US Long-Term Ecological Research Network

Spatially Distributed Lake Mendota EXO Multi-Parameter Sonde Measurements Summer 2019

Abstract
This data was collected over 9 sampling trips from June to August 2019. 35 grid boxes were generated over Lake Mendota. Before each sampling effort, sample point locations were randomized within each grid box. Surface measurements were taken with an EXO multi-parameter sonde at the 35 locations throughout Lake Mendota during each sampling trip. Measurements include temperature, conductivity, chlorophyll, phycocyanin, turbidity, dissolved organic material, ODO, pH, and pressure.
Core Areas
Dataset ID
388
Date Range
-
Maintenance
ongoing
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.
Publication Date
Version Number
1

Cascade project at North Temperate Lakes LTER - Daily Chlorophyll Data for Whole Lake Nutrient Additions 2013-2015

Abstract
Daily chlorophyll for surface water samples in Paul, Peter, and Tuesday lakes from mid-May to early September for the years 2013, 2014 and 2015. Inorganic nitrogen and phosphorus were added to Peter and Tuesday lakes each year while Paul Lake was an unfertilized reference.
Contact
Core Areas
Dataset ID
372
Date Range
-
Maintenance
completed
Methods
Methods are described in 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.

Version Number
1

Cascade Project at North Temperate Lakes LTER Core Data Process Data 1984 - 2016

Abstract
Data useful for calculating and evaluating primary production processes were collected from 6 lakes from 1984-2016. Chlorophyll a and pheophytin were measured by the same fluorometric method from 1984-2016. In some years chlorophyll and pheophytin were separated into size fractions (total, and a ‘small’ fraction that passed a 35 um mesh screen). Primary production was measured by the 14C method from 1984-1998. Dissolved inorganic carbon for primary production calculation was calculated from Gran alkalinity titration and air-equilibrated pH until 1987 when this method was replaced by gas chromatography. Until 1995 alkaline phosphatase activity was measured as an indicator of phosphorus deficiency.
Core Areas
Dataset ID
354
Date Range
-
Methods
General: Bade, D., J. Houser, and S. Scanga (editors). 1998. Methods of the Cascading Trophic Interactions Project. 5th edition. Center for Limnology, University of Wisconsin-Madison, and Cary Institute of Ecosystem Studies, Millbrook, NY.
Version Number
14

Cascade Project at North Temperate Lakes LTER Core Data Phytoplankton 1984 - 2015

Abstract
Data on epilimnetic phytoplankton from 1984-2015, determined by light microscopy from pooled Van Dorn samples at 100 percent, 50 percent, and 25 percent of surface irradiance. St. Amand (1990) and Cottingham (1996) describe the counting protocols in detail. Samples after 1995 were counted by Phycotech Inc. (http://www.phycotech.com). Sampling Frequency: varies; Number of sites: 5
Dataset ID
353
Date Range
-
Methods
Samples counted prior to 1996 were assigned one taxon name with all taxonomic information. This taxon name was split into distinct columns of genus, species and description for archival as best possible. Samples from 2013-2015 were sent to Phycotech inc. (http://www.phycotech.com/) to be counted.
Version Number
16

Cascade Project at North Temperate Lakes LTER Core Data Carbon 1984 - 2016

Abstract
Data on dissolved organic and inorganic carbon, particulate organic matter, partial pressure of CO2 and absorbance at 440nm. Samples were collected with a Van Dorn sampler. Organic carbon and absorbance samples were collected from the epilimnion, metalimnion, and hypolimnion. Inorganic samples were collected at depths corresponding to 100%, 50%, 25%, 10%, 5%, and 1% of surface irradiance, as well as one sample from the hypolimnion. Samples for the partial pressure of CO2 were collected from two meters above the lake surface (air) and just below the lake surface (water). Sampling frequency: varies; number of sites: 14
Core Areas
Dataset ID
350
Date Range
-
Methods
Detailed field and laboratory protocols can be found in the Cascade Methods Manual, found here: https://cascade.limnology.wisc.edu/public/public_files/methods/CascadeManual1998.pdf
POC, PON and DOC: 1. 100 - 300 ml (Typically ~200mL for PML, 150 metalimnion and 75 – 100 for the hypolimnion) of lake water from each depth was filtered through 153 um mesh to remove large zooplankton. Water was then filtered through a precombusted 25mm GF/F filter (0.7 um pore size) at less than 200 mm Hg pressure. Filters were placed in drying oven at 60 C to dry for at least 48 hours. 20mL of filtered water was stored in a scintillation vial and acidified with 200uL of 2N H2SO4 for DOC analysis. Blank samples for POC and DOC were prepared with deionized water to control for contamination. All samples were sent to the Cary Institute of Ecosystem Studies for analysis.

