Regime shifts and alternative stable states in intertidal rocky habitats: State of the art and new trends of research

The existence of regime shifts and alternative stable states in ecosystems is well known and has very large effects on their structure and dynamics. Since shifts between alternative stable states have significant implications for the ecosystems conservation, their prevention should be an aim of primary interest, and for this reason a particular attention has been paid to their study. Regarding marine ecosystems, rocky intertidal habitats, in particular, represent an ideal system for the study of alternative stable states because of their characteristics: they exhibit strong environmental gradients, are easy to manipulate, and most of the inhabiting species grow rapidly. Given the socio-ecological importance and the vulnerability of intertidal rocky systems to multiple pressures, a specific review on these habitats is valuable for a better understanding of the functioning mechanisms of regime shifts. In this review, we examine the different approaches, both experimental and modeling, used to explore regime shifts and alternative states within rocky intertidal habitats. We also analyse the development and use in intertidal systems of new metrics able to signal in advance an approaching transition. Lastly, we discuss the existing knowledge gaps and highlight the management weaknesses of the study of regime shifts in the framework of ecosystem conservation.