Lake Cycle Research Articles

Effects of Changing Snow and Ice Cover Conditions on Phytoplankton Chlorophyll‐a and Community Composition in a Mesotrophic Lake

ABSTRACT Ice and snow cover on lakes plays a fundamental role for under‐ice ecology by reducing water column mixing and light availability. Previous studies have shown that such reductions can significantly influence the growth and reproduction of phytoplankton, primarily focusing on changes in ice‐on and ice‐off dates in a warming climate. This study goes beyond studying the effects of ice phenology on phytoplankton by addressing two fundamental questions: (1) how does a snow cover on ice influence below‐ice phytoplankton chlorophyll‐a and community composition and (2) how do variations in ice phenology influence spring phytoplankton chlorophyll‐a and community composition after ice‐off? To address these two questions, we assessed long‐term monitoring data collected at least monthly on phytoplankton chlorophyll‐a and community composition. We combined the phytoplankton data with annual ice phenology and nearby meteorological data on daily snow depth between 1997 and 2019 in a mesotrophic lake (Erken) in Sweden. Snow cover resulted in an exponential decrease of phytoplankton chlorophyll‐a, with detectable effects during all 3 months studied (January–March). Deeper snow cover changed the community dominance from autotrophs to mixotrophs in two of the months studied (January and March), which we explain by reduced light availability caused by snow cover. In spring, phytoplankton chlorophyll‐a increased with longer ice periods and delayed ice‐off dates. A wide range of taxa in the spring community increased with delayed ice‐off dates, while delayed ice‐on dates mainly promoted diatoms. Convective mixing is important to keep non‐motile taxa in the photic zone and could explain the increased phytoplankton growth with longer ice duration. Our results highlight seasonal ice and snow cover as key regulators for the timing of growth and reproduction of primary producers below ice, with effects of the ice cover period lasting after ice‐off. Snow on ice causes light constraints, which commonly result in reduced under‐ice primary production and a higher proportion of mixotrophs in the phytoplankton community. Losing high nutritional phytoplankton groups such as mixotrophs following changes in ice phenology and snow cover can have consequences for the trophic transfer and the biogeochemical cycling in lakes.

Differences in microbial communities and phosphorus cycles between rural and urban lakes: Based on glyphosate and AMPA effects.

Differences in microbial communities and phosphorus cycles between rural and urban lakes: Based on glyphosate and AMPA effects.

Diversity of primary vegetation species of lake shore impacts largely carbon emissions in thermokarst lakes on the Qinghai-Tibet plateau.

Diversity of primary vegetation species of lake shore impacts largely carbon emissions in thermokarst lakes on the Qinghai-Tibet plateau.

Sulfate concentration and redox state control the pyrite formation and sulfur cycle in a T-OAE lake, Sichuan Basin, China

Sulfate concentration and redox state control the pyrite formation and sulfur cycle in a T-OAE lake, Sichuan Basin, China

Understanding the Relationship Between Water Quality and Soil Nutrient Dynamics in Qinghai Lake Through Statistical and Regression Models

Lakes are essential ecosystems that play a significant role in water quality and biodiversity, particularly in nutrient cycling. Nitrogen compounds, including ammonium (NH4+), nitrate (NO3−), and nitrite (NO2−), are critical elements in lake ecosystems, influencing productivity and water quality. This study aimed to investigate nitrogen compounds in Qinghai Lake, assess water and soil quality indicators, and evaluate the relationship between nitrogen (N) and phosphorus (P) levels in water and soil. Water samples from 17 locations around the lake and soil samples from nine sites at two depths were analyzed for various parameters. Statistical and regression analyses were performed to explore the correlations between N forms in water and other parameters in water and total P, total N, and pH in soil, as well as their interactions with environmental variables. The mean concentrations of NO3−-N, NH4+-N, and NO2−-N were 0.0189 mg/L, 0.112 mg/L, and 0.595 mg/L in Qinghai Lake, respectively. The regression models revealed that the total P in water and soil, along with other environmental factors, play crucial roles in regulating N levels. These findings contribute to our understanding of N cycling in high-altitude lakes and provide insight into managing eutrophication risks in Qinghai Lake.

Bacteriophages carry auxiliary metabolic genes related to energy, sulfur and phosphorus metabolism during a harmful algal bloom in a freshwater lake.

Bacteriophages carry auxiliary metabolic genes related to energy, sulfur and phosphorus metabolism during a harmful algal bloom in a freshwater lake.

