An Experiment  on the Feasibility of Rehabilitating Acidified Atlantic Salmon Habitat in Nova Scotia by the Addition of Lime
W. J. White et al., 1984. Fisheries Volume 9, “In 1981, the Department of Fisheries and Oceans carried out an experimental neutralization of an acidified lake in Nova Scotia…Although it is feasible to add lime to headwater lakes to regulate fluctuations in the pH of rivers and to maintain the pH at levels favourable to Atlantic salmon; in Nova Scotia where lakes are small and their rates of flushing are rapid, lime must be added at frequent intervals.”

The case for liming some Nova Scotia salmon rivers
Walton D. Watt. 1986 Water, Air, and Soil Pollution volume 31, pages775–789
“Long range transport of H2SO4 has caused many Nova Scotian rivers to decline in pH to the point where their Atlantic salmon (Salmo salar) stocks have been destroyed or much diminished. Chemical records show a declining pH trend in N.S. rivers since the early 1950’s. The annual variation in hydrogen ion activity is positively correlated with sulphate and Al and negatively correlated with organic anions. It is technically feasible to restore the acidified salmon habitat by the addition of limestone, and the total cost of mounting a liming program to restore the lost habitat has been calculated. The pre-acidification Atlantic salmon production capacity was estimated from physical habitat surveys and tag return data. The estimated costs of the liming program are much greater than the anticipated economic benefits of the salmon restoration. Present plans are for a small liming program to establish a series of refuges for the preservation of nuclei of native salmon stocks.”

Some perspective on the paper: I received the from a friend on 21Feb2022: “In the 1980’s I was friends with Walton D and Corry Watt, and had a number of interesting conversations with Walton regarding his inexpensive program of liming Nova Scotia rivers by driving carts loaded with lime out onto the frozen surface of rivers in winter and spreading lime on the ice surface which would then help reduce the acidity of the river in spring when the ice melted just in time to help vulnerable salmon smolts and fry survive in Nova Scotia’s acidic rivers. I especially remember that Walton was very frustrated with the lack of provincial support for what he had shown to be a very effective and low cost method of enhancing survival in young Atlantic salmon in this province. He was particularly upset when DFO pulled the plug on the monitoring research knew was yielding valuable results and information.”

The effect of lime on the zooplankton population of Sandy Lake, Halifax County, Nova Scotia
Strong, K.W. 1987. Proceedings of the Nova Scotian Institute of Science, 37(2), 63-70.
Liming of Sandy Lake, Nova Scotia, during July and August of 1981 produced an abrupt and transient increase in the pH of the lake and concurrent changes in the zooplankton community. Immediately following liming, the cladoceran Bosmina longirostris could not be recovered from the lake but returned the following year after pH levels had fallen to pre-liming levels. The acidophilic rotifer Keratella taurocephala was also less numerous subsequent to liming. Other species, particularly rotifer species, were either more numerous or were collected for the first time in the two years immediately following the liming.


Responses of Kidney, Liver, Muscle, and Bone in Atlantic Salmon ( Salmo salar ) to Diet and Liming in Acidic Nova Scotia Rivers
HS Majewski et al., 1990 Canadian Journal of Fisheries and Aquatic Sciences Atlantic salmon ( Salmo salar) maturing two-year-olds were placed in the Medway (pH 5.2–5.6) and Westfield (pH 4.7–5.2) rivers (Nova Scotia) for 149 and 126 j, during 1985 and 1986. Exposure to Westfield River water resulted in depletion of renal and hepatic acid-soluble thiol (AST) stores, and renal ascorbic acid stores , over the course of 2 years. Liming, or a high salt diet (3.0% NaCl), did not completely maintain these reserves at the level found in salmon from the River Medway. In 1986, decreases in electrolytes in bone (Ca and P) and muscle (Na and K) coincided with increases in hepatic glycogen, suggesting that gluconeogenesis was a mechanism of adaptation to ionoregulatory effects associated with acidic and low calcium ambient levels. Addition of lime to Westfield River water restored muscle electrolyte levels, but had no effect on lowering bone Ca and P.

Metazoan parasite communities of yellow eels ( Anguilla rostrata ) in acidic and limed rivers of Nova Scotia
D Cone et al., 1993. Canadian Journal of Zoology In eels from the deacidified portion of the basin, the parasite community had a higher species richness and multiple infections were more frequent there than in eels from the acidic river…The fish-parasitic metazoan community therefore appears to be a very useful ecological indicator and may also provide information on the dynamics of disturbed food webs.


