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Nicholas J. Gotelli - One of the best experts on this subject based on the ideXlab platform.

  • clockwise and counterclockwise hysteresis characterize state changes in the same Aquatic Ecosystem
    Ecology Letters, 2021
    Co-Authors: Amanda C. Northrop, Aaron M. Ellison, Bryan A. Ballif, Vanessa Avalone, Nicholas J. Gotelli
    Abstract:

    Incremental increases in a driver variable, such as nutrients or detritus, can trigger abrupt shifts in Aquatic Ecosystems that may exhibit hysteretic dynamics and a slow return to the initial state. A model system for understanding these dynamics is the microbial assemblage that inhabits the cup-shaped leaves of the pitcher plant Sarracenia purpurea. With enrichment of organic matter, this system flips within three days from an oxygen-rich state to an oxygen-poor state. In a replicated greenhouse experiment, we enriched pitcher-plant leaves at different rates with bovine serum albumin (BSA), a molecular substitute for detritus. Changes in dissolved oxygen (DO) and undigested BSA concentration were monitored during enrichment and recovery phases. With increasing enrichment rates, the dynamics ranged from clockwise hysteresis (low), to environmental tracking (medium), to novel counter-clockwise hysteresis (high). These experiments demonstrate that detrital enrichment rate can modulate a diversity of hysteretic responses within a single Aquatic Ecosystem, and suggest different management strategies may be needed to mitigate the effects of high vs. low rates of detrital enrichment.

  • clockwise and counterclockwise hysteresis characterize state changes in the same Aquatic Ecosystem
    bioRxiv, 2020
    Co-Authors: Amanda C. Northrop, Aaron M. Ellison, Bryan A. Ballif, Vanessa Avalone, Nicholas J. Gotelli
    Abstract:

    Incremental increases in a driver variable, such as nutrients or detritus, can trigger abrupt shifts in Aquatic ecosys-tems. Once these Ecosystems change state, a simple reduction in the driver variable may not return them to their original state. Because of the long time scales involved, we still have a poor understanding of the dynamics of ecosys-tem recovery after a state change. A model system for understanding Ecosystem recovery is the Aquatic microEcosystem that inhabits the cup-shaped leaves of the pitcher plant Sarracenia purpurea. With enrichment of organic matter, this system flips within 1 to 3 days from an oxygen-rich state to an oxygen-poor (hypoxic) state. In a replicated green-house experiment, we enriched pitcher plant leaves at different rates with bovine serum albumin (BSA), a molecular substitute for detritus. Changes in dissolved oxygen ([O2]) and undigested BSA concentration were monitored during enrichment and recovery phases. At low enrichment rates, Ecosystems showed a substantial lag in the recovery of [O2] (clockwise hysteresis). At intermediate enrichment rates, [O2] tracked the levels of undigested BSA with the same profile during the enrichment and recovery phases (no hysteresis). At high enrichment rates, we observed a novel response: changes in [O2] were proportionally larger during the recovery phase than during the enrichment phase (counter-clockwise hysteresis). These experiments demonstrate that detrital enrichment rate can modulate a diversity of hysteretic responses in a single Aquatic Ecosystem. With counter-clockwise hysteresis, rapid reduction of a driver variable following high enrichment rates may be a viable restoration strategy.

  • Environmental proteomics reveals taxonomic and functional changes in an enriched Aquatic Ecosystem
    Ecosphere (Washington D.C), 2017
    Co-Authors: Amanda C. Northrop, Rachel K. Brooks, Aaron M. Ellison, Nicholas J. Gotelli, Bryan A. Ballif
    Abstract:

