{"id":365,"date":"2017-12-29T14:43:38","date_gmt":"2017-12-29T14:43:38","guid":{"rendered":"http:\/\/versicolor.ca\/sandylakebedford\/?page_id=365"},"modified":"2026-03-05T11:28:34","modified_gmt":"2026-03-05T11:28:34","slug":"limnol-profiles","status":"publish","type":"page","link":"https:\/\/versicolor.ca\/sandylakebedford\/waters\/lakes\/limnol-profiles\/","title":{"rendered":"Limnological Profiles"},"content":{"rendered":"

Page Updated Sep 8, 2024.<\/span><\/p>\n

NAVIGATION
\nwww.versicolor.ca<\/strong><\/a>
\n\"\"\/sandylakebedford<\/strong><\/a> Home Page for Sandy Lake & Environs (Bedford, NS)<\/small>
\n\"\"\/Surface Waters<\/strong><\/a>
\n\"\"\/Sandy Lake<\/strong> <\/a> A Draft report On the State of Sandy Lake…Feb 21, 2021<\/small>
\n\"\"\/Limnological Profiles<\/a><\/strong> (This Page<\/strong>)<\/p>\n

Subpages:
\n– 2023 Limnological Profiles, effects of episodic precipitation and occurrence of a Metalimnetic Oxygen Minimum<\/strong><\/a>
\n– 2024 Limnological Profiles \u2013 return to historic trends<\/strong><\/a>
\n– –Addendum 1: Trends in Conductivity\/Salt Content<\/strong><\/a>
\n– – Addendum 2: On Wetlands<\/strong><\/a><\/p>\n

\n

On this page:<\/p>\n\n\n\n
BACKGROUND<\/a>
\nTHE PROFILES<\/a>
\n1. Oct 3, 2017<\/strong><\/a>
\n2. Sep 30, 2019<\/a><\/strong>
\n3. Apr 19, 2021<\/a>
\n4. Aug 16-23 period, 2021 Casey Doucet<\/a><\/strong>
\n5. May 7, 2022<\/a><\/strong>
\n6. Aug 22, 2022<\/strong><\/a>
\n6B. Comparison of May 7 and Aug 22, 2022 profiles<\/a><\/strong>
\n6C. Total P, chloride and Total P values on May 7 and Aug 22, 2022<\/a><\/strong><\/td>\n		7. April 21, 2023<\/strong><\/a>
\n7B. Notes*<\/strong><\/a>
\n8. Aug 14, 2023<\/strong><\/a>
\n8B. Comparison of Apr 21 and Aug 14, 2023 profiles<\/strong><\/a>
\n8C. Comparison of mid-August profiles 2022 and 2023<\/strong><\/a>
\n9. Apr 15. 2024<\/a><\/strong>
\n10. Aug 12, 2024<\/strong><\/a>
\n11. Apr 11, 2025<\/strong><\/a>
\n12, Aug 8, 2025<\/strong><\/a>
\n13. Sep 26, 2025<\/strong><\/a>
\nLIT\/LINKS CITED<\/a>
\n*Lake Watchers, Weight added to detect the bottom, Comparison Aquapro with YSI values<\/small><\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n

BACKGROUND<\/p>\n

For some background info on lake stratification, see this page<\/a>.<\/p>\n

\"\"<\/a>

Location of Deep Sampling site Apr 21, 2023 shown on Google Earth Map (top), Ed Glover Bathymetric Map<\/a> (bottom left) and DALTEC Bathymetric Map<\/a> (bottom right)
Click on images for larger versions<\/em><\/p><\/div>\n

Vertical profiles of temperature, oxygen, electrical conductivity were obtained at 3 locations on Oct 3, 2017 including a deep point in the lake (17.5 m), and only at or close to the deepest spot (19-21 m) in the lake on Sep 30, 2019, Apr 19, 2021, May 7, 2022, Aug 22, 2022, Apr 21, 2023, Apr 15, 2024, Aug 12, 2024,\u00a0 \u00a0Apr 11, 2025 and Aug 8, 2025. (Movement in the wind made it difficult to locate and\/or stay on precisely the same location each time.)<\/p>\n

