Methods and protocols used in the collection of this data package |
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We compiled temperature and dissolved oxygen (DO) profiles from academic, government, and not-for-profit sources. We sought datasets that had at least one profile sampled annually during the late summer period, which we defined as July 15 – August 31 in the northern hemisphere and January 15 – February 28 in the southern hemisphere. Additionally, we sought datasets having at least 15 years of data.
As a quality control step, we removed data points having ecologically unlikely values in excess of 40degreeC for temperature and 40 mg L-1 for DO. We removed profiles from further analysis if this process removed more than 95% of a profile or if there were less than three distinct depth points remaining.
In some cases, profiles did not have surface measurements (i.e. the shallowest depth was greater than 0 m). We made the assumption of uniform temperature and DO across the epilimnion for these profiles and added a 0 depth. We did this by 1) changing the minimum depth in the profile to 0 if the depth was less than 0.5 m, 2) adding a 0 depth point and assigning it the temperature and DO values equal to those of the minimum depth if the depth was less than or equal to 3 m. If the minimum depth in the profile exceeded 3 m, we removed it from further analysis. If a given depth point had multiple values for temperature or DO, we took the mean of these values. We conducted all analyses using the R statistical programming environment (R Core Team 2017).
Profile interpolation and strata delineation
We interpolated each profile at 0.5 m intervals from 0 m to the deepest point of each profile using the pchip function of the R package pracma (Borchers et al. 2018). Following this interpolation process, we calculated the top and bottom depths of the metalimnion for each profile using the meta.depths function of the R package rLakeAnalyzer (Winslow et al. 2017). If the range of temperatures through a given profile is less than 1degreeC, this function considers the profile to be unstratified.
Many lakes did not have a well-defined hypolimnion. If more than 10% of profiles were considered unstratified, we considered the lake not to have a hypolimnion. We define epilimnion as all depths less than or equal to the top metalimnion depth and hypolimnion as all depths deeper than the bottom metalimnion depth.
Calculating mean epilimnetic and hypolimnetic metrics
We calculated mean late summer temperature, DO concentration, and percent saturation for both the epilimnion and the hypolimnion. For temperature and DO, we first calculated the mean value across the epilimnion or hypolimnion for each profile, and then took the mean of these values across all profiles within the defined late-summer period for each year for each lake. DO percent saturation at each depth interval was calculated from water temperature, DO concentration, and lake elevation (Winslow et al. 2017). Mean epilimnetic and hypolimnetic percent saturation were then calculated in the same manner as temperature and DO concentration.
For lakes that had chlorophyll a data, we used data in the defined late-summer period. For each date in this period, we took the mean of all epilimnetic values. We then calculated the mean of these values for a given year and removed years that exceeded the range of DO data for the corresponding lake. We also excluded data from lakes that did not have at least ten years of chlorophyll a data. Following this, we then took a grand mean for each lake. Before doing these calculations, we first removed any negative values, which were roughly 0.2% of the data.
Calculating trends in meteorological variables
We downloaded meteorological variables using the ERA-5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) (Copernicus Climate Change Service 2019). The ERA-5 reanalysis is a global dataset gridded at a resolution of 0.25degree latitude by 0.25degree longitude. The data is available over the period 1979-2019 as monthly averages (air temperature, wind speed, and shortwave radiation) or totals (precipitation). We used data from the location nearest to each lake and over the two-month period corresponding most closely to that used for lake water data (July-August for Northern hemisphere lakes, January-February for Southern hemisphere lakes).
References
Borchers, H. W. (2018). pracma: Practical Numerical Math Functions. R package version 2.1.5 https://CRAN.R-project.org/package=pracma
Copernicus Climate Change Service (C3S). (2019). ERA5: Fifth generation of ECMWF atmospheric reanalyses of the global climate. Copernicus Climate Change Service Climate Data Store (CDS), Accessed 10/1/2019. https://cds.climate.copernicus.eu/cdsapp#!/home
R Core Team. (2017). R: a language and environment for statistical computing. R foundation for statistical computing, Vienna, Austria
Winslow, L. A., et al. (2017). rLakeAnalyzer: Lake Physics Tools. R package version 1.11.4 https://CRAN.R-project.org/package=rLakeAnalyzer
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This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: |
This method step describes provenance-based metadata as specified in the LTER EML Best Practices.
