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59 results for “Regime shifts”
Thresholds and Regime Shifts at Four LTER Sites (CCE, JRN, PAL, SBC) 1951-2009
The existence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states is of great concern because the likelihood of such transitions is predicted to increase. The science for measuring and responding to state changes, however, is not well developed. This limitation stems from a lack of data-supported case studies of abrupt transitions in all but a few well-studied ecosystems. We used 30-60 years of data on biological responses and putative drivers from ocean, coastal, polar, and dryland ecosystems to illustrate general approaches to analysis of abrupt transitions. The analyses indicate one case in which the state or response variable (krill abundance) tracked abrupt changes in the driver (Pacific Decadal Oscillation) in a linear fashion. Response variables in other cases (sea cucumber abundance, penguin abundance, and perennial grass production) exhibited hysteretic relationships to drivers (wave intensity, sea ice duration, and monsoonal rainfall amounts, respectively) through a variety of response mechanisms. The analyses illustrate that 1) a suite of common concepts and approaches can be used across disparate systems, 2) there are generally insufficient data for the use of leading indicators, particularly considering the abruptness of transition relative to the lifespan of long-lived organisms, 3) information on spatiotemporal context is useful for comparing transitions in similar systems, and 4) ancillary information from associated experiments and observations is critical for interpreting response-driver relationships.
Quantifying changes in fish population stability using statistical early warnings of regime shifts
This data package describes long-term trends in metrics describing population stability and used as statistical early warnings of regime shifts in 29 fish species that inhabit the San Francisco Bay-Delta in central California, USA. Metrics used in this study include spatial synchrony, temporal coefficient of variation (CV), and lag-1 temporal autocorrelation. Trends were measured using ordinary least squares linear regression. These derived data were developed from abundance (as CPUE) time series based on three long-term fish monitoring studies included in https://doi.org/10.6073/pasta/a29a6e674b0f8797e13fbc4b08b92e5b; the Fall Midwater Trawl Survey, Delta Juvenile Monitoring Program, and Bay Study. Selected data were from fall months (September to December) in 1980-2023, from midwater trawl and beach seine surveys for which sampling effort (e.g., tow volume) was recorded. Data on fish exceeding maximum length thresholds for age-0 fish were discarded, except for white sturgeon, where the maximum length threshold corresponded to approximately 10 years of age, the onset of reproductive maturity. Observations from different sampling stations were aggregated into 10 sub-regions (South San Francisco Bay, Central San Francisco Bay, San Pablo Bay, Napa River, Suisun Bay, Delta Confluence, South Delta, North Delta, San Joaquin River, Sacramento River, and midwater trawl samples and beach seine samples were considered separately because the methods sample distinct habitat types. Combinations of sub-region and sampling method were considered distinct spatial units. EWI metrics were measured in 5-year rolling windows to permit assessment of changes over time. The temporal CV and lag-1 autocorrelation were measured on individual spatial unit time series, ignoring windows with >1 year of missing data. The coefficient of variation divides the standard deviation by the mean. Lag-1 autocorrelation was measured as Pearson correlation. Spatial synchrony was measured across spatial un
FESOM-REcoM model data: A regime shift on Weddell Sea continental shelves with local and remote physical-biogeochemical implications is avoidable in a 2°C scenario
<p>This data set includes the minimal data necessary to reproduce the findings of Nissen et al. (2023). Output of model simulations with the global ocean biogeochemical model FESOM1.4-REcoM2 is provided. In particular, besides information on the model grid, the data set includes annual mean water mass properties (temperature, salinity, density, oxygen, pH) and freshwater fluxes from sea ice and ice shelves and decadal averages of air-sea CO2 fluxes and deep-ocean carbon accumulation rates. Model results are provided from 1980-2100 for the four emission scenarios SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 (sorted from low emission to high emission).</p> <p>Please see README for more information on the individual files. </p> <p>Data set belongs to: </p> <p>Nissen, C., R. Timmermann, M. Hoppema, and J. Hauck, 2023: A regime shift on Weddell Sea continental shelves with local and remote physical-biogeochemical implications is avoidable in a 2°C scenario. <em>J. Climate</em>, <a href="https://doi.org/10.1175/JCLI-D-22-0926.1">https://doi.org/10.1175/JCLI-D-22-0926.1</a>, in press.</p>
They Came From The Pacific: How changing Arctic currents could contribute to an ecological regime shift in the Atlantic Ocean - Lagrangian Data 1990-2002 (2 of 2)
