Stormwater ponds are intended to be used for mitigating floods, improving water quality, and recharging groundwater. The sediment-water interface (SWI) of stormwater ponds exhibits properties that influence surface water–groundwater exchanges similar to naturally occurring surface water bodies. However, these ponds are rarely monitored over time to account for their functionality. As organic and inorganic sediments accumulate on the pond bed, the ability of the SWI to conduct water is influenced by sediment deposition, accumulation, and compaction, as well as organic matter content and other biological processes. Two augmented methods, a sediment core permeability cell and an in situ aluminum tube and manometer, were evaluated for measuring the hydraulic conductivity of the SWI. The grain size, hydraulic conductivity, and percentage of organic matter were compared between two ponds constructed 22 years apart. Both methods were effective at measuring the hydraulic conductivities, especially in challenging encountered field situations, albeit with some shortcomings. The in situ method yielded data from sediments with low hydraulic conductivities due to thermal heating, expansion of the water, and the release of biogenic-derived gas from the sediments within the aluminum tube. The converted sediment core permeability cells generated the most consistent measurements. Grain size and hydraulic conductivities were correlated to pond age. The mean and effective grain sizes, as well as hydraulic conductivities of the older pond, were statistically lower than the younger pond in both shallow and deeper depths. Measurement of the changes in the SWI of stormwater ponds is important to protect urbanized areas from flood damage, control the quality and quantity of runoff, and maintain their groundwater recharge function.

Anthropogenic nonpoint source nutrient enrichment of lakes is a worldwide problem, but inputs from the watershed to Florida lakes may not be as severe as speculated. Long-term trends for total phosphorus (TP), total nitrogen (TN), chlorophyll (Chl), and Secchi disk transparency (SDT), enrichment surrogates, in 381 lakes monitored for 20-43 yr and having extensive management to none demonstrated improvements in trophic conditions following point source removals. Afterward, TP (R-2 = 0.85), TN (R-2 = 0.49), and Chl (R-2 = 0.50) continued to decline significantly (P < 0.05) and SDT (R-2 = 0.63) increased. For 99 state-designated "impaired" lakes, TP (R-2 = 0.73), TN (R-2 = 0.45), and Chl (R-2 = 0.44) also declined and SDT (R-2 = 0.69) increased. To consider natural background conditions, lakes were assigned to their ambient TP and TN zones. Geometric TP (93%) and TN (82%) zone averages for each lake after removal of point sources remained within each zone's 95% confidence interval. Individual lake trend analyses documented that similar to 80% showed no (most) or an improving trend for the trophic state variables. After correcting for "statistically meaningful" results or to remove false significances, <5% of the lakes had trophic state variable changes associated with eutrophication. If lakes are to be rehabilitated and/or protected to maintain designated uses, exclusive focus on watershed management of nonpoint source nutrients and associated regulatory actions should not be relied on to correct "impairments" in a timely manner. Management priorities should focus on actual causes of impairment and the most effective and efficient approaches for improvement.

Hoyer MA, Canfield DE, Jr. 2022. A Limnological Yardstick based on phosphorus limitation. Lake Reserv Manage. XX:XX-XX. A new tool called a Limnological Yardstick was developed using long-term (15 to 35 yr) lake chemistry data collected by volunteers of the Florida LAKEWATCH program. This yardstick can assist managers of aquatic systems with identifying where there is a great probability that phosphorus is not only the limiting nutrient, but the limiting environmental factor. When a lake's phosphorus-chlorophyll data lie below the yardstick's lower 95% confidence interval, phosphorus may be the limiting nutrient but not the limiting environmental factor, indicating where phosphorus control strategies will most likely fail. The Limnological Yardstick cannot directly identify the limiting environmental factor(s), as this requires a thorough limnological study of the lake because each lake has unique properties. Limiting environmental factors discussed are nitrogen, true color (Pt-Co units), nonalgal suspended solids, flushing rate, and aquatic macrophytes. The potential impacts of limiting environmental factors on the classification of lake trophic state and eutrophication are also discussed.