Impact of Grass Carp and Crucian Carp on Submerged Macrophyte and Phosphorus Cycling in Shallow Lake Mesocosms

Submerged macrophytes are essential for the restoration of shallow lakes for maintaining clear-water conditions. The presence of fish can affect the nutrient cycles and the growth of submerged macrophytes in lakes. In this study, a 28-day mesocosm experiment was carried out with an herbivorous fish Ctenopharyngodon idella (CID) and an omni-benthivorous fish Carassius auratus (CAU) to investigate their effects on the growth of a submerged macrophyte Hydrilla verticillata and phosphorus (P) cycle in shallow lakes. The results showed that CID slowed down the growth of H. verticillata while CAU showed no significant effect. In overlying water, CID only increased the ammonium nitrogen (NH3-N) concentration in the later stage due to excretion, while CAU elevated particulate phosphorus (PP) levels during the experiment through disturbance. Meanwhile, the radial oxygen loss and photosynthesis of H. verticillata in CAU might promote the formation of NaOH-P and HCl-P in the sediment, respectively. Changes in the water and sediment properties caused by CID and CAU can contribute to the increase in the eutrophication risk index (ERI). Our findings suggest that CID has the potential to be an indirect biological manipulation tool, while CAU should be controlled to minimize its negative impacts on the P cycle in lakes.

Satellite algorithms for retrieving dissolved organic carbon concentrations in Chinese lakes

Satellite algorithms for retrieving dissolved organic carbon concentrations in Chinese lakes

Iron as a precursor of aggregation and vector of organic carbon to sediments in a boreal lake

While organic matter (OM) interactions in the water column prevent iron (Fe) precipitation and sedimentation, Fe also acts as a precursor of aggregation and a vector of OM to sediments. This study aims to characterize Fe–OM interactions to understand the role of Fe in promoting aggregation and transport of OM. Samples of Fe and OM were collected from water, settling material, and sediment along a gradient starting from the inlet and continuing offshore within a boreal lake. Fe speciation was determined using X-ray absorption spectroscopy (XAS), and the chemical composition of OM was assessed using Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT IR) and Nuclear magnetic resonance spectroscopy (NMR). The results show a decrease in Fe and OM concentrations in the water column with increasing distance from the inlet. Winter sampling revealed a shift in Fe speciation from dominance of organically complexed Fe to an increase in Fe(oxy)hydroxide, accompanied by a loss of aromatic and carboxylate function of OM. Summer sampling revealed no significant changes along the gradient, with Fe(oxy)hydroxide and carbohydrates dominating the water phase. Interestingly, settling particles and surface sediments were dominated by Fe(oxy)hydroxides and aliphatic OM. We propose that phototransformation may be an important process that influences the interaction between Fe and OM and, as a consequence, their fate along the spatial gradient. Our study suggests a photochemically induced loss of carboxylate groups, reflected by an increased carbohydrate-to-carboxylate ratio along the gradient, particularly in winter, and generally lower levels during summer. Loss of carboxylate function promotes the formation of Fe(oxy)hydroxides, which in turn, facilitates the aggregation and sinking of OM, particularly aliphatic components. These insights contribute to a broader understanding of carbon cycling and storage in lakes. Future studies should assess the significance of photochemical processes to OM burial and it how may change given trends in Fe and OM in northern regions.

Functional Genes and Metabolic Pathways of Nitrogen Metabolism Microorganisms in Lake Sediments：A Case Study of Hongfeng Lake, Guizhou Province

The nitrogen cycle is of great importance for material circulation and energy flow in lake ecosystems. It is driven by microorganisms in lake sediments and can contribute to balancing lake ecosystems. In this study, physical and chemical properties of the sediments sampled from Hongfeng Lake in Guizhou Province were assayed and analyzed using metagenomics to reveal relevant microorganisms, functional genes, metabolic pathways, and their relationships throughout nitrogen metabolism. The results showed that bacteria were dominant, and the top three relative abundant genera were Thiobacillus （16.64%）, Rubrivivax（9.43%）, and Nitrospira （7.09%）. Only six pathways, including nitrogen fixation, nitrification, denitrification, assimilatory nitrate reduction, dissimilatory nitrate reduction, and complete nitrification, were detected in total, of which denitrification and dissimilatory nitrate reduction were the primary processes, but anaerobic ammonia oxidation was not detected. Bacteria and archaea participated in these six pathways, while eukaryotes only functioned in dissimilatory nitrate reduction, denitrification, and complete nitrification. Ammonia nitrogen, nitrate nitrogen, and total phosphorus, as main environmental factors affecting the distribution of functional genes for nitrogen metabolism, differentiated with each other in their respective real-world conditions. A positive correlation （95.04%） was observed between the functional genes and microorganisms, and narG, narZ, and nxrA possessed the highest abundance and the highest host genes. On this basis, these findings are expected to further elucidate the nitrogen cycle of typical karst lakes in Guizhou Province.

