Sources and major biogeochemical pathways of organic matter in the mangrove system of Rufiji estuary

Abstract

ABSTRACTFatty acids were extracted from the surface sediments (10 cm) of three sampling sites of Rufiji estuary to infer their sources and biogeochemical pathways. The fatty acids ranging from C8 to C24 were distinguished from this study, and were broadly classified into saturated (SFAs), monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs). SFAs were found to be the major fraction at station 1 and 3 where as at station 2, MUFAs dominated. A total of 19 fatty acids with a total concentration of 64.91 μg/g dry weight were characterised at station 1. C16:0 was the most abundant fatty acid contributing 21.94% of total fatty acids (TFAs). C22:2 was the second most abundant, which accounted for 9.46% of TFAs. Fatty acids ranging from C12 to C24 were identified at station 2. C20 fatty acid was the most abundant fatty acid contributing 21.94%, followed by C16:0. At station 3, fatty acids ranging from C8 to C24 were obtained. The PUFA C20:5n-3 was the most abundant fatty acid contributing 21.65%, followed by C24:0 (15.00% of TFAs). The ratio of lower molecular weight (LMW) to higher molecular weight (HMW) biomarkers was used as an indicators to distinguish higher plants organic matter from algae-derived fatty acids.