A completely independently observed profile was obtained by Casey Doucet in August 2021 in connection with her Master of Applied Science thesis research at Dalhousie University; the thesis is available at DalSpace<\/a> <\/a> As noted on this page and elsewhere, the general concurrence of Casey’s observations conducted with professional support and that include what otherwise might be regarded as ‘odd aberrations’ in the profiles\u00a0 concur with our observations in 2022, 2023 and 2024 (re: a Metalimnetic Oxygen Minimum”); thus they add credibility to our observations, conducted by volunteers borrowing equipment up until our support under the Halifax LakeWatchers program beginning in the spring of 2022.
\n\u00a0<\/small> <\/a><\/p>\n

pH values were also observed in most years but are not reported on this page. View Methods<\/a>.<\/p>\n

\"\"<\/a>

Sandy Lake Volunteers. Left on Sandy Lake, (Hybrid photo; David P, Ed G., Derek S). Right; stream water sampling (Bruce S).<\/p><\/div>\n

The Sandy Lake Volunteers.<\/strong> The limnological profiles on Sandy Lake were obtained by the “Sandy Lake Volunteers” which include myself (David P) and 3 residents on the lake, Derek S, Ed G. & Bruce S\u00a0 who provide a boat and assistance with the measurements. Ed G. had mapped the bathymetry of the lake in 2006<\/a>, and knew exactly where to find the deepest spot; he is also technically very proficient and handles the monitoring equipment and records and reports the observations. Bruce S. designed and constructed an attachment to the probe which enabled us to better detect when it reached the bottom of the lake.\u00a0 Beginning in April 2022, observations were conducted with equipment and specific directions provided by HRM under the new Halifax LakeWatchers water quality sampling program, often and now routinely without my (David P) involvement.\u00a0 The LakeWatcher protocol includes a limnological profile at or close to the deepest point with surface and bottom water samples for chlorophyll and phosphorous; and surface readings and water sample at the outlet, both 2x\/year (spring and late summer). These data are reported on the Halifax LakeWatchers website (as well as on this page).<\/p>\n

\n

THE PROFILES<\/p>\n

1. Oct 3, 2017<\/strong><\/p>\n

Profiles of temperature, oxygen, and electrical conductivity were obtained for 3 sites in Sandy Lake on Oct 3, 2017, as shown below.
\nThe depths for sites 1, 2 and 3 were 10, 17.5 and 5.5 m. Site 2 was intended to be conducted at the deepest site in the lake, but it was only 17.5 m versus the 20-21 m indicated by the Ed Glover Map<\/a>. In all subsequent profile observations, Ed Glover participated and we were able to locate the deepest spot more precisely.<\/p>\n

Profiles at Sites 1 and 2 were similar with a distinct surface layer in the top 7 m, and then continuous declines in temperature and oxygen, and increases in conductivity to the bottom. It’s likely that in the summer when surface water temperature want up to 25 degrees C or higher, there were distinct surface and deep layers (epilimnion and hypolimnion) with a thermal gradient between them (the metalimnion), and that on Oct 3, that 2 -layer systems was in the process of breaking down.<\/p>\n

Two features to note:<\/p>\n

(i) There is a distinct gradient in conductivity (a measure of dissolved ions).<\/p>\n

(ii) For the deepest profile (Site 1), the oxygen content of the deeper layers (2.25 mg\/L)\u00a0 is below guidelines for both salmonids and more generally, aquatic life.\u00a0 The 2017 value is less than half of the \u00a0value obtained on Aug 30 1971 <\/a>\u00a0when the lake was still in the oligotrophic range (that’s the only comparable historical data for Sandy Lake).<\/p>\n\n\n\n
\n

\n

\"\"<\/a>

Click on image above for the source document<\/em><\/p><\/div><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\n
\"Profiles\"<\/a>

