Lentic Research Articles

Significant diurnal variations in nitrous oxide (N2O) emissions from two contrasting habitats in a large eutrophic lake (Lake Taihu, China)

Algae and macrophytes in lake ecosystems regulate nitrous oxide (N2O) emissions from eutrophic lakes. However, knowledge of diurnal N2O emission patterns from different habitats remains limited. To understand the diurnal patterns and driving mechanisms of N2O emissions from contrasting habitats, continuous in situ observations (72 h) of N2O fluxes from an algae-dominated zone (ADZ) and reed-dominated zone (RDZ) in Lake Taihu were conducted using the Floating Chamber method. The results showed average N2O emission fluxes of 0.15 ± 0.06 and 0.02 ± 0.04 μmol m−2 h−1 in the ADZ and RDZ in autumn, respectively. The significantly higher (p < 0.05) N2O fluxes in the ADZ were mainly attributed to differences in nitrogen (N) levels. The results also showed significant diurnal differences (p < 0.05) in the N2O emission fluxes within the ADZ and RDZ, and daytime fluxes were significantly higher (p < 0.05) than nighttime fluxes. The statistical results indicated that N2O emissions from the ADZ were mainly driven by diurnal variations in N loading and the dissolved oxygen (DO) concentration, and those from the RDZ were more influenced by DO, redox potential, and pH. Finally, we determined the proper time for routine monitoring of N2O flux in the two habitats. Our results highlight the importance of considering diverse habitats and diurnal variations when estimating N2O budgets at a whole-lake scale.

Effects of water conservancy-project policies on lake ecology, rural economy, leisure-environment development, and local young people’s willingness to engage in leisure activities

Context No consensus has yet been formed on project development in lake-water conservancy on aspects such as lake quality, ecological environment, rural economy, social culture, leisure living environment and leisure aspirations due to the current lack of comprehensive discussion. Aims This study mainly uses the case of Sun Moon Lake in Taiwan to verify the impact of lake-tourism optimisation and water-conservancy projects on the rural economy, water quality, ecology and sustainable development of tourism for local young people in the area around the lake. Methods We employed open-sampling questionnaires and semistructured interviews to collect data and conducted multivariate analysis. Key results The study investigated the hypothesis that optimising water-conservancy projects for lake tourism creates a stable leisure and tourism environment in rural areas, enhances visibility, and increases emotional exchanges and the preservation of historic sites. However, problems such as excessive tourism waste and a lack of public facilities negatively affect local young consumers’ willingness to engage in tourism activities. Conclusions Improving problems in the villages, ecology and natural environment surrounding lakes that are being conserved can increase young local individuals’ willingness to engage in and share experiences of tourism activities. Implications If the local government can improve the issues of protected villages, ecology and the natural environment around the lake, it can increase the willingness of local young people to participate in and share their experiences in tourism activities.

Effects of Surface Area and Water Level Variability on Fisheries Production in Lake Naivasha, Kenya

Lake Naivasha is a freshwater, a Ramsar site and an Important Bird Area. It provides multiple services to the surrounding communities such as Fishing, Tourism and Agriculture. Lake Naivasha has been experiencing a water level variation cycle over the years as a result of it being shallow and experiencing high evaporation. Variation in water levels leads to flooding, and receding which disrupts the Lake ecosystem thus causing direct and indirect effects on fishing. The study was conducted to establish the relationship between Surface area and water level variability and fish yield and revenue in Lake Naivasha. Primary data was collected using a semi-structured questionnaire, and Key informant interviews. Secondary data was collected using Landsat images that provided the temporal and spatial water level variability and documentary analysis between 1989 to 2022. Both descriptive statistics and inferential statistics were used for data analysis. The results show a positive correlation between Surface area Variability and fish yield (r= 0.6261, R2= 0.3920) and fish revenue (r= 0.5219, R2= 0.2724). Surface area variability accounts for 39% of the variation in total fish yield, and 27% of the fish revenue. The study recommends continuous monitoring and surveillance of the lake level, and water quality by the relevant government agencies, as well as watershed management and conservation measures for the sustainability of the Lake’s fishery.