    Aquatic Ecosystem enrichment can lead to distinct and irreversible changes to undesirable states. Understanding changes in active microbial community function and composition following organic-matter loading in enriched Ecosystems can help identify biomarkers of such state changes. In a field experiment, we enriched replicate Aquatic Ecosystems in the pitchers of the northern pitcher plant, Sarracenia purpurea. Shotgun metaproteomics using a custom metagenomic database identified proteins, molecular pathways, and contributing microbial taxa that differentiated control Ecosystems from those that were enriched. The number of microbial taxa contributing to protein expression was comparable between treatments; however, taxonomic evenness was higher in controls. Functionally active bacterial composition differed significantly among treatments and was more divergent in control pitchers than enriched pitchers. Aerobic and facultative anaerobic bacteria contributed most to identified proteins in control and enriched Ecosystems, respectively. The molecular pathways and contributing taxa in enriched pitcher Ecosystems were similar to those found in larger enriched Aquatic Ecosystems and are consistent with microbial processes occurring at the base of detrital food webs. Detectable differences between protein profiles of enriched and control Ecosystems suggest that a time series of environmental proteomics data may identify protein biomarkers of impending state changes to enriched states.

  • Metaproteomics reveals biomarkers of system collapse in a dynamic Aquatic Ecosystem
    2016
    Co-Authors: Amanda C. Northrop, Rachel K. Brooks, Aaron M. Ellison, Nicholas J. Gotelli, Bryan A. Ballif
    Abstract:

    Forecasting and preventing rapid Ecosystem state changes is important but hard to achieve without functionally relevant early warning indicators. Here we use metaproteomic analysis to identify protein biomarkers indicating a state change in an Aquatic Ecosystem resulting from detrital enrichment. In a 14-day field experiment, we used detritus (arthropod prey) to enrich replicate Aquatic Ecosystems formed in the water-filled pitcher-shaped leaves of the northern pitcher plant, Sarracenia purpurea. Shotgun metaproteomics using a translated, custom metagenomic database identified proteins, molecular pathways, and microbial taxa that differentiated control oligotrophic Ecosystems that captured only ambient prey from eutrophic Ecosystems that were experimentally enriched. The number of microbial taxa was comparable between treatments; however, taxonomic evenness was higher in the oligotrophic controls. Aerobic and facultatively anaerobic bacteria dominated control and enriched Ecosystems, respectively. The molecular pathways and taxa identified in the enriched treatments were similar to those found in a wide range of enriched or polluted Aquatic Ecosystems and are derived from microbial processes that occur at the base of most detrital food webs. We encourage the use of metaproteomic pipelines to identify better early-warning indicators of impending changes from oligotrophic to eutrophic states in Aquatic and other detrital-based Ecosystems.

  • organic matter loading determines regime shifts and alternative states in an Aquatic Ecosystem
    Proceedings of the National Academy of Sciences of the United States of America, 2013
    Co-Authors: Jennie Sirota, Nicholas J. Gotelli, Benjamin Baiser, Aaron M. Ellison
    Abstract:

    Slow changes in underlying state variables can lead to “tipping points,” rapid transitions between alternative states (“regime shifts”) in a wide range of complex systems. Tipping points and regime shifts routinely are documented retrospectively in long time series of observational data. Experimental induction of tipping points and regime shifts is rare, but could lead to new methods for detecting impending tipping points and forestalling regime shifts. By using controlled additions of detrital organic matter (dried, ground arthropod prey), we experimentally induced a shift from aerobic to anaerobic states in a miniature Aquatic Ecosystem: the self-contained pools that form in leaves of the carnivorous northern pitcher plant, Sarracenia purpurea. In unfed controls, the concentration of dissolved oxygen ([O2]) in all replicates exhibited regular diurnal cycles associated with daytime photosynthesis and nocturnal plant respiration. In low prey-addition treatments, the regular diurnal cycles of [O2] were disrupted, but a regime shift was not detected. In high prey-addition treatments, the variance of the [O2] time series increased until the system tipped from an aerobic to an anaerobic state. In these treatments, replicate [O2] time series predictably crossed a tipping point at ∼45 h as [O2] was decoupled from diurnal cycles of photosynthesis and respiration. Increasing organic-matter loading led to predictable changes in [O2] dynamics, with high loading consistently driving the system past a well-defined tipping point. The Sarracenia microEcosystem functions as a tractable experimental system in which to explore the forecasting and management of tipping points and alternative regimes.

