Ecosystem State Changes Research Articles

Unexpected hydrologic response to ecosystem state change in tallgrass prairie

In grasslands around the world, climate change is occurring in tandem with woody encroachment (the spread of woody vegetation in grass-dominated ecosystems). State transitions from grassland to shrub/woodland have been identified aboveground via changes in species cover and composition, but the hydrological impact of these transitions is not well understood. Shifts from grass- to woody-dominance have the potential to impact evapotranspiration, soil moisture dynamics, and groundwater recharge. Therefore, it is possible that the consequences of aboveground vegetation change may be observable in the hydrological system. We leveraged long-term hydrological records from a tallgrass prairie site in northeastern Kansas, USA, to examine how concurrent changes in climate and land-cover have altered hydrological dynamics over the last century. Stream discharge has declined in recent decades despite > 100 years of climate wetting. The relationship between incoming precipitation and streamflow has weakened over the last 40 years, suggesting that shifts in the physical landscape are altering patterns of hydrological connectivity. Long-term isotope records show a divergence in the isotopic composition of precipitation (no change in δ18O) and stream/groundwater (decreasing δ18O) over the last decade. These results suggest that woody encroachment is accelerating the hydrological cycle, potentially by decreasing groundwater recharge (via increased evapotranspiration) and/or increasing infiltration rates (via creation of macropores). Holistically, these changes illustrate the interdependence of above- and below-ground processes in the local hydrological cycle, and the cascading long-term consequences (decades to centuries) for critical zone function once woody encroachment has occurred.

Modeling of Future Streamflow Hazards in Interior Alaska River Systems and Implications for Applied Planning

There is a growing need for proactive planning for natural hazards in a changing climate. Computational modeling of climate hazards provides an opportunity to inform planning, particularly in areas approaching ecosystem state changes, such as Interior Alaska, where future hazards are expected to differ significantly from historical events in frequency and severity. This paper considers improved modeling approaches from a physical process perspective and contextualizes the results within the complexities and limitations of hazard planning efforts and management concerns. Therefore, the aim is not only to improve the understanding of potential climate impacts on streamflow within this region but also to further explore the steps needed to evaluate local-scale hazards from global drivers and the potential challenges that may be present. This study used dynamically downscaled climate forcing data from ERA-Interim reanalysis datasets and projected climate scenarios from two General Circulation Models under a single Representative Concentration Pathway (RCP 8.5) to simulate an observational gage-calibrated WRF-Hydro model to assess shifts in streamflow and flooding potential in three Interior Alaska rivers over a historical period (2008–2017) and two future periods (2038–2047 and 2068–2077). Outputs were assessed for seasonality, streamflow, extreme events, and the comparison between existing flood control infrastructure in the region. The results indicate that streamflow in this region is likely to experience increases in seasonal length and baseflow, while the potential for extreme events and variable short-term streamflow behavior is likely to see greater uncertainty, based on the divergence between the models.

Microtopographic Variation as a Potential Early Indicator of Ecosystem State Change and Vulnerability in Salt Marshes

As global climate change alters the magnitude and rates of environmental stressors, predicting the extent of ecosystem degradation driven by these rapidly changing conditions becomes increasingly urgent. At the landscape scale, disturbances and stressors can increase spatial variability and heterogeneity — indicators that can serve as potential early warnings of declining ecosystem resilience. Increased spatial variability in salt marshes at the landscape scale has been used to quantify the propagation of ponding in salt marsh interiors, but ponding at the landscape scale follows a state change rather than predicts it. Here, we suggest a novel application of commonly collected surface elevation table (SET) data and explore millimeter-scale marsh surface microtopography as a potential early indicator of ecosystem transition. We find an increase in spatial variability using multiple metrics of microtopographic heterogeneity in vulnerable salt marsh communities across the North American Atlantic seaboard. Increasing microtopographic heterogeneity in vulnerable salt marshes mirrored increasing trends in variance when a tipping point is approached in other alternative stable state systems — indicating that early warning signals of marsh drowning and ecosystem transition are observable at small-spatial scales prior to runaway ecosystem degradation. Congruence between traditional and novel metrics of marsh vulnerability suggests that microtopographic metrics can be used to identify hidden vulnerability before widespread marsh degradation. This novel analysis can be easily applied to existing SET records expanding the traditional focus on vertical change to additionally encapsulate lateral processes.