Recommended Liming Strategies for Salmon Rivers in Nova Scotia, Canada
A. Hindar. 2000.Research report, Norsk institutt for vannforskning
The Southern Upland of Nova Scotia is acidified due the extreme sensitive ecosystems combined with being down-wind from large sulphur emission sites in southern Canada and northern US. Atlantic Salmon populations have disappeared from 14 rivers and populations have been damaged in another 35 rivers. Only rivers with pH>5.4 have non-damaged populations. Attempts to improve this situation have been restricted to the genereal emission control plans of Canada. No liming program exists at present. This report gives detailed information regarding liming strategies in general and for four major river systems in particular. East and West River, Sheet Harbour, together with La Have and Medway River are regarded as being typical representatives of the damaged rivers. Liming of these rivers is possible, and a combination of lake liming, river lime dosing and catchment liming is recommended. Suggestions are also made regarding the approach towards a relatively high-quality liming strategy for the province, and the establishment of a monitoring program for water chemistry and biology.

Effects on stream water chemistry and forest vitality after whole-catchment application of dolomite to a forest ecosystem in southern Norway
Hindar, A et al., 2003 Forest Ecology and Management 180(1/3): 509-525 “n acidified, 0.8 km2 coniferous-forested catchment was limed with 3 t ha−1 of coarse-grained dolomite powder in September 1994. The liming resulted in an immediate change in runoff water chemistry relative to the stream of an adjacent reference catchment…This experiment shows that liming of forested catchments may be a viable method to obtain long-term improvement in water quality and potential positive effects for acid-sensitive aquatic organisms.”

Liming for the mitigation of acid rain effects in freshwaters: A review of recent results
Thomas A. Clair & Atle Hindar. Environmental Reviews 13(3):91-128. PDF “Acid rain has affected freshwater ecosystems for more than 50 years in much of northern Europe and North America. The acidification of waters, along with concurrent reduction in acid neutralization capacity, has caused deleterious changes to aquatic populations in much of these regions. To reverse some of the changes to aquatic ecosystems, a number of governmental and nongovernmental groups have applied lime and other neutralizing substances to streams, rivers, lakes, and catchments in the most affected or most ecologically valuable regions. We review the scientific literature published since the late 1980s on liming to provide an overview of successes and failures of various approaches. We discuss the rationale behind liming programs and why certain approaches may not be helpful in mitigating acidification effects under varying conditions. One of our main conclusions is that though water chemistry may be restored if only temporarily, aquatic communities probably will not return to their original states, though targeted fish species can be restored using active management approaches. The communities restored, however, are usually more unstable than those from undisturbed, or pre-acidification conditions. We also show that liming may have to be conducted for 50 to 60 years in some affected locations, which should affect the choice of approaches used in mitigation.”

Initial Results of an Atlantic Salmon River Acid Mitigation Program
E.A. Halfyard, 2008. MSc thesis, Acadia University. The thesis provides photos and details of lime doser on The West River, Sheet Harbour and results of early monitoring.



Terrestrial liming to promote Atlantic Salmon recovery in Nova Scotia – approaches needed and knowledge gained after a trial application
S. M. Sterling et a;., 2014 Hydrol. Earth Syst. Sci. Discuss., 11, 10117–10156. PDF
Abstract. Populations of Atlantic salmon (Salmo salar) in Southwest Nova Scotia (SWNS) have plummeted since the 1980s. Acidification is considered a main threat to this population. The lakes and streams of SWNS were among the most heavily acidified in North America during the last century and calcium levels are predicted to continue to fall in coming decades. One of the most promising mitigation options to reduce the risk of extirpation of the SWNS Salmo salar is terrestrial liming; however, both the chemistry of SWNS rivers, and effective strategies for terrestrial liming in SWNS are poorly understood. Here we have launched the first terrestrial liming study in Nova Scotia, employing a test hydrologic source area liming strategy in a 5 ha experimental catchment in SWNS, Maria Brook; we apply an average local application rate of 13 t ha−1 to 10% of the 47 ha catchment. We employ high frequency stream monitoring to complement grab sampling to identify which constituents pose a threat to Salmo salar and to identify strategies for larger scale terrestrial liming that would fit the local conditions. Results indicate that the water chemistry conditions are currently at toxic levels for Salmo salar throughout the year, with levels of ionic aluminium exceeding toxic thresholds almost 100% of the time. The stream chemistry in Maria Brook is remarkably similar to pre-recovery conditions in other heavily acidified watersheds, such as Birkenes in Norway. Our results support the hypothesis that there has been no recovery from acidification in SWNS. Results from the first year of post-liming do not show an improvement in stream chemistry levels, and further lime application is needed to improve the water chemistry conditions to needed levels for the recovery of Salmo salar. Related:  The effects of catchment liming on the calcium budget of an acidified Nova Scotia watershed by Christine Angelidis. 2013. Honours thesis, Department of Environmental Science Supervisor: Dr. Shannon Sterling

