Investigating microbial response to environmental variables is of great importance for understanding of microbial acclimatization and evolution in natural environments. However, little is known about ...how microbial communities responded to environmental factors (e.g. salinity, geographic distance) in lake surface sediments of the Qinghai-Tibetan Plateau (QTP). In this study, microbial diversity and community structure in the surface sediments of nine lakes on the QTP were investigated by using the Illumina Miseq sequencing technique and the resulting microbial data were statistically analyzed in combination with environmental variables. The results showed total microbial community of the studied lakes was significantly correlated (r = 0.631, P < 0.001) with lake salinity instead of geographic distance. This suggests that lake salinity is more important than geographic distance in shaping the microbial diversity and community structure in the studied samples. In addition, the abundant and rare taxa (OTUs with relative abundance higher than 1% and lower than 0.01% within one sample, respectively) were significantly (P < 0.05) correlated (r = 0.427 and 0.783, respectively) with salinity, suggesting rare taxa might be more sensitive to salinity than their abundant counterparts, thus cautions should be taken in future when evaluating microbial response (abundant vs. rare sub-communities) to environmental conditions.
Ecological consequences of the increased input of allochthonous and autochthonous organic matter (OM) remains unknown in saline lakes. Here, we reported microbial mineralization of algal and grass OM ...(represented by autochthonous and allochthonous OM, respectively) in lake sediments with different salinity (1, 40, and 120 g L−1). The addition of algal and grass OM significantly increased the CO2 production rates in the studied sediments. Algal and grass OM input can induce positive priming effect (PE). PE intensity induced by grass OM input was significantly higher than that by algal OM input. PE intensity induced by algal and grass OM input decreased with increasing salinity. Bacterial taxa affiliated with Actinomycetia, Alphaproteobacteria, Bacilli, Bacteroidia, Clostridia, and Gammaproteobacteria played important roles in driving PE generation in the studied sediments. Our finding suggested that the PEs induced by allochthonous and autochthonous OM should be considered in saline lakes that are intensively influenced by climate change.
Plain Language Summary
Global warming changes the salinity of lakes and the load of allochthonous and autochthonous organic matter (OM) input into lakes. Yet, there is a knowledge gap about how allochthonous and autochthonous OM input affects microbial mineralization of organic carbon in lake sediments with different salinity. We find that allochthonous and autochthonous OM input can induce positive priming effect (PE) in saline lakes, which decreased with increasing salinity of saline lakes. PE intensity induced by allochthonous OM is significantly higher than that by algal OM. Therefore, allochthonous and autochthonous OM input will accelerate the mineralization of native OM in saline lakes, with allochthonous OM exhibiting stronger influence on microbial mineralization of native OM than autochthonous OM. Consequently, allochthonous and autochthonous OM input may affect the storage and stability of OM in saline lakes under global warming.
Key Points
Allochthonous and autochthonous OM input can induce positive priming effect (PE) in saline lake sediments
Allochthonous OM input caused stronger PE intensity than autochthonous OM in saline lake sediments
Positive PE intensity increased with decreasing salinity of saline lakes
A survey was carried out on the microbial community of 20 groundwater samples (4 low and 16 high arsenic groundwater) and 19 sediments from three boreholes (two high arsenic and one low arsenic ...boreholes) in a high arsenic groundwater system located in Hetao Basin, Inner Mongolia, using the 454 pyrosequencing approach. A total of 233,704 sequence reads were obtained and classified into 12-267 operational taxonomic units (OTUs). Groundwater and sediment samples were divided into low and high arsenic groups based on measured geochemical parameters and microbial communities, by hierarchical clustering and principal coordinates analysis. Richness and diversity of the microbial communities in high arsenic sediments are higher than those in high arsenic groundwater. Microbial community structure was significantly different either between low and high arsenic samples or between groundwater and sediments. Acinetobacter, Pseudomonas, Psychrobacter and Alishewanella were the top four genera in high arsenic groundwater, while Thiobacillus, Pseudomonas, Hydrogenophaga, Enterobacteriaceae, Sulfuricurvum and Arthrobacter dominated high arsenic sediments. Archaeal sequences in high arsenic groundwater were mostly related to methanogens. Biota-environment matching and co-inertia analyses showed that arsenic, total organic carbon, SO4(2-), SO4(2-)/total sulfur ratio, and Fe(2+) were important environmental factors shaping the observed microbial communities. The results of this study expand our current understanding of microbial ecology in high arsenic groundwater aquifers and emphasize the potential importance of microbes in arsenic transformation in the Hetao Basin, Inner Mongolia.