Diagnosis of The State and Changes in The Ecosystem of Lake Onego and Watershed Based on The Information-Analytical System

The results of the diagnosis of the state and changes in the ecosystem of Onegskoe Lake (Lake Onego) and the watershed are presented using the developed information and analytical system “Lake Onego-watershed” (IAS), consisting of a comprehensive database (DB), a combined database of Roshydromet and Northern water problems institute/Karelian Research Center of the Russian Academy of Sciences on the nutrient load for the modern period 1995–2022, the ILLM mathematical model for assessing the removal of nutrients from the watershed and the formation of the nutrient load on the lake and the 3D-mathematical model SPLEM, developed for Lake Onego. Information was collected on the main sources of nutrient load in the Lake Onego catchment area, as well as available field observation data on the flow of nitrogen and phosphorus into the lake. The contribution of different nutrient sources coming from river runoff, diffuse sources, urban discharges and from trout farms was calculated for the lake and the main limnic areas. Based on data from field observations over the past 30 years and the results of numerical experiments using the SPLEM model with a grid resolution of 1 km it is shown that the ecosystem of the lake not only did not restored after the reduction in anthropogenic load after 1991, but eutrophication of waters in the lips and bays continues due to the influence of industrial and agricultural enterprises, trout farms and noticeable climate warming. Functional for the IAS “Lake Onego-catchment” to visualize the main modeling results on a 1 km grid was developed, and a web application interface has been created.

About mathematical modeling in limnology, oceanology, ecology and economics in the works of V.V. Menchutkin

The article gives a brief review of the works of Doctor of Biological Sciences, Prof. V.V. Menshutkin for the 65-year period of scientific activity, which began in the 60s of the XX century with experimental works on the hydrophisics of Lake Baikal and the first mathematical models of the perch population of the small lake Kherya-Yarvi (Karelian Isthmus) and fish community in Lake Dalneye (Kamchatka). The latter was of great practical importance when concluding an agreement with Japan on catch quotas for sockeye salmon.V.V. Menshutkin’s range of interests was very wide and included mathematical modeling in biology, physiology, limnology, oceanology, demography, economics, ecology and rational nature management. The works on research of water objects and processes in them include modeling of dynamics of fish and aquatic invertebrate populations, Antarctic krill. He created mathematical models of ecosystems of Ladoga and Onega lakes, and during oceanic expeditions of the Academy of Sciences — of the Sea of Japan and the Peruvian upwelling area.His research in the field of physiology of blood circulation and water-salt metabolism, works related to space subjects, modeling of diagnostics and treatment of mental diseases are interesting. V.V. Menshutkin paid special attention to the issues of biological evolution. V.V. Menshutkin paid special attention to the issues of biological evolution and modeling of evolutionary process. The mathematical apparatus used by V.V. Menshutkin is very broad. The mathematical apparatus used by V.V. Menshutkin is very wide: from systems of differential equations to finite automata, neural networks, fuzzy logic and cognitive modeling (a new direction in artificial intelligence), with which the studies of ecological-socio-economic systems of water bodies catchments were connected.O.P. Savchuk and V.V. Menshutkin united research methods — mathematical modeling and objects under study: oceans, seas and lakes. However, their only joint work was the collective monograph on the results of “Nevskaya Guba” project, which conclusions became the basis for the important decision to complete the construction of the dam in St. Petersburg.

Forms and Migration Mechanisms of Phosphorus in the Ice, Water, and Sediments of Cold and Arid Lakes.

Phosphorus (P) is a crucial nutrient in lake ecosystems and organic phosphorus (Po) is a significant component. However, the distribution characteristics and migration behaviour of Po in ice-water-sediment systems under freezing and thawing conditions in cold and arid regions remain unclear. This study aims to investigate the forms of Po and its contribution to endogenous P pollution. We selected three lakes (Dai, Hu, and Wu Lake) and employed phosphorus nuclear magnetic resonance (31P-NMR) techniques to analyse the following: (1) The total phosphorus (TP) content, which was the highest in the water from Dai Lake (0.16 mg/L), with substantial seasonal variation observed in Wu Lake, where P content was four times higher in summer than in winter because of farmland drainage. (2) Eutrophication analysis, which indicated that Dai Lake had significantly higher eutrophication levels than Wu Lake, with P being the controlling factor in Dai Lake and both N and P in Wu Lake. The proportion of Po in the TP content was 90%, 70%, and 55% for Wu, Dai, and Hu Lake, respectively, indicating that Po was the main component of eutrophic lakes. (3) 31P-NMR, which revealed that orthophosphate (Ortho-P) and monoester phosphate (Mon-P) were the main P components in the winter, with a higher P content in Dai Lake. Ortho-P has a higher content in ice, indicating that inorganic phosphorus (Pi) migration is the main factor in ice-water media. Mon-P showed multiple peaks in Dai Lake, indicating a complex composition of adenosine monophosphate and glucose-1-phosphate. (4) The ice-water phase change simulation experiments, which showed that phosphate was the least repelled in ice, while pyrophosphate (Pyro-P) and macromolecular P were more repelled. Adding sediment enhanced the migration of P but did not change the repulsion of macromolecular P, suggesting the molecular structure as the main influencing factor. These results provide important scientific evidence for the quantitative analysis of Po pollution in lake water environments, aiding in P load reduction and risk prevention and control.