Version Number
24

Cascade project at North Temperate Lakes LTER - High-resolution spatial analysis of CASCADE lakes during experimental nutrient enrichment 2015 - 2016

Abstract
This dataset contains high-resolution spatio-temporal water quality data from two experimental lakes during a whole-ecosystem experiment. Through gradual nutrient addition, we induced a cyanobacteria bloom in an experimental lake (Peter Lake) while leaving a nearby reference lake (Paul Lake) as a control. Peter and Paul Lakes (Gogebic county, MI USA), were sampled using the FLAMe platform (Crawford et al. 2015) multiple times during the summers of 2015 and 2016. In 2015 nutrient additions to Peter Lake began on 1 June, and ceased on 29 June, Paul Lake was left unmanipulated. In 2016 no nutrients were added to either lake. Measurements were taken using a YSI EXO2 probe and a Garmin echoMap 50s. Sensor- data were collected continuously at 1 Hz and linked via timestamp to create spatially explicit data for each lake.

Crawford, J. T., L. C. Loken, N. J. Casson, C. Smith, A. G. Stone, and L. A. Winslow. 2015. High-speed limnology: Using advanced sensors to investigate spatial variability in biogeochemistry and hydrology. Environmental Science & Technology 49:442–450.
Contact
Dataset ID
343
Date Range
-
Maintenance
complete
Methods
In two consecutive years, we measured lake-wide spatial patterning of cyanobacteria using the FLAMe platform (Crawford et al. 2015). To evaluate early warning indicators of a critical transition, in the first year we induced a cyanobacteria bloom through nutrient addition in an experimental lake while using a nearby unmanipulated lake as a reference ecosystem (Pace et al. 2017). During the second year, both lakes were left unmanipulated. Proposed detection methods for early warning indicators were compared between the manipulated and reference lakes to test for their ability to accurately detect statistical signals before the cyanobacteria bloom developed.
Peter and Paul Lakes are small, oligotrophic lakes (Peter: 2.5 ha, 6 m, 19.6 m and Paul: 1.7 ha, 3.9 m, 15 m, for surface area, mean, and max depth respectively) located in the Northern Highlands Lake District in the Upper Peninsula of Michigan, USA (89°32’ W, 46°13’ N). These lakes have similar physical and chemical properties and are connected via a culvert with Paul Lake being upstream. Both lakes stratify soon after ice-off and remain stratified usually into November (for extensive lake descriptions, see Carpenter and Kitchell, 1993).
In the first year, Peter Lake was fertilized daily starting on 1 June 2015 (DOY 152) with a nutrient addition of 20 mg N m-2 d-1 and 3 mg P m-2 d-1 (molar N:P of 15:1) through the addition of H3PO4 and NH4NO3 until 29 June (day of year, DOY 180). The decision to stop nutrient additions required meeting four predefined criteria based on temporal changes in phycocyanin and chlorophyll concentrations indicative of early warning behavior of a critical transition to a persistent cyanobacteria bloom state. (Pace et al. 2017). Nutrients uniformly mix within 1-2 days after fertilization based on prior studies (Cole and Pace 1998). No nutrient additions were made to Paul Lake. In the second year (2016), neither lake received nutrient additions.
We mapped the surface water characteristics of both experimental lakes to identify changes in the spatial dynamics of cyanobacteria. In 2015, mapping occurred weekly from 4 June to 15 August (11 sample weeks). In 2016, when neither lake was fertilized, the lakes were mapped three times in early to mid-summer. In both years, mapping occurred between the hours of 07:00 to 12:00 (before the daily nutrient addition). We rotated the order that we sampled the lakes to avoid potential biases due to differences in time of day. Each individual lake sampling event was completed in approximately one hour.
The FLAMe platform maps the spatial pattern of water characteristics. A boat-mounted sampling system continuously pumps surface water from the lake to a series of sensors while geo-referencing each measurement (complete description of the FLAMe platform in Crawford et al. 2015). For this study, the FLAMe was mounted on a small flat-bottomed boat propelled by an electric motor and was outfitted with a YSI EXO2™ multi-parameter sonde (YSI, Yellow Springs, OH, USA). We focused for this study on measures of phycocyanin (a pigment unique to cyanobacteria) and temperature. Phycocyanin florescence was measured using the optical EXO™ Total Algae PC Smart Sensor. The Total Algae PC Smart Sensor was calibrated with a rhodamine solution based on the manufacturer’s recommendations. Phycocyanin concentrations are reported as ug/L; however, these concentrations should be considered as relative because we did not calibrate the sensor to actual phycocyanin nor blue-green algae concentrations. Geographic positions were measured using a Garmin echoMAP™ 50s. Sensor- data were collected continuously at 1 Hz and linked via timestamp to create spatially explicit data for each lake. Each sampling produced approximately 3500 measurements in the manipulated lake and 2000 in the reference lake. The measurements were distributed by following a gridded pattern across the entire lake surface to characterize spatial patterns over the extent of the lake.
Version Number
15

