Facilitation in Caribbean coral reefs: high densities of staghorn coral foster greater coral condition and reef fish composition
Recovery of the threatened staghorn coral (Acropora cervicornis) is posited to play a key role in Caribbean reef resilience. At four Caribbean locations (including one restored and three extant populations), we quantified characteristics of contemporary staghorn coral across increasing conspecific densities, and investigated a hypothesis of facilitation between staghorn coral and reef fishes. High staghorn densities in the Dry Tortugas exhibited significantly less partial mortality, higher branch growth, and supported greater fish abundances compared to lower densities within the same population. In contrast, partial mortality, branch growth, and fish community composition did not vary with staghorn density at the three other study locations where staghorn densities were lower overall. This suggests that density-dependent effects between the coral and fish community may only manifest at high staghorn densities. We then evaluated one facilitative mechanism for such density-dependence, whereby abundant fishes sheltering in dense staghorn aggregations deliver nutrients back to the coral, fueling faster coral growth, thereby creating more fish habitat. Indeed, dense staghorn aggregations within the Dry Tortugas exhibited significantly higher growth rates, tissue nitrogen, and zooxanthellae densities than sparse aggregations. Similarly, higher tissue nitrogen was induced in a macroalgae bioassay outplanted into the same dense and sparse aggregations, confirming greater bioavailability of nutrients at high staghorn densities. Our findings inform staghorn restoration efforts, suggesting that the most effective targets may be higher coral densities than previously thought. These coral-dense aggregations may reap the benefits of positive facilitation between the staghorn and fish community, favoring the growth and survivorship of this threatened species.
KeywordsPositive density-dependence Acropora cervicornis Haemulids Reef restoration Coral growth
Funding for this project was provided by the National Oceanic and Atmospheric Administration (NOAA) Coral Reef Conservation Program and the National Marine Fisheries Service Southeast Regional Office. Logistical support was provided by the National Park Service (T. Ziegler, T. Gottshall, and K. Nimmo), The Nature Conservancy (K. Amon-Lewis and C. Clade), and the NOAA Restoration Center (T. Moore and S. Griffin). Sampling was conducted under permits DRTO-2014-SCI-0005 from the National Park Service, STX026-12 from the US Virgin Islands Division of Fish and Wildlife, and SAL-14-1546-SRP from the Florida Fish and Wildlife Conservation Commission. Field assistance from A. Bright, C. Cameron, M. Ladd, K. Ondrasik, and C. Vilmar is gratefully acknowledged. This manuscript was greatly improved by the constructive comments of two anonymous reviewers and Dr. Stuart Sandin, handling editor.
Author contribution statement
BH and MM conceived and designed the monitoring study and experiments. All authors contributed to completing field surveys and experiments. LR and RP processed experiments in the laboratory. BH analyzed the data and led authorship of the manuscript; other authors provided substantial editorial advice during multiple manuscript revisions.
Compliance with ethical standards
Funding for this project was provided by the NOAA Coral Reef Conservation Program (CRCP Project ID 819), the National Marine Fisheries Service Southeast Regional Office, and a National Research Council Postdoctoral Research Fellowship (Huntington).
Conflict of interest
The authors declare that they have no conflict of interest.
- Griffin S, Spathias H, Moore T, Baums I, Griffin B (2012) Scaling up Acropora nurseries in the Caribbean and improving techniques, Cairns, Australia edn. James Cook University, Townsville, Queensland 4811, AustraliaGoogle Scholar
- Halpern BS, Walbridge S, Selkoe KA, Kappel CV, Micheli F, D’Agrosa C, Bruno JF, Casey KS, Ebert C, Fox HE, Fujita R, Heinemann D, Lenihan HS, Madin EM, Perry MT, Selig ER, Spalding M, Steneck R, Watson R (2008) A global map of human impact on marine ecosystems. Science 319:948–952. doi: 10.1126/science.1149345 CrossRefPubMedGoogle Scholar
- Herzlieb S, Kadison E, Blondeau J, Nemeth RS (2006) Comparative assessment of coral reef systems located along the insular platform south of St. Thomas, US Virgin Islands and the relative effects of natural and human impacts. Proceedings of 10th International Coral Reef Conference 4:1144–1151Google Scholar
- Jaap W (1998) Boom-bust cycles in Acropora. Reef Encounter 23:12–13Google Scholar
- Lirman D (1999) Reef fish communities associated with Acropora palmata: relationships to benthic attributes. Bull Mar Sci 65:235–252Google Scholar
- Miller M, Huntington B (2015) Coral, Fish and other data to inform staghorn coral recovery in the Caribbean Sea from 2012-04-05 to 2014-07-28 (NCEI accession 0127933). Version 1.1. NOAA National Centers for Environmental Information. DatasetGoogle Scholar
- Mumby PJ, Harborne AR, Williams J, Kappel CV, Brumbaugh DR, Micheli F, Holmes KE, Dahlgren CP, Paris CB, Blackwell PG (2007) Trophic cascade facilitates coral recruitment in a marine reserve. Proc Natl Acad Sci USA 104:8362–8367. doi: 10.1073/pnas.0702602104 CrossRefPubMedPubMedCentralGoogle Scholar
- National Marine Fisheries Service (2015) Recovery plan for elkhorn (Acropora palmata) and staghorn (Acropora cervicornis) corals. Prepared by the Acropora Recovery Team for the National Marine Fisheries Service, Silver Spring, MDGoogle Scholar
- Sandin SA, Smith JE, DeMartini EE, Dinsdale EA, Donner SD, Friedlander AM, Konotchick T, Malay M, Maragos JE, Obura D, Pantos O, Paulay G, Richie M, Rohwer F, Schroeder RE, Walsh S, Jackson JBC, Knowlton N, Sala E (2008) Baselines and degradation of coral reefs in the Northern Line Islands. PLoS One. doi: 10.1371/journal.pone.0001548 Google Scholar
- Shinn EA (1966) Coral growth-rate, an environmental indicator. J Paleontol 40:233–240Google Scholar