Assessment of the quality and quantity of organic matter in the Rufiji mangrove surface sediments using biochemical composition

Abstract

This study was carried out to investigate spatial changes in the quality and quantity of sedimentary organic matter in the Rufiji mangrove system, Tanzania. Sediment samples were collected from three sampling sites. Total organic matter in mangrove sediments ranged from 7.28 ± 2.02% to 10.58 ± 1.34%. Protein concentrations varied from 1,145.33 ± 20.33 μg/g to 2,747.50 ± 25.14 μg/g in the mangrove sediments. Total carbohydrates, lipids and biopolymeric carbon in mangrove sediments ranged between 1,110.50 ± 16.31 μg/g and 1,914.17 ± 27.79 μg/g, 1,436.50 ± 24.13 μg/g and 6,373.50 ± 25.79 μg/g, and 4,496 μg C/g and 10,231.50 μg C/g, respectively. Tannins and lignins in mangrove sediments varied from 817.67 ± 12.97 μg/g to 1786.50 ± 30.74 μg/g, while stable carbon isotope (δ13C) in Rufiji mangrove sediments ranged between –26.64 ± 0.10 ‰ and –25.48 ± 0.13 ‰. Higher protein:carbohydrate (PRT:CHO) at station 3 indicated the presence of freshly deposited organic matter. The high lipid:carbohydrate (LPD:CHO) ratios observed in the Rufiji mangrove systems pointed towards the high quality of labile organic matter which supports benthic fauna. PCA revealed the association of variables and their distribution on trends across sites of the Rufiji mangrove system. Keywords: Organic matter, biochemical composition, Rufiji, mangroves, sediments