Time-series metagenomics reveals changing protistan ecology of a temperate dimictic lake

BackgroundProtists, single-celled eukaryotic organisms, are critical to food web ecology, contributing to primary productivity and connecting small bacteria and archaea to higher trophic levels. Lake Mendota is a large, eutrophic natural lake that is a Long-Term Ecological Research site and among the world’s best-studied freshwater systems. Metagenomic samples have been collected and shotgun sequenced from Lake Mendota for the last 20 years. Here, we analyze this comprehensive time series to infer changes to the structure and function of the protistan community and to hypothesize about their interactions with bacteria.ResultsBased on small subunit rRNA genes extracted from the metagenomes and metagenome-assembled genomes of microeukaryotes, we identify shifts in the eukaryotic phytoplankton community over time, which we predict to be a consequence of reduced zooplankton grazing pressures after the invasion of a invasive predator (the spiny water flea) to the lake. The metagenomic data also reveal the presence of the spiny water flea and the zebra mussel, a second invasive species to Lake Mendota, prior to their visual identification during routine monitoring. Furthermore, we use species co-occurrence and co-abundance analysis to connect the protistan community with bacterial taxa. Correlation analysis suggests that protists and bacteria may interact or respond similarly to environmental conditions. Cryptophytes declined in the second decade of the timeseries, while many alveolate groups (e.g., ciliates and dinoflagellates) and diatoms increased in abundance, changes that have implications for food web efficiency in Lake Mendota.ConclusionsWe demonstrate that metagenomic sequence-based community analysis can complement existing efforts to monitor protists in Lake Mendota based on microscopy-based count surveys. We observed patterns of seasonal abundance in microeukaryotes in Lake Mendota that corroborated expectations from other systems, including high abundance of cryptophytes in winter and diatoms in fall and spring, but with much higher resolution than previous surveys. Our study identified long-term changes in the abundance of eukaryotic microbes and provided context for the known establishment of an invasive species that catalyzes a trophic cascade involving protists. Our findings are important for decoding potential long-term consequences of human interventions, including invasive species introduction.BaNPxYigHXA7H5uqkH8sryVideo

Contaminant and Assessment of Heavy Metals in Maninjau Lake, West Sumatera, Indonesia

Purpose: Water is an important fundamental resource to support human, animal and plant life. Global reports highlight widespread contamination of water sources due to various human activities. The high level of anthropogenic activity in the Lake Maninjau area, both in agriculture, animal husbandry and settlements, has an impact on decreasing the quality of the lake as indicated by the quality of the sediment and lake water. The research aims to evaluate heavy metal concentrations in sediments and heavy metal processing strategies. Theoretical Framework: Lake Maninjau is one of the lakes in Indonesia that experiences pollution. Recently, this lake has become one of the priority lakes to reduce high levels of pollution (Ministry of the Environment, 2011). The source of Lake Maninjau pollution comes from floating net cages, agriculture, settlements and livestock. This is shown by the accumulation of heavy metals in waters and sediments which is important information for the survival of fish, humans, plants, microorganisms and other aquatic ecosystems (Wibowo et al. , 2022a). Method: The five distinct sample locations were chosen to represent various activities within the Maninjau Lake region, as outlined in Figure 1 and Table 1. Sediment was taken at the surface at a depth of 0-10 cm. samples were processed and analyzed at the P3IN soil science laboratory, Andalas University, as well as assessing sediment quality through Geoaccumulation (Igeo), enrichment factor (EF), pollutant load index (PLI), contamination factor (CF), and potential ecological risk (PER) in five location of Lake Maninjau. Results and Discussion: The results of the research showed that Cu concentrations varied from 0.195 mg/kg to 0.290 mg/kg, with a moderate average of 0.246 mg/kg. Pb metal ranges between 0.325 mg/kg-0.412 mg/kg, with an average of 0.356 mg/kg. Cd metal 0.301 mg/kg- 0.365 mg/kg. The Igeo values for the metals Cr, Cd, Pb, and Cu at the five locations show Igeo &lt; 0, meaning they are not contaminated with heavy metals. The Potential Ecological Risk Index (PER) ranges from 14.8303-19.0094, which shows the low potential ecological risk related to heavy metal pollution Research Implications: It is hoped that this research can help stakeholders in managing the Maninjau Lake ecosystem against potential heavy metal contamination that threatens the lake ecosystem Originality/Value: The use of combination or hybrid technologies to treat heavy metals from wastewater is an effective solution, but it is important to carefully consider and mitigate potential negative impacts on the environment and human health.

