Iowa Lakes Survey

Summer 2002 Data

John A. Downing
Joy M. Ramstack
Kristian Haapa-aho
Kendra Lee

 

Department of Ecology, Evolution, and Organismal Biology
Iowa State University
January 2003

The objective of the Iowa Lakes Survey is to sample 132 of Iowa’s principle recreational lakes, and to characterize water quality over a five-year period.  The following data represent the third of five years of sampling of these lakes (averages from the summer of 2000 and 2001 are also included in the data tables).  One hundred and fifteen of the lakes were previously studied, and classified for restoration, by Roger Bachmann of Iowa State University in 1979 and again between 1990 and 1992 (Bachmann et. al, 1980; Bachmann et. al, 1994).

A five-year study window was chosen because a single year’s data can be very far from average conditions (Bachmann et al, 1994).  There is probably even more inter-annual variation in Iowa lakes than seen elsewhere because of land disturbance and extreme nutrient conditions.  In the summer of 2000, rainfall was 2.29 inches (5.82 cm) above normal in June, and 0.04 inches (0.10 cm) above normal in July.  However, the end of the summer was much drier (1.13 and 1.68 inches (2.87; 4.27 cm) below normal in August and September, respectively) (Iowa Department of Agriculture and Land Stewardship, State Climatologist’s Office, 2000).  In the summer of 2001, the beginning of the summer was wet (average rainfall in May was 3.05 inches (7.75 cm)).  However, rainfall was below average for the remainder of our sampling months in 2001 (0.29, 0.92, and 1.05 inches (0.74, 2.34, and 2.67 cm) below normal in June, July and August, respectively) (Iowa Department of Agriculture and Land Stewardship, State Climatologist’s Office, 2001).  During the summer of 2002, rainfall was close to average conditions during May, June, and July (0.32 inches (0.80 cm) above normal in May, 0.85 inches (2.17 cm) below normal in June, and 0.06 inches (0.15 cm) above normal in July).  The end of the summer was wetter, rainfall was 1.73 inches (4.40 cm) above normal in August (Iowa Department of Agriculture and Land Stewardship, State Climatologist’s Office, 2002).

The 132 study lakes (Appendix 1) were each sampled three times during the summer of 2002, between May 20 and August 14.  Sampling was conducted at the deepest point in each lake basin, as determined by sonar and existing bathymetric maps, and the spatial locations of sampling points were recorded using GPS.  YSI’s 6-Series, Multi-parameter Water Quality Monitors were used in the field to collect profiles of temperature, dissolved oxygen, specific conductivity, pH, turbidity, and chlorophyll.  As these probes were lowered through the water column, the depth of the thermocline was determined (if one was present).  After the depth of the thermocline was determined, an integrated column sampler (which consisted of plastic tubing, weighted on one end, and calibrated in meters) was used to collect water from the upper mixed zone of the lake.  If no thermocline was present, then the entire water column was sampled.  The water from the column sampler was placed into a bucket, thoroughly mixed, poured into polypropylene bottles, and kept cold until it was delivered to the laboratory for analysis the next day.  This method was used to collect water samples for analysis of nutrients, phytoplankton (with Lugol’s solution added as a preservative; American Public Health Association, 1998), chlorophyll, and suspended solids.  Zooplankton samples were collected by vertically towing a Wisconsin net (63 μm mesh size) through the upper mixed layer of the lake (or through the entire water column if no thermocline was present).  Samples were transferred to a polypropylene bottle with distilled water, and Formalin (5% solution, with sucrose added) was added as a preservative. 

Every effort was made to accurately determine the depth of the thermocline in the field.  After generating graphs of the data, however, there were a few cases where the decision made in the field did not accurately reflect the depth of the upper mixed layer.  In the following data tables, the depth of thermocline reflects the decision that was made in the field because this represents the depth from which samples were collected.  Graphs of water depth and temperature are provided to visualize thermal structure. 

Phosphorus, nitrogen, and silica analyses were performed on an HP 8453 Spectrophotometer, using standard water-analysis methods.  Ammonia and silica analyses were performed according to Standard Methods (American Public Health Association, 1998), using Hach chemicals and protocols.  Silica analyses followed the molybdosilicate method (American Public Health Association, 1998).  Phosphorus analyses were performed in accordance with Standard Methods and followed the ascorbic acid method, with persulfate digestion (American Public Health Association, 1998).  Nitrate and total nitrogen were analyzed using second derivative spectroscopy (Crumpton et. al, 1992).  Laboratory analyses of chlorophyll a were performed on a Turner Designs TD-700 Laboratory Fluorometer, with acetone and magnesium carbonate extraction (American Public Health Association, 1998).  Turbidity corrections were made to all of our visible wavelength colorimetric analyses (total phosphorus, PO₄, NH₃+NH₄, and silica). 

During the summer of 2002 we added particle size distribution, as well as dissolved organic carbon, to our analyses.  Sequoia Scientific’s LISST-100 laser particle sizer was used in the laboratory to determine the particle size distribution of our samples.  Dissolved organic carbon was measured with a Shimadzu TOC-V analyzer, following Shimadzu’s method for non-purgable organic carbon, which is equivalent to the EPA’s total organic carbon method.     