Lake Mendota Carbon and Greenhouse Gas Measurements at North Temperate Lakes LTER 2016

Abstract
This original dataset contains carbon and greenhouse gas (GHG) data collected in Lake Mendota during the summer of 2016. Data were collected between 15 April 2016 and 14 November 2016 on both Lake Mendota and its surrounding streams—four major inflows and the primary outflow of Lake Mendota. The dataset is comprised of four linked tables, corresponding to carbon and GHG measurements on Lake Mendota (lake_weekly_carbon_ghg), weekly physico-chemical sonde casts on Lake Mendota (lake_weekly_ysi), ebullition rate estimates on Lake Mendota (lake_weekly_ebullition), and carbon and physico-chemical data from the four major inflows and primary outflow of Lake Mendota (stream_weekly_carbon_ysi). These data were used to explore the relationship between organic carbon dynamics and greenhouse gas production on a eutrophic lake. From these data, it is possible to estimate daily oxygen, methane, and carbon dioxide flux on Lake Mendota during the study time period. Additional methods and applications of this data can be found in J.A. Harts Masters Thesis, University of Wisconsin-Madison Center for Limnology, May 2017.
Core Areas
Dataset ID
339
Date Range
-
Methods
lake_weekly_carbon_ghg.csv
Carbon Sample Analysis: Weekly observational data were collected on Lake Mendota between 15 April 2016 and 14 November 2016. All lake samples collected from the deep hole were taken at five discrete depths (3, 10, 12, 14, and 20 m), intended to span the seasonal thermocline. All lakes samples collected in littoral zones (Point, Ubay, and Yahara) were taken at two discrete depths (0.1 and 2 m). Two liters of water were collected at each sampling location and depth using a Van Dorn sampler for measurement of particulate organic carbon (POC), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC). Between 1200 mL and 1800 mL of water was passed through a ProWeigh 47 mm filter (Environmental Express, Charleston, SC, USA) depending on how quickly water became impassable. POC was estimated by performing loss on ignition on the filter. The difference in mass before and after combustion at 500°C was multiplied by 0.484 to account for the OC fraction of organic matter (Thomas et al. 2005). Filtrate was analyzed for DOC and DIC on a Shimadzu TOC-V-csh Total Organic Carbon Analyzer (Shimadzu Scientific Instruments, Kyoto, Japan), where organic carbon is measured by combustion and inorganic carbon after phosphoric acid digestion.
Dissolved Gas Analysis: Water samples for dissolved methane (CH4) and carbon dioxide (CO2) were collected at each depth in the lake using a Van Dorn sampler and stored in 30-mL serum vials. Serum vials were overfilled and capped in the field with a rubber septa and aluminum cap. Care was taken to ensure that no bubbles were present in the sample. Serum vials were then stored on ice until they could be placed in the refrigerator. Within 24 hours of collection, samples received a 3 mL N2 gas headspace, were shaken vigorously, and left to equilibrate at room temperature. Headspace CH4 and CO2 was analyzed on a Varian 3800 gas chromatograph, and headspace-water CH4 and CO2 partitioning was accounted for using Henrys Law.
Version Number
19

