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Triterpenols in mangrove sediments as a proxy for organic matter derived from the red mangrove (Rhizophora mangle) |
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| Authors: | Boris P Koch Pedro WM Souza FilhoHermann Behling Marcelo CL CohenGerhard Kattner Jürgen RullkötterBarbara Scholz-Böttcher Rubén J Lara |
| Institution: | a Alfred Wegener Institute for Polar and Marine Research, Ecological Chemistry, Am Handelshafen 12, D-27570 Bremerhaven, Germany b University of Applied Sciences, An der Karlstadt 8, D-27568 Bremerhaven, Germany c Federal University of Pará, Geoscience Institute, Faculty of Oceanography, Av. Augusto Correa 1, Campus da UFPA, Caixa Postal 1611, CEP 66075-110, Belém, Pará, Brazil d University of Göttingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Palynology and Climate Dynamics, Untere Karspüle 2, D-37073 Göttingen, Germany e Laboratory of Coastal Dynamics MADAM/UFPa/ZMT, Department of Geology, Av. Perimetral 2651, Terra Firme, CEP 66075-110, Belém, Pará, Brazil f Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, PO Box 2503, D-26111 Oldenburg, Germany g Center for Tropical Marine Ecology, Fahrenheitstr. 6, D-28359 Bremen, Germany |
| Abstract: | Mangroves are the dominant type of vegetation along many tropical coasts. Organic matter (OM) derived from mangrove leaf litter and root material is stored in sediments and is a major contributor to the amount and chemical composition of sedimentary OM. A set of organic biomarkers in sediments was applied as a palaeo-indicator for the Holocene dynamics of a mangrove Estuary (Rio Caeté, Pará, Brazil). Six sediment cores were collected perpendicular to the present coast line and analysed for triterpenols and sitosterol. The influence of microbial biomarker degradation was implemented from a previous study. Biomarker profiles were validated with pollen data and multivariate statistics to test whether these compounds were suitable indicators for the palaeo-vegetation. Sediments deposited up to 2 Ma BP showed biomarker assemblages similar to those of recent surface sediment. In two cores, the biomarker composition revealed a transition from marsh to mangrove vegetation. Taraxerol, germanicol and β-amyrin provided the most significant chemotaxonomical information and, especially in combination, served as reliable proxies for OM from Rhizophora mangle in northern Brazil. The maximum age of the mangrove system ranged between 1000 and 5100 yr depending on the topographic elevation of the drilling location. |
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