Effect of Phase Shift from Corals to Zoantharia on Reef Fish Assemblages

Abstract

Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated.

The effect of climate change on the distribution of a tropical zoanthid (Palythoa caribaeorum) and its ecological implications

“…The same study discusses the likelihood of a phase shift in the coming years due to natural disturbances and climate change. Phase shifts from reef-building corals to zoanthids were previously reported in the western Atlantic ( Cruz et al, 2015a ), where they reduced fish diversity associated with the reefs ( Cruz et al, 2015b ), and have the potential to adversely affect regional fisheries and tourism, which are main income sources for the local population.…”

“…Few studies have highlighted the importance of P. caribaeorum in association with other invertebrates ( Pérez, Vila-Nova & Santos, 2005 ), reef dynamics ( Silva et al, 2015 ), or the enrichment of the bottom fish community ( Mendonça-Neto et al, 2008 ). However, a study conducted in the Todos os Santos Bay in Brazil ( Cruz et al, 2015b ) showed that the increased abundance of Palythoa sp . decreased habitat heterogeneity, and consequently the richness of fish and benthic organisms, changing the local trophic structure in that region.…”

Regional variability in the sensitivity of Caribbean reef fish assemblages to ocean warming

“…On the contrary, our results suggest that even if such adaptive responses exist in some reef fishes, they may not be sufficient to fully counter the effects of warming across fish assemblages in these time scales. Finally, with the decline of corals in recent years, some scientists suggest that new configurations of reef habitat consisting of sponges, macroalgae, soft corals and smaller amounts of slow-growing but stress-tolerant hard corals may arise in the future and continue to provide refuge spaces in some capacity (Done 1992, Cruz et al 2015. Due to the novel nature of such benthic configurations (Norström et al 2009), their relative effects on the productivity of fisheries is yet to be properly understood.…”

Predatory association of Aeolidiopsis sp. on Palythoa mutuki (Haddon and Shackleton, 1891) along Gujarat coast, India

“…Studies by Belford and Philip (2011) and Kumari et al (2015) highlighted the hardiness of the species under present climatic variability over their famous scleractinian cousins. Yang et al (2013) demonstrated the rapid and aggressive growth of Palythoa tuberculosa under stressed conditions, while the consequence of reef phase shifts from corals to zoanthid dominant communities has been documented by Cruz et al (2015). These studies indicate the need for further in-depth analysis on the diversified role played by zoanthids in maintaining and managing coral reef ecosystems.…”