<p>Supporting data for Kelly et al.: They Came From The Pacific: How changing Arctic currents could contribute to an ecological regime shift in the Atlantic Ocean (Earth's Future, submitted)<br> <br> Trajectories saved by year of release in the Bering Strait. All months from that year are included in the same file, with the first 1000 trajectories corresponding to January release, second 1000 from February release, and so on. <br> <br> Due to the size of files, this is split into two uploads. Part 1 covers 1970-1989 releases, 1990 onward is saved in Part 2. </p>
They Came From The Pacific: How changing Arctic currents could contribute to an ecological regime shift in the Atlantic Ocean - Lagrangian Data 1970-1989 (1 of 2)
<p>Supporting data for Kelly et al.: They Came From The Pacific: How changing Arctic currents could contribute to an ecological regime shift in the Atlantic Ocean (Earth's Future, submitted)<br> <br> Trajectories saved by year of release in the Bering Strait. All months from that year are included in the same file, with the first 1000 trajectories corresponding to January release, second 1000 from February release, and so on. <br> <br> Due to the size of files, this is split into two uploads. Part 1 covers 1970-1989 releases, 1990 onward is saved in Part 2. </p>
A regime shift towards a more anoxic environment in a eutrophic sea in northern Europe - Datasets
<p>Dataset used to produce figures in the paper "A regime shift towards a more anoxic environment in a eutrophic sea in northern Europe"</p>
Using Unoccupied Aerial Vehicles (UAVs) to map and monitor changes in emergent kelp canopy after an ecological regime shift
<p>Kelp forests are complex underwater habitats that form the foundation of many nearshore marine environments and provide valuable services for coastal communities. Despite their ecological and economic importance, increasingly severe stressors have resulted in declines in kelp abundance in many regions over the past few decades, including the North Coast of California, USA. Given the significant and sustained loss of kelp in this region, management intervention is likely a necessary tool to reset the ecosystem and geospatial data on kelp dynamics are needed to strategically implement restoration projects. Because canopy-forming kelp forests are distinguishable in aerial imagery, remote sensing is an important tool for documenting changes in canopy area and abundance to meet these data needs. We used small unoccupied aerial vehicles (UAVs) to survey emergent kelp canopy in priority sites along the North Coast in 2019 and 2020 to fill a key data gap for kelp restoration practitioners working at local scales. With over 4,300 hectares surveyed between 2019 and 2020, these surveys represent the two largest marine resource-focused UAV surveys conducted in California to our knowledge. We present remote sensing methods using UAVs and a repeatable workflow for conducting consistent surveys, creating orthomosaics, georeferencing data, classifying emergent kelp, and creating kelp canopy maps that can be used to assess trends in kelp canopy dynamics over space and time. We illustrate the impacts of spatial resolution on emergent kelp canopy classification between different sensors to help practitioners decide which data stream to select when asking restoration and management questions at varying spatial scales. Our results suggest that high spatial resolution data of emergent kelp canopy from UAVs have the potential to advance strategic kelp restoration and adaptive management.</p>
Data and code from: Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires
<p class="MsoNormal"><span>Higuera, P.E., M.C. Cook, J.K. Balch, E.N. Stavros, A.L. Mahood, and L.A. St. Denis. 2023. Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus 2: In Press.</span></p> <p class="MsoNormal"><span>Structure loss is an acute, costly impact of the wildfire crisis in the western United States ("West"), motivating the need to understand recent trends and causes. We document a 246% rise in West-wide structure loss from wildfires between 1999–2009 and 2010–2020, driven strongly by events in 2017, 2018, and 2020. Increased structure loss was not due to increased area burned alone. Wildfires became significantly more destructive, with a 160% higher structure loss rate (loss/kha burned) over the past decade. Structure loss was driven primarily by wildfires from unplanned human-related ignitions (e.g. backyard burning, power lines, etc.), which accounted for 76% of all structure loss and resulted in 10 times more structures destroyed per unit area burned compared to lightning-ignited fires. Annual structure loss was well explained by area burned from human-related ignitions, while decadal structure loss was explained by state-level structure abundance in flammable vegetation. Both predictors increased over recent decades and likely interacted with increased fuel aridity to drive structure-loss trends. While states are diverse in patterns and trends, nearly all experienced more burning from human-related ignitions and/or higher structure loss rates, particularly California, Washington, and Oregon. Our findings highlight how fire regimes – characteristics of fire over space and time – are fundamentally social-ecological phenomena. By resolving the diversity of Western fire regimes, our work informs regionally appropriate mitigation and adaptation strategies. With millions of structures with high fire risk, reducing human-related ignitions and rethinking how we build are critical for preventing future wildfire disasters.</span></p>
Can regime shifts in reproduction be explained by changing climate and food availability?
