MEPS 647:149-160 (2020)  -  DOI: https://doi.org/10.3354/meps13414

ABSTRACT: In 1979, the Suess effect was described as decreasing δ¹³C in the oceans linked to anthropogenic CO₂ emissions. After years of over-fertilization of farming soils and runoff, we hypothesized that δ¹⁵N in coastal environments would also decline, whereby synthetic fertilizers lead to depletion of the heavy isotope ¹⁵N. We used museum-preserved and modern samples of 3 fishes from Otago, New Zealand, to reconstruct the isotopic baselines of C and N and assess specific trophic positions through time (1955-present) based on bulk and amino acid stable isotope values. Our sample set included Odax pullus, a strictly herbivorous species, and 2 commercially important species: Nemadactylus macropterus and Parapercis colias. Muscle tissue of the fishes recorded the change in δ¹³C_Bulk through time, which matched estimated Suess effect values for New Zealand. We also resolved the effects on the C isotopic baseline from natural changes in the food web using analysis of the δ¹³C of essential amino acids and found that while P. colias maintained a steady diet, the food web position of N. macropterus likely changed. Analysis of δ¹⁵N of phenylalanine in O. pullus indicated a decrease of 0.023‰ yr^-1 since 1955, which corroborates our coastal N-enrichment hypothesis. Furthermore, we found that isotopic changes for N. macropterus were consistent with overfishing and habitat degradation in the region. These data provide vital information for our resolution and understanding of how past environments have changed in terms of both anthropogenic influences on coastal food web structure and biogeochemical cycles of C and N in marine ecosystems.

KEY WORDS: Food web · Isotope baseline · Amino acid · Suess effect · Nitrogen enrichment · Coastal ecosystem

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Cite this article as: Sabadel AJM, Durante LM, Wing SR (2020) Stable isotopes of amino acids from reef fishes uncover Suess and nitrogen enrichment effects on local ecosystems. Mar Ecol Prog Ser 647:149-160. https://doi.org/10.3354/meps13414 Export citation Share:    Facebook - - linkedIn