MEPS 488:23-34 (2013)  -  doi:10.3354/meps10410

Trophic interactions and ecological stability across coral reefs in the Marshall Islands

Peter Houk1,2,*, Craig Musburger3

1University of Guam Marine Laboratory, Mangilao, Guam 96923, Guam
2Pacific Marine Resources Institute, Saipan, Northern Mariana Islands
3Department of Zoology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA

ABSTRACT: Coral reef assemblages, trophic interactions, and food web stability were examined across a remote and densely populated atoll, in the Republic of the Marshall Islands (RMI). The biomass of sharks, large-bodied piscivores, and secondary invertebrate consumers was expectedly larger in the absence of major human populations. Less intuitively, we report a doubling in the density and biomass of small-bodied acanthurids with significant human presence, whereas large-bodied parrotfishes were halved. These trends provided evidence for prey release of small acanthurids, but also indicated a reduction in grazing function given that power-law relationships govern fish size and physiology. Path analyses supported the conjecture that apex predator biomass enhanced the abundance of large-bodied herbivores, with ensuing benefits to calcifying benthic substrates and coral diversity. Human populations, as low as 40 individuals, had opposing linked interactions. The study next used species abundances to depict food chain interaction strengths, and multivariate measures of heterogeneity to depict food chain diversity. The removal of few strong links along the gradient of investigation (i.e. Acropora corals and sharks), as well as numerous weak links, was associated with fish assemblages and benthic substrates that had reduced grazing and calcification potential, respectively. The results inferred that a reduction in the functional response time of trophic guilds will follow perturbations (i.e. reduce stability), synonymous to food webs with low return rates to their modeled, stable configuration. This study provides a broader perspective for interpreting how humans and apex predators influence ecological stability across (RMI) coral reef ecosystems.

KEY WORDS: Remote atolls · Coral reef function · Anthropogenic effects · Trophic interactions · Top-down effects · Food webs · Apex predators

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Cite this article as: Houk P, Musburger C (2013) Trophic interactions and ecological stability across coral reefs in the Marshall Islands. Mar Ecol Prog Ser 488:23-34

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