Mirror Lake Water Quality Monitoring Proposal
Mirror Lake is a valuable resource to the Village of Lake Placid and the Town of North Elba. The lake provides a stunning scenic complement to the village and the surrounding mountains. Residents and tourists rely on its clean, clear waters and enjoy opportunities to paddle, swim, and fish. A reduction in the water quality of the lake and its ability to support fish and other aquatic life would have detrimental effects on local quality of life and the tourism industry. It is, therefore, important that the state of the lake is well understood, water quality issues are detected early, and action is taken to mitigate threats to the lake.
Thanks to the hard work and dedication of the Mirror Lake Watershed Association (MLWA) there is a history of water quality sampling on the lake going back to 1998. The majority of these data collection efforts have been organized through the Citizens Statewide Lake Assessment Program (CSLAP). This program does an excellent job of monitoring basic water quality parameters, particularly nutrient levels, as well as lake user perceptions. In 2014 Mirror Lake was also enrolled in the Adirondack Lake Assessment Program (ALAP) – a partnership program run by the Adirondack Watershed Institute and Protect the Adirondacks that relies on data gathered by organizations or citizens concerned about lakes they seek to understand and protect. ALAP does much of the same monitoring work that CSLAP does but also monitors major ions, most notably sodium and chloride. These additional data are essential to understanding the effects of winter road maintenance practices.
One of the more significant findings of the 2014 ALAP report for Mirror Lake was the surface water sodium and chloride concentrations. The average sodium and chloride concentrations in Adirondack lakes that are not affected by winter road maintenance practices are 0.5 mg/L and 0.24 mg/L, respectively (Kelting, Laxson, & Yerger, 2012). In 2014, the surface water of Mirror Lake had average concentrations of 22 mg/L for sodium and 39 mg/L for chloride. These levels are 44 and 163 times higher than the above averages. Further, out of the 72 lakes analyzed in 2014 through ALAP, Mirror Lake’s sodium and chloride concentrations were higher than 97%
of the other lakes.
Chloride toxicity to organisms is complex and not fully understood. Wildlife can be exposed in a wide variety of ways: birds ingest salt pellets mistaking it for grit, while fish and aquatic organisms are exposed to chloride throughout the year via dermal exposure and ingestion. Toxicity standards (based on LD50 or LC50 values, the dosage or concentration lethal to 50% of the tested population) are set by state and federal agencies based on the result of laboratory studies. They do not take into consideration the complex interactions that occur in natural ecosystems—effects of chronic exposure, or regional differences in sensitivity that may result from adaptions to local conditions.
EPA chloride guidelines for aquatic life are 230 mg/L for chronic exposure (four-day average) and 860 mg/L for acute exposure (one-hour average) (EPA 1998). The NYS DEC Water Quality Regulation for chloride in surface waters is 250 mg/L for class A, AS, and AA-S waters.
Some researchers have observed negative effects from chloride levels much lower than the EPA and NYS DEC guidelines. Certain zooplankton species may be affected at concentrations as low as 5 to 30 mg/L (Dalinsky et al., 2014; Palmer & Yan, 2013), and a study by the US Geological Survey showed very low tolerances (3.1 mg/L) to chloride for brook trout (Meador & Carlisle, 2007). Chloride toxicity may also depend upon a variety of biotic and abiotic factors. A study of chloride toxicity to zooplankton found that decreases in the quantity of food increases chloride toxicity (Brown & Yan, 2015). This means zooplankton in Adirondack lakes, which are generally low in nutrients (oligotrophic) may experience toxic effects at lower chloride concentrations than lakes with greater productivity. Elevated chloride levels have also been implicated in a reduction in the ability of lakes to recover from acidification (Jensen, Meland, Schartau, & Walseng, 2014). Finally, increased chloride concentrations may favor invasive over native species. Eurasian water milfoil, an invasive aquatic plant, has been shown to have higher tolerances to chloride than native milfoil species (Dalinsky et al., 2014).
In 2015 the Ausable River Association (AsRA) collected the Mirror Lake water samples for ALAP and also collected vertical profiles of temperature, dissolved oxygen, salinity, and pH. These additional data give a more complete picture of what is going on throughout the entire water column. Previous data collection efforts focused primarily on surface water conditions. AsRA’s 2015 monitoring revealed two notable findings detailed below. AsRA staff presented these to the MLWA on October 12th, 2015 and with MLWA support developed a proposal for further research.
The results from the 2015 sampling effort indicate that the lake undergoes chemical stratification due to road salt pollution and that the bottom waters are anoxic (lack oxygen) for much of the summer season. Chemical stratification means that the water at the bottom of the lake has higher salinity than the water at the top. In the Adirondacks, this phenomenon only occurs in lakes that receive hypersaline effluent during the spring runoff period (Sibert, Koretsky, & Wyman, 2014). The effluent running out of storm drains has such high salinity that the water is significantly more dense than the water in the lake, causing the effluent to flow along the bottom and into the deepest portion of the lake. This can inhibit spring mixing, which is a critically important process by which oxygen is infused into the water deep in a lake. The bottom water of Mirror Lake becomes hypoxic (low oxygen) by mid-June and anoxic (no oxygen) by July. Hypoxia isn’t necessarily an unnatural phenomenon in deep lakes, although it typically occurs later in the summer (Wetzel, 2001). By late summer only two meters of the water column remain suitable for healthy lake trout populations. They are “squeezed” into this zone due to surface waters that are too warm and bottom waters that lack sufficient oxygen. This is a common occurrence for lakes in the southern range of lake trout. The combination of climate change and local disturbances threaten the long-term viability of lake trout in the Adirondacks (Thill, 2014). The full results of the 2015 collection effort will be published at the end of 2015 or early 2016.
