Journal
MARINE ECOLOGY PROGRESS SERIES
Volume 647, Issue -, Pages 149-160Publisher
INTER-RESEARCH
DOI: 10.3354/meps13414
Keywords
Food web; Isotope baseline; Amino acid; Suess effect; Nitrogen enrichment; Coastal ecosystem
Categories
Funding
- National Science Challenge: Sustainable Seas (4.1.1 Ecosystem Connectivity) grant
- University of Otago PhD scholarship
- Sustainable Seas National Science Challenge (4.1.1 Ecosystem Connectivity)
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In 1979, the Suess effect was described as decreasing delta C-13 in the oceans linked to anthropogenic CO2 emissions. After years of over-fertilization of farming soils and runoff, we hypothesized that delta N-15 in coastal environments would also decline, whereby synthetic fertilizers lead to depletion of the heavy isotope N-15. 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 delta C-13(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 delta C-13 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 delta N-15 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.
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