Ecological benefits and risks arising from liming sugar maple dominated forests in northeastern North America. PDF
Jean-David Moore et al., 2015 Environmental ReviewsVolume 23, Number 1, March 2015 “Liming, the application of carbonate materials (e.g., CaCO3, CaMg(CO3)2) to soils and surface waters, has been used extensively in Europe, and to a lesser extent in Canada and the United States, to mitigate the effects of acid deposition on forest and aquatic ecosystems. This literature review was conducted to assess the effects of liming on ecologically and economically important sugar maple dominated ecosystems of northeastern North America, where it is increasingly used to treat sugar maple dieback. Potential direct and indirect effects were considered to determine whether the use of liming to revitalize these forests could negatively affect other ecological parameters, including those in adjacent aquatic habitats. Based on current scientific literature, it is not anticipated that liming at rates of 1–3 t ha−1 would have major detrimental effects on these ecosystems. However, liming could have negative effects on northern hardwood forests with regard to earthworm invasions. The choice of liming as a mitigation tool should be made not only after weighing the potentially negative effects against the benefits of restoring sugar maple dominated stands in poorly buffered soils, but also after considering ecological components that could be lost or never recovered if an acidified forest ecosystem is not limed.”

A new method for prioritizing catchments for terrestrial liming in Nova Dcotia
Marley Geddes, Honours Thesis. 2015.  Supervisor: Dr. Shannon Sterling Freshwater acidification is a chronic issue in South Western Nova Scotia (SWNS). Despite reductions in emissions causing acid deposition in SWNS, water quality in the region is not predicted to improve for another 60 years (Clair et al., 2004)…..I have developed a comprehensive and quantitative GIS decision model to prioritize catchments for terrestrial liming in Nova Scotia. The model identifies catchments that best support effective liming and the SU population; these catchments are the primary units of SU conservation when using terrestrial liming mitigation methods. Additionally this research identifies key information needs required for improved terrestrial liming catchment selection.

Effects of partial-catchment helicopter liming on stream water chemistry in West River Sheet Harbour, Nova Scotia
Lobke Rotteveel 2018 Honours thesis, Dalhousie University, Supervisors Dr. Shannon M. Sterling (Earth Sciences Department, Dalhousie University)
Dr. Edmund A. Halfyard (Nova Scotia Salmon Association). Ch 2 is a Literature Review of freshwater acidification research and mitigation efforts
published from the 1970’s onward.

Terrestrial Liming Guidebook for South Western Nova Scotia
2018 document. Posted on website of NS Department of Fisheries & Aquaculture Multi-Institutional authorship including Hydrology Research Group (Dal. Univ), Bluenose Coastal Action Foundation, Natural Sciences and Engineering Research Canada, Nova Scotia Government. It consists of a series of graphics. Referenced.

