Teal Lake Impairment Listing

Teal Lake Impairment Listing

BY: Dave Neuswanger
QLIA President
April 2, 2018

An article appearing in the November 29, 2017 edition of the Sawyer County Record (click here to read news article in separate window) listed Teal Lake as one of several others in Sawyer County that continue to be included on an official list of “impaired” lakes. Say what? Impaired? In what way? WDNR’s press release offered no explanation – the equivalent of a doctor saying only, “You’re sick,” before walking away to see the next patient. I was a professional aquatic ecologist before retiring in 2014, but I never imagined Teal Lake had any water quality problems before WDNR’s press release suggesting it continues to be impaired. Wow. This was a shocking revelation, not only to me, but to my wife, our Treasurer Gayle Little, and others who have since contacted me with worry in their voice to ask, “What’s wrong with our lake?” The short answer? Absolutely nothing is wrong with Teal Lake.

I do not believe Teal Lake belongs on the list of impaired waters WDNR submits to the Environmental Protection Agency (EPA) every other year as authorized under Section 303(d) of the Clean Water Act of 1972. I had several e-mail exchanges with WDNR program officials and their lead scientist regarding my concerns over the transparency and accuracy of Teal Lake’s inclusion on the impaired waters list. My former colleagues have been polite and professional but unyielding in defense of this listing. This is a very complex subject, but I will attempt to explain what we know, why I disagree with WDNR’s decision, and what I think we should do to get Teal Lake off the list of impaired waters in the future.

First, why should we care about this listing? “Peace of mind” tops the list for most of us. I want some assurance that household pets and other animals can drink safely from our lakes. I want to know that everyone can go swimming without concern. I want to know that our fish are safe to eat for humans and for our wild neighbors who depend on a diet of fish for their very survival (bald eagles, ospreys, great blue herons, kingfishers, common loons, mink, and river otters, to name a few). On an economical basis, I want to know our real estate will not lose value based on a seemingly arbitrary and unexplained listing of impairment that may give future buyers pause when comparing options for investment in lakefront property. If you care about these things as much as I do, read on. But rest assured, Teal Lake is just fine.

QLIA has participated in WDNR’s Citizen Lake Monitoring Network (CLMN) for many years. Statewide, more than 1,000 volunteers routinely collect data on water transparency, temperature, dissolved oxygen, total phosphorus concentration, and concentration of chorophyll-a, which is a universally accepted index to the biomass of microscopic algae in upper layers of the water column. As a CLMN volunteer, QLIA Past-President Jack Wellauer recorded observations and collected water samples for laboratory analysis from the “deep hole” station on Teal Lake from 2002 (when he assumed duties from Mary Witt) through 2017. Jack shipped mid-summer water samples to the State Lab of Hygiene for analysis through the 2017 monitoring season. Per established protocol, the five most recent years of total phosphorus and chlorophyll-a data (2012 through 2016) were used by WDNR in their 2018 assessment cycle for Section 303(d) listing. Those data, and WDNR’s conclusion of “impairment” based on those data, will stand until the next assessment cycle in 2020.

Teal Lake water quality data collected by Jack Wellauer, analyzed by the State Lab of Hygiene, and interpreted by the Wisconsin DNR are presented in Table 1 (click here to open Table 1 in separate window). By necessity, there is some statistical jargon in Table 1 that I have included for the sake of transparency so that statistically savvy readers will know I’m not just making stuff up. For readers not afflicted with my nerdy penchant for statistical analysis, here is the bottom line: The average concentration of phosphorus in Teal Lake samples during the summers of 2012-2016 was 27.8 parts per billion, and we are 90% confident the actual value (inferred from our samples) was between 24.8 and 30.7 ppb. In order to be classified as “impaired” based solely upon total phosphorus, Teal Lake would have had to exceed the 40 ppb threshold concentration for shallow lakes. Clearly it did not. WDNR agrees that phosphorus levels in Teal Lake were not high enough to prompt a listing of impairment. Our Teal Lake neighbors deserve a pat on the back for abandoning phosphorus-containing lawn fertilizer and household detergents, and for maintaining functional septic systems.