Location of three sites at which limnological profiles were obtained on Sandy Lake in 2017; bathymetric map at right <\/strong>. (Bathymetric map from P. Mandell, 1994. The effects of land use changes on water quality of urban lakes in the Halifax\/Dartmouth regio<\/em>n. MSc thesis, Dalhousie University. Also view Ed Glover Bathymetric Map<\/a><\/p>\n

Click on image for larger version<\/em><\/p><\/div>\n

\n

\"\"<\/a><\/p>\n

View 2017 profile data<\/a><\/p>\n

<\/a>
\n<\/a><\/p>\n

\n

2. Sep 30, 2019<\/strong>
\nThese data posted Dec 13, 2020<\/p>\n

Using the same equipment and procedure<\/a>, Ed Glover obtained these profiles at the deepest point in the lake on Sep 30, 2019:<\/p>\n

\"\"<\/a><\/p>\n

View 2019 data file<\/a><\/p>\n

These observations were at a deeper point than sampled at nearby site 1 in 2017.<\/p>\n

Distinct stratification with a hypolimnion, thermocline (metalimnion) and hypolimnion\u00a0 are evident.<\/p>\n

The overall patterns are similar to those for site #1 above with low O2 and saltier water in the deepest layer (hypolimnion).<\/p>\n

The deepest water in 2019 was warmer (7.3 degrees at 17 meters; 7.2 at 21 m) than in 2017 (5.7 at 17.5 meters degrees, the deepest point) and less salty (195 uS\/cm at 21 m in 2019 compared to 246 uS\/cm at 17.5 m in 2017). Surface temperatures and EC values were more similar (17.1 degrees\/169 uS\/cm in 2017; 16.9 degrees, 159 uS\/cm in 2019).<\/p>\n

It also appears that the profile on Sep 30, 2019 was still in its summer, full stratification mode, while on Oct 3, 2017 it appeared to be breaking up.<\/p>\n

Without measurements of chloride in the water, it cannot be said with absolute confidence that the higher\u00a0 EC in the hypolimnion compared to the epilimnion is entirely due to road salts.\u00a0 Mobilization of iron and manganese (and phosphorus) under anoxia\u00a0 is another possibility, however, the hypolimnion oxygen values on these two profiles, while low for salmonids,\u00a0 were still above 2 mg\/L, the value generally cited for “hypoxic” water (e.g., from Nurnberg 2004: “2 mg L\u20131<\/sup> measured by a DO probe about 1 m above the sediment usually coincides with anoxic conditions at the sediment surfaces located at that depth”. Such mobilization results in EC increases up to 30-40 uS\/cm (e.g., Mortimer, 1942; OME 1993); the difference top to bottom in\u00a0 2017 was about 80 uS\/cm, in 2019 about 40 uS\/cm.<\/p>\n

Some pertinent chemical data are available for 1998:<\/p>\n

\"\"<\/a>

From Nova Scotia Lake Inventory Program<\/a>. Files: Word doc<\/a> |\u00a0 Excel<\/a><\/p><\/div>\n

<\/a>
\nSamples taken at the surface, in the thermocline at 7 m depth, and at the bottom (18 m) on Sep 2, 1998 illustrate differences in EC and chloride, with equivalent differences between the surface and bottom for both EC and chloride: 34\/29*125=146.6, i.e. changes in chloride appear to account for the differences in Electrical Conductivity. At the same time, there is some evidence for some mobilization of iron, manganese and phosphorous in the hypolimnion at an oxygen concentration of 3 mg\/Lin early September.<\/p>\n

\n

<\/a><\/p>\n

\"\"<\/a>

Profiles for Apr 19, 2021<\/strong><\/p><\/div>\n

3. Apr 19, 2021<\/strong><\/p>\n

(David P and Ed G.) The profiles for temperature, oxygen and EC indicate that a normal spring turnover had occurred and the water column was well and uniformly oxygenated down to 19 m. A thermocline had been formed at 13-17 m (temperature 7 degrees dropping to 5 degrees).\u00a0 It was difficult to tell precisely when the probe was at the bottom. Separately, we lowered a bucket with rocks down;\u00a0 the bottom was at approx.\u00a0 20 m – so the deepest probe sample (21 m) was likely within soft sediment. There was a sharp increase in EC between 20 m ( 172 uS\/cm – compared to values of 169-171 uS\/cm for 0 to 19 m ) and 21 m (193 uS\/cm); oxygen declined from 86.3 to 78.5 mg\/L (compared to values of\u00a0 96 to 89 mg\/L, surface to 19 m depth). View Profile19Apr2021.xlsx<\/a><\/a><\/p>\n