Lakes receive large amounts of terrestrially derived dissolved organic matter (tDOM). However, little is known about how aquatic microbial communities interact with tDOM in lakes. Here, by performing ...microcosm experiments we investigated how microbial community responded to tDOM influx in six Tibetan lakes of different salinities (ranging from 1 to 358 g/l). In response to tDOM addition, microbial biomass increased while dissolved organic carbon (DOC) decreased. The amount of DOC decrease did not show any significant correlation with salinity. However, salinity influenced tDOM transformation, i.e., microbial communities from higher salinity lakes exhibited a stronger ability to utilize tDOM of high carbon numbers than those from lower salinity. Abundant taxa and copiotrophs were actively involved in tDOM transformation, suggesting their vital roles in lacustrine carbon cycle. Network analysis indicated that 66 operational taxonomic units (OTUs, affiliated with Alphaproteobacteria, Actinobacteria, Bacteroidia, Bacilli, Gammaproteobacteria, Halobacteria, Planctomycetacia, Rhodothermia, and Verrucomicrobiae) were associated with degradation of CHO compounds, while four bacterial OTUs (affiliated with Actinobacteria, Alphaproteobacteria, Bacteroidia and Gammaproteobacteria) were highly associated with the degradation of CHOS compounds. Network analysis further revealed that tDOM transformation may be a synergestic process, involving cooperation among multiple species. In summary, our study provides new insights into a microbial role in transforming tDOM in saline lakes and has important implications for understanding the carbon cycle in aquatic environments.
N-alkane-based proxies are widely employed to reconstruct paleoclimate and paleoenvironment in lacustrine environments. However, little is known about the influence of microbially mediated ...alkane-degradation on n-alkane-derived proxies. In this study, the chemical composition of n-alkanes and microbially mediated n-alkane degradation potential were investigated in the surface sediment samples collected from seven lakes with a range of salinity from freshwater to salt saturation on the northern Qinghai-Tibetan Plateau (QTP). The results showed that the chemical composition of n-alkanes differed among the studied QTP lakes. Significant correlations were observed between salinity and some n-alkane-based paleoclimate and paleoenvironment proxies, such as ratio of C21−/C22+, average chain length (ACL) and carbon preference index (CPI). This suggested that salinity may affect the validity of some n-alkane-based paleoclimate and paleoenvironment proxies. Alkane-degrading bacteria were abundant and widespread in the studied freshwater and saline/hypersaline lakes but were minor or absent in salt-saturation lakes. The obtained alkane-degrading bacterial strains showed active ability to degrade n-hexadecane. This suggested that the salinity influence on the n-alkane distribution may be partially related to microbial degradation, which awaits further in-situ investigation. So salinity variation should be taken into account when using n-alkane-based proxies for reconstructing paleoclimate and paleoenvironment in lakes.
•Chemical composition of n-alkanes differed among the studied lakes of different salinity•Salinity may affect the validity of n-alkane-based paleoclimate proxies.•Alkane-degrading bacteria showed active ability to degrade n-hexadecane.•Microbial degradation may partially account for salinity influence on n-alkane distribution.•Salinity variation should be taken into account when using n-alkane-based proxies.
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•Molecular composition of DOM differs significantly with lake salinity.•Oxidation state of carbon of DOM increases with lake salinity.•Molecular weight and number of carbon atoms in ...DOM decrease with lake salinity.•Environmental and microbial factors shape DOM composition in saline lakes.•Microbes explain lake DOM composition better than environmental factors.
Increased knowledege of the molecular composition of dissolved organic matter (DOM) is of great importance for an improved understanding of carbon cycling in lakes. However, such information remains limited for saline lakes. Here, DOM molecular compositions and microbial community structures were investigated in saline lakes with a full range of salinity from freshwater to hypersaline. An integrated approach, including Fourier transform-ion cyclotron resonance mass spectrometry and Illumina sequencing was employed. The results showed that in the studied saline lakes, aliphatic compounds, highly unsaturated and oxygen poor/rich compounds were the dominant DOM molecules. With increasing salinity, the molecular weight and carbon contents of the DOM molecules decreased, while their oxygen contents and carbon oxidation states increased. DOM molecular composition was significantly correlated with multiple environmental variables (i.e., chlorophyll a, salinity, pH) and with microbial components. The synergy of environmental and microbial factors exhibited great importance in explaining the variation of DOM molecular composition. Comparatively, microbial factors alone gave a much better explanation than environmental factors alone of the variation of DOM molecular composition, emphasizing the tight connection between DOM molecular composition and microbial communities. Taken together, these findings help improve our understanding of the molecular composition of DOM and its influencing factors in saline lakes.
Identifying interactions among river water, groundwater and salt lake brine is important for sustainable exploitation of brine mineral resources. In this study, we investigated the water exchange ...rate in dry and wet seasons, and assessed the influence of seasonal water exchange on brine concentration and crystallization process in the Nalenggele (NLGL) catchment of Qaidam Basin, China. The results show that the surface water infiltration and groundwater recharge rates in the wet season were 2.81 × 10
−3
and 1.15 × 10
−3
m
3
/(s·m) in upstream, 1.63 × 10
−2
and 1.53 × 10
−2
m
3
/(s·m) in midstream, and 2.83 × 10
−4
and 6.82 × 10
−5
m
3
/(s·m) in downstream, respectively; while their counterparts in the dry season were 9.81 × 10
−4
and 5.05 × 10
−4
m
3
/(s·m) in upstream, and 8.34 × 10
−3
and 7.78 × 10
−3
m
3
/(s·m) in midstream, respectively. The water exchange strongly influenced brine concentration and crystallinzation process, with brine chemistry belonging to 3K
2
SO
4
·Na
2
SO
4
and KCl types in wet and dry seasons, respectively. The strong water exchange in wet season destroyed the water-salt balance, while the low water exchange rate in dry season facilitated preparation of KCl products.