This provenance metadata does not contain entity specific information.
| Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: | This provenance metadata does not contain entity specific information. | Data Source | |
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Description: |
Source Dataset
This dataset is not publicly available
Rimov (Reservoir) (ID 5), please contact Josef Hejzlar
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Description: |
Source Dataset
This dataset is not publicly available
Maggiore (ID 6), created by CNR Water Research Institute, please contact Verbania Michela Rogora
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Description: |
Source Dataset
This dataset is not publicly available
Neversink and Cannonsville (IDs 7,8), created by NYC Environmental Protection - Bureau of Water Supply, please contact Lorraine Janus
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Description: |
Source Dataset
This dataset is not publicly available
ELA Lakes (IDs 9-13), created by IISD – Experimental Lakes Area Inc., please contact Scott Higgins
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Description: |
Source Dataset
This dataset is not publicly available
Caldonazzo (ID 23), created by Fondazione Edumund Mach, please contact Giovanna Flaim
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Description: |
Source Dataset
This dataset is not publicly available
Iseo (ID 24), please contact Barbara Leoni
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Description: |
Source Dataset
This dataset is not publicly available
New Zealand Lakes (Brunner, Tarawera, Taupo) (IDs 40, 44, 45), created by National Institute of Water and Atmospheric Research (NIWA), please contact Piet Verburg
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Description: |
Source Dataset
This dataset is not publicly available
Kortowskie (ID 41), created by University of Warmia and Mazury in Olsztyn, please contact Julita Dunalska
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Description: |
Source Dataset
This dataset is not publicly available
Swiss Lakes (IDs 99-104), created by City of Zurich Water Supply, Cantonal agencies of Bern (AWA), Zurich (AWEL), St. Gallen (AFU), and Neuchatel, please contact Martin Schmid
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Description: |
Source Dataset
This dataset is not publicly available
Qu'Appelle lakes, Saskatchewan (IDs 105-111), please contact Peter Leavitt
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Description: |
Source Dataset
This dataset is not publicly available
Naroch (ID 113), created by Belarusion State University, please contact Boris Adamovich
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Description: |
Source Dataset
This dataset is not publicly available
Oklahoma Lakes (IDs 117-120), please contact K. David Hambright
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Description: |
Source Dataset
This dataset is not publicly available
Stechlin (ID 122) created by IGB-Berlin, wollrab@igb-berlin.de, please contact Hans-Peter Grossart and Sabine Wollrab
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Description: |
Source Dataset
This dataset is not publicly available
Kivu (ID 123), please contact Wim Thiery
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Description: |
Source Dataset
This dataset is not publicly available
Otsego (ID 124), created by SUNY Oneonta Biological Field Station, please contact Kiyoko Yokota
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Description: |
Source Dataset
This dataset is not publicly available
Blelham Tarn (ID 125), created by UK Centre for Ecology and Hydrology, Funding – Natural Environment Research Council National Capability, please contact Eleanor Mackay
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Description: |
Source Dataset
This dataset is not publicly available
Itasca (ID 126), created by Itasca Biological Station and Labs, please contact Lesley Knoll
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Description: |
Source Dataset
This dataset is not publicly available
New Hampshire Lakes (IDs 243-278), created by Volunteer lake assessment program (VLAP) environmental monitoring dfata. New Hampshire Department of Environmental Services. Watershed mgmt. bureau – Biology section, Concord, NH., please contact Melanie Cofrin
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Description: |
Source Dataset
This dataset is not publicly available
New Hampshire Lakes, created by NHDES. Lake trophic survey environmental monitoring data. New Hampshire Department of Environmental Services, Watershed Mgmt Bureau – Biology section, Concord, NH., please contact Melanie Cofrin
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Description: |
Source Dataset
This dataset is not publicly available
New Zealand Lakes (IDs 402-410), created by Environmental Research Institute, please contact Christopher McBride
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Description: |
Source Dataset
This dataset is not publicly available
Leech (IDs 416, 417), created by Minnesota Department of Natural Resources, please contact Carl Pedersen and Gretchen Hansen
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Description: |
Source Dataset
This dataset is not publicly available
Nkuruba (ID 442) created by Lauren Chapman, please contact Emilie Saulnier-Talbot
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Description: |
Source Dataset
This dataset is not publicly available
Sunapee (IDs 78, 79), please contact Kathleen Weathers*
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Description: |
Source Dataset
This dataset is not publicly available
Lake George (IDs 130, 131), created by Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, please contact Sandra Nierzwicki-Bauer
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