Hypoxia cycle in shallow lakes during winter (ice-covered to melting period): Stable and decay, hypoxia, and recovery phases

Hypoxia cycle in shallow lakes during winter (ice-covered to melting period): Stable and decay, hypoxia, and recovery phases

Permafrost-dissolved organic carbon and cladoceran grazing regulate bacterial abundance and community structure

The thawing of frozen soils has resulted in the release of tremendous amounts of organic carbon. Permafrost-derived dissolved organic carbon (DOC) has been demonstrated to be biolabile to microbes in aquatic ecosystems. Cladoceran grazing is another regulatory force that may affect the properties and/or characteristics of the bacterial community. However, the effects of permafrost DOC and cladoceran grazing on bacterial abundance, community composition, and diversity in aquatic ecosystems have rarely been explored. In this study, DOC was extracted from frozen soils adjacent to the shoreline of a pristine alpine lake and used to culture bacteria. The bacterial abundance decreased over time during the bioincubation experiment, whereas Daphnia feeding had no significant effect on the bacterial abundance. The genera Pedobacter, Novosphingobium, Flavobacterium and Limnohabitans had relatively high abundances after a 27-d bioincubation period. The overall decrease in bacterial diversity in the Daphnia grazing experiment was higher than that in the bacterial incubation experiment. The co-occurrence network demonstrated that terrestrial and microbial humic-like components C1 and C2 had strong interactions with Pseudolabrys, and tyrosine-like component C3 presented ­correlations with Hyphomicrobium and Vampirovibrio. Bacterial communities in the two experiments were significantly different. Sphingomonadales, Sphingobacteriales, Burkholderiales, and Actinomycetales were the primary contributors to these differences. Our study contributes significantly to a broader understanding of carbon cycling and microbial food web in lakes, particularly in high-altitude and polar lakes.

Phosphorus cycle in shallow lakes affected by crucian carp (Carassius auratus): Effects of fish density and size

Phosphorus cycle in shallow lakes affected by crucian carp (Carassius auratus): Effects of fish density and size

Invasive mussels reduce community bioturbation but do not affect oxygen penetration or nutrient fluxes in organic‐poor Great Lakes sediments

Abstract Invasive zebra and quagga (dreissenid) mussels have disrupted nutrient cycling and benthic macrofauna communities in the Laurentian Great Lakes and other invaded ecosystems. Dreissenids are now the dominant benthic macroinvertebrate in the Great Lakes, replacing the formerly dominant native bioturbating amphipod Diporeia spp. Dreissenids and Diporeia interact with their environment in fundamentally different ways, and the consequences of this functional shift in benthic community structure on benthic–pelagic coupling are not well understood, particularly in unproductive offshore lake regions. To determine how functional biology and benthic community structure impact sediment mixing and biogeochemistry in low particulate organic matter (POM) lake regions, we conducted a 6‐week sediment microcosm experiment with dreissenids, Diporeia and oligochaete worms—the second most common Great Lakes benthic macroinvertebrate. We found that sediment mixing rate and depth varied significantly among the taxa. Diporeia mixed sediment the deepest and strongest, followed by oligochaetes, while dreissenids did not appreciably mix sediment. Despite these differences, we found no significant variations among treatments in sediment oxygen penetration depth, sediment respiration (oxygen uptake) or nutrient dynamics. Our results suggest that dreissenids mix sediment less than native Great Lakes taxa, but that differential mixing rates may not measurably affect nutrient and oxygen dynamics in low‐POM sediments. Therefore, mussel effects in these areas may be manifested more through direct mechanisms rather than via altered sediment geochemistry.

Antarctic lake viromes reveal potential virus associated influences on nutrient cycling in ice-covered lakes.

The McMurdo Dry Valleys (MDVs) of Antarctica are a mosaic of extreme habitats which are dominated by microbial life. The MDVs include glacial melt holes, streams, lakes, and soils, which are interconnected through the transfer of energy and flux of inorganic and organic material via wind and hydrology. For the first time, we provide new data on the viral community structure and function in the MDVs through metagenomics of the planktonic and benthic mat communities of Lakes Bonney and Fryxell. Viral taxonomic diversity was compared across lakes and ecological function was investigated by characterizing auxiliary metabolic genes (AMGs) and predicting viral hosts. Our data suggest that viral communities differed between the lakes and among sites: these differences were connected to microbial host communities. AMGs were associated with the potential augmentation of multiple biogeochemical processes in host, most notably with phosphorus acquisition, organic nitrogen acquisition, sulfur oxidation, and photosynthesis. Viral genome abundances containing AMGs differed between the lakes and microbial mats, indicating site specialization. Using procrustes analysis, we also identified significant coupling between viral and bacterial communities (p = 0.001). Finally, host predictions indicate viral host preference among the assembled viromes. Collectively, our data show that: (i) viruses are uniquely distributed through the McMurdo Dry Valley lakes, (ii) their AMGs can contribute to overcoming host nutrient limitation and, (iii) viral and bacterial MDV communities are tightly coupled.