Methods used were substantially identical to those employed by Bachmann et. al (1980; 1994).  Quality assurance/quality control procedures were routinely employed in the laboratory and in the field.  Calibration standards and blanks were run with each set of samples.  Phosphorus, nitrogen, and silica samples were run in triplicate.  Field duplicates were collected and analyzed at a rate of 10%. 

For any samples that fell below the detection limit, half of that limit was used in the calculation of summer averages.  When calculating NH₃ from the measurement of NH₃+NH₄, the calculation was not performed for samples that fell below the detection limit of NH₃+NH₄.

During the first week of sampling in 2002, we were unable to recover data from our YSI Multi-parameter Water Quality Monitors for the following lakes:  Big Spirit Lake in Dickinson County, Black Hawk Lake in Sac County, Center Lake in Dickinson County, Five Island Lake in Palo Alto County, Ingham Lake in Emmet County, Little Spirit Lake in Dickinson County, Moorehead Lake in Ida County, Silver Lake in Palo Alto County, Storm Lake in Buena Vista County, and Tuttle Lake in Emmet County.  We revisited these lakes the following week to collect profiles; consequently there is a discrepancy in dates between the laboratory analyses of these lakes and the field profiles for the first sampling round.

The field measurements of chlorophyll were determined by fluorometry.  Fluorometry performed in the field may be susceptible to interference by suspended particles in the water column, and provide an inaccurate measurement of chlorophyll.  Therefore, the graphical chlorophyll profiles should be interpreted as a relative amount of chlorophyll in the water column.  Chlorophyll data in the tables are accurate and were determined using standard lab methods.     

Phytoplankton and zooplankton samples from 2001 and 2002 are currently being processed and these data will be incorporated into future reports.

During the summer of 2002, lake water samples (taken as an integrated sample from the mixed zone, or from the entire water column when no thermocline was present) were also analyzed for a variety of metals during the second sampling round (between June 17 and July 18).  All metal analyses were performed by the Hygienic Laboratory at the University of Iowa, following standard EPA approved methods. 

The following report is arranged alphabetically by lake name.  Data tables of field measurements and water chemistry are presented for each lake; data are reported for each of the sampling dates, with summer averages from 2000 and 2001, as well as the summer average from 2002.  In the data tables, “--“ denotes a missing value (or absence of a thermocline), usually due to sample loss or destruction.  No averages are provided in the case of sampling depth and thermocline depth, because such averages were deemed of little meaning.  For each lake, there are depth profiles of temperature, dissolved oxygen, specific conductivity, pH, turbidity, and chlorophyll, for each of the sampling dates.  Deer Creek Lake in Plymouth County was dry during the summer of 2002.  The dam at Lacey Keosauqua Park Lake in Van Buren County failed during the summer of 2002 and the lake was closed, therefore this lake was not sampled.  These are the only two lakes of the 132 that were not sampled during this summer’s work.  Little Wall Lake in Hamilton County was being dredged during the summer of 2002, we were not able to access the lake during our first sampling round, however it was sampled during the second and third sampling rounds.         

References

American Public Health Association, American Water Works Association, and Water Environment Federation. 1998. Standard Methods for the Examination of Water and Wastewater, 20^th ed. American Public Health Association, Washington, D.C.

Bachmann, R.W., M.R. Johnson, M.V. Moore, and T.A. Noonan. 1980. Clean lakes classification study of Iowa’s lakes for restoration. Iowa Conservation Commission.

Bachmann, R.W., T.A. Hoyman, L.K. Hatch, and B.P. Hutchins. 1994. A Classification of Iowa’s Lakes for Restoration, Iowa Department of Natural Resources, final report.

Crumpton, W.G., T.M. Isenhart, and P.D. Mitchell. 1992. Nitrate and organic N analyses with second-derivative spectroscopy. Limnology and Oceanography, 37(4), 907-913.

Iowa Department of Agriculture and Land Stewardship, State Climatologist Office. Iowa Climate Review. 2000. v14(6-9).

Iowa Department of Agriculture and Land Stewardship, State Climatologist Office. Iowa Climate Review. 2001. v15(5-8).

Iowa Department of Agriculture and Land Stewardship, State Climatologist Office. Iowa Climate Review. 2002.

 

Acknowledgements

      We would like to thank everyone who assisted with the Iowa Lakes Project this year.  Jeremy Crandall, Amber Hoermann, Kelli Koshatka, Melissa Millman, and Jill Murray performed the laboratory analyses.  Tom Bruton, Ben Hucka, Jason Lee, and  David Schelling performed all of the field work associated with the project.  Elizabeth Carlson and Jacque Townsend assisted with the biological samples.  Christy Cherrier and Jeff Kopaska helped train summer personnel.  Carol Elsberry provided administrative support for the project.  Ryan Castro provided computer support for the project.  Terry Mayberry has flown to the field sites each morning to pick up samples since the project began in 2000, and the Department of Aerospace Engineering has allowed us to use their airplane.  Ramesh Kanwar and the Iowa State Water Resources Research Institute have provided us with additional laboratory space over the course of the project.