Distribution and sources of sedimentary organic matter in a tropical estuary, south west coast of India (Cochin estuary): A baseline study

• Published in: Marine pollution bulletin Vol. 66; no. 1-2; pp. 239 - 245
• Main Authors: Gireeshkumar, T.R., Deepulal, P.M., Chandramohanakumar, N.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15-01-2013; Elsevier
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Brackish; Brackish water ecosystems; carbon; Carbon - analysis; Carbon Isotopes; coasts; Ecotoxicology, biological effects of pollution; Environmental Monitoring; Estuaries; Fundamental and applied biological sciences. Psychology; Geochemistry; Geologic Sediments - chemistry; India; Isotopes; Marine; Marine and brackish environment; mixing; monsoon season; Nitrogen; Nitrogen - analysis; nitrogen content; Nitrogen Isotopes; organic matter; sampling; Sea water ecosystems; Seawater - chemistry; sediment; sediments; statistical models; Synecology; Total organic carbon; Water Pollutants, Chemical - analysis; water pollution; Asia; Kerala; South Asia; India; ISW, India, Kerala, Ernakulam Dist., Cochin; ISW, India; Geochemistry; Estuaries; Total organic carbon; Nitrogen; Isotopes; Marine environment; Brackish water environment; Organic matter; Tropical zone
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2012.10.002

► We report δ13C and δ15N values of sedimentary organic matter from the Cochin estuary. ► δ13C and δ15N values ranged from −27.5‰ to −21.7‰ and δ15N 3.1–6.7‰ respectively. ► Organic matter is found to be mixture terrestrial and marine derived materials. ► The δ15N values displayed a complex behavior in the study region. ► The fraction of terrestrial derived organic matter was estimated.
Surface sediments samples were collected from 9 stations of the Cochin estuary during the monsoon, post-monsoon and pre-monsoon seasons and were analyzed for grain size, total organic carbon (OC), total nitrogen (TN) and stable isotopic ratios of carbon (δ13C) and nitrogen (δ15N) to identify major sources of organic matter in surface sediments. Sediment grain size is found to be the key factor influencing the organic matter accumulation in surface sediments. The δ13C values ranges from −27.5‰ to −21.7‰ in surface sediments with a gradual increase from inner part of the estuary to the seaward side that suggest an increasing contribution of marine autogenous organic matter towards the seaward side. The δ15N value varies between 3.1‰ and 6.7‰ and it exhibits complex spatial and seasonal distributions in the study area. It is found that the dynamic cycling of nitrogen through various biogeochemical and organic matter degradation processes modifies the OC/TN ratios and δ15N to a considerable degree. The fraction of terrestrial organic matter in the total organic matter pool ranges from 13% to 74% in the surface sediments as estimated by δ13C based two end member mixing model.