\"\"<\/a>

Profiles for Temperature, Dissolved Oxygen and Total P shown in Doucet (2022)<\/strong>, with permission.<\/p><\/div>\n

4. Casey Doucet Profile during Aug 16-23 period, 2021<\/strong>
\n– see Identifying lake water quality trends and effective monitoring strategies in a rapidly urbanizing region<\/a> by Casey Doucet. Master of Applied Science thesis 2022-12-08, Dalhousie University; and Fig B1 supplement<\/a>. The Fig for Sandy Lake in the supplement shows Temperature, Dissolved Oxygem (mg\/L) and Total P(ug\/L) down to approx 19 m. The oxygen profiles exhibits a curious decline in the area of the thermocline with a min value circa 3 mg\/l at approx. 6 m; it then increases to close to 5 mg\/L at about 8 m, and then declines gradually until 15 m and then sharply between 15 and 19 m reaching a minimum of approx. 0.4 mg\/L in the deepest sample at approx. 19 m. (We observed A similar decline of oxygen in the thermocline area in out August 2022 sampling shown below). The Total P sampled at 5 points only (approx.\u00a0 0, 3, 7, 10 and 18 m is close to 10 ug\/L for 0 to 10 m and increases from approx 10 ug\/L at 10 m to approx. 22 ug\/L at 18 m, suggesting some mobilization of P stimulated by anoxia in the bottom sediments,<\/p>\n

\n

<\/a><\/p>\n

\"\"<\/a>

Profiles for May 7, 2022<\/strong><\/p><\/div>\n

<\/a><\/p>\n

5. May 7, 2022<\/strong>
\nEd G. & Derek S). The profiles for temperature, oxygen and EC indicate that a normal spring turnover had occurred. On May 7, a thermocline is developing at 5-7 m. EC values are close to uniform\u00a0 top (222 uS.cm) to bottom (224 uS\/cm). Oxygen shows a sharp decline 12-21 m; however these values are a bit uncertain as the meter gave quite different values going down versus coming up. View file: SL_Data<\/a>. The EC values are well above the values for Apr 19, 2021, likely reflecting higher salt loading over the winter in 2022 compared to 2021.<\/p>\n

\n

6. Aug 22, 2022<\/strong>
\n(Ed G, Derek S. David P. Secchi Disk: 2.5 m
\nThese observations were conducted with equipment and specific directions provided by HRM under their new lake water quality sampling program. There were some oddities issues with the oxygen values – note curious dip in oxygen in the thermocline –\u00a0 however, the observations are consistent between the 2 sets\u00a0 of measurements in showing very low oxygen at the deepest point\/not in the sediment (1.36 and 1.09 mg\/L).<\/p>\n

\"\"<\/a>

Profiles for Aug 22, 2022<\/strong><\/p><\/div>\n

\"\"<\/a>

Image of Excel File<\/strong>. Click on image for larger version<\/p><\/div>\n\n\n\n
Comments by David P in Letter to HRM
\nHi Emma,<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

A few notes:<\/p>\n

It was a windy day, and we anticipated issues with the boat moving, detecting the bottom etc.<\/p>\n

We attached the probe to a rope with bucket with rocks in it so all of the tension was on the rope. (see pic, attached). So you might add 30 cm to the observed depth values.<\/p>\n

Ed navigated to the spot you gave as the location; we did it twice (with some anchoring issues); it was clear the bottom was at 15 meters, so we decided to go to the spot where we had sampled before when Ed was with us – (Sep 30, 2019, Apr 19, 2021, May 7, 2022), bottom at 21 m – http:\/\/versicolor.ca\/sandylakebedford\/waters\/lakes\/limnol-profiles\/<\/p>\n