Guoliang Bai - One of the best experts on this subject based on the ideXlab platform.

  • spatial and seasonal variation of water parameters sediment properties and submerged macrophytes after ecological restoration in a long term 6 year study in hangzhou west lake in china submerged macrophyte distribution influenced by environmental var
    Water Research, 2020
    Co-Authors: Lingwei Kong, Yi Zhang, Chuan Wang, Guoliang Bai, Pan Yan, Wenhao Yan, Lai Wang, Z Q Liu
    Abstract:

    Abstract Submerged macrophyte restoration is the key stage in the reestablishment of an Aquatic Ecosystem. Previous studies have paid considerable attention to the effect of multiple environmental factors on submerged macrophytes. Meanwhile, few studies have been conducted regarding the spatial and seasonal characteristics of water and sediment properties and their long-term relationship with submerged macrophytes after the implementation of the submerged macrophytes restoration project. On a monthly basis, we monitored the spatial and seasonal variation in water parameters, sediment properties, and the submerged macrophyte characteristics of West Lake in Hangzhou from August 2013 to July 2019. From these measurements, we characterized the relationship between environmental factors and submerged macrophytes. Water nutrient concentrations continuously decreased with time, and the accumulation of sediment nutrients was accelerated as the submerged macrophyte communities developed on a long-term scale. The results indicated that the difference in water parameters was due to seasonal changes and land-use types in the watershed. The differences in the sediment properties were mainly attributed to seasonal changes and changes in the flow field. Redundancy analysis showed that the influence of water nutrients on the submerged macrophyte distribution was greater than that of sediment nutrients. The result also suggested that the developed root system, high stoichiometric homeostasis coefficients of P, and compensation ability of substantial leaf tissue may lead to a large distribution of Vallisneria natans in West Lake in Hangzhou. The correlation of water parameters and sediment properties with submerged macrophytes for a long time was very important as the restoration was achieved. To ensure the stability of the Aquatic Ecosystem after performing the submerged macrophyte restoration, a greater emphasis must be placed on reestablishing the entire Ecosystem, including the restoration of Aquatic animals and fish stocks. We expect these findings to serve as a reference for researchers and government agencies in the field of Aquatic Ecosystem restoration.

Karsten Bolding - One of the best experts on this subject based on the ideXlab platform.

  • introducing qwet a qgis plugin for application evaluation and experimentation with the wet model environmental modelling and software
    Environmental Modelling and Software, 2021
    Co-Authors: Anders Nielsen, Karsten Bolding, Dennis Trolle, Nicolas Azana Schnedlermeyer, Tobias Kuhlmann Andersen
    Abstract:

    Abstract We wish to introduce QWET, a new version of the free and open-source QGIS plugin for the Aquatic Ecosystem model WET. QWET is as a graphical user interface for the application, evaluation and experimentation of WET. Several new features have been incorporated since its predecessor and, here, we demonstrate elements of the new plugin by applying it to Danish Lake Ravn. Among others, we compare model simulations against observations and describe how the scenario platform now supports scheduling of state-variable manipulation, which allows users to explore lake or reservoir restoration interventions such as biomanipulation and oxygenation. With QWET, we seek to aid practitioners who do not possess the sufficient technical expertise to operate a state-of-the art complex model system, such as WET, and thereby hope to facilitate a wider use and adaptation of Aquatic Ecosystem models.

  • predicting Ecosystem state changes in shallow lakes using an Aquatic Ecosystem model lake hinge denmark an example
    Ecological Applications, 2020
    Co-Authors: Karsten Bolding, Anders Lade Nielsen, Erik Jeppesen, T Andersen, Zhengwen Liu, Martin Sondergaard
    Abstract:

    In recent years, considerable efforts have been made to restore turbid, phytoplankton-dominated shallow lakes to a clear-water state with high coverage of submerged macrophytes. Various dynamic lake models with simplified physical representations of vertical gradients, such as PCLake, have been used to predict external nutrient load thresholds for such nonlinear regime shifts. However, recent observational studies have questioned the concept of regime shifts by emphasizing that gradual changes are more common than sudden shifts. We investigated if regime shifts would be more gradual if the models account for depth-dependent heterogeneity of the system by including the possibility of vertical gradients in the water column and sediment layers for the entire depth. Hence, bifurcation analysis was undertaken using the 1D hydrodynamic model GOTM, accounting for vertical gradients, coupled to the Aquatic Ecosystem model PCLake, which is implemented in the framework for Aquatic biogeochemical modeling (FABM). First, the model was calibrated and validated against a comprehensive data set covering two consecutive 7-yr periods from Lake Hinge, a shallow, eutrophic Danish lake. The autocalibration program Auto-Calibration Python (ACPy) was applied to achieve a more comprehensive adjustment of model parameters. The model simulations showed excellent agreement with observed data for water temperature, total nitrogen, and nitrate and good agreement for ammonium, total phosphorus, phosphate, and chlorophyll a concentrations. Zooplankton and macrophyte coverage were adequately simulated for the purpose of this study, and in general the GOTM-FABM-PCLake model simulations performed well compared with other model studies. In contrast to previous model studies ignoring depth heterogeneity, our bifurcation analysis revealed that the spatial extent and depth limitation of macrophytes as well as phytoplankton chlorophyll-a responded more gradually over time to a reduction in the external phosphorus load, albeit some hysteresis effects still appeared. In a management perspective, our study emphasizes the need to include depth heterogeneity in the model structure to more correctly determine at which external nutrient load a given lake changes Ecosystem state to a clear-water condition.

  • Exploring, exploiting and evolving diversity of Aquatic Ecosystem models: a community perspective
    Aquatic Ecology, 2015
    Co-Authors: Annette B. G. Janssen, Karsten Bolding, Arthur Beusen, Louise Bruce, J. Alex Elliott, Jorn Bruggeman, Andrea S. Downing, George B Arhonditsis, Raoul-marie Couture, Marieke A. Frassl
    Abstract:

    Here, we present a community perspective on how to explore, exploit and evolve the diversity in Aquatic Ecosystem models. These models play an important role in understanding the functioning of Aquatic Ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 Aquatic Ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of Aquatic Ecosystem modelling might develop in the next 5–10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary.

  • A community-based framework for Aquatic Ecosystem models
    Hydrobiologia, 2011
    Co-Authors: Dennis Trolle, Karsten Bolding, Jorn Bruggeman, David P. Hamilton, Matthew R. Hipsey, Wolf M. Mooij, Jan H. Janse, Anders Lade Nielsen, Erik Jeppesen, J. Alex Elliott
    Abstract:

    Here, we communicate a point of departure in the development of Aquatic Ecosystem models, namely a new community-based framework, which supports an enhanced and transparent union between the collective expertise that exists in the communities of traditional ecologists and model developers. Through a literature survey, we document the growing importance of numerical Aquatic Ecosystem models while also noting the difficulties, up until now, of the Aquatic scientific community to make significant advances in these models during the past two decades. Through a common forum for Aquatic Ecosystem modellers we aim to (i) advance collaboration within the Aquatic Ecosystem modelling community, (ii) enable increased use of models for research, policy and Ecosystem-based management, (iii) facilitate a collective framework using common (standardised) code to ensure that model development is incremental, (iv) increase the transparency of model structure, assumptions and techniques, (v) achieve a greater understanding of Aquatic Ecosystem functioning, (vi) increase the reliability of predictions by Aquatic Ecosystem models, (vii) stimulate model inter-comparisons including differing model approaches, and (viii) avoid ‘re-inventing the wheel’, thus accelerating improvements to Aquatic Ecosystem models. We intend to achieve this as a community that fosters interactions amongst ecologists and model developers. Further, we outline scientific topics recently articulated by the scientific community, which lend themselves well to being addressed by integrative modelling approaches and serve to motivate the progress and implementation of an open source model framework.

J C Fischenich - One of the best experts on this subject based on the ideXlab platform.