LTREB experimental chironomid mesocosms at Myvatn, Iceland

Abstract
During the summer of 2014, we conducted experiments testing whether increasing numbers of chironomid larvae would increase primary production and standing chlorophyll a concentrations. We incubated experimental mesocosms with varying numbers of chironomid larvae for 12 days in July. We tested sediments for chlorophyll a concentrations, as sediments are primarily composed of benthic diatoms. We tested the oxygen production in these mesocosms. We did this by sealing the mesocosms and incubating them in Lake Myvatn for 3 hours, and taking measurements of dissolved oxygen before and after the incubations.
We were also interested in whether this increase in food resources might translate to increased growth rates of chironomid larvae at high larval densities. After stocking experimental mesocosms with varying numbers of chironomid larvae, we set these mesocosms in Lake Myvatn for 12 days. We collected the larvae at the end of the 12 day experiment and obtained the average dry weights of the Chironomus islandicus larvae in each mesocosm.
We hypothesized that the tubes that chironomid larvae build would be a superior substrate for algal growth, as compared to loose sediments. Because there are two taxa (Chironomus islandicus and Tanytarsus gracilentus) that are overwhelmingly dominant at our study site, we wondered whether there would be differences in this effect between the two species. We stocked mesocosms with larvae from one of the two species, and mesocosms were then incubated in Lake Myvatn. We collected sediments and larval tubes from each mesocosm and tested their chlorophyll a concentrations.
We hypothesized that one mechanism that chironomid larvae might alleviate algal nutrient limitation by depositing concentrated nutrients near algae in the form of larval excretions. We collected chironomid larvae from Lake Myvatn and placed them in distilled water. We then sieved out the larvae and their fecal passings, and transported the water samples to Madison, WI, USA, where nutrient concentrations were analyzed
Contact
Dataset ID
334
Date Range
-
Methods
Please refer to the following manuscript for a description of methods:
Herren, Cristina M., Webert, Kyle C., Drake, Michael D., Vander Zanden, M. Jake, Einarsson, Árni, Ives, Anthony R., Gratton, Claudio. 2016. Positive feedback between chironomids and algae creates net mutualism between benthic primary consumers and producers, Ecology, DOI: 10.1002/ecy.1654
Short Name
Myvatn midge experiment chlorophyll
Version Number
11

WSC - Yield and water table depth shapefiles from Wibu field site

Abstract
Yield data from the Wibu field site combined with a variety of water table depth metrics (mean, percentiles, sum exceedance values, moving averages). It was collected as part of a study of the impacts of water table depth, soil texture, and growing season weather conditions on corn production at the Wibu field site, described in Zipper et al. (in review). The Wibu field site is a commercial agricultural field, which grew corn in the 2012, 2013, and 2014 growing seasons. See Zipper and Loheide (2014) Ag. For. Met. for more information about the field site.
Dataset ID
317
Date Range
-
Maintenance
completed
Metadata Provider
Methods
Yield data was collected at the time of harvest following the 2012 and 2013 growing season using a John Deere 9660 combine equipped with a Greenstar yield monitoring system. Yield data was cleaned by removing any polygons collected during pre-harvest check strips, turn-around at the end of rows, any polygons less than 6 m2, and any polygons where yield exceeded the record reported yield for Dane County WI (327 bu ac-1). Yield was normalized by calculating z-scores (the number of standard deviations away from the mean) within each field and each year. 2012 data was resampled to the 2013 polygon boundaries by taking the mean of all 2012 polygons with their centroid within each 2013 polygon. For each polygon, 2013 interpolated groundwater metrics were extracted using ArcMAP 10.2 software. A full description of this methodology is contained in Zipper et al. (in review).
Version Number
16

WSC - Leaf area index (LAI) at various points within Wibu field site, 2012-2014

Abstract
Leaf area index (LAI) measurements collected at various points within the Wibu field site between 2012-2014. Measurements were collected approximately weekly from plant emergence until appr. 1 month past the onset of senescence. The Wibu field site is a commercial agricultural field, which grew corn in the 2012, 2013, and 2014 growing seasons; therefore, these are all LAI values for corn. See Zipper and Loheide (2014) Ag. For. Met. for more information about the field site and use of the LAI data.
Dataset ID
314
Date Range
-
Maintenance
completed
Metadata Provider
Methods
Measurements were made using a Licor-brand LAI-2200 device at approximately weekly intervals during the 2012, 2013, and 2014 growing seasons. At each point, the measurements are the average LAI value calculated from 20 subcanopy measurements ranging from in-line with planted rows to the area between rows. In 2012 and 2013, measurements were taken exclusively during diffuse light conditions (sunrise, sunset, or full cloud cover). In 2014, measurements were taken during daylight hours and corrected for light scattering using the LAI-2200C correction described on their website. This means that 2014 data is less accurate than 2012-2013 data. Note that, for each growing season, a date is listed with 0 LAI – this corresponds to the date prior to emergence at each site.After installation of wells and soil monitoring gear in each of the 2012, 2013, and 2014 growing seasons, we used a Topcon GR5 RTK-GPS to collect the location of each relevant point within the field. In 2014, a gridded set of soil sampling points was also measured.
Version Number
13
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