Methods

Data included in this package include output, driving data, and supplemental calculated information for a modeling study.<br/>

Methods

Nutrients were added to Peter and Tuesday lakes to cause algal blooms. Details on nutrient additions (start/end dates, loading rates, N:P ratios) are described in Wilkinson et al. 2018. (Ecological Monographs 88:188-203). Methods are described in Pace et al. 2021 (Limnology and Oceanography linked 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.<br/>Nutrients were added to Peter and Tuesday lakes to cause algal blooms. Details on nutrient additions (start/end dates, loading rates, N:P ratios) are described in Wilkinson et al. 2018. (Ecological Monographs 88:188-203). Methods are described in Pace et al. 2021 (Limnology and Oceanography linked 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.<br/>Nutrients were added to Peter and Tuesday lakes to cause algal blooms. Details on nutrient additions (start/end dates, loading rates, N:P ratios) are described in Wilkinson et al. 2018. (Ecological Monographs 88:188-203). Methods are described in Pace et al. 2021 (Limnology and Oceanography linked 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.<br/>Nutrients were added to Peter and Tuesday lakes to cause algal blooms. Details on nutrient additions (start/end dates, loading rates, N:P ratios) are described in Wilkinson et al. 2018. (Ecological Monographs 88:188-203). Methods are described in Pace et al. 2021 (Limnology and Oceanography linked 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.<br/>

Methods

Data were collected from two lakes, Sparkling Lake (46.008, -89.701) and Peter Lake (46.253, -89.504), both located in the northern highlands Lake District of Wisconsin and the Upper Peninsula of Michigan over a 10 day period on each lake in July and August of 2007. Refer to Van de Bogert et al. 2011 for limnological characteristics of the study lakes.Measurements of dissolved oxygen and temperature were made every 10 minutes using multiple sondes dispersed horizontally throughout the mixed-layer in the two lakes (n=35 sondes for Sparkling Lake and n=27 sondes for Peter Lake). Dissolved oxygen measurements were corrected for drift.Conductivity, temperature compensated specific conductivity, pH, and oxidation reduction potential were also measured by a subset of sensors in each lake. Of the 35 sondes in Sparkling Lake, 31 were from YSI Incorporated: 15 of model 600XLM, 14 of model 6920, and 2 of model 6600). The remaining sondes placed in Sparkling Lake were 4 D-Opto sensors, Zebra-Tech, LTD. In Peter Lake, 14 YSI model 6920 and 13 YSI model 600XLM sondes were used.Sampling locations were stratified randomly so that a variety of water depths were represented, however, a higher density of sensors were placed in the littoral rather than pelagic zone. See Van de Bogert et al. 2012 for the thermal (stratification) profile of Sparkling Lake and Peter Lake during the period of observation, and for details on how locations were classified as littoral or pelagic. In Sparkling Lake, 11 sensors were placed within the shallowest zone, 12 in the off-shore littoral, and 6 in each of the remaining two zones, for a total of 23 littoral and 12 pelagic sensors. Similarly, 15 sensors were placed in the two littoral zones, and 12 sensors in the pelagic zone.Sensors were randomly assigned locations within each of the zones using rasterized bathymetric maps of the lakes and a random number generator in Matlab. Within each lake, one pelagic sensor was placed at the deep hole which is used for routine-long term sampling.Note that in Sparkling Lake this corresponds to the location of the long-term monitoring buoy. After locations were determined, sensors were randomly assigned to each location with the exception of the four D-Opto sensor is Sparkling Lake, which are a part of larger monitoring buoys used in the NTL-LTER program. One of these was located near the deep hole of the lake while the other three were assigned to random locations along the north shore, south shore and pelagic regions of the lake. Documentation: Van de Bogert, M.C., Bade, D.L., Carpenter, S.R., Cole, J.J., Pace, M.L., Hanson, P.C., Langman, O.C., 2012. Spatial heterogeneity strongly affects estimates of ecosystem metabolism in two north temperate lakes. Limnology and Oceanography 57, 1689-1700.

