Seabirds enhance coral reef productivity and functioning in the absence of invasive rats

Graham, Nicholas A.J., Wilson, Shaun K., Carr, Peter, Hoey, Andrew S., Jennings, Simon, and MacNeil, M. Aaron (2018) Seabirds enhance coral reef productivity and functioning in the absence of invasive rats. Nature, 559. pp. 250-253.

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Abstract

Biotic connectivity between ecosystems can provide major transport of organic matter and nutrients, influencing ecosystem structure and productivity1, yet the implications are poorly understood owing to human disruptions of natural flows2. When abundant, seabirds feeding in the open ocean transport large quantities of nutrients onto islands, enhancing the productivity of island fauna and flora3,4. Whether leaching of these nutrients back into the sea influences the productivity, structure and functioning of adjacent coral reef ecosystems is not known. Here we address this question using a rare natural experiment in the Chagos Archipelago, in which some islands are rat-infested and others are rat-free. We found that seabird densities and nitrogen deposition rates are 760 and 251 times higher, respectively, on islands where humans have not introduced rats. Consequently, rat-free islands had substantially higher nitrogen stable isotope (δ15N) values in soils and shrubs, reflecting pelagic nutrient sources. These higher values of δ15N were also apparent in macroalgae, filter-feeding sponges, turf algae and fish on adjacent coral reefs. Herbivorous damselfish on reefs adjacent to the rat-free islands grew faster, and fish communities had higher biomass across trophic feeding groups, with 48% greater overall biomass. Rates of two critical ecosystem functions, grazing and bioerosion, were 3.2 and 3.8 times higher, respectively, adjacent to rat-free islands. Collectively, these results reveal how rat introductions disrupt nutrient flows among pelagic, island and coral reef ecosystems. Thus, rat eradication on oceanic islands should be a high conservation priority as it is likely to benefit terrestrial ecosystems and enhance coral reef productivity and functioning by restoring seabird-derived nutrient subsidies from large areas of ocean.

Item ID: 55243
Item Type: Article (Research - C1)
ISSN: 1476-4687
Additional Information:

Any methods, including any statements of data availability and Nature Research reporting summaries, along with any additional referencesand Source Sata files, are avaailable in the online version of the paper and have been attached to the pdf in this record.

Funders: Australian Research Council (ARC), Royal Society (RS), National Sciences and Engineering Research Council (NSERC)
Projects and Grants: ARC Centre of Excellence Program CE140100020, RS University Research Fellowship UF140691, NSERC Tier II Canada Research Chair
Date Deposited: 29 Aug 2018 02:03
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 50%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 40%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 60%
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