Quantifying the functional genes of C, N, P, and S cycling in a deep lake: Depth patterns and drivers

Quantifying the functional genes of C, N, P, and S cycling in a deep lake: Depth patterns and drivers

Seasonal dynamics and driving mechanisms of microbial biogenic elements cycling function, assembly process, and co-occurrence network in plateau lake sediments

Seasonal dynamics and driving mechanisms of microbial biogenic elements cycling function, assembly process, and co-occurrence network in plateau lake sediments

Antibiotic Pollution and Its Effects on the Spatiotemporal Variation in Microbial Community Structure and Functional Genes in Sediment of Baiyangdian Lake

Microbial communities play an important role in water quality regulation and biogeochemical cycles in lakes, and their community structure and function are affected by environmental factors. Therein, antibiotics affect the abundance, diversity, composition, and function of microbial communities. In this study, Baiyangdian Lake was selected as the study area. Sediment samples of 16 sites were collected in August 2018 and April 2019, respectively. Ultra-high performance liquid chromatography-mass spectrometry （HPLC-MS/MS） was used to determine the content of typical antibiotics-quinolones （QNs） in sediment. Through high-throughput sequencing technology, the structure and function of microbial communities was analyzed in the sediments to explore the spatiotemporal variation. Thereinto, redundancy analysis （RDA） was used to identify the key influencing factors of spatiotemporal variation of microbial communities. The results showed that： ① From August to April, the average ω（QNs） showed an increasing trend, and its mean value changed from 3.91 ng·g-1 to 6.34 ng·g-1, with significant seasonal differences in oxolinic acid （OXO） and total QNs content （P < 0.05）. ② In terms of temporal variation, the dominant bacteria were Proteobacteria and Chloroflexi. The relative abundance of Proteobacteria showed a decreasing trend, whereas Chloroflexi showed an increasing trend； at the genus level, the dominant bacteria genera in August were norank_ f__Anaerolineaceae and Thiobacilus, and the dominant bacteria genera in April were Acinetobacter and norank_ f_Anaerolineaceae, and the dominant bacteria genera had significant seasonal differences （P < 0.05）. ③ In terms of temporal variation, the index of Simpson, Chao, Ace, and OTU number all showed an increasing trend, and the seasonal differences were significant （P < 0.05）. ④ In terms of spatial variation, there were no significant spatial differences among functional genes of COG. In terms of temporal variation, there were significant seasonal differences in functional genes of energy production and conversion, carbohydrate transport and metabolism, transcription, cell wall/membrane/envelope biogenesis, and signal transduction mechanisms （P < 0.01 and P < 0.05）. ⑤ Microbial community structure and functional genes were significantly correlated with QNs （P < 0.01 and P < 0.05）, and QNs were the main influencing factors. Therefore, QNs were the main factor affecting the changes in microbial community structure and functional genes in sediments of Baiyangdian Lake. Thus, comprehensive control of antibiotic pollution in sediments should be further strengthened.

Both nutrients and macrophytes regulate organic carbon burial: Insights from high-resolution spatiotemporal records of a large shallow lake (Baiyangdian) in eastern China

Both nutrients and macrophytes regulate organic carbon burial: Insights from high-resolution spatiotemporal records of a large shallow lake (Baiyangdian) in eastern China

Spatial differences of dissolved organic matter composition and humification in an artificial lake.

The depth-dependent dynamics of dissolved organic matter (DOM) structure and humification in an artificial lake limits the understanding of lake eutrophication and carbon cycling. Using fluorescence regional integration (FRI) and parallel factor analysis (PARAFAC) models to analyze the 3D fluorescence spectroscopy dataset, we revealed the depth-dependent structure and vertical distribution of DOM in the estuarine and center regions of Lake Hongfeng. The percentage fluorescence response (Pi,n) showed humic acid is an important part of DOM in Lake Hongfeng. Fluorescence results show that the fulvic-like and protein-like materials in HF1-DOM located at the estuarine position showed greater variation in the middle stage, probably due to human influence and sediment suspension. Fluorescence index (PI+II+IV,n/PIII+V,n and FIC4/FIC3) can be used to indicate the degree of humification of DOM in artificial lakes. Results of each index show that the estuary is more affected by human activities, and the humification degree is significantly lower than that of the center of the lake. The evaluation index system of the humification degree of artificial lake established in this study can effectively predict the eutrophication state of the typical area of artificial lake and deeply understand the possible important influence of human activities on the carbon cycle of lake.