MEPS 413:267-276 (2010)  -  DOI: https://doi.org/10.3354/meps08626

ABSTRACT: A major challenge to ecologists is identifying factors that make a system susceptible to regime shifts or state transitions. Theory and modelling have suggested a number of indicators to warn of approaching tipping points, but empirical tests of their validity are few. We tested 2 indicators, change to a key species and increased temporal variability, in a harbour, a system type rarely studied for regime shifts and alternate states. Long-term monitoring over 20 yr on a number of intertidal sandflats allowed us to document change and determine potential contributing factors. We detected decreasing abundance in the key species and increased temporal variability (flickering) of community composition before a trophic and functional change to an alternate community type. Detection of these indicators occurred despite cyclic patterns in community and population dynamics and a relatively fast and permanent change of one external condition (nutrients). We provide evidence that this shift was the product of a relatively small change in management of sewage disposal, combined with climate dynamics and mediated through changes in a key species, a tubeworm that provides biogenic habitat structure, stabilises sediment and affects dispersal and recruitment. These factors all interacted to escalate the effect of the relatively small changes in nutrients across a tipping point.

KEY WORDS: Tipping point · Thresholds · Key species · Regime shift · Macrofauna

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Cite this article as: Hewitt JE, Thrush SF (2010) Empirical evidence of an approaching alternate state produced by intrinsic community dynamics, climatic variability and management actions. Mar Ecol Prog Ser 413:267-276. https://doi.org/10.3354/meps08626 Export citation Share:    Facebook - - linkedIn