Hoyer, MV, Canfield, DE Jr. 2021. Volunteer-collected water quality data can be used for science and management. Lake Reserv Manage. XX:XXX-XXX. This study addresses concerns that comparison studies between professional and volunteer-collected data have been of limited scope, conducted under experimental conditions, and that results may not be applicable to existing large-scale, long-term volunteer monitoring datasets. Historical (2008 to 2019) phosphorus, nitrogen, chlorophyll, and Secchi data collected by 5 Florida organizations charged with monitoring water quality were compared with Florida LAKEWATCH volunteer-collected data from 216 lakes. The state organizations had National Environmental Laboratory Accreditation Conference (NELAC)-certified laboratories and LAKEWATCH used modified procedures needed to accommodate a volunteer program. The lakes are located in central Florida, range in trophic status from oligotrophic to hypereutrophic, and provided approximately 650 independent overlapping annual geometric mean pairs for comparison. Paired t-tests comparing logarithmic transformed annual geometric mean data pooled from all professional organizations with similar overlapping volunteer-collected data showed significant (P < 0.05) differences for phosphorus, nitrogen, and Secchi depth but not for chlorophyll. The significant differences when reported arithmetically were only 1.1 mu g/L, -1.1 mu g/L, and 0.1 m, respectively. Regression analyses on the same data showed strong significant (P < 0.05) relations with coefficient of determinations (R-2 ) of 0.91, 0.98, 0.79, and 0.78 for phosphorus, nitrogen, chlorophyll, and Secchi depth, respectively. Slopes for each paired regression were not significantly different from 1. These results demonstrate that volunteer-collected data were equivalent to data collected professionally, that the quality of volunteer data can be similar to that produced by NELAC-certified laboratories, and thus that data are adequate for both research and management.

ABSTRACT Rapid climate changes may potentially have strong impacts on the ecosystem structure and nutrient dynamics of lakes as well as implications for water quality. We used a space-for-time approach to elucidate such possible effects by comparing data from 1656 shallow lakes (mean depth <3 m) in north temperate Denmark (DK) and subtropical Florida (FL). The lakes were categorized into 7 total phosphorus (TP) classes within the range of 2 to 300 µg L−1. Physicochemical variables showed significant seasonal differences, which can be attributed to different sunlight regimes and temperatures. The FL lakes had overall higher fish biomasses (notably in the littoral zone) but a substantially lower zooplankton biomass and body mass of microcrustaceans, a much lower zooplankton:phytoplankton biomass ratio (lower grazing on phytoplankton), and a markedly lower biomass of benthic invertebrates, indicating much greater control of consumers by fish in the FL lakes. Accordingly, the summer phytoplankton biomass was higher in the FL lakes. Cyanobacteria in summer were proportionally more important in the FL lakes at all TP levels, whereas the proportion of dinophytes, chrysophytes, and cryptophytes was higher in the DK lakes at low TP. Submerged macrophytes occurred at higher TP (>100 µg L−1) in the FL lakes, but coverage was higher in the DK lakes at low TP. We also found lower oxygen saturation in the nutrient-rich FL lakes than in the DK lakes, suggesting lower net ecosystem production in the FL lakes. We discuss our results within the framework of climate warming.

Canfield DE Jr, Bachmann RW, Hoyer MV. 2020. Restoration of Lake Okeechobee, Florida: mission impossible? Lake Reserv Manage. XX:XXX-XXX. Legally mandated eutrophication restoration goals for Lake Okeechobee (FL) are unachievable, therefore assigning managers a "mission impossible." Since the 1970s, restoration efforts have focused on reducing pelagic total phosphorus (TP) to similar to 40 mu g/L. A total daily maximum load (TMDL) of 140 metric tons (t)/yr was adopted by the Florida Department of Environmental Protection in 1999 (effective date 2015) to restore the lake's balance of flora and fauna. Phosphorus (P) loads (1975-2018) averaged 516 t/yr with no significant change over time, yet average TP significantly increased from 51 mu g/L (1974-1977) to 146 mu g/L (2015-2019). Greater TP values in 2019 were due to Hurricane Irma and an early June storm event. Annual P-loads and pelagic TP were not significantly correlated. Instead, TP was strongly correlated with turbidity (R (2) = 0.85), which is generated by wave-driven resuspension of P-rich unconsolidated sediments. Since 1973, >13,000 t of TP has been added to Okeechobee's sediments that have accumulated over the past century due to the lowering of water levels and the construction of the Herbert Hoover Dike. Prior to settlement, high water levels allowed turbid lake waters to flood large areas of adjacent wetlands, where suspended sediments were removed from the lake. With the minimization of this self-cleansing mechanism after construction of the Herbert Hoover Dike, P-rich fine sediments accumulated, and periodic hurricanes disrupted consolidated sediments. Unconsolidated sediments are easily resuspended into the water column, raising TP. Efforts to reduce Okeechobee's pelagic TP through reductions of P-loads alone will not work due to sediment accumulation and resuspension.