<p><span>Marine populations often show considerable variation in their productivity, including regime shifts. Of special interest are prolonged shifts to low recruitment and low abundance which occur in many fish populations despite reductions in fishing pressure. One of the possible causes for the lack of recovery has been suggested to be the Allee effect (depensation). Nonetheless, both regime shifts and the Allee effect are empirically emerging patterns but provide no explanation about the underlying mechanisms. Environmental forcing, on the other hand, is known to induce population fluctuations and </span><span>has also been suggested as one of the primary challenges for recovery.</span> <span>Yet, traditional stock-recruitment models used in fisheries management have been time-invariant and considered only density-dependence. </span><span>In the present study, we build upon recently developed Bayesian change-point models to explore the contribution of food and climate as external drivers in recruitment regime shifts, while accounting for density-dependent mechanisms (compensation and depensation). Food availability is approximated by the copepod community. Temperature is included as a climatic driver. Three demersal fish populations in the Irish Sea are studied: Atlantic cod (<em>Gadus morhua</em>), whiting (<em>Merlangius merlangus</em>), and common sole (<em>Solea solea</em>). </span><span>We demonstrate that while spawning stock biomass undoubtedly impacts recruitment, abiotic and biotic drivers can have substantial additional impacts, which can explain regime shifts in recruitment dynamics or low recruitment at low population abundances. Our results stress the fact that traditional abundance-based stock-recruitment models are not sufficient to capture variability in fish recruitment. </span></p>
Can regime shifts in reproduction be explained by changing climate and food availability?
Open the record for dataset details and reuse information.
Data and code from: Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires
Open the record for dataset details and reuse information.
Using Unoccupied Aerial Vehicles (UAVs) to map and monitor changes in emergent kelp canopy after an ecological regime shift
Open the record for dataset details and reuse information.
Data from: Ecological regime shift preserved in the Anthropocene stratigraphic record
Paleoecological data are unique historical archives that extend back far beyond the last several decades of ecological observations. However, the fossil record of continental shelves has been perceived as too coarse and incomplete to detect processes occurring at decadal scales relevant to ecology and conservation. Here we show that the youngest (Anthropocene) fossil record on a continental shelf of the Adriatic Sea provides decadal-scale temporal resolution that is adequate for documenting an abrupt ecological shift affecting benthic communities during the 20th century. The magnitude and the duration of the 20th century shift in body size of a dominant bivalve species (Corbula gibba) is unprecedented given that this species was consistently small throughout the Holocene in the whole northern Adriatic Sea. The size shift coincided with compositional change of the benthic community, with the median per-assemblage abundance of C. gibba increasing from ~25% to ~70% in the late 20th century, and occurred at sites that experienced at least one hypoxic event per decade in the 20th century. This regime shift, which coincided with mass mortality of competitors and predators associated with higher frequency of seasonal hypoxic events, may reflect ecological release. The observed body size shift is coupled with a decline in the depth and rate of bioturbational mixing. This decline in burrowing benthic organisms resulted in the improved stratigraphic resolution of fossil assemblages, making it possible to detect sub-centennial ecological changes in the stratigraphic record on continental shelves.
