The vertical distribution of temperature and dissolved oxygen in 15 lakes was monitored from June 16 – October 15, 2021 using chains of high-frequency temperature and dissolved oxygen loggers. In most cases chains were located at the deepest point in each lake. In the three deepest lakes (Little Moose, First Bisby, Honnedaga), strings were located deep enough to capture the entire metalimnion and several meters of the hypolimnion, but not at the deepest point. Honnedaga was outfitted with temperature loggers only based on oxygen profiles that indicated absence of low-oxygen water (< 5 mg/L). Dissolved oxygen loggers were positioned to best capture low-oxygen zones based on prior data, monitoring 1-5 depths per lake. Dissolved oxygen loggers were either PME miniDOTs or Onset U26 loggers. Temperature loggers were positioned throughout the water column. Dissolved oxygen loggers were set at ten-minute logging frequencies while temperature loggers ranged from ten minutes to one hour. All loggers were checked for calibration accuracy prior to deployment. Dissolved oxygen loggers had a mean difference between observed values and expected values at 100% saturation of 0.10 mg/L with a standard deviation of 0.20 among 30 loggers. In anoxic conditions, sensors had a mean value of -0.06 mg/L from anoxic with a standard deviation of 0.12. Calibration checks were done both before and following deployment, with no observable drift beyond the analytical uncertainty of the instruments.
One lake (Green) had sparse vertical temperature coverage. For this lake we added modeled high-frequency temperature data at a depth of 6 meters. We used lakes having similar size and clarity (Wilmurt, Canachagala) to understand the seasonal development of temperature at 6 m. We observed that 6 m temperatures tended to increase linearly until mid-August after which they plateaued through the remainder of the warm period. Eventually surface temperatures cooled to match temperatures at 6 m. To get the equation in Green for the linear increase until mid-August we used periodic temperature profiles in Green Lake and fit a linear regression to the 6 m temperature values, using the resulting equation to calculate 6 m temperatures from mid-June until mid-August every 15 minutes. From mid-August we kept temperatures constant at the peak value obtained to date to represent the plateau period. Once temperatures at the surface cooled to equal those at 6 m depth in the fall, we set the remaining values at 6 m equal to the values measured at the surface.
This high-frequency data was supplemented with periodic manually collected temperature and dissolved oxygen profiles. These profiles were collected using either a YSI EXOII multiparameter sonde or a YSI 550a probe. Profiles were collected most often at 0.5 m intervals in the water column. The EXOII recorded continuous digital readings every second but was held every 0.5 m until stabilization, at which point DO and temperature readings were manually recorded.
Data from ALSC lakes are historical data originally collected by the Adirondack Lakes Survey Corporation during four years in the mid-1980s. We used DOC samples from the months of June, July, and August and where samples were collected within 1.5 m of the surface. We took the average of all values sampled in these months for each lake to use as a representative DOC concentration in each lake.
We also present long-term summer DOC concentrations from our 15 intensively monitored lakes. These data are from surface grab samples in the months of July and August. Samples are averaged to yield mean summer DOC concentrations.
Tagged fish were used to gather data regarding temperature occupancy of brook trout in two of these lakes during June and July of 2023.
