LAKEWATCH Volunteers & Methods Pass Muster
As published in the Volunteer Monitor Newsletter, Volume 15, Number 1, Winter 2003
by Amy Richard

The Florida LAKEWATCH program, founded in 1986 by University of Florida professor Dan Canfield, now encompasses 1,000 volunteers who sample nearly 600 lakes all over the state. The rich body of data collected by LAKEWATCH volunteers guides local lake management decisions, is used extensively by University of Florida researchers, and accounts for about 18 percent of the total information on Florida lakes that is provided to the Florida Department of Environmental Protection. (For more on LAKEWATCH data use, see The Volunteer Monitor, Summer 2002, p. 18.)

With so much data being collected and put to so many uses, LAKEWATCH naturally places a strong emphasis on data quality. And our affiliation with the University of Florida gives us access to scientists and graduate students who are ready and willing to conduct studies evaluating our methods and volunteers. The results of three such studies were recently published in Lake and Reservoir Management. Interested readers can download a copy of the article from lakewatch.ifas.ufl.edu/.

Taken together, the three studies attest to the reliability of LAKEWATCH data. We're particularly excited about the publication of this article because we think it goes a long way toward answering many of the concerns that have been raised over the years regarding volunteer-collected water quality data.

Volunteer vs. professional samplers
In the first study (carried out in 1991 and summarized in The Volunteer Monitor, Spring 1997, p. 17), professional staff from the university's Department of Fisheries and Aquatic Sciences conducted side-by-side sampling with trained LAKEWATCH volunteer monitors on 125 lakes. Both volunteers and professionals measured Secchi depths and collected water samples that were later analyzed at a university laboratory for nutrients (total phosphorus and total nitrogen) and chlorophyll. Results for all parameters were found to be equivalent whether samples were collected by volunteers or professionals.

Chlorophyll extraction methods
For chlorophyll analysis, LAKEWATCH initially followed the acetone extraction method described in APHA's Standard Methods, but in 1993 we switched to ethanol extraction because it is less hazardous to human health, involves fewer problems with disposal, and requires less technician time. A comparison study of duplicate samples from a number of lakes covering a range in chlorophyll concentration found no significant difference between measurements made by the two methods. This finding may be of interest to other volunteer monitoring programs since, according to an informal survey conducted by The Volunteer Monitor (see Fall 2000 issue, p.16), the majority use the acetone method.

Fresh vs. frozen water samples
LAKEWATCH decided early on to ask volunteer monitors to freeze their water samples and the filters they prepare for chlorophyll analysis. Many volunteers live hours away from the university water chemistry laboratory, making it logistically impossible for them to deliver fresh samples within a 24-hour time frame. Freezing also avoids the use of dangerous chemicals sometimes used to preserve water samples. Volunteers keep the samples and filters in their home freezers for up to three months, then deliver them (still frozen) either to the university laboratory or to a regional collection site.

To determine whether freezing is a valid means of preserving water samples prior to chemical analysis, researchers compared fresh water samples and freshly prepared filters with samples and filters that had been stored frozen for 15, 30, 60,90, 120, and 150 days. The samples were collected from lakes of varying size, depth, and trophic category. All samples were analyzed for the three basic LAKEWATCH parameters (chlorophyll, total phosphorus, and total nitrogen) as well as three additional parameters (total alkalinity, specific conductance, and pH). For all parameters except pH, only small differences were found between fresh and frozen samples, even after 150days of frozen storage. For pH values above 6.5, agreement was less close. This result was not unexpected, and confirmed that freezing is not a reliable method of preserving samples for pH determination, especially at higher pH levels.

While frozen water samples might not be acceptable for certain types of research work, Dan Canfield, the lead author on the paper, says the study shows that "frozen water can be used any time you're interested in broad trends." He adds, "The use of frozen samples has enabled us to collect more data, on more lakes, in a more cost-effective way."

The authors of the paper conclude that "volunteer monitoring provides a source of credible data." Apparently others agree, at least as far as LAKEWATCH is concerned. Mark Hoyer, a coauthor on the paper, points out that local, state, and federal agencies regularly use our data for their reporting purposes and also that some two dozen manuscripts based in whole or in part on LAKEWATCH data have been accepted for publication in peer-reviewed scientific journals. He says, "This is a clear indication that the scientists reviewing these articles have accepted the integrity of LAKEWATCH water quality data."

Note: Other volunteer monitoring groups who may be interested in freezing water samples for nutrient analysis should be sure to conduct their own comparison studies first, as results may differ from region to region depending on characteristics such as water hardness or nutrient concentrations.

Amy Richard is Information Specialist for Florida LAKEWATCH, University of Florida, Gainesville, Florida; 352-392-9617,ext. 228; arich@mail.ifas.ufl.edu.

Reference: Canfield, D. E., Jr., C. D. Brown, R.W. Bachmann, and M. V. Hoyer. 2002.Volunteer lake monitoring: Testing the reliability of data collected by the Florida LAKEWATCH program. Lake and Reservoir Management 18(1):1-9.