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Updated: Apr 3, 2026

Author Spotlight: Understanding Riverine Nitrogen Impacts and Primary Productivity for Effective Nutrient Management
Published on: July 14, 2023
Inputs of anthropogenic nitrogen influence isotopic composition and trophic structure in SE Australian estuaries
Debashish Mazumder1, Neil Saintilan2, Brendan Alderson3
1Australian Nuclear Science and Technology Organisation, Locked Bag 2001 Kirrawee DC, NSW 2232, Australia.
Abstract:
Urban development in coastal settings has increased the input of nitrogen into estuaries globally, in many cases changing the composition of estuarine ecosystems. By focussing on three adjacent estuaries with a gradient of anthropogenic N loadings, we used stable isotopes of N and C to test for changes due to increased anthropogenic N input on the structure of some key trophic linkages in estuaries. We found a consistent enrichment in δ(15)N corresponding to increased anthropogenic N at the three ecosystem levels studied: fine benthic organic matter, grazing invertebrate, and planktivorous fish. The degree of enrichment in δ(15)N between fine benthic organic matter and the grapsid crab Parasesarma erythrodactyla was identical across the three sites. The glassfish Ambassis jacksoniensis showed lower levels of enrichment compared to basal food sources at the higher N-loaded sites, suggesting a possible effect of anthropogenic N in decreasing food-chain length in these estuaries.
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