Carbon and nitrogen cycling in the Zhubi coral reef lagoon of the South China Sea as revealed by 210Po and 210Pb

• Published in: Marine pollution bulletin 2011-05, Vol.62 (5), p.905-911
• Main Authors: Yang, W.F., Huang, Y.P., Chen, M., Qiu, Y.S., Li, H.B., Zhang, L.
• Format: Article
• Language: English
• Subjects: 210Pb; 210Po; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Carbon; Carbon - analysis; Carbon Cycle; China; Coral reef lagoon; Coral Reefs; corals; Cycles; Degradation; Environmental Monitoring - methods; Exports; Fundamental and applied biological sciences. Psychology; International trade; Lagoons; lead; Lead Radioisotopes - analysis; Marine; nitrogen; Nitrogen - analysis; Nitrogen Cycle; Oceans and Seas; organic matter; particulates; POC; Polonium - analysis; Radioactive Tracers; radionuclides; Recycled; recycling; Sea water ecosystems; Seawater - chemistry; South China Sea; Synecology; Water Pollutants, Chemical - analysis; water pollution
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2011.02.058

► 210Po/210Pb disequilibria were used to trace export of POC and PON in a coral lagoon. ► Recycling of POC and PON were quantified by a mass balance budget in a coral lagoon. ► 210Po excess could be used to qualify the degradation of particulate organic matter. ► Degradation rate constant of POM was much more in the lagoon than in the open sea. The radionuclides 210Po and 210Pb were examined to trace the cycling of particulate organic carbon (POC) and particulate organic nitrogen (PON) in the Zhubi coral reef lagoon. The net export flux of POC to the open sea is 14mgCm−2d−1. However, the net exchange of PON has not yet been observed. On average, the vertical export fluxes in the lagoon of POC and PON, as derived from 210Po/210Pb disequilibria, are 43mgCm−2d−1 and 13.8mgNm−2d−1, respectively. The deficit of 210Po relative to 210Pb in particulate matter provides evidence for the degradation of particulate organic matter. According to the mass balance budgets, 310mgCm−2d−1 and 121mgNm−2d−1 were recycled into dissolved fractions. Based on a first-order kinetics model, the degradation rate constants of POC and PON are 0.28 and 0.30m−1, respectively. Thus, 210Po and 210Pb can quantify the cycling of carbon and nitrogen in this coral lagoon.