Characteristics and degradation of carbon and phosphorus from aquatic macrophytes in lakes: insights from solid-state 13C NMR and solution 31P NMR spectroscopy

Authors: LIU, SHASHA - Beijing Normal University; ZHU, YUANRONG - Chinese Research Academy Of Environmental Sciences; MENG, WEI - Chinese Research Academy Of Environmental Sciences; He, Zhongqi; FENG, WEIYING - Beijing Normal University; ZHANG, CHEN - Chinese Research Academy Of Environmental Sciences; GIESY, JOHN - Chinese Research Academy Of Environmental Sciences

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2015
Publication Date: 12/9/2015
Citation: Liu, S., Zhu, Y., Meng, W., He, Z., Feng, W., Zhang, C., Giesy, J.P. 2015. Release and transformation of carbon and phosphorus from aquatic macrophytes of lakes: Insight from solid-state 13C NMR and solution 31P NMR spectroscopy. Science of the Total Environment. 543:746-756.

Interpretive Summary: Aquatic macrophytes are important participants of lake ecological systems, which can be involved in biogeochemical cycling of nutrients, such as carbon (C) nitrogen (N) and phosphorus (P). This study aimed to explore the composition of water extracted organic matter (WEOM) in aquatic macrophyte biomass collected from freshwater lake Tai and the relationships between the abundances of carbon (C) and phosphorus (P) components in these WEOM fraction, as well as their transformations in waters and sediments. This study observed that the extracted C and P from aquatic macrophytes were closely related to the labile structural components of plant biomass in East Tai Lake ecosystem. The degradation of biological membranes from decaying debris of aquatic plants can release phospholipid and glycolipid, which links C functional groups with compounds containing P. The degradation of phospholipid and RNA and production of DNA by bacteria play an important role in biogeochemical cycles of phosphorus in East Tai Lake. Therefore, we should pay more attention to endogenic biological factors in the management of lake eutrophication.

Technical Abstract: Water extractable organic matter (WEOM) derived from macrophytes plays an important role in biogeochemical cycling of nutrients, including carbon (C), nitrogen (N) and phosphorus (P) in lakes. However, reports of their composition and degradation in natural waters are scarce. Therefore, compositions and degradation of WEOM derived from six aquatic macrophytes species of Tai Lake, China, were investigated by use of solid-state 13C NMR and solution 31P NMR spectroscopy. Carbohydrates were the predominant constituents ofWEOM fractions, followed by carboxylic acid. Orthophosphate (ortho-P) was the dominant form of P (78.7% of total dissolved P) in the water extracts, followed by monoester P (mono-P) (20.6%) and little diester P (0.65%). The proportion ofmono-P in total P species increased with the percentage of O-alkyl and O–C–O increasing in the WEOM, which is likely due to degradation and dissolution of biological membranes and RNA from aquatic plants.Whereas the proportion of mono-P decreased with alkyl-C, NCH/OCH3 and COO/N–C_O increasing, which may be owing to the insoluble compounds including C functional groups of alkyl-C, NCH/OCH3 and COO/N–C_O, such as aliphatic biopolymers, lignin and peptides. Based on the results of this study and information in the literature about water column and sediment, we propose that WEOM, dominated by polysaccharides, are the most labile and bioavailable component in debris of macrophytes. Additionally, these WEOMs would also be a potential source for bioavailable organic P (e.g., RNA, DNA and phytate) for lakes.