title: Millennial-scale isotope records from a wide-ranging predator show evidence of recent human impact to oceanic food webs.
abstract: Human exploitation of marine ecosystems is more recent in oceanic than near shore regions, yet our understanding of human impacts on oceanic food webs is comparatively poor. Few records of species that live beyond the continental shelves date back more than 60 y, and the sheer size of oceanic regions makes their food webs difficult to study, even in modern times. Here, we use stable carbon and nitrogen isotopes to study the foraging history of a generalist, oceanic predator, the Hawaiian petrel (Pterodroma sandwichensis), which ranges broadly in the Pacific from the equator to near the Aleutian Islands. Our isotope records from modern and ancient, radiocarbon-dated bones provide evidence of over 3,000 y of dietary stasis followed by a decline of ca. 1.8‰ in δ(15)N over the past 100 y. Fishery-induced trophic decline is the most likely explanation for this sudden shift, which occurs in genetically distinct populations with disparate foraging locations. Our isotope records also show that coincident with the apparent decline in trophic level, foraging segregation among petrel populations decreased markedly. Because variation in the diet of generalist predators can reflect changing availability of their prey, a foraging shift in wide-ranging Hawaiian petrel populations suggests a relatively rapid change in the composition of oceanic food webs in the Northeast Pacific. Understanding and mitigating widespread shifts in prey availability may be a critical step in the conservation of endangered marine predators such as the Hawaiian petrel.
authors.affiliation: Department of Zoology, Michigan State University, East Lansing, MI 48824, USA. wileyann@msu.edu
authors.forename: Anne E
authors.initials: AE
authors.lastname: Wiley
authors.forename: Peggy H
authors.initials: PH
authors.lastname: Ostrom
authors.forename: Andreanna J
authors.initials: AJ
authors.lastname: Welch
authors.forename: Robert C
authors.initials: RC
authors.lastname: Fleischer
authors.forename: Hasand
authors.initials: H
authors.lastname: Gandhi
authors.forename: John R
authors.initials: JR
authors.lastname: Southon
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Stafford
authors.forename: Jay F
authors.initials: JF
authors.lastname: Penniman
authors.forename: Darcy
authors.initials: D
authors.lastname: Hu
authors.forename: Fern P
authors.initials: FP
authors.lastname: Duvall
authors.forename: Helen F
authors.initials: HF
authors.lastname: James
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D001717:Birds / Q000378:metabolism / Q000502:physiology*; D001842:Bone and Bones / Q000737:chemistry; D002247:Carbon Isotopes / Q000032:analysis; D002250:Carbon Radioisotopes / Q000032:analysis; D002980:Climate; D004032:Diet; D005241:Feathers / Q000737:chemistry; D020387:Food Chain; D006254:Hawaii; D006802:Human Activities; D006801:Humans; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes / Q000032:analysis; D010140:Pacific Ocean; D011137:Polystyrenes
chemical_list: D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D009587:Nitrogen Isotopes; D011137:Polystyrenes; C003771:Amberlite XAD-2 resin
keywords: fishing; seabird; stable isotope