Latitudinal patterns of shifts in cladoceran communities throughout the Holocene: A paleoecological case study of northwestern Russia

Paleolimnology is a rapidly expanding field within the natural sciences. To date, many scientific papers have been published focusing on studies of remains from single sediment cores in specific lakes, or a few cores from the same water body. However, few previous publications have provided a comprehensive comparative analysis of taphocenosis (and maternal community) changes in different water bodies from a large geographical region during whole Holocene using multivariate statistical methods. We conducted a joined statistical analysis of data obtained as a result of the cladoceran analysis of the sediment samples from six cores taken along the North-South transect from the Kola Peninsula to the Karelian Region (North-West Russia). Our aim was to identify, based on quantitative statistical methods, general whole-Holocene patterns in cladoceran taphocenosis changes. All taphocenoses in all cores from six lakes can be classified into six clusters based on their species composition. Our unexpected conclusion is that different taphocoenoses are formed by the same set of species, but their proportions vary significantly. This suggests that the same species may play different functional roles in different maternal communities. During whole Holocene, we observed a single taphocenosis cluster in the Holocene core from Lake Antyukh-Lambina, and four taphocenosis clusters in the Lake Medvedevskoe, with an intermediate number of clusters in the lakes between them. Furthermore, it can be asserted that the potential for cluster changes in the core is greater for the more southern studied water bodies (0–3 clusters for northern lakes vs. 4 clusters for southern lakes). Based on our data, we hypothesize that the diversity of cladoceran associations during the Holocene was lower in Arctic/Subarctic lakes, possibly due to their formation by ubiquitous species. Our study suggests that at least some Arctic lake ecosystems have remained unchanged since deglaciation times. Further studies are necessary to determine if this is a general rule.

North American crayfish harbour diverse members of the Nudiviridae

Three novel crayfish-infecting nudiviruses from crayfish in North America represent the first genomic confirmation of nudiviruses in crayfish: Faxonius propinquus nudivirus (FpNV), Faxonius rusticus nudivirus (FrNV), and Faxonius virilis nudivirus (FvNV). Histopathology and electron microscopy revealed nuclear infections, including nuclear hypertrophy in hepatopancreatic epithelial cells and the presence of membrane-bound bacilliform virions. Metagenomic sequencing resulted in complete circular genome assembly, and phylogenetic analyses (based on nudivirus core genes) placed these viruses within the unofficial Epsilonnudivirus genus. One of the nudiviruses was detected in the antennal gland of its host, and another is correlated with invasive crayfish decline in one infected lake ecosystem - suggesting a potential route for viral transmission through water, and possible population level impact. This study highlights the importance of genomic and ecological data in elucidating the diversity and evolutionary relationships of the Nudiviridae, while expanding their known diversity and range of host species.

Submerged macrophyte self-recovery potential behind restoration treatments: sources of failure.

