Stable isotope record from a resident New Zealand seabird community suggests changes in distribution but not trophic position since 1878

M. J. Rayner, B. J. Dunphy, K. Lukies, N. J. Adams, M. Berg, L. Kozmian-Ledward, M. H. Pinkerton, S. J. Bury

Research output: Contribution to journalArticlepeer-review

Abstract

Globally, human population growth, its associated pollution and the vast scale of industrialised fisheries are having negative impacts on oceanic food webs, affecting top predators such as seabirds. We used stable isotope (δ15N and δ13C) analyses of feathers to investigate the contemporary structure and long-term changes in a near-shore community of 5 seabird species in northern Aotearoa New Zealand. Feathers were collected from museum specimens or live individuals (collected between 1878 and 2019) in Tikapa Moana, the Hauraki Gulf, a marine habitat increasingly threatened by overfishing and urbanisation. To tease out the effects of baseline ecosystem versus seabird distributional changes, we analysed muscle isotope values of forage fishes collected over 43 yr (1976-2019) and provide isotopic data from contemporary prey species sampled within the region. Contemporary δ 15N and δ13C values were consistent with existing data on diet and foraging distribution of the 5 seabird species. Values of δ15N declined in only 1 of 5 species studied, suggesting little change in the trophic position of the other species over time. However, δ13C values declined in 3 species, and a lack of change in the δ15N and δ13C values of forage fish suggests that this change is reflective of a behavioural shift in the distribution of the birds. However, changes in isotopic baselines over the sampling period cannot be ruled out and require further investigation. Our results demonstrate the value of stable isotope analyses of contemporary and archived samples as a cost effective, non-invasive method for monitoring coastal seabirds in a changing world.

Original languageEnglish
Pages (from-to)171-182
Number of pages12
JournalMarine Ecology Progress Series
Volume678
DOIs
Publication statusPublished - 2021
Externally publishedYes

Subject classification (UKÄ)

  • Biological Sciences

Keywords

  • Carbon and nitrogen isotope
  • Euphausiids
  • Feathers
  • Forage fish
  • Hauraki Gulf
  • Museum collections
  • Salps

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