A robust approach and analytical tool for identifying early warning signals of forest mortality

Forests are facing unprecedented stressors, evidenced by increases in the rate of forest mortality. Characterizing the state of forest ecosystems and their responses to disturbances remains a complex and crucial task. Existing methodologies have rarely been evaluated in real-world ecosystems due to challenges such as limitations in data availability and analytical techniques. To address these gaps, this study employs remotely sensed spatio-temporal data to identify early warning signals of forest mortality using satellite imagery. Utilizing local spatial autocorrelation methods, specifically local Geary's c and local Moran's I, a robust approach that yielded consistent results across multiple study sites is developed. This approach successfully generated early warning signals based on time-series analysis of local spatial autocorrelation metrics, providing up to a two-year advance notice of impending forest mortality events. The results demonstrated that the proposed approach could outperform previous techniques in reliably generating early warning signals of forest mortality, as shown by significant trend analysis. Additionally, a new R software package, “stew”, is introduced that is designed to facilitate user-friendly spatio-temporal analysis of ecosystem state changes. In summary, this study corroborates the potential of spatio-temporal indicators as valuable tools for predicting climate-induced forest mortality up to two years in advance.

Biophysical factors control invasive annual grass hot spots in the Mojave Desert

Invasive annual grasses can promote ecosystem state changes and habitat loss in the American Southwest. Non-native annual grasses such as Bromus spp. and Schismus spp. have invaded the Mojave Desert and degraded habitat through increased fire occurrence, severity, and shifting plant community composition. Thus, it is important to identify and characterize the areas where persistent invasion has occurred, identifying where subsequent habitat degradation has increased. Previous plot and landscape-scale analyses have revealed anthropogenic and biophysical correlates with the establishment and dominance of invasive annual grasses in the Mojave Desert. However, these studies have been limited in spatial and temporal scales. Here we use Landsat imagery validated using an extensive network of plot data to map persistent and productive populations of invasive annual grass, called hot spots, across the entire Mojave Desert ecoregion over 12 years (2009–2020). We also identify important variables for predicting hot spot distribution using the Random Forest algorithm and identifying the most invaded subregions. We identified hot spots in over 5% of the Mojave Desert mostly on the western and eastern edges of the ecoregion, and invasive grasses were detected in over 90% of the Mojave Desert at least once in that time. Across the entire Mojave Desert, our results indicate that soil texture, aspect, winter precipitation, and elevation are the highest-ranking predictive variables of invasive grass hot spots, while anthropogenic variables contributed the least to the accuracy of the predictive model. The total area covered by hot spots varied significantly among subregions of the Mojave Desert. We found that anthropogenic variables became more important in explaining invasive annual establishment and persistence as spatial scale was reduced to the subregional level. Our findings have important implications for informing where land management actions can prioritize reducing invasive annual persistence and promoting restoration efforts.

Identifying the true drivers of abrupt changes in ecosystem state with a focus on time lags: Extreme precipitation can determine water quality in shallow lakes

A better understanding of abrupt ecosystem changes is needed to improve prediction of future ecosystem states under climate change. Chronological analysis based on long-term monitoring data is an effective way to estimate the frequency and magnitude of abrupt ecosystem changes. In this study, we used abrupt-change detection to differentiate changes of algal community composition in two Japanese lakes and to identify the causes of long-term ecological transitions. Additionally, we focused on finding statistically significant relationships between abrupt changes to aid with factor analysis. To estimate the strengths of driver–response relationships underlying abrupt algal transitions, the timing of the algal transitions was compared to that of abrupt changes in climate and basin characteristics to identify any synchronicities between them. The timing of abrupt algal changes in the two study lakes corresponded most closely to that of heavy runoff events during the past 30–40 years. This strongly suggests that changes in the frequency of extreme events (e.g., heavy rain, prolonged drought) have a greater effect on lake chemistry and community composition than do shifts in the means of climate and basin factors. Our analysis of synchronicity (with a focus on time lags) could provide an easy method to identify better adaptative strategies for future climate change.

Rewilding soil-disturbing vertebrates to rehabilitate degraded landscapes: benefits and risks.