Because warming water temperatures have widespread consequences for freshwater communities, we were interested in estimating the patterns and rates of change of near-surface summer water temperatures in United States lakes. We developed multiple regression models to relate daily surface water temperatures in lakes of the conterminous United States to 8-day average air temperatures, latitude, elevation, and sampling month and year using data from 5723 lake samples in the months of June-September during the period 1981–2018. Our model explained 79% of the variation with a root-mean-square error of 1.69 °C. We predicted monthly average near-surface water temperatures for 1033 lakes for each year from 1981 through 2018. Lakes across the conterminous United States have been warming for the period 1981–2018 at an average heating rate of 0.32 °C per decade for the summer months (June–September). The average summer warming from 1981–2018 would be the equivalent of a lake decreasing 259 m in elevation or moving 233 km south. On the basis of national air temperatures starting in 1895, it was inferred that lake water temperatures are variable from year to year and have been steadily increasing since 1964, but that maximum temperatures in the 1930s were just as warm as those in 2008–2018.

Abstract Canfield DE, Jr., Bachmann RW, Hoyer MV, Johansson LS, Søndergaard M, and Jeppesen E. 2018. To measure chlorophyl or phytoplankton biovolume: an aquatic conundrum with implications for the management of lakes. Lake Reserv Manage. 35:181–192. The log10-transformed relationship between measured phytoplankton biovolumes and chlorophyll concentrations, surrogates for algal biomass, was examined using 13,000-plus paired samples collected from lakes in Denmark (250), the continental United States (1835), and Florida (159). A positive (R2 = 0.57) relationship was found but predicted biovolumes had a 95% confidence interval of 11–912%. Regressing chlorophyll as opposed to phytoplankton biovolume against total phosphorus (TP) (R2 = 0.43 vs. R2 = 0.21), total nitrogen (TN) (R2 = 0.24 vs. R2 = 0.08), and Secchi disk (SD) (R2 = 0.60 vs. R2 = 0.39) yielded stronger relationships. Three algal groups (Cyanophyta, Chlorophyta, and Bacillariophyceae) contributed approximately 100% of the biovolume in some samples. For these groups and samples, biovolume increased significantly with chlorophyll (R2 = 0.35, R2 = 0.27, and R2 = 0.31, respectively) and TP (R2 = 0.18, R2 = 0.13, and R2 = 0.13) and decreased significantly with increases in SD (R2 = 0.29, R2 = 0.31, and R2 = 0.17). All empirical relationships had substantial confidence intervals. Contingency tables for variance within the independent (horizontal variance) and dependent (vertical variance) variables are presented, providing managers information on how much change is required to insure noticeable effects. If resources are limited, chlorophyll is recommended for monitoring long-term trends because it provides an estimate of biomass magnitude and has better relationships with nutrients and SD. Managers may integrate occasional biovolume measurements if concerned with Cyanophyta abundance, taste and odor production, or changing algal population dynamics.

The goals of the study were: (i) To describe the distribution of summer near-surface water temperatures in lakes of the coterminous United States and southern Canada (ii) to determine the geographic, meteorological and limnological factors related to summer water temperatures and (iii) to develop and test predictive models for summer near-surface water temperatures. We used data from the United States National Lakes Assessments of 2007 and 2012 as well as data collected from several different studies of Canadian lakes. Using multiple regressions, we quantified the general observations that summer water temperatures decreased when going from south to north, from east to west, and from lower elevations to higher elevations. Our empirical model using 8-day average air temperatures, latitude, longitude, elevations and month was able to predict water temperatures in individual lakes on individual summer days with a standard deviation of 1.7 °C for United States lakes and 2.3 °C for lakes in the southern regions of Canada.

