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Updated: Jul 3, 2026

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
Published on: August 3, 2016
Source and depositional pattern of bulk organic matter in a subtropical eco-sensitive lake sediment in Bihar, India:
Nutan Nandan Patel1, Avinash Dass1, Rajesh Kumar Ranjan1
1Department of Environmental Science, Central University of South Bihar, Gaya, 824236, Bihar, India.
Abstract:
Lake sediments play a critical role in regulating nutrient cycling; however, unmanaged nutrient inputs can disrupt these processes and degrade aquatic ecosystems. This study focuses on Ghora Katora Lake, an eco-sensitive site in Rajgir, Nalanda district of Bihar, India. The study aims to determine the source apportionment of bulk organic matter (OM) in lake sediment by analyzing proxies such as Total Organic Carbon (TOC), Total Nitrogen (TN), TOC/TN, and stable isotopes (δ13C and δ15N). Surface sediments were collected seasonally (pre-monsoon, monsoon, post-monsoon) from 21 locations, along with one-time core sediments from six sites. TOC-TN concentrations were analyzed using an Elemental Analyzer, and stable isotopes using Isotope Ratio Mass Spectrometry (IRMS). Bayesian model (MixSIAR) was applied for probabilistic OM source apportionment. In surface sediment, TOC (0.16-2.42%) and TN (0.03-0.59%) vary seasonally (i.e., post-monsoon < monsoon < pre-monsoon) alongside δ13C (-27.1‰ to -21.3‰) and δ15N (-1.1‰ to 4.7‰), reflecting changing productivity and runoff inputs. The mean TOC/TN ratio (7.42 ± 2.3) suggests a mixed OM contribution: vascular/terrestrial input (TOC/TN 11-20) and phytoplankton/protein-rich material (TOC/TN 4-10). Core sediments indicate declining TOC (0.09-0.62%) and TN (0.02-0.13%) with depth, alongside modest isotopic variation (δ13C -26.7‰ to -21.5‰), evidencing microbial degradation. Among the potential sources, C3 vegetation exhibited comparatively higher TOC (39.34% to 51.38%) along with a wide δ13C range (-31.8‰ to -15.3‰). Given substantial isotopic overlap among potential sources, MixSIAR results indicate terrestrial dominance of ~46% (95% CI: 37-55%) from C3 plants, ~33% (95% CI: 26-40%) from C4 vegetation, and lower, ~21% (95% CI: 15-27%) algal input. Overall, isotopic and elemental signatures highlight the dominance of allochthonous OM with discernible algal input, shaping sediment nutrient dynamics.
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