Methods

Light (PAR) extinction coefficient is calculated by linearly regressing ln (FRLIGHT (z)) on depth z where the intercept is not constrained. FRLIGHT(z) = LIGHT(z) or DECK(z) where LIGHT(z) is light measured at depth z and DECK(z) is light measured on deck (above water) at the same time. For open water light profiles, the surface light measurement (depth z = 0) is excluded from the regression. For winter light profiles taken beneath the ice, the first light data are taken at the bottom of the ice cover and are included in the regression. The depth of uppermost light value is equal to the depth of the ice adjusted by the water level in the sample hole, i.e., the depth below the surface of the water. The water level can be at, above or below the surface of the ice. If the water level was not recorded, it is assumed to be 0.0 and the calculated light extinction coefficient is flagged. If ice thickness was not recorded, a light extinction coefficient is not calculated. For light data collected prior to March, 2007, light values less than 3.0 (micromolesPerMeterSquaredPerSec) are excluded. For light data collected starting in March 2007, light values less than 1.0 (micromolesPerMeterSquaredPerSec) are excluded. Except for bog lakes before August 1989, a light extinction coefficient is not calculated if there are less than three FRLIGHT values to be regressed. For bog lakes before August 1989, a light extinction coefficient is calculated if there are least two FRLIGHT values to be regressed. In these cases, the light extinction coefficient is flagged as non-standard. FRLIGHT values should be monotonically decreasing with depth. For light profiles where this is not true, a light extinction coefficient is not calculated. For samples for which light data at depth are present, but the corresponding deck light are missing, a light extinction coefficient is calculated by regressing ln (LIGHT (z)) on depth z. Note that if actual deck light had remained constant during the recording of the light profile, the resulting light extinction coefficient is the same as from regressing ln(FRLIGHT(z)). In these cases, the light extinction coefficient is flagged as non-standard. Oxygen and Temperature: We sample at the deepest part of the lake, taking a temperature and oxygen profile at meter intervals from the surface to within 1 meter of the bottom using a YSI Pro-ODO temporDO meter. We sample biweekly during open water and approximately every five weeks during ice cover. Protocol Log: Prior to 2011, we used a YSI Model 58 temporDO meter.

Methods

see abstract for methods description

Methods

The instrumented raft on Sparkling Lake is equipped with a D-Opto dissolved oxygen sensor, a thermistor chain, and meteorological sensors that provide fundamental information on lake thermal structure, weather conditions, evaporation rates, and lake metabolism. Estimating the flux of solutes to and from lakes requires accurate water budgets. Evaporation rates are a critical component of the water budget of lakes. Data from the instrumented raft on Sparkling Lake includes micrometeorological parameters from which evaporation can be calculated. Raft measurements of relative humidity and air temperature (2 m height), wind velocity (2m) , and water temperatures (from thermistors placed throughout the water column at intervals varying from 0.5 to 3m) are combined with measurements of total long-wave and short-wave radiation data from a nearby shore station to determine evaporation by the energy budget technique. Comparable evaporation estimates from mass transfer techniques are calibrated against energy budget estimates to produce a lake-specific mass transfer coefficient for use in estimating evaporation rates. After correcting for flux to or from the atmosphere and vertical mixing within the water column, high frequency measurements of dissolved gases such as carbon dioxide and oxygen can be used to estimate gross primary productivity, respiration, and net ecosystem productivity, the basic components of whole lake metabolism. Other parameters measured include precipitation, wind direction (beginning in 2008), and barometric pressure (beginning in 2008). Sampling Frequency: one minute; averaged to hourly and daily values as well as higher resolution values such as 2 min and 10 min.Dissolved oxygen sensors: 2004-2006: Greenspan Technology series 1200; 2007-2016: Zebra-Tech Ltd. D-Opto; 2018+: OTT HydrolabCO2 sensors: 2018+: ProOceanos MiniCO2 for dissolved CO2; Eosense Inc. eosGP for atmospheric CO2

Methods

The instrumented buoy on Sparkling Bog North is equipped with a thermistor chain that measures water temperature at the surface, at 0.25 m and at every .5 m from 0.5 m to 4.5 m. The buoy is also equipped with a dissolved oxygen sensor, meteorological sensors, a CO2 sensor and a YSI AutoProfiler that provide fundamental information on lake thermal structure, weather conditions, and lake metabolism. Prior to May 2009, data were collected at 1 minute or 10 minute intervals. Since May 2009, data are being collected each minute. Hourly and daily water temperature averages are computed from high resolution data. Hourly and daily values may not be current with high resolution data. In 2008, the instrumented buoy was deployed in Sparkling Bog North from March 24 to November 10. In 2009, the buoy was deployed on the ice on March 7 and was not removed for the winter of 2009 to 2010. Sampling Frequency: varies for instantaneous sample.

Methods

see abstract for methods description

Methods

See abstract for methods description