When exploring the challenges of restoring degraded lakes, we often do not observe the expected results despite executing all planned activities. Our study elucidates the reasons that impede the recovery of submerged macrophytes despite ameliorated light conditions. When prolonged lake degradation occurs, subsequent efforts to increase light availability often prove insufficient, resulting in a persistent turbid water state. In this study, we attempted to determine the reasons for these failures through a germination test and propagule bank analysis conducted in bottom sediments from a severely degraded lake, which underwent restoration. Although the bottom sediments indicate relative potential in the number of oospores and seeds, their germination efficacy remained dismally low. Based on the germination test results and factors affecting the development of submerged macrophytes (physical and chemical parameters, lake morphology), we stated that improvement of light conditions in the lake could be insufficient to recover the vegetation, especially when the potential to renew diverse plant communities from sediments naturally is low. Our findings advocate for a paradigmatic shift in lake restoration strategies. A holistic approach that includes propagule bank assessments before embarking on restoration initiatives and enabling the identification of macrophyte resurgence potentials is recommended. We also advocate for a multifaceted restoration framework, emphasizing the indispensability of augmenting natural recovery mechanisms with targeted interventions. Consequently, in some cases, macrophyte reintroduction could be the only solution. By reintroducing autochthonic species to site-specific ecological dynamics, we anticipate an increased success rate in restituting submerged vegetation, thus catalyzing ecological regeneration within degraded lake ecosystems.

Groundwater inputs could be a significant but often overlooked source of phosphorus in lake ecosystems

Freshwater lakes are severely threatened, due largely to excess inputs of nutrients and other contaminants. Phosphorus (P) is receiving renewed attention due to recent increases in toxic cyanobacteria blooms in lakes worldwide. We investigated groundwater seepage for its role in P loading dynamics at Oneida Lake, New York, USA—one of the most well-studied lakes globally. P loading was measured at representative sites along the 88 km shoreline over three summers by directly measuring groundwater flow using seepage meters and porewater samplers. Groundwater seepage was a continuous and significant source of dissolved P over the summer months, comparable to tributary sources to the lake during that time. This constant input has enriched the concentrations of P in the nearshore surface waters, significantly above levels in the pelagic zone. Pore Total Phosphorus (TP) concentrations and loads reached extremely high values (up to 100 mg/L), with inorganic P representing only ~ 10% of TP per site. Groundwater seepage flows and P loadings were highly variable across space and time, partially explained by adjacent land uses and precipitation. Our research concludes that groundwater seepage is a significant, but overlooked, source of dissolved P and a crucial factor driving summer primary production at Oneida Lake, and likely other temperate lakes.

Environmental drivers of food webs in charr and trout‐dominated cold‐water lakes

AbstractCold‐water lakes situated in high latitudes and altitudes have pivotal socio‐ecological importance both globally and locally. However, they are increasingly threatened by multiple anthropogenic stressors, such as climate change, hydropower and invasive species. The development of efficient management strategies is therefore urgently needed and requires a comprehensive understanding of the factors influencing the biodiversity and ecological processes of these ecosystems. We provide a holistic knowledge base for informed future research and management by addressing the interplay between local and global environmental drivers of food webs in Arctic charr (Salvelinus alpinus, Salmonidae) and brown trout (Salmo trutta, Salmonidae) dominated cold‐water lakes in Fennoscandia. The trophic niche and population dynamics of these generalist top consumers provide extensive insights into the effects of natural and anthropogenic drivers on food webs in intensively studied Fennoscandian cold‐water lakes, covering marked biogeographical gradients in abiotic and biotic conditions. Drawing on a synthesis of existing literature, our focus is on three pivotal drivers: (1) lake location and connectivity, (2) lake area and morphometry and (3) fish community composition. These drivers significantly influence the complexity and the origin and flow of energy in lake food webs, and ultimately the size structure of the charr and trout populations. Furthermore, we highlight ongoing environmental changes in Fennoscandian cold‐water lakes caused by hydropower and invasive species. Finally, we identify crucial knowledge gaps and propose management actions for improving the future state of Fennoscandian cold‐water lake ecosystems and their charr and trout populations.

Molecular Phylogeny of Chlorophyta Species Isolated from a Shallow Lake Ecosystem

Studying the algal diversity of lentic ecosystems is an important issue for identifying the alteration in aquatic ecosystems. Morphological characterization of algae is inadequate to identify different types of microalgae and it is also necessary to depend on molecular evidence which is more crucial and a precise tool. In this study, two Chlorophyta species were identified; Tetradesmus dimorphus (Turpin) M.J.Wynne (Basionym: Scenedesmus dimorphus) and Chlorella sorokiniana Shihira &amp; R.W.Krauss), in a shallow lake. The evolutionary tree was constructed for both species and the results showed that the Iraqi Tetradesmus dimorphus isolate was placed in clade 4, more closely related to the Tetradesmus dimorphus from USA, China, Pakistan, and Sweden with similarity 99 %, 99%, 97 %, and 96 % for all respectively. The Iraqi isolated Chlorella sorokiniana (OP718564.1) is within the clade 2, and composed sister group with Chlorella sorokiniana (KU29188.1) from the USA, with 99 % similarity.