According to WDNR, Teal Lake’s 2018 “impairment” listing was based on chlorophyll-a levels during 2012-2016. This tripped a red flag for me, because chlorophyll-a is very strongly correlated with total phosphorus in lakes like ours. That’s because phosphorus is the least abundant of the vital nutrients needed for growth of microscopic freshwater algae. The amount of phosphorus available in the water column places an upper limit on algal biomass, and therefore on how much chlorophyll-a can be found within algal cells. Because average phosphorus concentration (27.8 ppb) was well below the threshold level for impairment (40 ppb), chlorophyll-a also should be too low to raise concern. And it was! The average concentration of chlorophyll-a in Teal Lake samples during the summers of 2012-2016 was 15.5 ppb, and we are 90% confident the actual value (again, inferred from our samples) was between 11.4 and 19.5 ppb. In order to be classified as “impaired” based on chlorophyll-a, Teal Lake would have had to exceed the 20 ppb threshold concentration for shallow lakes. It did not. It might have been close at 19.5 ppb, but it might also have been as low as 11.4 ppb. So how is WDNR able to reach a conclusion of impairment based on chlorophyll-a concentration? In a nutshell, they changed their analytical protocols to lower the threshold for impairment.

WDNR decided to disregard the late June samples despite the fact that water-based recreation was in full swing by then, analyzing only data collected in July and August when chlorophyll-a concentrations tend to be highest. And while they continue to use the “threshold concentration method” for assessing impairment due to total phosphorus, they adopted a new statistical protocol for assessing impairment due to excessive algae (as indicated by chlorophyll-a concentration). Under this new protocol, the test statistic is no longer the average, but rather the 30th percentile of chlorophyll-a concentration (the value estimated to be exceeded 30% of the time). In effect, this lowers the bar for concluding that a waterbody is impaired. And because these statistics are calculated with complex formulas not accessible to the general public, the process creates a transparency problem. Frankly, it all got above my head, so I enlisted the aid of my oldest son, Dr. Jason Neuswanger, who is a quantitative fishery ecologist working for a consulting firm near Seattle.

I asked Jason to duplicate WDNR’s analysis if possible. In the interest of transparency, his results and conclusions are attached (click here for detailed analysis), though most people (including me) will not understand all the codes and computations. WDNR has acknowledged these computations and analyses as accurate. However, they insist the new question is not whether Teal Lake’s chlorophyll-a levels warrant an impairment listing, but rather, whether recent levels have decreased enough to warrant de-listing. You heard that right. There is a subtle difference between the levels required to list a lake initially and the slightly lower levels required to de-list it. This changes the statistical “hypothesis testing” procedure. And in this case, by the slightest of margins, it allows WDNR to maintain an impairment listing based on 30th percentile chlorophyll-a levels that are too low to trigger an initial listing of impairment. In summary, the statistical bar is slightly higher for purposes of proving “all is clear” and a lake is no longer impaired. If you are still reading, congratulations. If your head is hurting, my sincere apologies.

To this point, everything I have reported assumes 2012 data were legitimately included in the various analyses. I do not believe that to be the case. Referring back to Table 1, note that total phosphorus and chlorophyll-a levels were much higher in 2012 than in subsequent years. That’s because we were still under the influence of a long-term drought. Table 1 shows the Palmer Drought Severity Index for northwestern Wisconsin was moderate to severe in 2012 – making it an atypical year. During droughts, stream inflow decreases, water clarity increases, and lake volume is reduced by evaporation, resulting in temporarily higher nutrient concentrations and greater utilization of those nutrients (like phosphorus) by algae in clearer water. (Sunlight penetrates deeper, allowing microscopic algae to thrive at greater depths than usual.) Therefore, chlorophyll-a was predictably higher than the threshold impairment level of 20 ppb in Teal Lake in July and August of 2012. What can be done with such anomalous data?

According to WDNR’s Consolidated Listing and Methodology (WisCALM) guidance published in 2014, under the subject heading of Representative Data on page 8, “If a prescribed sampling schedule falls during an extreme weather year, exhibiting unusual average air temperature, precipitation, stream flow or water levels, a determination should be made as to whether that year was an extreme weather year that resulted in unrepresentative conditions… If it is determined that a year was an extreme weather year resulting in unrepresentative conditions, that year’s data points should not be excluded, but rather should be supplemented with data from an additional year of monitoring. In this case, combined data from a minimum of two years should be used for assessments to account for variability between years.”

In the case of Teal Lake, we had representative data from four recent years (2013 through 2016). Therefore, the 2012 data could easily have been omitted as an outlier from the current analysis, especially since it was already used to justify the initial listing of impairment in the previous assessment cycle that covered more drought-stricken years beginning in 2010. WDNR’s guidance further states, “Best professional judgment may be used to determine whether data were collected from an extreme weather year and are considered unrepresentative of normal conditions.” Representing the partner group (QLIA) that collected all the data, I was unable to persuade WDNR to use best professional judgement in the interpretation and use of those data. July-August data from 2012 “spiked the samples” with unusually high concentrations of chlorophyll-a. Without those unrepresentative data, no statistical analysis, regardless of method, would have led to an impairment listing. But this horse has already left the barn. WDNR has no interest in reversing a poor decision. In fairness, dedicated employees performing the day-to-day work lack the time (funding) and executive leadership needed to consider nuanced cases, admit mistakes, and correct them. I just hope WDNR is still a viable agency if and when we need them to deal with a real water quality problem should one develop in the future. For now, we must live with the current listing until at least the next review cycle in 2020.