In the course of events we lost Bruce’s large Danforth Anchor.. fortunately we were able to get another anchor from Bruce and anchored firmly on the desired second site. Observations are those as the we lowered the probe. In the first set we allowed only 5-10 secs at each level. Because of peculiar oxygen mid-way, we repeated with a second set, this time leaving the probe until the % oxygen had stabilized or was changing very slowly, that was often 1 minute plus<\/p>\n

In both sets, we observed an exceptionally low O2 at 5 m, the value was lower in the second set than in the first.
\nThe nearer the surface value s were higher in the second set than in the first, the values 15 m and deeper were more similar.<\/p>\n

So I am wondering (i) the O2 probe\/membrane might need to be replaced; (ii) regardless it seems there was something peculiar at ~4.5 to 6 meters or so which is also where the temperature started to drop.<\/p>\n

For the the very last measurement in the second set, I allowed the rope to sink into the bottom (after the bucket had hit bottom) there is a jump in electrical conductivity which is what I have observed before then you allow the probe to go right onto the bottom (so EC values may provide some indication of where the bottom is when a bucket or other bottom-detecting device is not used; I did not do that with the first set and there is no jump in the final EC value).<\/a><\/p>\n

Ed I am thinking it would be helpful if you send Emma your lake bathymetry map with both locations shown; please add additional comments as you might think appropriate.<\/p>\n

— David P<\/p>\n

Thx to Bruce Sarty for anchors!<\/p>\n

\n

6B. Comparison of\u00a0 May 7 and Aug 22, 2022 profiles<\/strong><\/p>\n

\"\"<\/a>

Of particular notice: Drop in EC in surface waters and some increase in EC of deeper waters in Aug compared to May; oxygen minimum at 5 m in Aug,<\/p><\/div>\n

<\/a><\/p>\n

\n
\"\"<\/a>

Extract from Encyclopedia of Inland Waters<\/span><\/a> <\/strong>Accessed via ScienceDirect<\/a><\/p><\/div>\n

6C. Total P, chloride and Total P values on May 7 and Aug 22, 2022<\/strong>
\nOur observations of May and Aug 22, 2022 were conducted in collaboration with HRM’s LakeWatcher program; the profile monitoring equipment was provided by HRM.<\/p>\n

In addition,\u00a0 HRM provided a Van Dorn bottle for taking water samples and the top and bottom at the deepest site and at the outlet.<\/p>\n

The water samples were analyzed for Total P, and Chlrophyll-a, whihc are measures of the tropic status of a lake (see fig at right).<\/p>\n

 <\/p>\n

The deep-water P values compared to surface values in the late summer provide some indication whether “internal P-loading” is occurring – as documented by C. Doucet<\/a> in her Aug 2021 sampling of Sandy Lake cited above. Deep water P was not elevated according to these data, in 2022:<\/a><\/p>\n

\"\"<\/a><\/p>\n

\n

7. April 21, 2023<\/strong><\/p>\n

\"\"<\/a>

Profiles for April 21, 2023<\/p><\/div>\n

\"\"<\/a><\/p>\n

SandyLake_WaterQualityData_21Apr2023.xlsx<\/a>
\n<\/a><\/p>\n

LAB RESULTS FOR APR 21, 2023 SAMPLING<\/p>\n

\"\"<\/a><\/p>\n

\n
\"\"<\/a>

Ed S. with YSI instrument Right) and probe with weight (left)<\/p><\/div>\n

7B. Notes<\/strong>: As on Aug 22, 2022, these observations were conducted with equipment and specific directions provided by HRM under their new lake water quality sampling program. We also sampled water at the outlet. In the past, we have attached the probe to a separate line with a weighted bucket at the end of it to facilitate our sensing when the probe\/bucket reaches the bottom. This year Bruce S. made special weight\u00a0 that goes directly on the probe (there was already a threaded groove on the bottom of the probe). This worked very well. The 19.5 m sample above was with the probe sitting freely on the bottom.<\/p>\n