Soil-disturbing animals are common globally and play important roles in creating and maintaining healthy functional soils and landscapes. Yet many of these animals are threatened or locally extinct due to habitat loss, predation by non-native animals or poaching and poisoning. Some reintroduction and rewilding programmes have as their core aims to increase animal populations and reinstate processes that have been lost due to their extirpation. Here we use a meta-analytical approach to review the effects of soil-disturbing vertebrates on ecosystem processes, and advance the argument that they can be used to rehabilitate degraded ecosystems by altering mainly composition and function, but with fewer positive effects on structure. We describe four examples where the loss or reintroduction of soil-disturbing vertebrates leads to ecosystem state changes and highlight the role of spatial scale, covarying management changes, and species co-occurrence in modulating their effects. We discuss the advantages and disadvantages of using soil-disturbing vertebrates over mechanized engineering approaches such as pitting and furrowing, considering some advantages to include more self-sustainable and heterogeneous disturbances, creation of new habitats and added recreational values. Finally, we identify key knowledge gaps in our understanding of the use of soil-disturbing vertebrates for rehabilitating degraded ecosystems.

Leaving more than footprints: Anthropogenic nutrient subsidies to a protected area

AbstractMobile animals that traverse ecosystem boundaries can fundamentally reshape environments by providing critical nutrient and energy inputs to the ecosystems they inhabit. In particular, aggregations of seabirds often transform coastal and island ecosystems through large amounts of nutrient‐rich guano deposition. Anthropogenically driven losses of these subsidies can occur through changes in abundance of mobile species, including seabirds, and have been shown to drive whole‐scale ecosystem state change on islands. However, even though many species that forage on anthropogenic food sources are highly mobile and may thus play important roles in moving nutrients from urban systems to otherwise conserved ecosystems, the impacts of anthropogenic supplements on spatial subsidies have been largely ignored. Here we examine the effects of large nesting colonies of Western Gulls (Larus occidentalis), a generalist carnivore known to forage on human refuse, on the Channel Islands of California. Specifically, we explore how their foraging on human subsidies may change nutrient deposition patterns at their relatively remote and protected breeding islands. We equipped gulls with GPS loggers to assess the frequency of urban foraging, and we partnered this tracking data with bird density data to estimate the rate of wild and urban‐derived guano deposition on two different islands. Consistent with research on other gull species, we found high (up to 40%) but island‐specific rates of urban foraging, resulting between 66 and 93 kg ha−1 of guano in these two sites during the breeding season, a level greater than half the amount of fertilizer applied annually in typical commercial agricultural settings and likely the primary source of nitrogen and phosphorus inputs to this system. Specifically, we estimate that 27 kg ha−1 year−1 of nutrient‐rich guano is shuttled to these otherwise isolated islands from anthropogenic sources. This research highlights the large shadow (i.e., footprint) that human activity can cast on even remote ecosystems by driving significant nutrient enrichment through impacts on animal behavior and connectivity.

Uncovering ecological regime shifts in the Sea of Marmara and reconsidering management strategies

Ecosystem regime shifts can alter ecosystem services, affect human well-being, and trigger policy conflicts due to economic losses and reductions in societal and environmental benefits. Intensive anthropogenic activities make the Sea of Marmara ecosystem suffer from nearly all existing available types of ecosystem pressures such as biological degradation, exposure to hydrological processes, nutrient and organic matter enrichment, plastic pollution, ocean warming, resulting in deterioration of habitats. In this study, using an integrated ecosystem assessment, we investigated for the first time the historical development and ecosystem state of the Sea of Marmara. Multivariate analyses were applied to the most comprehensive and unique long-term data sets of 9 biotic and 15 abiotic variables for ecosystem state and drivers respectively, from 1986 to 2020. Observed changes were confirmed by detecting shifts in the datasets. The Sea of Marmara ecosystem was classified into three regimes: i) an early initial state regime under the top-down control of predatory medium pelagic fish and fisheries exploitation until mid-1990s, ii) a transitional regime between mid-1990s and mid-2010s as from ecosystem restructuring, and iii) an alternate state late regime with prevailing impacts of climate change from mid-2010s until 2020. During the 20 years transitional regime, three different phases were also characterized; i) the 1st phase between mid-1990s and early 2000s with its gradual change in ecosystem state from a decrease in predators and significant shift in physical drivers of the ecosystem, ii) the 2nd phase between 2000 and mid-2000s with a strong shift in ecosystem state, an ongoing increase in climate indices and fishing mortality, and a gradual decrease in water quality; and iii) the 3rd phase between mid-2000s and mid-2010s with the reorganization of the ecosystem dominated by small pelagic fish and ameliorated water quality. During late regime, we observed that most of the biotic variables, mainly fish biomass, and climate variables did not return to their initial state despite the improvement in some abiotic variables such as water quality. We identify these observed changes in the SoM ecosystem as a non-linear regime shift. Finally, we also developed concrete suggestions for improved regional management.