Little is known about the relative importance of spatial and environmental factors to structuring aquatic and sedimentary microbial biogeography in lakes. Here, we investigated the microbial ...community composition (MCC) of the water (
= 35) and sediment (
= 35) samples from 16 lakes in western China (salinity: freshwater to salt saturation; pairwise geographical distance: 9-2027 km) using high-throughput sequencing and evaluated the relative importance of spatial and environmental factors to microbial (including total, abundant, and rare) distributions. Our results showed that spatial factors were more important than environmental factors in shaping the biogeography of aquatic and sedimentary microbial communities in the studied lakes, and spatial factors on abundant microbial community was stronger than that on the total/rare microbial communities. Moreover, sedimentary rare MCC might be more sensitive to environmental factors than its aquatic counterpart. Such different biogeography responses of total, abundant, and rare communities to environmental and spatial factors could be ascribed to different physiochemical properties between water and sediment. Collectively, this study expands our understanding of factors shaping microbial biogeography of total, abundant, and rare communities between waters and sediments of lakes.
Past studies have revealed the important roles of certain types of microbes in precipitating dolomite in coastal hypersaline lakes and lagoons, and marine sediments, however, it is still poorly known ...if other types of microbes can precipitate dolomite in low-salinity lakes without any marine influence. The objective of this study was therefore to expand the microbial dolomite precipitation model by investigating the origin of dolomite in the sediments of Qinghai Lake, an inland, slightly saline lake (salinity 12.5
g/L) on the Tibetan Plateau, NW China. This objective was accomplished via an integrated approach combining geochemical investigations of natural dolomite present in the lake sediments with laboratory precipitation experiments. A 5-m sediment core was collected and pore water chemistry was analyzed. Calculation of saturation index indicated that dolomite was oversaturated in sediment pore water. Sub-spherical grains of dolomite with abundant pores and microstructures, similar to microbially precipitated dolomite, were found in the sediments, suggesting a biogenic origin. Dolomite precipitation experiments were set up in the laboratory to simulate the natural conditions of the Qinghai Lake. Dolomite was precipitated using sulfate reducing bacterium (SRB)
Desulfotomaculum ruminis and aerobic halophilic bacterium
Halomonas marina present in the Qinghai Lake sediments. Aqueous geochemistry and mineral characterization data collectively suggest that dolomite precipitation was accomplished via increase of pH and alkalinity to overcome the kinetic inhibitors and exopolymeric substances (EPS) and cell walls as possible nucleation sites. These results expand the current microbial dolomite precipitation model and have implications for dolomite formation in slightly saline, inland lake environments.
►Biogenic dolomite was revealed in a non-hypersaline inland lake, Qinghai Lake, NW China. ►Pore water of the Qinghai Lake sediments was supersaturated with respect to dolomite. ►Laboratory experiment confirmed the role of SRB and halophilic bacteria in dolomite precipitation. ►Increase of pH and alkalinity overcame the kinetic inhibitors to dolomite formation. ►Exopolymeric substances and cell walls serve as nucleation sites for dolomite precipitation.
Uncovering the limiting factors for benthic algal distributions in lakes is of great importance to understanding of their role in global carbon cycling. However, limited is known about the benthic ...algal community distribution and how they are influenced by geographic distance and environmental variables in alpine lakes. Here, we investigated the benthic algal community compositions in the surface sediments of six lakes on the Qinghai-Tibetan Plateau (QTP), China (salinity ranging from 0.8 to 365.6 g/L; pairwise geographic distance among the studied lakes ranging 8-514 km) employing an integrated approach including Illumina-Miseq sequencing and environmental geochemistry. The results showed that the algal communities of the studied samples were mainly composed of orders of
,
,
,
,
,
, and
. The benthic algal community compositions in these QTP lakes were significantly (
< 0.05) correlated with many environmental (e.g., dissolved inorganic and organic carbon, illumination intensity, total nitrogen and phosphorus, turbidity and water temperature) and spatial factors, and salinity did not show significant influence on the benthic algal community structures in the studied lakes. Furthermore, geographic distance showed strong, significant correlation (
= 0.578,
< 0.001) with the benthic algal community compositions among the studied lakes, suggesting that spatial factors may play important roles in influencing the benthic algal distribution. These results expand our current knowledge on the influencing factors for the distributions of benthic alga in alpine lakes.
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