Attempted management of cyanobacteria by Phoslock (lanthanum-modified clay) in Canadian lakes: water quality results and predictions

Figures & data

Figure 1. Location of Canadian lakes with previous or proposed Phoslock as described in Table 1 (scale units are 300 km).

Table 1. Limnological characteristics and Phoslock application information for the Canadian water bodies with previous or planned Phoslock treatment.

Lake characteristics	Scanlon Creek Reservoir	Swan Lake	Henderson Lake	Lac Bromont	Elk Lake
Custodian	Lake Simcoe Region Conservation Authority	City of Markham	City of Lethbridge	City of Bromont	Elk Lake Water Quality Improvements Steering Committee
Province	Ontario	Ontario	Alberta	Quebec	British Columbia
Location (N,W)	44°09′, 79°33′	43°54′, 79°15′	49° 41′, 112° 47′	45°15, 72°40	48°32′ 123°24′
Surface area (m^2)	34,000	54,800	258,000	480,000	1,870,000
Watershed area (km^2)^1	n.a.	0.457	controlled	23.5	8.6
Maximum depth (m)	7.0	4.4	5.5	7.2	18.0
Mean depth (m)	n.a.	1.9	2.6	4.4	9.2
Water residence time (yr)^2	<0.019	∼20, no outflow	1.7	0.25	4.4
Alkalinity (mg/L as CaCO3)	220	118	104	43–56^3	139
Trophic state^4	hypereutrophic	hypereutrophic	hypereutrophic	mesotrophic	oligotrophic
TP Load (g/m^2/yr): external^5		1.9–3.4	0.665	1.752	0.12
TP Load (g/m^2/yr): internal		6.0–10.5	0.652	5.405	0.71–0.94

Note. n.a. = not available.

¹Watershed area is expressed without lake area. Henderson Lake does not have a natural watershed because its inflow is controlled by the St. Mary River Irrigation District.

²Elk Lake water residence time includes downstream Beaver Lake.

³Said Yasseri, Institut Novak, pers. comm. 2016.

⁴Based on growing period trophic state variables, including average TP and chlorophyll concentrations and Secchi disk transparency (Nürnberg 1996).

⁵Lac Bromont external load includes only stream input, not atmospheric deposition and ground water.

Table 2. Treatment success, as evaluated by observed and modeled TP concentration before and after treatment, and application details.

Application evaluation and details	Scanlon Creek Reservoir	Swan Lake	Henderson Lake	Lac Bromont	Elk Lake
TP concentration (mg/L), mixed layer, growing period
Observed: before	0.02–0.07	0.25	0.22	0.02	0.009
Observed: after	no trend	0.06	0.024^1	n.a.	n.a.
Predicted: before	n.a.	0.27	0.20	n.a.	n.a.
Predicted: after (longterm average)	n.a.	0.10^2	0.10	n.a.	n.a.
Application details
Dates	2 times: 2008; once: 2009	29 April–1 May 2013	25–29 Apr 2016	Expected 2017	In discussion
Total Phoslock applied (t)	3.2; 15.0	25.2	64	174	tbd
Areal application rate (kg/m^2)^3	0.10; 0.44	0.46	0.25	0.36	tbd
	River section	Increasing waterfowl #	Many different treatments: herbicides, mixing, aeration, grass carp	Summer and fall cyanobacterial blooms	Summer and winter cyanobacterial blooms

Note. n.a. = not available; tbd = to be determined.

¹Average for 10 dates and 5 sites between 3 May and 14 Sep 2016.

²Includes P input from increased water fowl abundance.

³The areal application rate is computed as total applied Phoslock mass divided by lake surface area.

Figure 2. TP, SRP, and chlorophyll in surface water at Elk Lake, main station (Feb 2014–Aug 2015).

Nürnberg GK. 1996. Trophic state of clear and colored, soft- and hardwater lakes with special consideration of nutrients, anoxia, phytoplankton and fish. Lake Reserv Manage. 12:432–447.

 Google Scholar