Evidence of Acidification of Some Nova Scotian Rivers and Its Impact on Atlantic Salmon, Salmo solar

Abstract

1983. Evidence of acidification sf some Nova Scotian rivers and its impact on Atlantic salmon, Salmo snlar. Can. J. Fish. Aquat. Sci. 40: 462-473.River pH's in Nova Scotia are closely reIated to geology, and seasonal pH variation is well correlated with river discharge rates. In the geologically sensitive areas (granite and metamorphic rocks), river pH's have fallen significantly over the past 27 yr at an apparent average rate of 0.017 pH units/year. Concomitant with this decrease are a decline in HCOi concentrations and increases in AIWC and SOT. On average, 73% of the increase in acid is attributabie to increased SOT. Changes in Na', K9, Ca'+. and Mg" concentrations were not significant. In rivers presently at mean annual pH's c4.7, the Atlantic salmon (S~lrno s a k r ) runs have disappeared and are presumed extinct. Rivers in the pH range 4.7-5.0 show a decline in salmon angling returns of 2.8%/yr, beginning about 1854, and low densities of juvenile salmon. Rivers presently of pH > 5.0 generally have normal juvenile densities and show no significant trend in angling returns. WATT, W. D., $1. B. SCOTT, AND W. J. WHITE. 1983. Evidence of acidification of some Nova Scotian rivers and its impact on Atlantic salmon, Snlrno solar. Can. 5. Fish. Aquat. Sci. 44): 462-473. En Pdouvelle-kcosse, le pH des rivieres est en ktroite relation avec la geologic. et les variations saisonnihes le sorat avec le dkbit des rivikres. Dans les regions gt5ologiques plus sensibaes (granite et r o c k s mktamorphiques). le pH des rivikres a baisse de faqon significative au cours des 27 dernikres annkes et cela 5 un taux moyen de 0.017 unit& pH/annCe. 11 s'est produit en m6me temps un dCclin de concentration de HCOi et un aceroissement de Al"' et SO:. En moyenne, 73 % de I'augmentation de l'acide est attribuable a l'augmentation de SO:. Drarant la mCme @riode, il ne s'est produit aucun ehangement significatif des concentrations de Na', K', Ca'* et Mg". Les populations de saumsns ataantiques (Saltno salar) ont disparu des rivi5res dont le pH annuel moyen est infbrieur B 4,7 et sont pr6sumkes Cteintes.Les rivikres B pH de 4,7-5,0 montrent un dCclin des prises sportives de 2,8 % par annie patir de 1954 et de faibies densites de juvkniles. Les rivieres B pH srm@rieur a 5,0 snt en gCn6ral des densitCs de saumoneaux normales et ne montrent abscune tendance significative des prises sportives.

Impacts of short-term acid and aluminum exposure on Atlantic salmon (Salmo salar) physiology: A direct comparison of parr and smolts

“…Chronic (year-round) acidification and its associated aluminum (Al) toxicity is a known cause of Atlantic salmon population decline in Norway (Hesthagen, 1989) and Nova Scotia (Watt et al, 1983). Recent studies have suggested that episodic acidification (single or re-occurring episodes lasting several days) may also have effects on Atlantic salmon populations in regions of the northeastern United States including Maine, where several salmon rivers have been listed as endan-gered (Magee et al, 2001(Magee et al, , 2003; National Academy of Science, 2004).…”

Applying landscape genetics to evaluate threats affecting endangered Atlantic salmon populations

“…The specific threats identified as contributing to the sedimentation, fragmentation and water quality indices are very interesting from a recovery planning perspective, and contradict some current perceptions. It is generally accepted that pH has an extremely large influence on Atlantic salmon in the Southern Upland, where increases in acid precipitation from the 1950s have been implicated in population extirpations and severe population decline (Watt et al 1983;Lacroix 1989). However, the influence of past mining activities on current water quality has never been identified as a pressing issue for mitigation, although it has been identified as a potential threat (e.g.…”

“…For example, agricultural activities, industrial sites (like gravel quarries) and roads are considered to be chronic sources of sediments (Gilvear et al 2002), where increased sedimentation has been linked to reduced habitat quality for salmonids as well as to acute mortality of eggs or juveniles (Soulsby et al 2001;Julien and Bergeron 2006), particularly during storm events (Lisle 1989). Furthermore, the bedrock geology of the Southern Upland region has little buffering capacity (Watt et al 1983;Korman et al 1994), which makes Southern Upland salmon particularly vulnerable acid deposition from either precipitation or land-based sources (Farmer et al 1980;Watt 1987). Atmospheric deposition in the form of acid rain has substantially reduced pH in many rivers throughout the Southern Upland (Watt 1987).…”

Probable changes in lake chemistry in Canada’s Atlantic Provinces under proposed North American emission reductions

“…Firstly, many lakes are influenced by sea-spray (Watt et al, 1983), which though neutral overall in terms of acidification, can cause temporary imbalances in ANC and acidity (Heath et al, 1992); these must be taken into account when modelling water chemistry. Secondly, the abundance of wetlands in this region causes high concentrations of natural organic acids (NOAs) that can reduce pH in these waters (Clair and Freedman, 1986).…”