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MEPS 690:1-13 (2022)  -  DOI: https://doi.org/10.3354/meps14046

Amino acid nitrogen stable isotopes as biomarkers of coastal phytoplankton assemblages and food web interactions

A. J. M. Sabadel1,*, M. Décima2,7, K. McComb3, M. Meyers4,5, Neill Barr2, Mark Gall2, Karl Safi6, C. S. Law2,5

1Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
2National Institute of Water and Atmospheric Research, Kilbirnie, Wellington 6021, New Zealand
3Department of Chemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
4Department of Botany, University of Otago, PO Box 56, Dunedin 9054, New Zealand
5Department of Marine Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand
6National Institute of Water and Atmospheric Research, Hamilton 3216, New Zealand
7Present address: Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
*Corresponding author:

ABSTRACT: Marine phytoplankton and zooplankton face rapidly changing environments in the face of global warming and climate change. We investigated the effect of warmer water and lower pH conditions—projected for New Zealand coastal waters at the start of the next century—on both phytoplankton and zooplankton in a 20 d mesocosm experiment to determine whether amino acid stable isotopes could be used as biomarkers of environmental change. We also assessed whether key environmental drivers, such as those linked to climate change, altered the processing of amino acids at the base of the food web. Despite changes in phytoplankton biomass and community composition, we found no significant difference in either particulate organic matter (POM) bulk or amino acid-specific δ15N values, indicating that the trophic status of POM was not significantly influenced by lower pH and warming. Threonine δ15N values were the most sensitive to changes in the phytoplankton community and showed correlations with diatoms (positive) and small flagellates (negative), demonstrating potential as a biomarker for detecting changes related to these phytoplankton groups and thus making threonine a promising indirect indicator of climate change. Finally, δ15NPhe values tracked changes in the lower food web, likely due to faster turnover times, showing its valuable role as a tracer of the nitrogen baseline, even during accelerated metabolism in zooplankton.


KEY WORDS: Trophic ecology · Stable isotopes · Environmental change · Ocean acidification · Ocean warming · Zooplankton


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Cite this article as: Sabadel AJM, Décima M, McComb K, Meyers M and others (2022) Amino acid nitrogen stable isotopes as biomarkers of coastal phytoplankton assemblages and food web interactions. Mar Ecol Prog Ser 690:1-13. https://doi.org/10.3354/meps14046

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