Research ArticleMARINE ECOSYSTEMS

Temporal variation in pelagic food chain length in response to environmental change

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Science Advances  18 Oct 2017:
Vol. 3, no. 10, e1701140
DOI: 10.1126/sciadv.1701140
  • Fig. 1 The SCB with dolphin sampling locations and oceanographic stations.

    Sampling sites of D. delphis (n = 204) from 1990 to 2008 are indicated with red circles (○). The CalCOFI stations used to obtain in situ oceanographic data from the SCB are indicated with black crosses (+).

  • Fig. 2 Time series of nitrogen-stable isotope records.

    Interannual variation (mean ± 1 SE) in δ15N (‰) of D. delphis skin tissue for bulk tissue (n = 204) and individual amino acids (n = 28): bulk tissue, Glu, Phe, average trophic amino acids (Av. trophic AAs), and average source amino acids (Av. source AAs) in the SCB.

  • Fig. 3 Interannual variation (mean ± 1 SE) in δ15N (‰) FCL proxies: Δ15NGlu-Phe and Δ15NTro-Src.

    Solid lines connect annual mean values. Horizontal lines represent the mean values for each FCL proxy as follows: Δ15NGlu-Phe (dashed blue line) and Δ15NTro-Src (solid gray line).

  • Fig. 4 Time series of environmental variables.

    The MEI (www.cdc.noaa.gov/people/klaus.wolter/MEI/mei.html) and five in situ oceanographic data anomalies (www.calcofi.org/data): surface temperature (°C), nitrate (mean nitrate concentration in the euphotic zone; mM/kg), chlorophyll (mean chlorophyll concentration in the euphotic zone; mg/m3), hypoxic depth (m; axis reversed), and zooplankton (total and small plankton volume; cm3/1000 m3). Series are LOWESS (locally weighted scatterplot smoothing) smoothed with a 1-year window (13 months for MEI, five quarters for the in situ CalCOFI variables).

  • Fig. 5 FCL, measured as trophic amino acids–source amino acids (Δ15N Tro-Src) or Glu-Phe (Δ15NGlu-Phe), as a function of six oceanographic variables.

    The solid lines are the medians of the posteriors from the hierarchical Bayesian model. The shaded areas include the central 50%, and the broken lines include the central 95% of the posterior density.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/10/e1701140/DC1

    fig. S1. Biplot for the principal component analysis of short-beaked common dolphin (D. delphis) δ15N values.

    fig. S2. The δ15N values of individual amino acids in skin samples of D. delphis: trophic amino acids are those amino acids strongly enriched in 15N (blue), and source amino acids refer to those amino acids with low isotopic fractionation (green).

    fig. S3. Correlation matrix among oceanographic variables.

    table S1. Summary of WAIC (widely applicable information criterion) scores for food web length at a 6-month lag using hierarchical Bayesian models.

    table S2. Mean δ15N values of bulk skin tissue samples and individual amino acids (for abbreviations, see description in amino acid stable isotope analysis) from D. delphis collected in the SCB.

    References (6576)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Biplot for the principal component analysis of short-beaked common dolphin (D. delphis) δ15N values.
    • fig. S2. The δ15N values of individual amino acids in skin samples of D. delphis: trophic amino acids are those amino acids strongly enriched in 15N (blue), and source amino acids refer to those amino acids with low isotopic fractionation (green).
    • fig. S3. Correlation matrix among oceanographic variables.
    • table S1. Summary of WAIC (widely applicable information criterion) scores for food web length at a 6-month lag using hierarchical Bayesian models.
    • table S2. Mean δ15N values of bulk skin tissue samples and individual amino acids (for abbreviations, see description in amino acid stable isotope analysis) from D. delphis collected in the SCB.
    • References (66–76)

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