Direct Aquatic Application of Crushed Dolomite Reduces CO2 Evasion in an Acidified River
S Sterling et al., 2021 EGU21, the 23rd EGU General Assembly, held online 19-30 April, 2021, id.EGU21-13633
Acidified rivers may have increased CO2 emissions because their low pH transforms inorganic carbon in the form of bicarbonate anions to CO2, which can evade to the atmosphere, thus interrupting the delivery inorganic carbon to the oceans, a key flux in the long-term carbonate silicate cycle. Enhanced weathering (EW) is a carbon dioxide removal (CDR) strategy aiming to increase drawdown of atmospheric CO2 through accelerated carbonation weathering of crushed minerals with targeted carbonate sequestration in oceanic stores. To date, EW research has been focused on terrestrial application of crushed minerals, and the CDR capability of enhancing weathering via addition of crushed minerals to rivers from lime dosers is essentially unexplored. Lime dosers have been used for decades to directly deposit crushed carbonate rock to rivers as a function of river flow in Norway and Nova Scotia, Canada, yet their potential as a CDR tool has yet to be verified in the field. In this study, we adapt CO2 flux sensors (eosFD) designed for soils to be deployed in rivers. We conducted field trials on the Killag River, Nova Scotia, upstream and downstream of a lime doser over a period of six weeks in the autumn of 2020. Preliminary analysis shows elevated CO2 evasion rates upstream of the lime doser and decreased evasion rates downstream. Aside from flood waves, CO2 evasion at the downstream (treated) site is reduced to almost zero for extended periods of time. Next steps are to identify whether the reduced CO2 evasion is due to CO2 drawdown via increased carbonation weathering of the crushed dolomite or through reduced CO2 evasion due to increased pH, or from a combination of the two processes. The results of this study may have implications for carbon credit programs for acidification mitigation and may encourage more widespread use of enhanced weathering as a CDR tool in rivers.

Websites & Facebook Pages  for Community Liming Projects

Nova Scotia Salmon Association
Acid Rain Mitigation Project (Old Webpage)
“Nova Scotia has suffered more than any other region of North America as a percent of fish habitat lost from the effects of acid rain. Acid rain has negatively impacted the salmon populations in at least 50 of the 65 salmon rivers draining the coastal plain that extends the full length of the Atlantic coast of mainland Nova Scotia, the Southern Upland. The combined effects of acid rain and low marine survival are hastening the extirpation of all but a small number the Southern Upland salmon stocks.The Nova Scotia Salmon Association has initiated an ambitious project to restore one of the rivers damaged by acid rain. The West River was selected as the site for the demonstration Project through an extensive review exercise carried out by the NSSA’s Acid Rain Mitigation Committee (ARMC), comprised of representatives from NSSA, ASF, Trout Nova Scotia, Nova Scotia Power (EMERA), and both federal and provincial governments. The ARMC’s exercise was guided by a report that detailed plans for liming 4 of the Southern Upland rivers. The report was contracted by the NSSA and prepared by Dr. Atle Hindar, a leading Norwegian researcher on liming strategies to combat acid rain effects.”- Acid Rain Mitigation
History with photos 2001-2016West River Acid Rain Mitigation Project
Facebook Page.

Helicopter Liming to Help Restore Acidified Forest Soil Productivity
Caitlin McCavour et al., 2021. EGU General Assembly 2021
Decades of acid deposition across northeastern North America has caused excess leaching of soil base cations (Ca2+, Mg2+, K+) and increases in bioavailable aluminum (Al3+) that, in combination, have resulted in widespread decreases in potential forest productivity. Despite major reductions in SO2 and NOx emissions since the 1990s, forest soils across the region have shown few signs of recovery from acid deposition impacts and it could take decades or centuries for natural recovery to occur. As a result, affected forests are stressed, less productive, and more prone to climate change-induced damage. Helicopter liming of upland forests may be an effective way to jump-start the soil recovery process. Here we report on early results (one-year) from a helicopter liming trial in Nova Scotia, Canada where 10 tonnes/ha of dolomitic limestone was applied to approximately 8 ha of mature red spruce (Picea rubens) and mature tolerant hardwood (Acer spp. and Betula spp.) forest. Data are presented on (i) the effectiveness of helicopter liming in forests; (ii) the initial chemical response of forest floor organic and mineral soil horizons; and (iii) the initial chemical response of red spruce foliage, maple foliage, and ground vegetation. Preliminary results showed that despite non-uniform lime distribution, there were significant increases (P < 0.05) in Ca2+, Mg2+, pH, and base saturation (BS), and significant decreases in total acidity in forest floor organic horizons in both the mature red spruce and tolerant hardwood stands; however, there were no significant changes in Al3+. The initial chemical response in sugar maple and red spruce foliage showed significant increases in the Ca/Al molar ratio . The initial response in ground vegetation (Schreber’s moss; Pleurozium schreberi and wood fern; Dryopteris intermedia) showed significant increases in Ca2+ and decreases in K+ for both species; however, Schreber’s moss also showed significant increases in Mg2+ and Al3+ while wood fern did not. These early chemical results are promising and further support the use of helicopter liming as an effective tool to combat lingering effects from acid deposition in acidified forests.