1 3 Oecologia DOI 10.1007/s00442-015-3282-x COMMUNITY ECOLOGY - ORIGINAL RESEARCH Phase shift facilitation following cyclone disturbance on coral reefs George Roff · Christopher Doropoulos · Mirta Zupan · Alice Rogers · Robert S. Steneck · Yimnang Golbuu · Peter J. Mumby Received: 26 December 2014 / Accepted: 21 February 2015 © Springer-Verlag Berlin Heidelberg 2015 (2.5- and sixfold, respectively), and cage exclusion resulted in a significant increase in Lobophora cover. Experimental removal of Liagora canopies resulted in a 53.1 % decline in the surface area of Lobophora after 12 days, compared to a 51.7 % increase within canopies. Collectively, these results indicate that Liagora canopies act as ecological facilitators, providing a ‘nursery’ exclusion zone from the impact of herbivorous fish, allowing for the establishment of under- story Lobophora. While the ephemeral Liagora bloom had disappeared entirely 9 months post-typhoon, the facilitated shift to Lobophora has persisted for over 18 months, domi- nating ~40 % of the reef substrate. While acute disturbance events such as typhoons have been suggested as a mecha- nism to reverse algal phase shifts, our results suggest that typhoons may also trigger, rather than just reverse, phase shifts. Keywords Macroalgae · Positive interaction · Recruitment · Liagora sp. · Lobophora variegata Introduction Positive interactions play an important role in controlling large-scale landscape processes, shaping assemblages and regulating population dynamics in physically stressful hab- itats (Bertness and Callaway 1994; Bertness and Leonard 1997; Bruno et al. 2003). Positive interactions (or ‘facilita- tions’) are defined as ‘encounters between organisms that benefit at least one of the participants and cause harm to neither’ (Bruno et al. 2003; Stachowicz 2001), and occur when one organism renders the local environment more favourable for another either directly [e.g. reducing ther- mal stress via shading (Baumeister and Callaway 2006)] or indirectly [e.g. predator removal (Duffy 2003)]. Facilitation Abstract While positive interactions have been observed to influence patterns of recruitment and succession in marine and terrestrial plant communities, the role of facili- tation in macroalgal phase shifts is relatively unknown. In December 2012, typhoon Bopha caused catastrophic losses of corals on the eastern reefs of Palau. Within weeks of the typhoon, an ephemeral bloom of monospecific mac- roalgae (Liagora sp.) was observed, reaching a peak of 38.6 % cover in February 2013. At this peak, we observed a proliferation of a second macroalgal species, Lobophora variegata. Lobophora was distributed non-randomly, with higher abundances occurring within the shelter of Liagora canopies than on exposed substrates. Bite rates of two com- mon herbivorous fish (Chlorurus sordidus and Ctenochae- tus striatus) were significantly higher outside canopies Communicated by Deron E. Burkepile. Electronic supplementary material The online version of this article (doi:10.1007/s00442-015-3282-x) contains supplementary material, which is available to authorized users. G. Roff (*) · C. Doropoulos · M. Zupan · A. Rogers · P. J. Mumby Marine Spatial Ecology Lab, School of Biological Sciences, University of Queensland, St Lucia, QLD 4072, Australia e-mail: g.roff@uq.edu.au C. Doropoulos · M. Zupan · Y. Golbuu Palau International Coral Reef Center, Koror, Palau A. Rogers · P. J. Mumby Marine Spatial Ecology Lab, College of Life Sciences, University of Exeter, Exeter, Devon EX4 4PS, UK R. S. Steneck School of Marine Sciences, Darling Marine Center, University of Maine, Walpole, ME 04573, USA