Methods

Nutrients were added to Peter (2013-2015, 2019) and Tuesday (2013-2015)
lakes to cause algal blooms. Details on nutrient additions (start/end dates,
loading rates, N:P ratios) are described in Buelo et al. 2022 (Ecological
Applications, link below), Wilkinson et al. 2018 (Ecological Monographs 88:
188-203), and Pace et al. 2017 (Proceedings of the National Academy of
Sciences USA 114: 352-357). These publications including supplements should
be consulted for details. These lakes have been used for whole-ecosystem
experiments over the past decades; see Carpenter and Pace 2018 (Limnology
and Oceanography Letters 3(6): 419-427) for an overview.<br/>Nutrients were added to Peter (2013-2015, 2019) and Tuesday (2013-2015)
lakes to cause algal blooms. Details on nutrient additions (start/end dates,
loading rates, N:P ratios) are described in Buelo et al. 2022 (Ecological
Applications, link below), Wilkinson et al. 2018 (Ecological Monographs 88:
188-203), and Pace et al. 2017 (Proceedings of the National Academy of
Sciences USA 114: 352-357). These publications including supplements should
be consulted for details. These lakes have been used for whole-ecosystem
experiments over the past decades; see Carpenter and Pace 2018 (Limnology
and Oceanography Letters 3(6): 419-427) for an overview.<br/>Nutrients were added to Peter (2013-2015, 2019) and Tuesday (2013-2015)
lakes to cause algal blooms. Details on nutrient additions (start/end dates,
loading rates, N:P ratios) are described in Buelo et al. 2022 (Ecological
Applications, link below), Wilkinson et al. 2018 (Ecological Monographs 88:
188-203), and Pace et al. 2017 (Proceedings of the National Academy of
Sciences USA 114: 352-357). These publications including supplements should
be consulted for details. These lakes have been used for whole-ecosystem
experiments over the past decades; see Carpenter and Pace 2018 (Limnology
and Oceanography Letters 3(6): 419-427) for an overview.<br/>Nutrients were added to Peter (2013-2015, 2019) and Tuesday (2013-2015)
lakes to cause algal blooms. Details on nutrient additions (start/end dates,
loading rates, N:P ratios) are described in Buelo et al. 2022 (Ecological
Applications, link below), Wilkinson et al. 2018 (Ecological Monographs 88:
188-203), and Pace et al. 2017 (Proceedings of the National Academy of
Sciences USA 114: 352-357). These publications including supplements should
be consulted for details. These lakes have been used for whole-ecosystem
experiments over the past decades; see Carpenter and Pace 2018 (Limnology
and Oceanography Letters 3(6): 419-427) for an overview.<br/>Nutrients were added to Peter (2013-2015, 2019) and Tuesday (2013-2015)
lakes to cause algal blooms. Details on nutrient additions (start/end dates,
loading rates, N:P ratios) are described in Buelo et al. 2022 (Ecological
Applications, link below), Wilkinson et al. 2018 (Ecological Monographs 88:
188-203), and Pace et al. 2017 (Proceedings of the National Academy of
Sciences USA 114: 352-357). These publications including supplements should
be consulted for details. These lakes have been used for whole-ecosystem
experiments over the past decades; see Carpenter and Pace 2018 (Limnology
and Oceanography Letters 3(6): 419-427) for an overview.<br/>Nutrients were added to Peter (2013-2015, 2019) and Tuesday (2013-2015)
lakes to cause algal blooms. Details on nutrient additions (start/end dates,
loading rates, N:P ratios) are described in Buelo et al. 2022 (Ecological
Applications, link below), Wilkinson et al. 2018 (Ecological Monographs 88:
188-203), and Pace et al. 2017 (Proceedings of the National Academy of
Sciences USA 114: 352-357). These publications including supplements should
be consulted for details. These lakes have been used for whole-ecosystem
experiments over the past decades; see Carpenter and Pace 2018 (Limnology
and Oceanography Letters 3(6): 419-427) for an overview.<br/>Nutrients were added to Peter (2013-2015, 2019) and Tuesday (2013-2015)
lakes to cause algal blooms. Details on nutrient additions (start/end dates,
loading rates, N:P ratios) are described in Buelo et al. 2022 (Ecological
Applications, link below), Wilkinson et al. 2018 (Ecological Monographs 88:
188-203), and Pace et al. 2017 (Proceedings of the National Academy of
Sciences USA 114: 352-357). These publications including supplements should
be consulted for details. These lakes have been used for whole-ecosystem
experiments over the past decades; see Carpenter and Pace 2018 (Limnology
and Oceanography Letters 3(6): 419-427) for an overview.<br/>