The role of Anchoviella spp. as forage species in different stages of reservoir development in the upper Tocantins River, Central Brazil.

We report the spatiotemporal increase in abundance of Anchoviella spp. (Engraulidae) through the diet of fish consumers after reservoir formation in the upper Tocantins River, Central Brazil. The increase in the abundance of this planktivorous fish evidences the growing importance of autochthonous herbivory food chains as the reservoir stabilized in this novel lentic ecosystem. These changes would otherwise remain unnoticed only through fish sampling, highlighting the importance of assessing trophic interactions to understand responses to damming at the community and ecosystem levels.

Emergence of lake conditions that exceed natural temperature variability

Lake surface temperatures are projected to increase under climate change, which could trigger shifts in the future distribution of thermally sensitive aquatic species. Of particular concern for lake ecosystems are when temperatures increase outside the range of natural variability, without analogue either today or in the past. However, our knowledge of when such no-analogue conditions will appear remains uncertain. Here, using daily outputs from a large ensemble of SSP3-7.0 Earth system model projections, we show that these conditions will emerge at the surface of many northern lakes under a global warming of 4.0 °C above pre-industrial conditions. No-analogue conditions will occur sooner, under 2.4 °C of warming, at lower latitudes, primarily due to a weaker range of natural variability, which increases the likelihood of the upper natural limit of lake temperature being exceeded. Similar patterns are also projected in subsurface water, with no-analogue conditions occurring first at low latitudes and occurring last, if at all, at higher latitudes. Our study suggests that global warming will induce changes across the water column, particularly at low latitudes, leading to the emergence of unparalleled climates with no modern counterparts, probably affecting their habitability and leading to rearrangements of freshwater habitats this century.

Ecological restoration enhanced the stability of epiphytic microbial food webs of submerged macrophytes: Insights from predation characteristics of epiphytic predators

The application of various submerged macrophytes for ecological restoration has gained increasing attention in urban lake ecosystems. The multitrophic microbial communities that colonized in various submerged macrophytes constitute microbial food webs through trophic cascade effects, which affect the biogeochemical cycles of the lake ecosystem and directly determine the effects of ecological restoration. Therefore, it is essential to reveal the diversity, composition, assembly processes, and stability of the microbial communities within epiphytic food webs of diverse submerged macrophytes under eutrophication and ecological restoration scenarios. In this study, we explored the epiphytic microbial food webs of Vallisneria natans and Hydrilla verticillata in both eutrophic and ecological restoration regions. The obtained results indicated that the two regions with different nutrient levels remarkably affected the diversity and composition of epiphytic multitrophic microbial communities of submerged macrophytes, among them, the community composition of epiphytic predators were more prone to change. Secondly, environmental filtering effects played a more important role in driving the community assembly of epiphytic predators than that of prey. Furthermore, the generality and intraguild predation of epiphytic predators were significantly improved within ecological restoration regions, which increased the stability of epiphytic microbial food webs. Additionally, compared with Hydrilla verticillata, the epiphytic microbial food webs of Vallisneria natans exhibited higher multitrophic diversity and higher network stability regardless of regions. Overall, this study focused on the role of the epiphytic microbial food webs of submerged macrophytes in ecological restoration and uncovered the potential of epiphytic predators to enhance the stability of microbial food webs, which may provide new insights into the development of ecological restoration strategies.

Hydrometeorological conditions drive long-term changes in the spatial distribution of Potamogeton crispus in a subtropical lake.