Trajectories of nutrients concentrations and ratios in the French coastal ecosystems: 20 years of changes in relation with large-scale and local drivers

Along with their important diversity, coastal ecosystems receive various amounts of nutrients, principally arising from the continent and from the related human activities (mainly industrial and agricultural activities). During the 20th century, nutrients loads have increased following the increase of both the global population and need of services. Alongside, climate change including temperature increase or atmospheric circulation change has occurred. These processes, Ecosystem state changes are hard to monitor and predict. To study the long-term changes of nutrients concentrations in coastal ecosystems, eleven French coastal ecosystems were studied over 20 years as they encompass large climatic and land pressures, representative of temperate ecosystems, over a rather small geographical area. Both univariate (time series decomposition) and multivariate (relationships between ecosystems and drivers) statistical analyses were used to determine ecosystem trajectories as well as typologies of ecosystem trajectories. It appeared that most of the French coastal ecosystems exhibited trajectories towards a decrease in nutrients concentrations. Differences in trajectories mainly depended on continental and human influences, as well as on climatic regimes. One single ecosystem exhibited very different trajectories, the Arcachon Bay with an increase in nutrients concentrations. Ecosystem trajectories based on ordination techniques were proven to be useful tools to monitor ecosystem changes. This study highlighted the importance of local environments and the need to couple uni- and multi-ecosystem studies. Although the studied ecosystems were influenced by both local and large-scale climate, by anthropogenic activities loads, and that their trajectories were mostly similar based on their continental influence, non-negligible variations resulted from their internal functioning.

Climate change and altered fire regimes: impacts on plant populations, species, and ecosystems in both hemispheres

Extreme fire seasons in both hemispheres in 2019 and 2020 have highlighted the strong link between climate warming and altered fire regimes. While shifts in fire regimes alone can drive profound changes in plant populations, communities, and ecosystems, the direct effects of warming climate conditions can impose added stress on key demographic processes prior to and immediately following fire. Altered survival-, growth-, and reproductive- rates in periods between fires, coupled with post-fire recruitment failure from increasingly stressful environmental conditions (including both heatwave and drought) can pose serious threats for conservation in fire-adapted ecosystems worldwide, raising concerns of ecosystem conversion and state change. In this special issue, a collection of 11 papers from fire-prone ecosystems in both hemispheres documents key insights into how changes are unfolding—and mechanisms underpinning such changes—across a diverse range of species and ecosystems. Here, we synthesize this work that uses latitudinal observational surveys, experiments, and simulation modeling to understand how climate warming and altered fire regimes are reshaping our planet. We place these studies in the context of broader advances, and highlight additional research directions to uncover how altered fire regimes, fires interacting with other disturbances, and pre-and post-fire demographic processes can erode resilience in a warming climate.

Woody plant encroachment of grassland and the reversibility of shrub dominance: Erosion, fire, and feedback processes

AbstractMany grass‐dominated ecosystems in dryland regions have experienced increasing woody plant density and abundance during the past century. In many cases, this process has led to land degradation and declines in ecosystem functions. An example is the Chihuahuan Desert in the southwestern United States, which experienced different stages of shrub encroachment in the past 150 years. Among a wide variety of mechanisms to explain the grass–shrub transitions in this dryland system, soil erosion (both wind and water) and fire are particularly well studied. Here, we synthesize recent developments on the drivers and feedback in the process of shrub encroachment in the Chihuahuan Desert through the intercomparison of two Long Term Ecological Research (LTER) sites, namely Jornada and Sevilleta. Experimental and modeling studies support a conceptual framework, which underscores the important roles of erosion and fire in woody plant encroachment. Collectively, research at the Jornada LTER provided complementary, quantitative support to the well‐known fertile‐islands framework. Studies at the Sevilleta LTER expanded the framework, adding fire as a major disturbance to woody plants. Conceptual models derived from the synthesis represent the general understanding of shrub encroachment that emerged from research at these two sites, and can guide management interventions aimed at reducing or mitigating undesirable ecosystem state change in many other drylands worldwide.

