Source, composition, and environmental implication of neutral carbohydrates in sediment cores of subtropical reservoirs, South China

Abstract

Abstract. Neutral monosaccharides, algal organic matter (AOM), and carbon stable isotope ratios in three sediment cores of various trophic reservoirs in South China were determined by high-performance anion-exchange chromatography, Rock-Eval pyrolysis, and Finnigan Delta Plus XL mass spectrometry, respectively. The carbon isotopic compositions were corrected for the Suess effect. The concentrations of total neutral carbohydrates (TCHO) range from 0.51 to 6.4 mg g −1 at mesotrophic reservoirs, and from 0.83 to 2.56 mg g −1 at an oligotrophic reservoir. Monosaccharide compositions and diagnostic parameters indicate a predominant contribution of phytoplankton in each of the three cores, which is consistent with the results inferred from the corrected carbon isotopic data and C/N ratios. The sedimentary neutral carbohydrates are likely to be structural polysaccharides and/or preserved in sediment minerals, which are resistant to degradation in the sediments. Moreover, the monosaccharide contents are highly related to the carbon isotopic data, algal productivity estimated from the hydrogen index, and increasing mean air temperature during the past 60 years. The nutrient input, however, is not a key factor affecting the primary productivity in the three reservoirs. The above evidence demonstrates that some of the resistant monosaccharides have been significantly elevated by climate change, even in low-latitude regions.

Influence of dominant environmental processes in the tropical Cuban basin Hanabanilla and reservoir on sediment composition

“…The principal physical-chemical variables studied in sediment include: nitrogen (N), phosphorus (P), organic carbon (OC), organic matter, C/N/P ratios, metals and particle size (Ahiablame et al, 2010). The C/N ratio has been used as a representative proxy to reconstruct the depositional environment of freshwater lake sediments (Duan et al, 2017). Major (Na, K, Ca, Mg, and Si) and trace (Al, Fe, Mn, Zn, Cu, and Cr) element concentrations in reservoir sediment can help inform the aquatic ecosystem history and the process and impacts of human activities that occur at the watershed scale (Mora et al, 2017).…”