How do we explain this to family, friends, vacationers, and prospective buyers of lakefront property who ask why Teal Lake appears on this list of impaired waters? I believe you can tell them with total confidence that Teal Lake is actually one of the healthiest aquatic ecosystems in the State of Wisconsin. Teal Lake water quality is better, in my view, than either Lost Land or Ghost lakes, neither of which appear on WDNR’s list of impaired waters simply because there was not enough data from those lakes to perform a listing evaluation. Those lakes are fine too, but you get my point.

Teal Lake is the flagship of the Quiet Lakes from an environmental quality standpoint. If you are ever challenged to support that statement, feel free to share the following:

1) Among the 15,000 lakes and impoundments in Wisconsin, Teal Lake is one of only 103 to have “Outstanding Resource Water” (ORW) status under NR 102.10, Wisconsin Administrative Code. ORWs are defined as lakes, streams, or flowages having excellent water quality, high recreational and aesthetic value, high quality fishing, and are free from point-source pollution. Between 1992 and 2016, Carlson’s Trophic State Index (TSI) has ranged between 45 and 60, allowing us to classify Teal Lake as slightly eutrophic. There has been no detectable upward or downward trend in TSI regardless of the metric used to calculate it during the past 24 years at Teal Lake (click here to view long-term trend in Trophic State Index for Teal Lake).”

2) Our 2016 aquatic plant survey revealed that Teal Lake has one of the highest Floristic Quality Indexes (FQI = 35.3) of any lake in northern Wisconsin (FQI average = 28.3). Such a healthy macrophyte community would not exist in a lake frequently plagued by nuisance algae blooms during the summer season.

3) Walleye and muskellunge generally do not spawn successfully in “impaired waters” due to excessive oxygen demand at the sediment-water interface where fertilized eggs must have adequate dissolved oxygen to develop and hatch. Teal Lake is one of the increasingly rare lakes in Sawyer County that continues to exhibit satisfactory natural reproduction of walleyes and muskellunge; and it serves as one of only three sources of fertilized muskellunge eggs cultured at WDNR’s Thompson Hatchery in Spooner every three years.

4) Teal Lake’s typical summer water transparency of 6 feet (as determined by lowering a Secchi disk until it can no longer be seen) has been experimentally determined to be optimal for purposes of sustaining the walleye-dominated fish community desired by local stakeholders and visiting anglers alike. In a lake like Teal, 6-foot water transparency provides ideal underwater visibility for juvenile walleyes to evade predation and for adult walleyes to feed efficiently on their primary prey – yellow perch. From an angling standpoint, we would not want Teal Lake to be any “cleaner” (more transparent) than it is currently, because the current levels of total phosphorus and chlorophyll-a favor dominance by walleye and help to nourish a food chain that supports a harvestable surplus of gamefish and panfish. We don’t want pea soup, and we don’t want distilled water. We want lakes in the goldilocks zone. We want Teal Lake, as is.

What can we do about this? The QLIA Executive Committee voted on March 13, 2018 to continue voluntary participation in the Clean Lakes Monitoring Network (CLMN) provided that WDNR continues to fund and support that program. It is particularly important that we collect data from Teal Lake on total phosphorus and chlorophyll-a during July-August for at least the next couple years, so that more recent and representative data (assuming no severe drought) is available for WDNR to use in their next impairment listing evaluation in 2020. If we do this and nothing changes for the worse in Teal Lake, I am confident the data will support a de-listing in 2020. We have already purchased a high-quality, hand-held meter to measure temperature and dissolved oxygen at various depths. But we have work to do in training volunteers and updating the kits used by volunteers to collect and ship water samples. To date, Steve Fiala, Norm Bratteig, and Bryan Neuswanger have indicated interest in collecting data and shipping samples for analysis to the State Lab of Hygiene, but I know they would appreciate additional help. It would be good to have a pair of volunteers assigned to each lake, including Ghost. If you are interested in helping with this important project, please contact me (Dave Neuswanger) at 715-462-4485 or dneuswanger@gmail.com.

A water quality monitoring volunteer heads out in search of data on dissolved oxygen, temperature, and water transparency… and to collect water samples for laboratory analysis of total phosphorus and chlorophyll-a.

Leave a Reply