Identifying the True Drivers of Abrupt Changes in Ecosystem State with a Focus on Time Lags: Extreme Precipitation Can Determine Water Quality in Shallow Lakes

Identifying the True Drivers of Abrupt Changes in Ecosystem State with a Focus on Time Lags: Extreme Precipitation Can Determine Water Quality in Shallow Lakes

The long-term changes in food web structure and ecosystem functioning of a shallow lake: Implications for the lake management

The food web structure (FWS) and ecosystem functioning (EF) of lakes worldwide are impacted by multiple disturbances. The historical evolution of the FWS and EF are not well understood due to the lack of sufficient long-term records of biotic variations. This study reconstructed the food web models in the 1950s, 1980s, 1990s, 2000s, and 2010s for Baiyangdian Lake (BYDL), the largest shallow lake in northern China, using the Linear Inverse Modeling (LIM) and investigated EF in different periods. Our results confirmed that the FWS and EF of BYDL have undergone significant changes. The biomass of phytoplankton continuously increased, and the primary productivity of phytoplankton began to replace the primary productivity of submerged macrophytes in the 2000s and became the largest energy flow in the food web. Changes in the energy flow of primary producers are transmitted to high-trophic functional groups, which affects the diet composition of fish. Based on the ecological network analysis indices and food web stability indicators, it was concluded that after a turning point in the 1990s, the ecosystem showed initial stability and then gradually became unstable. Water level fluctuations and nutrient enrichment may be the key driving factors for changes in ecosystem state. Therefore, to maintain a good state of the ecosystem, we recommend implementing comprehensive management measures of hydrological management, nutrient-loading reduction, and biomanipulation. Furthermore, this study extended LIM to lake ecosystems, which may provide a new method for lake ecological environment management.

Effects of spatial variation in benthic phototrophs along a depth gradient on assessments of whole‐lake processes

Abstract Phytobenthos are often underrepresented in both limnological and paleolimnological studies but may play key roles in whole‐lake production and ecosystem processes including eutrophication, food‐web dynamics, and ecosystem state changes. Photosynthetic pigments, stables isotopes, and diatoms were quantified from surface sediments (0–1 cm) collected across a depth transect of a small, DOC‐rich, mesotrophic lake in boreal northwestern Ontario to assess spatial variation in phytobenthos abundance and production. Maximal concentrations of siliceous algae and cyanobacteria pigments occurred at ~2–6 m depth, with abundant tychoplanktonic diatoms, depleted sedimentary δ13C values, and elevated ratios of precursor chlorophyll a to product pheophytin a, all aligning well with the depths of the thermocline, epilimnetic mixing, and maximum light penetration. These patterns demonstrated the presence of three discrete community assemblages, with greatest mass accumulation occurring at intermediate depths where warm illuminated sediments provide habitat for tychoplanktonic diatoms and cyanobacteria between turbulent shallows and cold and dark depths. If widespread among boreal lakes, this tychoplanktonic zone may exert important effects on whole‐lake production, carbon sequestration, benthic‐pelagic food‐web coupling, eutrophication, and ecosystem state change.

Asymmetric root distributions reveal press-pulse responses in retreating coastal forests.

The impacts of climate change on ecosystems are manifested in how organisms respond to episodic and continuous stressors. The conversion of coastal forests to salt marshes represents a prominent example of ecosystem state change, driven by the continuous stress of sea-level rise (press), and episodic storms (pulse). Here, we measured the rooting dimension and fall direction of 143 windthrown eastern red cedar (Juniperus virginiana) trees in a rapidly retreating coastal forest in Chesapeake Bay (USA). We found that tree roots were distributed asymmetrically away from the leading edge of soil salinization and towards freshwater sources. The length, number, and circumference of roots were consistently higher in the upslope direction than downslope direction, suggesting an active morphological adaptation to sea-level rise and salinity stress. Windthrown trees consistently fell in the upslope direction regardless of aspect and prevailing wind direction, suggesting that asymmetric rooting destabilized standing trees, and reduced their ability to withstand high winds. Together, these observations help explain curious observations of coastal forest resilience, and highlight an interesting nonadditive response to climate change, where adaptation to press stressors increases vulnerability to pulse stressors.

A coordinated three-dimensional network for observing large-scale terrestrial ecosystem status changes and the consequences on resources and environment

Co-driven by environmental change and human activity, global ecosystem has been experiencing rapid changes, with cascading effects on resources and environment. The changes of ecosystem status and its spatiotemporal evolution drivers, and the related resource and environmental effects have been recognized as the long standing topics of large-scale terrestrial ecosystem science. The coordinated observation networks distributed across different continents and the globe provide the valuable tools for observing and evaluating ecosystem state change, for revealing and elaborating mechanisms underlying ecosystem response, for cognizing and understanding ecosystem evolution, and for predicting and early-warning of ecosystem change. Committing to serving the continental-scale ecosystem science and supporting regional ecological environmental governance, this review first comprehensively analyzed the current status of ecological environment observation research networks, then proposed their development directions. This review advocated to develop a collaborative observation system with characteristics of multi-element, multi-interface, multi-medium, multi-process, multi-scale and multi-method, and to establish the new generation of continental ecosystem observation-experiment research network composed of high technology integration, regional distribution network, network management intellectualization, long-term observation & experiment, multi-functional model simulations, and remote data integration and resource sharing. We elaborated on the function orientation, design philosophy, design scheme, construction objectives and technical system of the research network. We hoped provide references for the development of terrestrial ecosystem observation network in China.