Methods

Two lakes were studied for two years to test for spatial early warning
statistics (EWS) prior to an experimentally induced algal bloom. In 2018,
both Peter and Paul lakes were unmanipulated and spatial measurements of
each lake were taken weekly from June 6th to August 21st to establish
baseline conditions and EWS values. In 2019, nutrients were added to Peter
Lake while Paul Lake remained an unmanipulated reference lake. Both lakes
were measured three times per week from May 29th to September 4th. More
details on nutrient additions (loading rates, N:P ratios) are provided in
Buelo et al. 2022 (Ecological Applications, link below). <br/>Two lakes were studied for two years to test for spatial early warning
statistics (EWS) prior to an experimentally induced algal bloom. In 2018,
both Peter and Paul lakes were unmanipulated and spatial measurements of
each lake were taken weekly from June 6th to August 21st to establish
baseline conditions and EWS values. In 2019, nutrients were added to Peter
Lake while Paul Lake remained an unmanipulated reference lake. Both lakes
were measured three times per week from May 29th to September 4th. More
details on nutrient additions (loading rates, N:P ratios) are provided in
Buelo et al. 2022 (Ecological Applications, link below). <br/>Two lakes were studied for two years to test for spatial early warning
statistics (EWS) prior to an experimentally induced algal bloom. In 2018,
both Peter and Paul lakes were unmanipulated and spatial measurements of
each lake were taken weekly from June 6th to August 21st to establish
baseline conditions and EWS values. In 2019, nutrients were added to Peter
Lake while Paul Lake remained an unmanipulated reference lake. Both lakes
were measured three times per week from May 29th to September 4th. More
details on nutrient additions (loading rates, N:P ratios) are provided in
Buelo et al. 2022 (Ecological Applications, link below). <br/>Two lakes were studied for two years to test for spatial early warning
statistics (EWS) prior to an experimentally induced algal bloom. In 2018,
both Peter and Paul lakes were unmanipulated and spatial measurements of
each lake were taken weekly from June 6th to August 21st to establish
baseline conditions and EWS values. In 2019, nutrients were added to Peter
Lake while Paul Lake remained an unmanipulated reference lake. Both lakes
were measured three times per week from May 29th to September 4th. More
details on nutrient additions (loading rates, N:P ratios) are provided in
Buelo et al. 2022 (Ecological Applications, link below). <br/>Two lakes were studied for two years to test for spatial early warning
statistics (EWS) prior to an experimentally induced algal bloom. In 2018,
both Peter and Paul lakes were unmanipulated and spatial measurements of
each lake were taken weekly from June 6th to August 21st to establish
baseline conditions and EWS values. In 2019, nutrients were added to Peter
Lake while Paul Lake remained an unmanipulated reference lake. Both lakes
were measured three times per week from May 29th to September 4th. More
details on nutrient additions (loading rates, N:P ratios) are provided in
Buelo et al. 2022 (Ecological Applications, link below). <br/>

Methods

Dissolved gas samples were collected at 0.5, 3, 5 and 7 m using the
headspace method. From January to March 2020, water at each discrete depth
was pumped directly into the bottom of a 1-L Nalgene bottle and flushed with
at least three times the volume before being capped with a rubber stopper.
60 mL of ambient air was added while 60 mL of sample water was removed from
the bottle and equilibrated by shaking for 90 seconds. From May 2020
onwards, water was pumped into a closed bottle system, and using syringe,
105mL of water was extracted and 35mL of ambient air was added. The
headspace was then equilibrated for 2 minutes by shaking and 10 mL of
equilibrated gas sample was then removed from the bottle and injected into a
5.9 mL Labco Exetainer vial that had been previously vacuumed. While in the
field, samples were stored in pouches within a survival suit to prevent
extreme temperature change. We analyzed the gas samples for CO2 and CH4 with
a gas chromatograph (GC-2014; Shimadzu Scientific Instruments) equipped with
a methanizer and flame ionization detector. Greenhouse gas concentrations
were calculated according to Henry’s law and corrected by measured ambient
air.<br/>

Methods

Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>Field measurements and lab analysis<br/>

Methods

Conducted weekly data sampling (9 boat trips in June-August 2019) using an EXO multi-parameter sonde to collect temperature, conductivity, chlorophyll (ug/L), phycocyanin (ug/L), turbidity, dissolved organic material, ODO, pH, and pressure at 35 locations based on GPS guided stratified random sampling. 35 grid boxes were generated over Lake Mendota using qGIS. Point locations within each grid box were randomized before each sampling effort. At each point, variables were recorded continuously with the EXO sonde for a two-minute period. Continuous data was overaged over the two-minute period for each sample point.