\"\"<\/a>

Samplimg sites<\/p><\/div>\n

It’s notable that the temperature at 5 m and above were approx, 2 deg warmer than they were on April 19, 2022; also it appears the water column has turned over and is developing a thermocline at ~ 5 to 7.5 m. Comparison with the two spring profiles obtained in 2022 (Apr 19 and May 7) suggests faster warming and earlier turnover. Ice cover of Sandy Lake in 2022\/2023 was much more restricted than in 2021\/2022.<\/p>\n

For comparison of YSI Specific Conductivity values with values we measure with the pocket Aquapro Water Tester (see Seasonal Monitoring<\/a>), I made measurements as below:<\/p>\n\n\n\n\n\n\n
Location<\/strong><\/td>\n\u00a0 Water Temperature<\/strong> (degC)<\/td>\n\u00a0\u00a0 \u00a0 EC<\/strong>(uS\/cm)<\/td>\n<\/tr>\n
Outlet (Surface water)<\/td>\n\u00a0 12.1<\/td>\n\u00a0 207<\/td>\n<\/tr>\n
At Deep Spot Surface<\/td>\n\u00a0 11.8<\/td>\n\u00a0 198<\/td>\n<\/tr>\n
At Deep Spot.V-D bottle at 0.5 m<\/td>\n\u00a0 10.5<\/td>\n\u00a0 205<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

<\/a><\/p>\n

\n

8. Aug 14, 2023<\/strong><\/p>\n

\"\"<\/a>

Profiles for Aug 14, 2023<\/p><\/div>\n

\"\"<\/a><\/a><\/p>\n

SandyLake_WaterQualityData_14Aug2023<\/a><\/p>\n

Comment: We had very high rainfall events in July and August with flash floods associated with the rainfall on July 21 & 22, and Aug 5 affecting the Sandy Lake\/Bedford area, the latter much less so than the earlier date (Weather Network Aug 5, 2023<\/a>; Reuters July 24, 2023<\/a>).\u00a0 Sandy Lake was impacted by overflow from a sewage pumping station on Farmers Dairy Lane: “A wastewater treatment facility in Bedford, N.S., has flooded due to heavy rainfall in the area over the weekend. Its pump and electrical systems have failed. Halifax Water said in a statement Sunday night its wastewater pump station on Farmer\u2019s Dairy Lane is now offline and untreated waste water is overflowing directly into nearby Sandy Lake.” (CTV news July 24, 2023<\/a>) That overflow was contained by July 26 (HalifaxWater message July 26, 2023<\/a>).\u00a0 The water level in Sandy lake went 5-6ft higher (B. Sarty, lakeside resident). The surface EC was 182 uS\/cm on the June 7th sampling, and 101 uS\/cm on Aug 2 (see Seasonal Monitoring page<\/a>)<\/a><\/p>\n

\"\"<\/a><\/p>\n

\n

8B. Comparison of\u00a0 Apr 21 and Aug 14, 2023 profiles<\/strong><\/p>\n

\"\"<\/a>

Of particular note: Freshening of entire water column in Aug.<\/p><\/div>\n

<\/a><\/p>\n

\n

8C. Comparison of\u00a0 mid-August profiles 2022 and 2023<\/strong><\/p>\n

\"\"<\/a>

In 2023 compared to 2022<\/strong>: (i) weakening of thermal stratification; (ii) “freshening” of entire water column & increased salt stratification; (iii) Hypolimnion oxygen increased; Metalimnion Oxygen Minimum at 5 m retained;\u00a0 there is a second minimum\u00a0 at 12 m\u00a0 – is that the “old” 5 m minimum pushed deeper, or a new one?<\/p><\/div>\n

Also see this subpage for more discussion of the 2023 results: 2023 Limnological Profiles & effects of episodic precipitation<\/a><\/p>\n

