Linking isotopic signatures of nitrogen in nearshore coral skeletons with sources in catchment runoff. (December 2021)

• Record Type: Journal Article
• Authors: Marion, Guy S.; Jupiter, Stacy D.; Radice, Veronica Z.; Albert, Simon; Hoegh-Guldberg, Ove
• Is Part Of: Marine pollution bulletin. Volume 173:Part B(2021)
• Publication Date: 2021-12
• Subjects: Water quality -- Nitrogen cycle -- River runoff -- Microbial remineralization -- Denitrification -- Pioneer River catchment; Marine pollution -- Periodicals; Marine Biology -- Periodicals; Water Pollution -- Periodicals; Mer -- Pollution -- Périodiques; Publications périodiques; Pollution des mers; Lutte antipollution; Electronic journals; 363.7394
• DOI: 10.1016/j.marpolbul.2021.113054
• Languages: English
• ISSNs: 0025-326X

Abstract

Abstract: We use a multi-tracer approach to identify catchment sources of nitrogen (N) in the skeletons of nearshore Porites corals within the Great Barrier Reef. We measured δ 15 N, δ 13 C and C:N ratios of particulate organic matter (POM) sampled from the Pioneer River catchment and identified five distinct end-members: (1) marine planktonic and algal-dominated matter with higher δ 15 N values from the river mouth and coastal waters; (2) estuarine planktonic and algal matter with lower δ 15 N values associated with estuarine mixing; (3) lower river freshwater phytoplankton and algal-dominated matter in stratified reservoirs adjacent to catchment weirs, with the 15 N-enriched source likely caused by microbial remineralization and denitrification; (4) upper river low δ 15 N terrigenous soil matter eroded from cane fields bordering waterways; and (5) terrestrial plant detrital matter in forest streams, representing a low δ 15 N fixed atmospheric nitrogen source. The δ 15 N values of adjacent, nearshore Porites coral skeletons is reflective of POM composition in coastal waters, with 15 N-enriched values reflective of transformed N during flood pulses from the Pioneer River. Highlights: End-member source δ 15 N values were identified in the Pioneer River catchment. High biological activity around weir likely produced 15 N-enriched signatures. Nearshore Porites coral skeletons exhibited 15 N-enrichment during flood years.