PRINCIPAL INVESTIGATOR
      Gene E. Likens
      Institute of Ecosystem Studies

OTHERS INVOLVED
      see References

BEGIN DATE
      June 1967

END DATE
      On-going

LOCATION
      Central buoy station on Mirror Lake

LOCATION DESCRIPTION
       Collected in a boat from an anchored buoy station, or from the ice surface located at the deepest part (11 m at full pool) of Mirror Lake. Mirror Lake is 15 ha in area, and an oligotrophic (low productivity), clearwater (Secchi transparency 6 to 7 m), natural water body adjacent to HBEF. The lake normally mixes in spring and fall, and is ice-covered from about 1 December to about 15 April each year. Numerous studies have been conducted on Mirror Lake since the mid-1960s, including extensive physical, chemical, biological, and paleoecological research which are described in detail in the book: An Ecosystem Approach to Aquatic Ecology (Likens, 1985).

DATA DESCRIPTION
       Concentrations (mg/L) in lake water samples from discrete depths. Base cation, pH, and dissolved oxygen data are available since 1967. Ammonium, anions, phosphate, and dissolved silica have been measured routinely since 1970, although some data are available prior to these dates for each solute. Other standard data include temperature and specific conductance at each depth. Prior to 1990, not all records have complete solute arrays. Since 1990, dissolved in-organic carbon (DIC) and acid neutralizing capacity (ANC; alkalinity) have also been measured on a routine basis, although prior data do exist.

SAMPLING DESIGN
       Samples for ion analysis are collected in acid-washed, deionized water-rinsed, polyethylene bottles, using a manual closure, plastic VanDorn collector bottle (before 1990), triggered at discrete depths, or lifted to the surface through weighted vinyl tubing by peristaltic pump (since 1990). DO and DIC samples are collected in standard glass BOD bottles. Typically, water samples are taken from the surface (<0.5m), and at depths of 2, 4, 6, 8, and 10 meters. The usual sampling interval is 4 to 6 times each year, especially at times of maximum and minimum thermal stratfication. Temperatures are determined by thermistor probe (Whitney, YSI, or Digisense Models).

REFERENCES

• Likens, G. E. 1972. Mirror Lake: its past, present and future? Appalachia 39(2):23- 41.
• Likens, G. E. (editor). 1985. An Ecosystem Approach to Aquatic Ecology: Mirror Lake and its Environment. Springer-Verlag New York Inc. 516 pp.
• Buso, D.C., G.E. Likens, and J.S. Eaton. 2000. Chemistry of precipitation, streamwater, and lakewater from the Hubbard Brook Ecosystem Study: a record of sampling protocols and analytical procedures. Gen. Tech. Rep. NE-275. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 52 p.

DATA LOCATION
      Institute of Ecosystem Studies, Robert S. Pierce Ecosystem Laboratory, Hubbard Brook Experimental Forest, W.Thornton, NH

LAST UPDATED
      April, 2001

CONTACT PERSON
      Gene Likens
      Institute of Ecosystem Studies
      Millbrook, NY 12545
      Telephone: (845) 677-5343
      E-mail: LikensG@ecostudies.org

VARIABLES
      Records: 1657 total samples in 4 separate files
      Columns: supplied with the following headers:
            ws - watershed
            year - year
            mo - month
            dy - day
            z - depth in meters
            Ca - calcium concentration in mg/L
            Mg - magnesium concentration in mg/L
            K - potassium concentration in mg/L
            Na - sodium concentration in mg/L
            NH4 - ammonium concentration in mg/L
            pH - pH
            SO4 - sulfate concentration in mg/L
            NO3 - nitrate concentration in mg/L
            Cl - chloride concentration in mg/L
            PO4 - phosphate concentration in mg/L (soluble-reactive phosphate)
            SiO2 - silica concentration in mg/L (measured as silicate)
            ANC - acid neutralizing capacity in meq/L
            DIC - dissolved inorganic carbon in mmoles/L
            DO - dissolved oyxgen in mg/L
            TEMP - temperature in degrees C
            SpCond - specific conductance corrected to 25C

CODES
       Missing data are coded with -3.
Values of 0.0 (zero) are below the detection limit of analysis.

DATA FILE NAME(S)
       Data were separated and downloaded from spreadsheets onto 3 individual files to make handling and data checking easier.
      ASCII file names:
            mlake-69.txt covering the period 1967 to 1969 264 records
            mlake-79.txt covering the period 1970 to 1979 643 records
            mlake-89.txt covering the period 1980 to 1989 516 records
            mlake-95.txt covering the period 1990 to 1995 234 records