LAB RESULTS FOR AUG 14, 2023 SAMPLING\"\"<\/p>\n

All Report Files received from the HRM LakeWatchers Program for analyses of water samples from Aug 14, 2023 (titles inserted) :
\nChlorophyllaResults.pdf<\/a>
\nChainOfCustory.pdf<\/a>
\nChloridePhosphorusEcoli.pdf<\/a>
\nResults in Excel File Saved as PDF.pdf\u00a0<\/a>
\nResults in Excel File<\/a>.xlsx<\/a>
\nCCME Guidelines for Chloride .pdf<\/a>
\nCCME Guidliens for dissolved-oxygen.pdf<\/a>
\nCCME Guideleins for phosphorus.pdf<\/a><\/a><\/p>\n

& this link given to help in interpretation: A MONITOR\u2019S GUIDE TO WATER QUALITY<\/a><\/p>\n

\n

9. Apr 15. 2024<\/strong><\/p>\n

\"\"<\/a>

Ed G, Chris K (foreground), photo by Derek S<\/p><\/div>\n

\u00a0<\/strong><\/p>\n

Courtesy of Sandy Lake volunteers Ed G. Derek S., and Lake Watchers Halifax’s Chris K.<\/em><\/p>\n

Normal spring turnover!<\/p>\n

A sharp increase in conductivity between 19 and 20 m (see table below) indicates the 20 m sample was on\/within the bottom, so the plotted profiles go to 19 m, not 21.<\/p>\n

SandyLake_WaterQualityData_15Apr2024.xlsx<\/a><\/p>\n

\"\"<\/a>

Vertical Profiles for Apr 15, 2024.<\/strong> Note narrow ranges of the variables (1.1 deg for temperature; 2.5 uS\/cm for conductivity, 1.25 mg\/L for oxygen with all values above 10 and 89% saturation.<\/p><\/div>\n

\"\"<\/a><\/a><\/p>\n

LAB RESULTS FOR APR 15, 2024 SAMPLING
\n\"\"<\/a><\/p>\n

\n

10. Aug 12, 2024<\/strong><\/p>\n

\"\"<\/a>

Vertical Profiles for Aug 12, 2024. <\/strong>Note the narrow range of SPC values. “B” is bottom* It is curious that water between 5 & 17 m is sightly\u00a0 fresher than 0-5 m; also colder, so still stratified. Possibly reflects saltier water entering the lake as the summer progressed. The D.O. plot again shows the “Metalimnion Oxygen Minimum” (arrow 1)at approx 5 m as in 2021, 2022 and 2023, and a weaker minimum at about 10 m (arrow 2) – observed also in 2023 but not in 2021 and 2022 – and the deep water\/Bottom\u00a0 oxygen is again very low, unlike last year when heavy summer rains appeared to\u00a0 flush the lake top to bottom.
See Subpages:
– 2023 Limnological Profiles & effects of episodic precipitation…<\/strong><\/a>
– 2024 Limnological Profiles \u2013 return to historic trends<\/a><\/strong>
*Typically SPC increases suddenly once the probe in on the bottom. On this occasion we did not have the weight we usually attach to the probe -see photo above, which allows us to sense the bottom, however when the Van Dorn bottle was lowered, we detected the bottom at 20 m.\u00a0<\/small><\/p><\/div>\n

 <\/p>\n

\"\"<\/a>

Screen capture from data files (below)<\/p><\/div>\n

LAB RESULTS FOR AUG 12, 2024 SAMPLING
\nReceived Sep 12, 2024 from LakeWatchers:
\nNote the excoeptonally high Deep Sample P – given the very low oxygen near the bottom, 1.16 mg\/L at 20 m, this likely is due to sediment P mobilization under anoxic conditions.\"\"<\/p>\n

<\/a><\/p>\n

SandyLake_WaterQualityData_12Aug2024.PDF<\/a>
\nSandyLake_WaterQualityData_12Aug2024.xlsx<\/a> <\/a><\/p>\n