Field measurements of water quality in Iowa lakes contradict paleolimnological studies that used 210Pb dating techniques in 33 lakes to infer accelerating eutrophication and sediment accumulation in recent decades. We tested this hypothesis by analyzing a series of water quality measurements taken in 24 of these lakes during the period 1972–2010. There was little change in the trophic state variables. Total phosphorus and algal chlorophylls did not increase, and Secchi depths did not decrease with no evidence that the lakes had become more eutrophic. Changes in daily sediment loads in the Raccoon River also did not match the paleolimnological inferred rates of soil erosion for the period 1905–2005, and an independent estimate of soil erosion rates showed a decline of 40% in the 1977 to 2012 period rather than an increase. We hypothesized that sediment mixing by benthivorous fish could be responsible for violating the basic assumption of 210Pb sediment dating that the sediments are not disturbed once they are laid down. We developed a mathematical model that demonstrated that sediment mixing could lead to false inferences about sediment dates and sediment burial rates. This study raises the possibility that sediment mixing in Iowa lakes and similar shallow, eutrophic lakes with benthivorous fish may cause significant sediment mixing that can compromise dating using 210Pb dating of sediment cores.

North American Journal of Fisheries ManagementVolume 37, Issue 4 p. 809-815 Comment Comment: Do Something or Do Nothing—the Fisheries Management Conundrum Daniel E. Canfield Jr., Corresponding Author Daniel E. Canfield Jr. decan@ufl.edu School of Forest Resources and Conservation, University of Florida, 7922 Northwest 71st Street, Gainesville, Florida, 32653 USAE-mail: decan@ufl.eduSearch for more papers by this author Daniel E. Canfield Jr., Corresponding Author Daniel E. Canfield Jr. decan@ufl.edu School of Forest Resources and Conservation, University of Florida, 7922 Northwest 71st Street, Gainesville, Florida, 32653 USAE-mail: decan@ufl.eduSearch for more papers by this author First published: 30 June 2017 https://doi.org/10.1080/02755947.2017.1320341 Published online June 30, 2017 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume37, Issue4August 2017Pages 809-815 RelatedInformation

A probabilistic sample of lakes in the 48 coterminous US lakes was made by the United States Environmental Protection Agency in the 2007 National Lakes Assessment. Because of the statistical design, the results of our analyses of Secchi depths (SD) apply to a population of 45,265 lakes. We found statistically significant differences in mean Secchi depths between natural (1.57 m) and man-made lakes (1.18 m). The most important variable correlated with SD was turbidity, an optical measure related to suspended particles in the water column. For most lakes, chlorophyll a was highly correlated with both turbidity and SD, but several lakes had more turbidity and lower SD than expected based on chlorophyll a alone, indicating that non-algal suspended solids were an important factor. On an ecoregion basis, the non-algal suspended solids in the lake waters were related to the average levels of suspended solids in streams located in that ecoregion, and the non-algal suspended solids were more important in man-made than natural lakes. Phosphorus and nitrogen were directly correlated with chlorophyll a and turbidity and inversely correlated with SD. Based on diatom-inferred Secchi depths for the tops and bottoms of sediment cores from lakes in Ecoregions VIII and VII (excluding lakes in Minnesota) representing 40% of the natural lakes in the US, there has been no decrease in water transparency in that population of lakes in the past 70 or more years when the US population increased by 134%. We do not have information to determine if the other 60% of lakes have or have not changed.