Data from: Climate change-driven regime shifts in a planktonic food web
<p>Predicting how food webs will respond to global environmental change is difficult because of the complex interplay between the abiotic forcing and biotic interactions. Mechanistic models of species interactions in seasonal environments can help understand the effects of global change in different ecosystems. Seasonally ice-covered lakes are warming faster than many other ecosystems and undergoing pronounced food web changes, making the need to forecast those changes especially urgent. Using a seasonally forced food web model with a generalist zooplankton grazer and competing cold-adapted winter and warm-adapted summer phytoplankton, we show that with declining ice cover, the food web moves through different dynamic regimes, from annual to biennial cycles, with decreasing and then disappearing winter phytoplankton blooms and a shift of maximum biomass to summer season. Interestingly, when predator-prey interactions were not included, a declining ice cover did not cause regime shifts, suggesting that both are needed for regime transitions. A cluster analysis of long-term data from Lake Baikal, Siberia supports model results, revealing a change from regularly occurring winter blooms of endemic diatoms to less-frequent winter bloom years with decreasing ice cover. Together, the results show that even gradual environmental change, such as declining ice cover duration, may cause discontinuous or abrupt transitions between dynamic regimes in food webs.</p>
Regime shift in secondary inorganic aerosol formation and nitrogen deposition in the rural US
<p>Secondary inorganic aerosols (SIA) play an important role in air pollution and climate change, and their formation modulates atmospheric deposition of reactive nitrogen (N<sub>r</sub>; including oxidized and reduced nitrogen), impacting the nitrogen cycle. Large-scale and long-term analyses of SIA formation based on model simulations have significant uncertainties. Here, we improve constraints on SIA formation using decade-long in-situ observations of aerosol composition and gaseous precursors from multiple monitoring networks across the US. We reveal a shift in the formation regime of SIA in the rural US between 2011 – 2020, making rural areas less sensitive to changes in ammonia (NH<sub>3</sub>) concentrations and shortening the effective atmospheric lifetime of reduced forms of N<sub>r</sub>.<sub> </sub>This leads to potential increases in N<sub>r</sub> deposition near NH<sub>3</sub> emission hotspots, with ecosystem impacts warranting further investigation. NH<sub>3</sub>, a critical but not directly regulated precursor of fine particulate matter (PM<sub>2.5</sub>) in the US, has been increasingly scrutinized to decrease PM<sub>2.5</sub>. Our findings, however, show controlling NH<sub>3</sub> became significantly less effective for mitigating PM<sub>2.5</sub> in the rural US. We highlight the need for more collocated aerosol and precursor observations for better characterization of SIA formation in urban areas and regions increasingly impacted by wildfires and dust.</p>
Stoichiometric mismatch causes a warming-induced regime shift in experimental plankton communities
<p>Many plant and algal communities respond to warming with shifts towards more carbon-rich species and growth forms, thus diluting essential elements in their biomass and intensifying the stoichiometric mismatch with herbivore nutrient requirements. The dataset is from a 95-day mesocosm experiment on the spring succession of an assembled plankton community in which we manipulated temperature (ambient vs. +3.6°C) and presence vs. absence of two types of grazers (ciliates and <i>Daphnia</i>) in a 2x2x2 factorial design with 3 replicates of each treatment (= 24 mesocosms in total). All mesocosms were initially stocked with low amounts of 6 phytoplankton taxa and were spontaneously colonized by an additional 6 taxa over the course of the experiment.</p> <p>At ambient temperatures, a typical spring succession developed, where a moderate bloom of nutritionally adequate phytoplankton was grazed down to a clear-water phase by a developing <i>Daphnia</i> population.</p> <p>Warming accelerated initial <i>Daphnia</i> population growth but speeded up algal growth rates even more, triggering a massive phytoplankton bloom of poor food quality (i.e. high carbon to phosphorus ratio of phytoplankton biomass). Consistent with the predictions of a stoichiometric producer-grazer model, accelerated phytoplankton growth promoted the emergence of an alternative system attractor, where extremely low phosphorus content of abundant algal food eventually drove <i>Daphnia</i> to extinction. Where present, ciliates slowed down the phytoplankton bloom and the deterioration of its nutritional value, but this only delayed the regime shift. Eventually, phytoplankton grew out of grazer control also in presence of ciliates, and the <i>Daphnia</i> population crashed. The results support the notion that warming can exacerbate the stoichiometric mismatch at the plant-herbivore interface and limit energy transfer to higher trophic levels.</p> <p>One replicate of the 'ambient temperature, <em>Daphnia </em>present, ciliates absent' treatment failed. The dataset therefore consists of data from 23 mesocosms including measurements of the following variables: water temperature, chlorophyll a concentration (a proxy for total phytoplankton biomass), abundances of ciliates and <em>Daphnia </em>(no. of individuals per volume), the concentrations of soluble reactive phosphorus (SRP) and total phosphorus (TP), the carbon to phosphorus ratio (C_P) of seston, and the proportional contribution of different phytoplankton taxa to total phytoplankton biovolume.</p> <p>The zenodo folder (see link https://doi.org/10.5281/zenodo.4715500 below) contains the Matlab and excel files that were used to run a dynamical mathematical model of the study system that were used to generate the model output shown in Figs. 2, 6 and 7 of the publication.</p>
