Compositional variations in algal organic matter during distinct growth phases in karst water

Abstract

Inland surface water plays an important role in global carbon cycling, which responds to transformation between dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). Studies have shown that algae in karst lakes and reservoirs can convert DIC to organic matter (OM) and form stable carbon sinks via photosynthesis. However, the pathways of conversion of inorganic carbon to organic carbon during algal growth remain unclear and need further investigation. In this study, spectroscopic techniques were applied to investigate the variations in algal organic matter (AOM) composition in the growth metabolism of Chlorella vulgaris and Scenedesmus obliquus under simulated karst water condition. The results showed that algal extracellular organic matter (EOM) contained high DIC concentration during the adaptation phase, which formed the carbon source for algal photosynthesis. In addition, DOC in algae increased after entering the stationary phase, while more OM was released into water. As algal growth proceeded, the amino groups in EOM were consumed to produce more aromatic protein-like material, while more lipid material was produced in intracellular organic matter (IOM). The spectral characterization results could intuitively determine AOM dynamics in different growth stages of algae, which can be used for establishing effective approaches for detecting organic carbon variations and responding to regional carbon cycling in karst water.

Annotation of DOM metabolomes with an ultrahigh resolution mass spectrometry molecular formula library

“…Dissolved organic matter (DOM) represents a major conduit of energy, fixed carbon, and nutrients through the environment. Various factors, including species, growth phase, and nutrient stress, have been shown to alter the chemical characteristics and bioavailability of dissolved organic matter (DOM) released by microorganisms (Grossart and Simon, 2007; Becker et al, 2014; Wear et al, 2015; Tian et al, 2023). However, the specific metabolic processes that govern DOM composition remain a mystery.…”

Algal Organic Matter Fluorescence Analysis of Chlorella sp. for Biomass Estimation

“…Different techniques have been used to characterize organic matter in aquatic systems, which can be used to understand the composition of AOM in natural waters. These include specific ultraviolet absorption (SUVA), excitation-emission matrix (EEM) fluorescence spectroscopy, and lidar systems [6][7][8][9]. These techniques are promising tools for understanding the behaviors and composition of AOM and the pigment chlorophyll-a in natural waters.…”