\"\"<\/a>

1) Holm-Hansen O, Lorenzen CJ, Holmes RW, Strickland JDH (1965) Fluorometric determination of chlorophyll. J Conseil 30:3-15
2) Welschmeyer NA (1994) Fluorometric analysis of chlorophyll a <\/i>in the presence of chlorophyll b <\/i>and phaeopigments. Limnol Oceanogr 39:1985-1992<\/p><\/div>\n

11. April 11, 2025<\/strong><\/p>\n

Normal Spring Turnover! Ice-out was March 21, 2025 (Bruce S.)<\/p>\n

EC values bumped up from prev few years, reflecting colder winter, more salting<\/p>\n

\"\"<\/a><\/p>\n

\"\"<\/a>
\n<\/a><\/p>\n

\n

12. Aug 8, 2025<\/strong><\/p>\n

\"\"<\/a>

Vertical Profiles for Aug 8, 2025. <\/strong>Note the narrow range of SPC values. “B” is bottom* Temperature profile very similar to 2024 (shown below this figure, as well as above).\u00a0 Conductivity exhibits small but consistent decline between 4 and 16 m, similar to 2024 when the decline occurred between 4 and 19 m; it begins with beginning of thermocline, suggesting it reflects fresher water trapped by rising temperature as stratification developed in the spring. Dissolved oxygen at 20 m, the inferred bottom at 20 m (based on conductivity and pH changes) slightly higher than in 2024 but still below 2 mg\/L Weaker if any MOM in shallow water, but a clear deeper water minimum 7 to 13 m (in 2024 between approx 8 an 13 m). View Excel File for original data<\/strong>: SandyLakeWaterSamplingData_8Aug2025<\/a><\/p><\/div>\n

<\/a><\/p>\n

\"\"<\/a>

Vertical Profiles for Aug 12, 2024, for comparison with 2025, above.<\/strong><\/p><\/div>\n

Sep 26, 2025<\/strong>
\nSampling was conducted in relation to research being conducted by Prof Linda Campbell and Jessica Younker at St. Mary’s University with the help of the Sandy Lake Volunteers for an international study<\/a>\u00a0 looking at the impact of ice cover (in the context of climate change causing shorter and less intense winters) on algae growth in lakes. Hypoxic conditions (oxygen levels 2.o0 mg\/L and lower) occurred from 8.5 m to the bottom (though most of the hypolimnion).<\/p>\n

\"\"<\/a><\/p>\n

LIT\/LINKS CITED
\n<\/strong><\/p>\n

Quantified Hypoxia and Anoxia in Lakes and Reservoirs<\/a><\/strong>
\nGertrud K. N\u00fcrnberg. 2004\u00a0 The Scientific World Journal<\/em> 4, 42\u201354<\/p>\n

The Exchange of Dissolved Substances between Mud and Water in Lakes<\/strong><\/a>
\nClifford H. Mortimer 1942. Journal of Ecology 30: 147-201<\/p>\n

Chesley Lake 1991 Water Quality Assessment<\/strong><\/a><\/strong>
\nOntario Ministry of Environment, 1993<\/p>\n

On the Metalimnion Oxygen Minimum<\/strong>:
\nSee
\n– Surface Waters\/ Lit & Links: Metalimnetic Oxygen Minima<\/strong><\/a>
\n– 2023 Limnological Profiles & effects of episodic precipitation<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Page Updated Sep 8, 2024. NAVIGATION www.versicolor.ca \/sandylakebedford Home Page for Sandy Lake & Environs (Bedford, NS) \/Surface Waters \/Sandy Lake A Draft report On the State of Sandy Lake…Feb 21, 2021 \/Limnological Profiles (This Page) Subpages: – 2023 Limnological … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":157,"menu_order":5,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-365","page","type-page","status-publish","hentry"],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/365","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/comments?post=365"}],"version-history":[{"count":261,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/365\/revisions"}],"predecessor-version":[{"id":11179,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/365\/revisions\/11179"}],"up":[{"embeddable":true,"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/pages\/157"}],"wp:attachment":[{"href":"https:\/\/versicolor.ca\/sandylakebedford\/wp-json\/wp\/v2\/media?parent=365"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}