Microherbivores are significant grazers on Palau’s forereefs
Herbivory plays an important role in controlling benthic dynamics on coral reefs. The previous studies have highlighted the importance of grazing herbivorous fishes in removing algal turf biomass, but fewer studies have investigated the impact of invertebrate microherbivore grazing. This study examined the impact of microherbivore grazing in areas of high- and low-wave exposure on the forereefs of Palau, Micronesia, in June 2015. Experimental tiles were placed on open benthos, and in benthic and suspended herbivore exclusion cages at exposed and sheltered sites to partition the grazing impacts of microherbivores from fish grazers while examining the effect of exposure on algal turf productivity. Microherbivore grazing significantly impacted algal turf biomass, and this impact was greater in exposed sites than sheltered sites. Exposure did not significantly affect algal turf biomass on experimental tiles in the suspended exclusion cages. Surveys of microherbivore density revealed only Paguroidea (hermit crabs, especially of family Diogenidae) were more abundant at exposed sites than sheltered sites. Furthermore, tank trials of grazing rates showed diogenid hermit crabs removed over four times as much algal turf biomass as Columbellidae (marine gastropods), the second most abundant microherbivores. These results show that microherbivores are significant grazers on Palau’s forereefs, and may play an important role in maintaining reef resilience as reef health continues to decline worldwide. The significant role of invertebrate microherbivores in removing algal turf biomass should be investigated when considering the ecological role of herbivory on coral reefs.
The authors would like to thank the Princeton Environmental Institute’s Undergraduate Research fund for senior thesis research at Princeton University, the Mountlake Field Research Fund, and the Council on Science and Technology for financial support (grants to NAK). Additional funding was provided by the Australian Research Council’s Centre of Excellence for Coral Reef Studies (grant to PJM), the Australian Endeavour Award Postdoctoral Fellowship, and PADI Foundation Award (grants to AM) We also thank the Palau International Coral Reef Center for graciously hosting this study, Steve Lindfield for field assistance, Jessica Stella for help with invertebrate identification, and Stephen Pacala for additional guidance. We thank the reviewers for their comments, which improved our final manuscript.
Funding was provided by the Princeton Environmental Institute’s Undergraduate Research fund for senior thesis research at Princeton University, the Mountlake Field Research Fund, and the Council on Science and Technology (grants to NAK), as well as the Australian Research Council’s Centre of Excellence for Coral Reef Studies (grant to PJM), the Australian Endeavour Award Postdoctoral Fellowship, and PADI Foundation Award (grants to AM).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
- Adey WH, Steneck RS (1985) Highly productive eastern Caribbean reefs: synergistic effects of biological, chemical, physical and geological factors. Ecol Coral Reefs 3:163–187Google Scholar
- Australian Bureau of Meteorology and CSIRO (2014) Palau. In: Climate variability, extremes and change in the western tropical Pacific: new science and updated country reports. Pacific-Australia climate change science and adaptation planning program technical report. Australian Bureau of Meteorology and Commonwealth Scientific and Industrial Research Organisation, Melbourne, Australia, pp 201–218Google Scholar
- Carpenter KE, Abrar M, Aeby G, Aronson RB, Banks S, Bruckner A, Chiriboga A, Cortes J, Delbeek JC, Devantier L, Edgar GJ, Edwards AJ, Fenner D, Guzman HM, Hoeksema BW, Hodgson G, Johan O, Licuanan WY, Livingstone SR, Lovell ER, Moore JA, Obura DO, Ochavillo D, Polidoro BA, Precht WF, Quibilan MC, Reboton C, Richards ZT, Rogers AD, Sanciangco J, Sheppard A, Sheppard C, Smith J, Stuart S, Turak E, Veron JEN, Wallace C, Weil E, Wood E (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science 321:560–563CrossRefPubMedGoogle Scholar
- Choat JH (1991) The biology of herbivorous fishes on coral reefs. In: Sale PF (ed) The ecology of fishes on coral reefs. Academic Press Inc, San Diego, pp 120–155Google Scholar
- Clarke KR, Gorley RN (2006) PRIMERv6: user manual/tutorial. Primer-E, Plymouth Marine Laboratory, PlymouthGoogle Scholar
- Cronin G, Paul VJ, Hay ME, Renical W (1997) Are tropical herbivores more resistant than temperate herbivores to seaweed chemical defences? Diterpenoid metabolites from Dictyota acutiloba as feeding deterrents for tropical versus temperate fishes and urchins. J Chem Ecol 23:289–302CrossRefGoogle Scholar
- Doropoulos C, Roff G, Bozec Y, Zupan M, Werminghausen J, Mumby PJ (2016) Characterizing the ecological trade-offs throughout the early ontogeny of coral recruitment. Ecol Monogr 86:20–44Google Scholar
- Froese R, Pauly D (2016) Fishbase. http://www.fishbase.org/. Accessed 27 July 2015
- Jyoti J, Awatshi M (2013) Factors affecting algal growth. In: Kumar S, Tyagi SK (eds) Recent advances in bioenergy research, vol 2. Sardar Swaran Singh National Institute of Renewable Energy, Kapurthala, pp 315–324Google Scholar
- Kulbicki M, Guillemot N, Amand M (2005) A general approach to length-weight relationships for New Caledonian lagoon fishes. Cybium 29:235–252Google Scholar
- Mathieson AC, Fralick RA, Burns R, Flahive W (1971) Comparative studies of subtidal vegetation in the Virgin Islands and New England coastlines. In: Miller JW, VanDerwalker JG, Waller RA (eds) Scientists in the sea. Department of the Interior, Washington, DC, pp 106–129Google Scholar
- Mumby PJ, Dahlgren CP, Harborne AR, Kappel CV, Micheli F, Brumbaugh DR, Holmes KE, Mendes JM, Broad K, Sanchirico JN, Buch K, Box S, Stoffle RW, Gill AB (2006b) Fishing, trophic cascades, and the process of grazing on coral reefs. Science 311:98–101. https://doi.org/10.1126/science.1121129 CrossRefPubMedGoogle Scholar
- Muthiga N, McClanahan TR (1987) Population changes of sea urchin (Echinometra mathaei) on an exploited fringing reef. Afr J Ecol 25:1–8Google Scholar
- Netchy K, Hallock P, Lunz KS, Daly KL (2015) Epibenthic mobile invertebrate diversity organized by coral habitat in Florida. Mar Biodivers 46:1–13Google Scholar
- Russ GR (2003) Grazer biomass correlates more strongly with production than with biomass of algal turfs on a coral reef. Coral Reefs 22:63–67Google Scholar
- Schlichting H (1979) Boundary-layer theory. McGraw-Hill, New YorkGoogle Scholar
- Steneck RS (1988) Herbivory on coral reefs: a synthesis. In: Proceedings of the 6th international coral reef symposium, vol 1, pp 37–49Google Scholar
- Vermeij MJA, Moorselaar IV, Engelhard S, Hornlein C, Vonk SM, Visser PM (2010) The effects of nutrient enrichment and herbivore abundance on the ability of turf algae to overgrow coral in the Caribbean. PLoS ONE 5(12):e14312. https://doi.org/10.1371/journal.pone.0014312 CrossRefPubMedPubMedCentralGoogle Scholar
- Vogel S (1984) Drag and flexibility in sessile organisms. Integr Comp Biol 24:37–44Google Scholar
- Wilson SK, Bellwood DR, Choat JH, Furnas MJ (2003) Detritus in the epilithic algal matrix and its use by coral reef fishes. Oceanogr Mar Biol 41:279–309Google Scholar