The Santa Fe Lake System (SFS) is an Outstanding Florida Water system in northern peninsular Florida and receives special protection from governmental agencies to prevent impairment of water quality from anthropogenic activities. Since 1986, periods of sudden nutrient increases and declines have occurred along with changes in water clarity documented within a 28-year monthly database. Changes were linked to stochastic events such as an influx of gulls in 1986, the adjacent 5100-ha Dairy Road forest fire in 2007, 3 Category 3 hurricanes that struck Florida in 2004, and droughts. However, increasing trends at SFS were also observed for the yearly measured minimum water chemistry values, as were synchronous changes in these baseline conditions at other nearby lakes, suggesting the lakes were being impacted by a regional environmental factor. These changes corresponded to a period of decreasing precipitation and were related to climate variability, perhaps reflecting phase changes in the Atlantic Multidecadal Oscillation. The possible mechanism for the observed changes most likely relates to alterations in regional precipitation/evaporation rates and resulting changes in groundwater chemistry and hydrology. Long-term trends in water quality at SFS may reverse if Florida enters a long-term period of increasing precipitation.

Using data collected with 3 different methods, we found no decreases in the average water clarity of Maine ( USA) lakes over different periods of time. Field measurements of Secchi disk depths in the summer months by volunteer samplers in several hundred lakes showed a small, statistically significant increase in water transparency during the period 1976 through 2013. A reanalysis of satellite-inferred Secchi depths between 1990 and 2010 showed no trend over time. In addition, diatom-inferred Secchi depths from short sediment cores in a randomly selected group of Maine lakes analyzed by the US Environmental Protection Agency showed no statistically significant difference between the average Secchi depths in a pre-1850 time period and the early 1990s. Lake maximum depth was the most important morphological variable associated with water clarity among Maine lakes. In individual lakes, both water color and chlorophyll were inversely correlated with Secchi disk depths. The statewide annual average Secchi depths for the summer months were inversely correlated with water color and the amount of precipitation for the months of January through June. Drought years led to increased Secchi depths.

Individual Secchi disk measurements (975,760) were gathered from across the United States to understand regional distribution inwater transparency. Compiled Secchi diskmeasurements represented 14,421 US waterbodies. Average water transparency ranged from <0.1 to 31.6 m withwater transparencies <1.1 min 25% of the sampled waterbodies, <2.0 m in 50% of the waterbodies, and <3.3 m in 75% of the waterbodies. Of the population of examined waterbodies, 10% had mean Secchi measurements exceeding 4.8 m. US states with the lowest water transparency (<0.7 m) were Delaware, Louisiana, Mississippi, Nebraska, Oklahoma, and South Dakota, while the greatest water transparencies (>3.5 m) were in Alaska, Maine, Montana, New Hampshire, and Vermont. Regional differences in water transparency were identified across the US Environmental Protection Agency ecoregions (Level III), with lower water transparencies occurring in nutrient-rich regions and higher water transparencies occurring in nutrient-poor regions. Regional variability should be considered in the management of waterbodies at local to national levels.

Florida LAKEWATCH is a successful example of a long-term volunteer water qualitymonitoring program that started in 1986. Working with thousands of volunteers, these dedicated citizen scientists have collected reliable long-term water quality data for over 1100 lakes, 175 coastal sites, 120 rivers, and 5 springs. These data encompass water resources in 57 Florida counties. This manuscript describes the start and evolution of LAKEWATCH, including discussions of the following two major (of the many) hurdles to the continued success of the program: 1) demonstrating to professional groups that trained volunteers are capable of collecting credible (research and regulatory quality) data, and 2) maintaining consistent long-term funding. Funding is especially critical because trained and committed core staff is needed to work along with volunteers. Quality staff members are also important to provide direction, ensuring consistent data are collected and enough sites are monitored to answer statewide questions such as how geology impacts water chemistry in Florida. Examples are also provided on how LAKEWATCH data have been used to address lake management issues (i.e., ‘‘fixing’’ the problem) in the State of Florida. We hope the Florida LAKEWATCH experience assists other groups who have a vast army of citizen scientists waiting to get involved and then to best develop a successful monitoring program.