A regime shift in Southeast Greenland marine ecosystem
<p><span>Two major oceanographic changes have recently propagated through several trophic levels in coastal areas of Southeast Greenland (SEG). Firstly, the amount of drift-ice exported from the Fram Strait and transported with the East Greenland Current (EGC) has decreased significantly over the past two decades, and a main tipping element (summer sea ice) has virtually disappeared since 2003 leading to a regime shift in oceanographic and ecological conditions in the region. The following 20-year period with low or no coastal sea ice is unique in the 200-year history of ice observations in the region, and the regime shift is also obvious in the volume of ice export through the Fram Strait after 2013. In the same period the temperature of the EGC south of 73.5N has increased significantly (>2<sup>o</sup>C) since 1980. Secondly, the warm Irminger Current, that advects warm, saline Atlantic Water into the region, has become warmer since 1990. The lack of pack ice in summer together with a warming ocean generated cascading effects on the ecosystem in SEG that are manifested in a changed fish fauna with an influx of boreal species in the south and the subarctic capelin further north. At higher trophic levels there has been an increase in the abundance of several boreal cetaceans (humpback, fin, killer and pilot whales and dolphins) that are either new to this area or occur in historically large numbers. It is estimated that the new cetacean species in SEG are responsible for an annual predation level of 700.000 tonnes of fish. In addition, predation on krill species is estimated at >1.500.000 tonnes mainly consumed by the fin whales. Simultaneously there has been a reduction in the abundance and catches of narwhals and walrus in SEG and it is suggested that these species have been impacted by the habitat changes. </span></p>
Multi-omics analysis reveals regime shifts in the gastrointestinal ecosystem in chickens following anticoccidial vaccination and Eimeria tenella challenge
<p>A multi-omics study integrating gut microbiota and host metabolome to investigate the gastrointestinal health markers in broiler chickens (Cobb500) from an anti-coccidiosis vaccine trial.</p>
Data for Haid et al.: On the drivers of regime shifts in Antarctic marginal seas... Part I
<p>Data behind the figures in the article; 4D potential temperature and salinity in Weddell region for reference experiments REF and H20C, and reversal experiments R_ERA and R_H20C.</p>
Data from: Emergent spatial patterns can indicate upcoming regime shifts in a realistic model of coral community
<p class="western"><span>Increased stress on coastal ecosystems, such as coral reefs, seagrasses, kelp forests and other habitats can make them shift towards degraded, often algae-dominated or barren communities. This has already occurred in many places around the world, calling for new approaches to identify where such regime shifts may be triggered. Theoretical work predicts that the spatial structure of habitat-forming species should exhibit changes prior to regime shifts,</span><span><em> </em></span><span>such as an increase in spatial autocorrelation. However, extending this theory to marine systems requires theoretical models connecting field-supported ecological mechanisms to data and spatial patterns at relevant scales. To do so, we built a spatially-explicit model of sub-tropical coral communities based on experiments and long-term datasets from Rapa Nui (Easter Island, Chile), to test whether spatial indicators could signal upcoming regime shifts in coral communities. Spatial indicators anticipated degradation of coral communities following increases in frequency of bleaching events or coral mortality. However, they were generally unable to signal shifts that followed herbivore loss, a widespread and well-researched source of degradation, likely because herbivory, despite being critical for the maintenance of corals, had comparatively little effect on their self-organization. Informative trends were found both under equilibrium and non-equilibrium conditions, but were determined by the type of direct neighbor interactions between corals, which remain relatively poorly documented. These inconsistencies show that while this approach is promising, its application to marine systems will require detailed information about the type of stressor, and filling current gaps in our knowledge of interactions at play in coral communities. </span></p>
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
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DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.