The high sodium and chloride levels, chemical stratification, and early onset of anoxic conditions in the lake warrant further investigation. If these conditions continue to get worse Mirror Lake may not be able to support healthy fish populations, may loose its cold water fish species (lake trout and rainbow trout), experience algal blooms, and be more vulnerable to invasive species infestations.
The Ausable River Association can provide the following services to the Mirror Lake community on a cost basis – significantly lower than for-profit firms. The budget is valid for the period October 2015 through October 2016.
Adirondack Lake Assessment Program
Mirror Lake has been enrolled in a volunteer based citizen monitoring program since 1998. This monitoring effort allows us to understand long-term changes that may be occurring to surface water quality in the lake. This effort should serve as the backbone for all additional work done on the lake. AsRA will collect the surface water samples, as well as vertical profiles of temperature, dissolved oxygen, salinity, and pH on a monthly basis from May 2016 through October 2016.
Extended Monitoring of Salinity through Winter
Mirror Lake exhibits chemical stratification during the spring and summer months due to hypersaline effluent entering the lake. This results in the bottom water of the lake (hypolimnion) having higher salinity than the surface water. If this chemical stratification becomes strong enough it may inhibit the natural process of lake turnover. Monitoring the lake during the fall, winter, and spring will allow us to understand if the lake is fully turning over and when the chemical stratification develops. AsRA staff will collect vertical profiles of temperature, dissolved oxygen, salinity, and pH on a bi-weekly basis from October 2015 until the lake is no longer stratified (approximately the end of November 2015), we will then switch to monthly monitoring through the winter months, and will return to bi-weekly monitoring during the spring mixing period of 2016 (approximately April through May).
Stormwater Outfall Inventory and Monitoring
Mirror Lake receives water flowing from the downtown portion of the Village of Lake Placid as direct discharge through numerous stormwater outfalls. Monitoring the salinity of the water running out of these outfalls will help us better understand where the problem areas are around the lake. These data will help prioritize efforts to reduce the impacts of stormwater effluent, particularly road salt. On a minimum of two days AsRA will measure specific conductance at each of the 38 outfalls entering Mirror Lake. These days will be chosen during high runoff event days in the spring.
Staff Time ……………………………$1,280
Hypolimnetic Water Sampling
The data from the 2014 sampling effort indicates that the lake is both chemically stratified and lacks oxygen in the deep water. These conditions can dramatically change the water chemistry of the water in the deep portion of the lake. Currently, detailed water chemistry analysis is only done on surface water samples. Collecting and processing water samples from deeper in the water column will help us better understand the nutrient cycling in the lake and the specific concentrations of sodium and chloride in the deep portion of the lake. These are the waters that cold water fish such as lake trout and rainbow trout live in. Understanding the conditions they are experiencing is important if we wish to conserve these species. AsRA staff will collect water samples to processed through the Adirondack Watershed Institute’s lab on a monthly basis from May 2016 through October 2016. These samples will be paired with the surface water samples collected as part of the ALAP program outlined above, therefore no additional staff time is required to conduct this sampling.
*One time purchase of additional equipment needed to collect deep water samples
** No additional staff time required for this sampling.
AsRA staff will produce a written report of the findings of this study at the end of the 2016 field season. This report will be delivered to the Mirror Lake Watershed Association and made publicly available by December 2016.
Staff Time ………………………….…..$700
Total for all Monitoring: $4,330
Questions concerning this proposal should be directed to Brendan Wiltse, Science and Stewardship Director, firstname.lastname@example.org, 518-637-6859.
Brown, A. H., & Yan, N. D. (2015). Food Quantity Affects the Sensitivity of Daphnia to Road Salt. Environmental Science & Technology, 49(7), 4673–4680. doi:10.1021/es5061534
Dalinsky, S. A., Lolya, L. M., Maguder, J. L., Pierce, J. L. B., Kelting, D. L., Laxson, C. L., & Patrick, D. a. (2014). Comparing the effects of aquatic stressors on model temperate freshwater aquatic communities. Water,
Air, & Soil Pollution, 225(6), 2007. doi:10.1007/s11270-014-2007-9
Jensen, T. C., Meland, S., Schartau, A. K., & Walseng, B. (2014). Does road salting confound the recovery of the microcrustacean community in an acidified lake? Science of the Total Environment, 478(November 2015),
Kelting, D. L., Laxson, C. L., & Yerger, E. C. (2012). Regional analysis of the effect of paved roads on sodium and chloride in lakes. Water Research, 46(8), 2749–2758. doi:10.1016/j.watres.2012.02.032
Meador, M. R., & Carlisle, D. M. (2007). Quantifying tolerance indicator values for common stream fish species of the United States. Ecological Indicators, 7(2), 329–338. doi:10.1016/j.ecolind.2006.02.004
Palmer, M. E., & Yan, N. D. (2013). Decadal-scale regional changes in Canadian freshwater zooplankton: the likely consequence of complex interactions among multiple anthropogenic stressors. Freshwater Biology,
58(7), 1366–1378. doi:10.1111/fwb.12133
Sibert, R. J., Koretsky, C. M., & Wyman, D. A. (2014). Cultural meromixis: Effects of road salt on the chemical stratification of an urban kettle lake. Chemical Geology, 395, 126–137. doi:10.1016/j.chemgeo.2014.12.010
Thill, B. M. (2014). Lake Trout and Climate Change in the Adirondacks. Keene Valley.
Wetzel, R. G. (2001). Limnology, Lake and River Ecosystems (3rd Editio.). New York: Academic Press.