Methods

water temperature and dissolved oxygen were measured at 1 meter intervals with a opto sonde

Methods

Inorganic and organic carbon
Inorganic carbon is analyzed by phosphoric acid addition on a Shimadzu TOC-V-csh Total Organic Carbon Analyzer.
Organic carbon is analyzed by combustion, on a Shimadzu TOC-V-csh Total Organic Carbon Analyzer.

Methods

The state of Wisconsin is comprised of about 15,000 inland lakes ranging from 0.5 to 53,394 ha (WDNR 2009). Most lakes occur in the northern and eastern part of the state as a result of glaciation. about 3,620 lakes are greater than 20 ha and together comprise about 93% of the state's inland lake surface area (Wisconsin Department of Natural Resources 2009). Wisconsin lakes constitute a wide range of physical and biological characteristics. Wisconsin inland lakes support valuable recreational fisheries for a variety of species, including Walleye (Sander vitreus), Northern Pike (Esox lucius), Muskellunge (Esox masquinongy), Yellow Perch (Perca flavescens), Largemouth Bass (Micropterus salmoides), Smallmouth Bass (Micropterus dolomieu), Lake Sturgeon (Acipenser fulvescens), and a variety of sunfish species (Lepomis spp.).

Methods

We collect water samples for color at the deepest part of the lakes. The samples are surface water, filtered in the field through 0.45u polycarbonate membrane filters. We run a wavelength scan from 800 to 200nm, using a 5cm rectangular quartz cell in a Beckman Coulter Model DU800 spectrophotometer. Any samples that display absorbance values above 2AU are run again from 400 to 200nm using a 1cm quartz cuvette. Inititally the full range of wavelengths were run again and two values may be found in the database even if the original measurement with the large cuvette did not exceed 2AU. The user should discard values above 2AU and use values from the smaller cuvette instead. All values are given as measurements at the path lenth of the employed cuvette and need to be devided by the cuvette length for a comparable value at a pathlength of 1 cm.

The single beam Beckman Coulter DU800 spec is blanked first on a sample of DI water. Additional blank values are from a scan run on DI after that blanking as a check and are reported alongside the scans but are not subtracted from the scan values.

Methods

We collect zooplankton samples at the deepest part of the lake using two different gear types. We take one vertical tow with a Wisconsin Net (80um mesh), and a series of Schindler Patalas (53um mesh) samples spanning the water column. All samples are preserved in cold 95percent EtOH.
After collection we combine subsamples of the individual Schindler Patalas trap samples to create one hypsometrically pooled sample for each lakeordate. The individual depth samples are discarded after pooling except from one August sampling date per year. The Hypsometrically Pooled sample and the Wisconsin Net sample are archived in the UW Zoology museum.
We count zooplankton in one or two subsamples, each representing 1.8L of lake water, of the hypsometrically pooled samples to calculate zooplankton abundance. We count one sample date per month from the open water season, and the February ice cover sample. We identify individuals to genus or species, take length measurements, and count eggs and embryos.
Protocol log: 1981-May1984 -- a 0.5m high, 31L Schindler Patalas trap with 80um mesh net was used. Two Wisconsin Net tows were collected. Preservative was 12percent buffered formalin.
June1984 -- changed to 53um mesh net on Schindler trap.
July1986 -- began using the 2m high, 45L Schindler Patalas trap. Changed WI Net collection to take only one tow.
2001 -- changed zooplankton preservative from 12percent buffered formalin to 95percent EtOH.
The number of sample dates per year counted varies with lake and year, from 5 datesoryear to 17 datesoryear.
1981-1983 -- pooled samples are of several types: Total Pooled (TP) were created using equal volume subsamples of the Schindler samples. Epi, Meta, Hypo pooled used equal volume subsamples from the Schindler samples collected from each of the thermal strata. Strata Pooled used equal volume subsamples from the Epi, Meta, Hypo pooled samples to create an entire lake sample. Hypsometrically Pooled (HP) is our standard, which uses subsample volumes weighted to represent the hypsometry of the lake.