Elemental (C, N, H and P) and stable isotope (δ15N and δ13C) signatures in sediments from Zeekoevlei, South Africa: a record of human intervention in the lake

Das, S.K., Routh, J., Roychoudhury, A.N. and Val Klump, J. (2008) Elemental (C, N, H and P) and stable isotope (δ15N and δ13C) signatures in sediments from Zeekoevlei, South Africa: a record of human intervention in the lake. Journal of Paleolimnology, 39(3), pp. 349-360. (doi: 10.1007/s10933-007-9110-5)

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Publisher's URL: http://dx.doi.org/10.1007/s10933-007-9110-5

Abstract

We used elemental carbon, nitrogen, phosphorus and hydrogen ratios (C/N, N/P and H/C) with total organic carbon (TOC) and total phosphorus (TP) as well as stable carbon and nitrogen isotopes (δ13C and δ15N) to investigate the source and depositional conditions of organic matter in sediments from Zeekoevlei, the largest freshwater lake in South Africa. Typical C/N (10–12), H/C ratios (≥1.7) and δ13Corganic values (−22 to −19‰) together with the increase in TOC concentration indicate elevated primary productivity in lower middle (18–22 cm) and top (0–8 cm) sections of the sediment cores. Seepage of nutrients from a nearby waste water treatment plant, rapid urbanization and heavily fertilized farming in the catchments are responsible for the increased productivity. Consistent with this, measured δ15Norganic values (∼11‰) indicate increased raw sewage input towards the top-section of the core. Although cyanobacterial blooms are evident from the low δ15N values (∼3‰) in mid-section of the core, they did not outnumber the phytoplankton population. Low N/P ratio (∼0) and high TP (100–2,200 mg l−1) support cyanobacterial growth under N limited condition, and insignificant input of macrophytes towards the organic matter pool. Dredging in 1983, caused sub-aerial exposure of the suspended and surface sediments, and affected organic matter preservation in the upper mid-section (12–14 cm) of the core.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Das, Dr Supriyo
Authors: Das, S.K., Routh, J., Roychoudhury, A.N., and Val Klump, J.
Subjects:Q Science > QE Geology
G Geography. Anthropology. Recreation > GB Physical geography
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Journal of Paleolimnology
ISSN:0921-2728
ISSN (Online):1573-0417
Published Online:06 June 2007

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