic Institution, examine the mechanisms that can cause regime shifts in ecosystems and use oceanographic and ecological theory to shed light on the relationships between forcing and response variables.

The focus of the paper is to establish a theoretical basis for the occurrence of regime shifts in the ocean. Our understanding of regime shifts relies on observations of organisms and their marine environment taken on times scales of years and decades. Given the size, scope and interrelatedness of marine ecosystems, experimental manipulation is infeasible. Ecological theory and mathematical models are therefore essential tools for developing this understanding.

Regime shifts can occur, for example, when changes in ocean conditions, such as warming, affect plankton production, an event that easily propagates up the food chain. Changes in ocean conditions can also affect migration patterns, growth rates, and mortality of fish species.

Overfishing a species can also force a regime shift, changing the population dynamics of an entire ecosystem. A regime shift occurred at several levels of the food web in the English coinciding with lower phosphate levels. Other well-documented regime shifts have occurred in the northeast Pacific Ocean and in the North Sea zooplankton populations.

Using diagnostic criteria for regime shifts developed by Scheffer and Carpenter in 2003, Collie, Richardson, and Steele adapted this protocol for examining marine data for the occurre
'"/>

Contact: Lisa Cugini
lcugini@gso.uri.edu
401-874-6642
University of Rhode Island
29-Apr-2004