Prof. Steve Dudgeon1, Prof. Peter Petraitis2
1California State University Northridge, Northridge, United States, 2University of Pennsylvania, Philadelphia, United States
Resilience has been widely studied over the last twenty years and here two fucoid macroalgae (Ascophyllum nodosum and Fucus vesiculosus), which are common on rocky shores in the Gulf of Maine, USA, are used to examine of role of resilience in the formation of alternative states. Sheltered bays are dominated by A. nodosum while F. vesiculosus occurs sporadically in disturbed patches, and long-term experiments were used to manipulate the resilience of both species. Experimental clearings of different sizes were established in A. nodosum stands in 1996-97 and half were re-scraped in 2010-11. Short-term experiments were also done to examine how hydrodynamic exposure, clearing size, and consumers affect recruitment and drive resilience. A. nodosum was resilient and recovered in small clearings within 15-18 years, but resilience lessened with increasing clearing size, leaving nearly half of large clearings dominated by F. vesiculosus after 25 years. F. vesiculosus, if it recruited early, was resilient against invasion by A. nodosum and dominated clearings within three years. When A. nodosum established a foothold prior to dominance by F. vesiculosus, F. vesiculosus was a long transient state. Water motion, lack of consumers and large clearings favor rapid domination by F. vesiculosus, which inhibits establishment of A. nodosum. For A. nodosum, its longevity and large biomass per unit area are key to A. nodosum inhibiting F. vesiculosus. We hypothesize the trade-offs in resilience not only account for the pattern of abundance of these species but also leads to them being alternative states.
Presentation Slides – Steve Dudgeon
Biography:
Steve Dudgeon received his PhD in Biological Sciences 1992 from the University of Maine. He has been a Professor at California State University, Northridge since 1999 following postdoctoral positions at Yale and Penn. His principal research interests are in community ecology and the evolution of eukaryotic life cycles. He has collaborated with Dr. Peter Petraitis since 1996 on experimental tests of alternative stable community states and their resilience on rocky shore ecosystems in the Gulf of Maine.