Metabolic regime shifts and ecosystem state changes are decoupled in a large river

AbstractAquatic ecosystem recovery from anthropogenic degradation can be hampered by internal feedbacks that stabilize undesirable states. The challenges of managing and predicting alternative states in lakes are well known, but state shifts in rivers and their attendant effects on ecosystem function remain understudied despite strong recent evidence that such shifts can and do occur. Using three decades of measurements of key state variables such as turbidity, nutrient concentrations, Corbicula fluminea clam densities, and chlorophyll a, including hourly dissolved oxygen, we investigated a sudden shift from phytoplankton to macrophyte dominance in the middle Loire River (France), and its associated effects on the rivers metabolic regime. We show, instead, that despite large and synchronous shifts across all state variables, changes in gross primary production and ecosystem respiration were modest (25% and 14% declines, respectively) and that these shifts lagged the ecosystem state changes by a decade or more. The shift to a macrophyte‐dominated state reduced the sensitivity of primary production to abiotic drivers, altered element cycling efficiency, flipped the net carbon balance from positive to negative, and, crucially, weakened the temporal coupling between production and respiration. This weakened coupling, detected using Granger causality, increased the temporal autocorrelation of net ecosystem production, yielding a robust early warning indicator of both state‐ and metabolic‐shifts that may provide valuable guidance for river restoration.

Accelerating permafrost collapse on the eastern Tibetan Plateau

Permafrost collapse can rapidly change regional soil-thermal and hydrological conditions, potentially stimulating production of climate-warming gases. Here, we report on rate and extent of permafrost collapse on the extensive Tibetan Plateau, also known as the Asian Water Tower and the Third Pole. Combined data from in situ measurements, unmanned aerial vehicles (UAV), manned aerial photographs, and satellite images suggest that permafrost collapse was accelerating across the Eastern Tibetan Plateau. From 1969 to 2017, the area of collapsed permafrost has increased by approximately a factor of 40, with 70% of the collapsed area forming since 2004. These widespread perturbations to the Tibetan Plateau permafrost could trigger changes in local ecosystem state and amplify large-scale permafrost climate feedbacks.

Hydrologic and nutrient-driven regime shifts of cyanobacterial and eukaryotic algal communities in a large shallow lake: Evidence from empirical state indicator and ecological network analyses

The detection and prediction of lake ecosystem responses to environmental changes are pressing scientific challenge of major global relevance. Specifically, an understanding of lake ecosystem stability over long-term scales is urgently needed to identify impending ecosystem regime shifts induced by human activities and improve lake ecosystem protection. This study investigated regime shifts in cyanobacterial and eukaryotic algal communities in a large shallow lake over a century in response to nutrient enrichment and hydrologic regulation using evidence from empirical state indicators and ecological network analyses of sedimentary-inferred communities. The diversity and structure of cyanobacterial and eukaryotic algal communities were investigated from sedimentary DNA records and used, for the first time, as state variables of the lake ecosystem to detect lake stability. Two regime shifts were inferred in the 1970s and 2000s based on temporal analysis of empirical indicators. Co-occurrence network analysis based on taxonomic abundance distributions and presence/absence patterns also supported the two regime shifts based on architectural features of the ecological networks. Moreover, the associations of cyanobacterial and eukaryotic algal taxa were observed to be non-random across time. The abrupt driver-mediated regime shift in the 1970s is characterized by the disappearance of submerged vegetation, significantly increased relative abundances of Microcystis and Chlorophyta taxa, and was primarily caused by sluice construction. The critical transition observed in the 2000s was manifested by the occurrence of serious cyanobacterial blooms and was triggered by increased nutrient loading with the development of urbanization and agricultural intensification. This study reveals the important roles of hydrologic regulation and nutrient loading in the temporal successional dynamics of a shallow lake ecosystem, providing new insights into regime shifts of lake ecosystems that can help inform future efforts to predict important lake ecosystem state changes.