Limnology and OceanographyVolume 59, Issue 6 p. 2231-2239 CommentFree Access Response to comments: Quantification of the extent of cultural eutrophication of natural lakes in the United States Roger W. Bachmann, Roger W. Bachmann Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida, Gainesville, FloridaSearch for more papers by this authorMark V. Hoyer, Mark V. Hoyer Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida, Gainesville, FloridaSearch for more papers by this authorDaniel E. Canfield Jr., Daniel E. Canfield Jr. Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida, Gainesville, FloridaSearch for more papers by this author Roger W. Bachmann, Roger W. Bachmann Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida, Gainesville, FloridaSearch for more papers by this authorMark V. Hoyer, Mark V. Hoyer Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida, Gainesville, FloridaSearch for more papers by this authorDaniel E. Canfield Jr., Daniel E. Canfield Jr. Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida, Gainesville, FloridaSearch for more papers by this author First published: 12 October 2014 https://doi.org/10.4319/lo.2014.59.6.2231Citations: 5 Corresponding author: [email protected] AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume59, Issue6November 2014Pages 2231-2239 RelatedInformation

We used paleolimnological data for 240 lakes from the U.S. Environmental Protection Agency's (USEPA) 2007 National Lakes Assessment to estimate the extent that natural lakes in the coterminous United States have been changed by anthropogenic activities. In order to detect cultural eutrophication, we analyzed data on diatom‐inferred concentrations of total nitrogen (TN), total phosphorus (TP), specific conductance (SC), and pH as determined from lake sediments from the tops and bottoms of sediment cores from 240 natural lakes where the bottom of the core was judged to represent conditions prior to European settlement. We found no statistically significant increases in the average concentrations of TN, while TP decreased by 14% in this population of lakes since the time of European settlement. We also analyzed data from 48 reference lakes used by the USEPA to determine the relative condition of the sample lakes. Paired t‐tests showed the TN concentrations were not significantly different between the two time periods (p > 5%), while the average TP concentrations had significantly decreased by 26% since presettlement times (p < 5%). There were statistically significant increases in SC (17%) and pH (0.05 pH units). There were no statistically significant differences between the changes in TP, TN, SC, and pH in the 240 sample lakes and the changes in the 48 reference lakes. The proportions of lakes categorized as oligotrophic, mesotrophic, eutrophic, and hypereutrophic for the presettlement time period were not significantly different from the proportions found in 2007.

AbstractStocking of largemouth bass is an important management tool for fish management. The stocking of hatchery‐produced fingerling or advanced‐fingerling bass to supplement bass year‐classes, however, has exhibited varying success. Utilizing a different approach, a multiyear stocking programme using wild adult largemouth bass was initiated at the Harris Chain of Lakes (3800 ha Lake Griffin; 1811 ha Lake Dora) in central Florida. Wild adult bass (24 781 fish), ranging in size from 200 mm total length (TL) to over 600 mm TL, were stocked in Lake Griffin (13 932 fish) and Lake Dora (10 849 fish). One month after stocking, the number of stocked bass caught in electrofishing catches in Lake Griffin and Lake Dora was ~10% and 22%, respectively. Estimates of mortality were similar to the native largemouth bass, although the movement of stocked fish into other connecting water bodies was extensive. For the Lake Griffin/Lake Dora stocking programme, bass were transferred at a cost of $10.09–19.89 per fish, depending on how the costs of the project are calculated ($250 000 for just the capture and transport of the fish vs. $492 775 for the total project). Considering only capture and transport costs, conservative benefit/cost ratio estimates would be $1.77/$1.00 spent for replacement and $1.85/$1.00 spent recreational costs, although the benefit/cost ratios could exceed $10/$1. Based on the present study, stocking wild adult largemouth bass is a cost‐effective tool for managing largemouth bass.

We found that the Florida Lake Vegetation Index (LVI) did not identify Florida lakes that were impaired due to excess loading of phosphorus or nitrogen from anthropogenic sources. The index is based on 4 plant metrics: the Coefficient of Conservatism of the dominant or co-dominant taxa, the percent of sensitive taxa, the percent of native taxa, and the percent of invasive exotic taxa. Our analysis of the data used by the Florida Department of Environmental Protection to establish and calibrate this biotic index found no link between nutrient concentrations and the LVI. The LVI was primarily associated with the pH and specific conductance of the lake waters, with the best scores found in acidic lakes and the poorest scores in more alkaline lakes. These variables are the result of natural gradients, not pollution, and are not included in the calculation of the LVI. Our study illustrates the importance of considering natural factors that determine the value of any index of biological integrity before it is used to indicate anthropogenic pollution.