Herbivory versus corallivory: are parrotfish good or bad for Caribbean coral reefs?
- 1.7k Downloads
With coral cover in decline on many Caribbean reefs, any process of coral mortality is of potential concern. While sparisomid parrotfishes are major grazers of Caribbean reefs and help control algal blooms, the fact that they also undertake corallivory has prompted some to question the rationale for their conservation. Here the weight of evidence for beneficial effects of parrotfishes, in terms of reducing algal cover and facilitating demographic processes in corals, and the deleterious effects of parrotfishes in terms of causing coral mortality and chronic stress, are reviewed. While elevated parrotfish density will likely increase the predation rate upon juvenile corals, the net effect appears to be positive in enhancing coral recruitment through removal of macroalgal competitors. Parrotfish corallivory can cause modest partial colony mortality in the most intensively grazed species of Montastraea but the generation and healing of bite scars appear to be in near equilibrium, even when coral cover is low. Whole colony mortality in adult corals can lead to complete exclusion of some delicate, lagoonal species of Porites from forereef environments but is only reported for one reef species (Porites astreoides), for one habitat (backreef), and with uncertain incidence (though likely <<10%). No deleterious effects of predation on coral growth or fecundity have been reported, though recovery of zooxanthellae after bleaching events may be retarded. The balance of evidence to date finds strong support for the herbivory role of parrotfishes in facilitating coral recruitment, growth, and fecundity. In contrast, no net deleterious effects of corallivory have been reported for reef corals. Corallivory is unlikely to constrain overall coral cover but contraints upon dwindling populations of the Montastraea annularis species complex are feasible and the role of parrotfishes as a vector of coral disease requires evaluation. However, any assertion that conservation practices should guard against protecting corallivorous parrotfishes appears to be unwarranted at this stage.
KeywordsConservation Mortality Coral Herbivore
I thank the Marine Spatial Ecology Lab for stimulating discussions on this topic and the helpful comments of Laurence McCook and two anonymous referees. Andy Bruckner kindly provided photographs to illustrate the article.
- Birkeland C (1977) The importance of rate of biomass accumulation in early successional stages of benthic communities to the survival of coral recruits. Proc 3rd Int Coral Reef Symp: 16–21Google Scholar
- Box SJ (2008) The dynamics of macroalgae on a Caribbean coral reef: Modelling the availability of settlement space and dominant algae and evaluation the effect of macroalgal competition on the growth and survival of juvenile corals. PhD Thesis. University of Exeter, Exeter p146Google Scholar
- Done TJ, Ogden JC, Wiebe WJ, Rosen BR (1996) Biodiversity and ecosystem function of coral reefs. In: Mooney HA, Cushman JH, Medina E, Sala OE, Schulze E-D (eds) Functional roles of biodiversity: A global perspective. John Wiley & Sons, pp 393–429Google Scholar
- Edmunds PJ (2002) Long-term dynamics of coral reefs in St. John, US Virgin Islands. Coral Reefs 21:357–367Google Scholar
- Garzon-Ferreira J, Reyes-Nivia MC (2001) Incidence of fish predation on stony corals at four atolls of the archipelago of san andres and providencia (Colombian Caribbean). Bol Inv Mar Cost 30:133–150Google Scholar
- Gygi RH (1975) Sparisoma viride (Bonnaterre), the stoplight parrotfish, a major sediment producer on coral reefs of Bermuda. Eclogae Geol Helv 68:327–359Google Scholar
- Hoegh-Guldberg O, Mumby PJ, Hooten AJ, Steneck RS, Greenfield P, Gomez E, Harvell CD, Sale PF, Edwards AJ, Caldeira K, Knowlton N, Eakin CM, Iglesias-Prieto R, Muthiga N, Bradbury RH, Dubi A, Hatziolos ME (2007) Coral reefs under rapid climate change and ocean acidification. Science 318:1737–1742PubMedCrossRefGoogle Scholar
- Kramer PA (2003) Synthesis of coral reef health indicators for the western Atlantic: Results of the agrra program (1997–2000). Atoll Res Bull 496:1–58Google Scholar
- Mascarelli PE, Bunkley-Williams L (1999) An experimental field evaluation of healing in damaged, unbleached and artificially bleached star coral, Montastraea annularis. Bull Mar Sci 65:577–586Google Scholar
- Meesters EH, Wesseling I, Bak RPM (1996) Partial mortality in three species of reef-building corals and the relation with colony morphology. Bull Mar Sci 58:838–852Google Scholar
- Reyes-Nivia MC, Garzon-Ferreira J, Rodriquez-Ramirez A (2003) Depradación de coral vivo por peces en el Parque Nacional Natural Tayrona, Caribe Colombiano. Rev Biol Trop 52:883–895Google Scholar
- Sanchez JA, Gil MF, Chasqui LH, Alvarado EM (2004) Grazing dynamics on a Caribbean reef-building coral. Coral Reefs 23:578–583Google Scholar
- Steneck RS (1988) Herbivory on coral reefs: A synthesis. Proc 6th Int Coral Reef Symp 1:37–49Google Scholar
- Steneck RS (1997) Crustose corallines, other algal functional groups, herbivores and sediments: Complex interactions along reef productivity gradients. Proc 8th Int Coral Reef Symp 1:695–700Google Scholar
- Williams ID, Polunin NVC (2000) Large-scale associations between macroalgal cover and grazer biomass on mid-depth reefs in the Caribbean. Coral Reefs 19:358–366Google Scholar