Aaron M. Ellison - One of the best experts on this subject based on the ideXlab platform.

  • clockwise and counterclockwise hysteresis characterize state changes in the same Aquatic Ecosystem
    Ecology Letters, 2021
    Co-Authors: Amanda C. Northrop, Aaron M. Ellison, Bryan A. Ballif, Vanessa Avalone, Nicholas J. Gotelli
    Abstract:

    Incremental increases in a driver variable, such as nutrients or detritus, can trigger abrupt shifts in Aquatic Ecosystems that may exhibit hysteretic dynamics and a slow return to the initial state. A model system for understanding these dynamics is the microbial assemblage that inhabits the cup-shaped leaves of the pitcher plant Sarracenia purpurea. With enrichment of organic matter, this system flips within three days from an oxygen-rich state to an oxygen-poor state. In a replicated greenhouse experiment, we enriched pitcher-plant leaves at different rates with bovine serum albumin (BSA), a molecular substitute for detritus. Changes in dissolved oxygen (DO) and undigested BSA concentration were monitored during enrichment and recovery phases. With increasing enrichment rates, the dynamics ranged from clockwise hysteresis (low), to environmental tracking (medium), to novel counter-clockwise hysteresis (high). These experiments demonstrate that detrital enrichment rate can modulate a diversity of hysteretic responses within a single Aquatic Ecosystem, and suggest different management strategies may be needed to mitigate the effects of high vs. low rates of detrital enrichment.

  • clockwise and counterclockwise hysteresis characterize state changes in the same Aquatic Ecosystem
    bioRxiv, 2020
    Co-Authors: Amanda C. Northrop, Aaron M. Ellison, Bryan A. Ballif, Vanessa Avalone, Nicholas J. Gotelli
    Abstract:

    Incremental increases in a driver variable, such as nutrients or detritus, can trigger abrupt shifts in Aquatic ecosys-tems. Once these Ecosystems change state, a simple reduction in the driver variable may not return them to their original state. Because of the long time scales involved, we still have a poor understanding of the dynamics of ecosys-tem recovery after a state change. A model system for understanding Ecosystem recovery is the Aquatic microEcosystem that inhabits the cup-shaped leaves of the pitcher plant Sarracenia purpurea. With enrichment of organic matter, this system flips within 1 to 3 days from an oxygen-rich state to an oxygen-poor (hypoxic) state. In a replicated green-house experiment, we enriched pitcher plant leaves at different rates with bovine serum albumin (BSA), a molecular substitute for detritus. Changes in dissolved oxygen ([O2]) and undigested BSA concentration were monitored during enrichment and recovery phases. At low enrichment rates, Ecosystems showed a substantial lag in the recovery of [O2] (clockwise hysteresis). At intermediate enrichment rates, [O2] tracked the levels of undigested BSA with the same profile during the enrichment and recovery phases (no hysteresis). At high enrichment rates, we observed a novel response: changes in [O2] were proportionally larger during the recovery phase than during the enrichment phase (counter-clockwise hysteresis). These experiments demonstrate that detrital enrichment rate can modulate a diversity of hysteretic responses in a single Aquatic Ecosystem. With counter-clockwise hysteresis, rapid reduction of a driver variable following high enrichment rates may be a viable restoration strategy.

  • Environmental proteomics reveals taxonomic and functional changes in an enriched Aquatic Ecosystem
    Ecosphere (Washington D.C), 2017
    Co-Authors: Amanda C. Northrop, Rachel K. Brooks, Aaron M. Ellison, Nicholas J. Gotelli, Bryan A. Ballif
    Abstract:

    Aquatic Ecosystem enrichment can lead to distinct and irreversible changes to undesirable states. Understanding changes in active microbial community function and composition following organic-matter loading in enriched Ecosystems can help identify biomarkers of such state changes. In a field experiment, we enriched replicate Aquatic Ecosystems in the pitchers of the northern pitcher plant, Sarracenia purpurea. Shotgun metaproteomics using a custom metagenomic database identified proteins, molecular pathways, and contributing microbial taxa that differentiated control Ecosystems from those that were enriched. The number of microbial taxa contributing to protein expression was comparable between treatments; however, taxonomic evenness was higher in controls. Functionally active bacterial composition differed significantly among treatments and was more divergent in control pitchers than enriched pitchers. Aerobic and facultative anaerobic bacteria contributed most to identified proteins in control and enriched Ecosystems, respectively. The molecular pathways and contributing taxa in enriched pitcher Ecosystems were similar to those found in larger enriched Aquatic Ecosystems and are consistent with microbial processes occurring at the base of detrital food webs. Detectable differences between protein profiles of enriched and control Ecosystems suggest that a time series of environmental proteomics data may identify protein biomarkers of impending state changes to enriched states.

  • Metaproteomics reveals biomarkers of system collapse in a dynamic Aquatic Ecosystem
    2016
    Co-Authors: Amanda C. Northrop, Rachel K. Brooks, Aaron M. Ellison, Nicholas J. Gotelli, Bryan A. Ballif
    Abstract:

    Forecasting and preventing rapid Ecosystem state changes is important but hard to achieve without functionally relevant early warning indicators. Here we use metaproteomic analysis to identify protein biomarkers indicating a state change in an Aquatic Ecosystem resulting from detrital enrichment. In a 14-day field experiment, we used detritus (arthropod prey) to enrich replicate Aquatic Ecosystems formed in the water-filled pitcher-shaped leaves of the northern pitcher plant, Sarracenia purpurea. Shotgun metaproteomics using a translated, custom metagenomic database identified proteins, molecular pathways, and microbial taxa that differentiated control oligotrophic Ecosystems that captured only ambient prey from eutrophic Ecosystems that were experimentally enriched. The number of microbial taxa was comparable between treatments; however, taxonomic evenness was higher in the oligotrophic controls. Aerobic and facultatively anaerobic bacteria dominated control and enriched Ecosystems, respectively. The molecular pathways and taxa identified in the enriched treatments were similar to those found in a wide range of enriched or polluted Aquatic Ecosystems and are derived from microbial processes that occur at the base of most detrital food webs. We encourage the use of metaproteomic pipelines to identify better early-warning indicators of impending changes from oligotrophic to eutrophic states in Aquatic and other detrital-based Ecosystems.

  • organic matter loading determines regime shifts and alternative states in an Aquatic Ecosystem
    Proceedings of the National Academy of Sciences of the United States of America, 2013
    Co-Authors: Jennie Sirota, Nicholas J. Gotelli, Benjamin Baiser, Aaron M. Ellison
    Abstract:

    Slow changes in underlying state variables can lead to “tipping points,” rapid transitions between alternative states (“regime shifts”) in a wide range of complex systems. Tipping points and regime shifts routinely are documented retrospectively in long time series of observational data. Experimental induction of tipping points and regime shifts is rare, but could lead to new methods for detecting impending tipping points and forestalling regime shifts. By using controlled additions of detrital organic matter (dried, ground arthropod prey), we experimentally induced a shift from aerobic to anaerobic states in a miniature Aquatic Ecosystem: the self-contained pools that form in leaves of the carnivorous northern pitcher plant, Sarracenia purpurea. In unfed controls, the concentration of dissolved oxygen ([O2]) in all replicates exhibited regular diurnal cycles associated with daytime photosynthesis and nocturnal plant respiration. In low prey-addition treatments, the regular diurnal cycles of [O2] were disrupted, but a regime shift was not detected. In high prey-addition treatments, the variance of the [O2] time series increased until the system tipped from an aerobic to an anaerobic state. In these treatments, replicate [O2] time series predictably crossed a tipping point at ∼45 h as [O2] was decoupled from diurnal cycles of photosynthesis and respiration. Increasing organic-matter loading led to predictable changes in [O2] dynamics, with high loading consistently driving the system past a well-defined tipping point. The Sarracenia microEcosystem functions as a tractable experimental system in which to explore the forecasting and management of tipping points and alternative regimes.