Toward Quantitative Understanding of the Bioavailability of Dissolved Organic Matter in Freshwater Lake during Cyanobacteria Blooming

Abstract

Occurrence of cyanobacterial harmful algal blooms (CyanoHAB) can induce considerable patchiness in the concentration and bioavailability of dissolved organic matter (DOM), which could influence biogeochemical processes and fuel microbial metabolism. In the present study, a laboratory 4-stage plug-flow bioreactor was used to successfully separate the CyanoHAB-derived DOM isolated from the eutrophic Lake Taihu (China) into continuum classes of bioavailable compounds. A combination of new state-of-the-art tools borrowed from analytical chemistry and microbial ecology were used to characterize quantitatively the temporary evolution of DOM and to get deeper insights into its bioavailability. The results showed a total 79% dissolved organic carbon loss over time accompanied by depletion of protein-like fluorescent components, especially the relatively hydrophilic ones. However, hydrophilic humic-like fluorescent components exhibited bioresistant behavior. Consistently, ultrahigh resolution mass spectrometry (FTICR-MS) revealed that smaller, less aromatic, more oxygenated, and nitrogen-rich molecules were preferentially consumed by microorganisms with the production of lipid-like species, whereas recalcitrant molecules were primarily composed of carboxylic-rich alicyclic compounds. Moreover, the bioavailability of DOM was negatively correlated with microbial community diversity in the bioreactor. Results from this study provide deeper insights into the fate of DOM and relevant biogeochemical processes in eutrophic lakes.

Chemodiversity of Soil Dissolved Organic Matter and Its Association With Soil Microbial Communities Along a Chronosequence of Chinese Fir Monoculture Plantations

“…Consistent with the results of Thieme et al (2019) in conifer species (Picea abies and P. sylvestris), the lignin/CRAM-like structures accounted for the largest proportion of DOM, followed by tannin-like structures (Figure 3). This soil DOM composition is consistent with the chemical composition of Chinese fir litter, which mainly comprise lignin, tannin, and resin (Bai et al, 2017). During decomposition of leaf litter, loss of labile compounds (e.g., carbohydrates and amino acids) occurs, and the dominance of lignin-like structures increases (Bai et al, 2017).…”

Character and environmental lability of cyanobacteria‐derived dissolved organic matter

“…In the lability test experiment, we found that heterotrophs could indeed consume the majority of ionizable cyanobacteria‐derived DOM within less than 2 d. Most of the peaks removed by bacterial degradation were located in the labile region of the van Krevelen diagram, confirming the fast turnover of the aliphatic material (D'Andrilli et al 2015). Contrarily to Bai et al 2017, saturated compounds were preferentially transformed and removed below the detection limit for peak identification along with the most hydrophilic and hydrophobic species, as shown in Fig. 3.…”

“…This does not include polysaccharides and proteins, which have previously been characterized in extracellular mixtures from cyanobacteria, including M. aeruginosa (Myklestad 2005; Pivokonsky et al 2014). Instead, our study focuses on the ionizable metabolite portion (Bittar et al 2015 a ; Bai et al 2017; Powers et al 2019), with a view to assessing the importance of this autochthonous material in studies that use a similar analytical pipeline to characterize freshwater DOM.…”

“…Mass spectrometry coupled to liquid chromatography has the potential advantage of detecting individual analytes (metabolites) produced by autotrophs (Petras et al 2017), but has so far not been used for comprehensive characterization of autochthonous DOM in aquatic systems. However, a few recent studies have begun to use high‐resolution mass spectrometry in direct infusion mode, enabling detection of a wide range of compounds produced by microbes (Osterholz et al 2015; Bai et al 2017; Gonsior et al 2019). These previous efforts have shown that primary producers generate compounds with hundreds to thousands of different molecular formulas, but due to the lack of chromatography or other modes of separation prior to infusion, the isomeric complexity of the mixture cannot be assessed.…”

Nutrient limitation and enzymolysis of phosphorus in Meiliang Bay, Lake Taihu, during algal blooms

“…However, bioavailable phosphorus could be supplemented when required by enzymatic hydrolysis of EHP. There are numerous nutrient supplementation pathways for freshwater lakes, such as nitrogen fixation from the atmosphere (Jean, Cassar, Setzer, & Bellenger, ), release of nutrients from sediments (Cao, Wang, He, Luo, & Zheng, ; Ding et al., , ), and microbial activity (Bai et al., ). Recent study indicated that Fe‐P‐S system in water–sediment interface has great impacts on phosphorus circulation in aquatic systems (Chen et al., ).…”