Globally, anthropogenic disturbance and climate change caused a rapid decline of submerged macrophytes in lake ecosystems. Potamogeton crispus (P. crispus), a species that germinates in winter, explosively expanded throughout many Chinese lakes, yet the underlying mechanism remained unclear. Here, this study examined the long-term changes in the distribution patterns of P. crispus in Lake Gaoyou by combining remote sensing images and hydrometeorological data from 1984 to 2022 and water quality data from 2009 to 2022. It aims to unravel the relationships between the distribution patterns of P. crispus and hydrometeorological and water quality factors. The results showed that the area of P. crispus in Lake Gaoyou showed a slight increase from 1984 to 2009, a marked increase from 2010 to 2019, followed by a decline after 2020. Spatially, P. crispus was primarily distributed in the western and northern parts of Lake Gaoyou, with less distribution in the central and southeastern parts of the lake. Wind speed (WS), temperature (Temp), water level (WL), ammonia nitrogen (NH3-N), and Secchi depth (SD) were identified as the key factors regulating the variation in the P. crispus area in Lake Gaoyou. We found that the P. crispus area showed an increasing trend with increasing Temp, WL, and SD and decreasing WS and NH3-N. The influence of environmental factors on the area of P. crispus in Lake Gaoyou varied among seasons. The results indicated that hydrometeorology (WS, Temp, and WL) may override water quality (NH3-N and SD) in driving the succession of P. crispus distribution. The findings of this study offer valuable insights into the recent widespread expansion of P. crispus in shallow lakes across Eastern China.

The dominant role of human activity intensity in spatial pattern of ecosystem health in the Poyang Lake ecological economic zone

Human activities are the main factors threatening ecosystems, and ecological management should place a strong emphasis on guiding their positive development. More targeted and differentiated ecological preservation strategies can be proposed with research on the regional variability of the interaction between ecosystems and human activities. Utilizing the Vigor-Organization-Resilience-Services (VORS) model and the land surface human activity intensity model, the ecosystem health index (EHI) and human activity intensity (HAI) of the Poyang Lake Ecological Economic Zone (PLEEZ) were evaluated, respectively. Furthermore, their spatial association was investigated using spatial autocorrelation analysis, and the effect of HAI on EHI was analyzed using Geographic Detector and Geographic Weighted Regress. The results revealed that in the PLEEZ, (1) The zones of intensified human activity were highly consistent with the expansion of built-up land, and the EHI here has always been the lowest; (2) The HAI and EHI showed a significant and increasing spatial negative correlation, manifested as high HAI with low EHI clustering in the central plains and the adverse in the peripheral mountainous areas. (3) The HAI has the highest explanatory power on the spatial pattern of EHI, and its influence was greatest at the lower EHI. (4) Natural ecosystems with high EHI were highly sensitive to HAI, while areas with low EHI were less sensitive. The research can offer theoretical guidance for ecological construction in the future. The adverse effects of human activities in PLEEZ can be reduced through strict regulation of natural ecological sources, intensive utilization of human gathering areas, and promotion of green production and lifestyle.

20th century climate warming and human disturbance triggered high aquatic production and strong water-column mixing in maar Lake Xiaolongwan, northeastern China

Lake ecosystems in northeastern (NE) China are sensitive to global environmental change, and are currently under threats of eutrophication and hypolimnetic anoxia. However, the lack of long-term records of lake production and anoxia in this region makes it difficult to discriminate the impacts of recent anthropogenic activity on lake ecosystems from natural ecosystem variability. This study investigates varved sediments from remote maar Lake Xiaolongwan, NE China and reconstructs high-resolution changes in lake primary production, anoxia, nutrient cycling and catchment processes over the past 1500 years using hyperspectral imaging inferred sedimentary total chlorophyll-a and bacteriopheophytin-a (Bphe-a), combined with sedimentary iron and phosphorus fractions data. Results show that, prior to discernible human impacts in this area from ∼600 CE to 1900 CE, lake primary production was higher during warm periods and reduced during cold periods. Bphe-a records show that hypolimnetic anoxia persisted regardless of temperature variability. Cluster analysis suggests that lake algal communities and biogeochemical conditions in the twentieth-century warm period are unprecedented and significantly different from any other time over the past 1500 years. This phenomenon mostly results from global warming and stronger local catchment disturbance in the early 1900s, combined with atmospheric pollution after the 1950s. Human-driven climate warming has caused stronger seasonal mixing (due to shortened ice-cover duration) and overall better oxygenation in the lake. This study demonstrates clear anthropogenic impacts to lake ecosytems in a relatively pristine region in NE China. We anticipate that our findings will have implications for understanding the status of aquatic ecosystems in NE China under future interacting stressors of anthropogenic climate warming and pollution.