Acid stress and extinction of a spring-spawning fish population

Investigation of Heeney Lake, 21.7 ha, revealed a small population of white sucker, Catostomus commersoni. Only four age-classes were represented in this normally abundant and long-lived species. By 1984 only one new age-class had been recruited into the population. As these fish spawned in the outlet stream in early spring, the potential toxicity of these waters was assessed at two snow-melt events. Rainbow trout, Oncorhynchus mykiss, of hatchery origin were held in the outlet stream as pH declined from 6.5 to 4.7 during a snow melt, late February. Trout showed a loss of 19% in plasma Na and 24% in Cl concurrent with gill Al concentration increasing from 10 to 250 μg'g^?1 dry wt. At the mid-April snow melt, pH fell to 4.1, and rainbow trout held in the outlet showed a decline in plasma sodium of 42% and gill Al increased from 10 to 415 μg'g^?1 dry wt. Control rainbow trout held in Harp L. at pH 6.3 showed no significant change in plasma and muscle ion concentrations, or in gill Al concentration. White sucker from nearby waters were held in Heeney Lake outlet, late April, and muscle Na and Cl declined significantly as gill Al concentration increased from 11 to 50 μg'g^?1 dry wt during 48 hr exposure. White sucker hekl in Heeney L. outlet, mid-May, showed no significant change in plasma ions. No white sucker have been captured in Heeney L. since 1984 and the population is presumed to be extinct. Acid deposition has declined in recent years but lake and stream pH have not recovered and fish populations may still decline or disappear.     

Physiological responses of rainbow trout Salmo gairdneri exposed to plastic lake inlet and outlet stream waters

In Plastic Lake, Ontario, stocked rainbow trout (Salmo gairdneri) have failed to survive, one endemic fish species has become extinct and annual fish kills included up to five species, but especially pumpkinseeds (Lepomis gibbosus). The potential toxicity of Plastic Lake water was assessed by holding (hatchery) rainbow trout in the major inlet stream, the outlet, and in a portion of the outlet stream acidified to the pH of inlet No. 1. Stress on rainbow trout was assessed by measuring plasma and muscle concentrations of Na ⁺ Cl^?, and K⁺, plus gill A1 concentration. Trout held in Plastic Lake inlet No. 1 showed a rapid loss of plasma Na⁺ from 138 to 85 meq.L^?1and Cl^? from 120 to 75 meq.L^?1 within 24 hr. Gill A1 concentration increased from 20 to 105 μg.g^?1 dry weight. Trout held in the outlet steam showed only slight loss of plasma Na⁺ and Cl^? and no accumulation of Al on the gills. Trout held in the acidified outlet showed a significant loss of ions with plasma Na⁺ depressed from 140 to 115 meq.L^?1 and plasma Cl^? from 125 to 95 meq.L^?1over 24 hr. Gill Al concentration increased from 18 to 30 μg.g^?1 dry weight. The differences in stress response of rainbow trout held in the inlet and acidified outlet are likely due primarily to the difference in Al species concentrations in the two waters.     

Acid precipitation and surface-water vulnerability on the western slope of the high colorado rockies

Precipitation and surface waters in a high-elevation watershed on the western slope of the Colorado Rockies were studied over a three-year period. The volume-weighted average pH for summer events was 4.61, for winter events was 5.11 and for the entire period was 4.91. Within the watershed, both low- and medium-alkalinity surface waters exist. Weekly alkalinity measurements ranged from 10 to 70 μeq L^?1 in the former and 100 to 900 μeq L^?1 in the latter.     

Localization of aluminum in tissues of fish

The concentrations of Al in fish gills has been used as a measure of fish exposure to this metal in acidified waters. This experiment was designed to determine if other fish tissues also accumulate Al and thus possibly contribute to the cause of death. Rainbow trout (Salmo gairdneri) were exposed to the following fours test conditions for 48 hr or until death: (1) pH 6.8, <0.001 mg.L^?1 Al (n=6); (2) pH 5.2, <0.001 mg₁L^?1 Al (n=2);(3) pH 5.2,1.0 mg.L^?1 Al (n=5); (4) pH 6.8, 1.0 mg.L^?1 Al (n=3). The trout were held in synthetic, low Ca water prior to, and during, experimentation. Esophagus-stomach, gonad, gall bladder, gill (left and right), heart, intestine, kidney, liver, muscle (epaxial), and spleen were digested in a 4:1 mixture of HNO₃:HClO₄ and analyzed by Inductively Coupled Plasma Emission Spectrophotometry. Elevated Al concentrations were found in gill and gastrointestinal tissues. Left and right gills of fish exposed to pH 5.2, 1.0 mg.L^?1 Al were the only tissues found to be significantly different (p<0.01) between the test conditions. The mean total Al concentrations of these test 3 fish, for the left and right gill were 3.61 and 4.33 mg.g^?1 Al dw. The Al concentration in thle gastrointestinal tissues of the fish exposed to pH 6.8 at 1.0 mg.L^?1 Al was greater than that of the control fish, but not statistically significant. These results suggest that the analysis of whole gill remains an effective indicator of Al exposure in fishes at low pH.     

The effects of low pH,low calcium concentrations and elevated aluminium concentrations on sodium fluxes in brown trout,Salmo Trutta L.

The effects of pH (c. 7.0, 5.4, 4.5 and 4.0), nominal Al levels (0 and 8 μmol L^?1) and Ca levels (10 and 50 μmol L^?1) on Na influx, efflux and netflux of brown trout have been investigated using artificial lake water of known composition. Low pH had little effect on influx, but tended to increase efflux, particularly in the low Ca treatments. A nominal addition of 8 μmol Al L^?1 at pH 4.5 and 4.0 reduced influx significantly. Efflux was unaffected. Aluminium addition at pH c. 7.0 and 5.4 had no such effect. The measured Al concentrations at the end of the static 8 hr flux measuring experiments were markedly lower than the nominal amount of A1 added to the start.     

Mortality and physiological stress of year-classes of landlocked and migratory Atlantic salmon,brown trout and brook trout in acidic aluminium-rich soft water

Physiological stress, measured as changes in plasma chloride, and mortality were measured on different year-classes of landlocked and migratory Atlantic salmon, two strains of brown trout, and brook trout, in a flow-through system with acidic Al-rich soft water. The oldest year-classes of salmon were smolts. Water from Lake Byglandsfjord (pH = 5.9), was enriched 1 th inorganic Al (as AlCl₃) and H₂SO₄ to pH = 5.1, total Al = 225 ug L^?1 , and labile Al = 135 ug L^?1 . As a reference, lake water was limed by means of a shellsanj filter to pH = 6.2, increasing Ca-concentration from 1.0 to 1.5 mg L^?1. During the 83 hr experiment, neither mortality nor physiological stress occurred in any species or year-class in the limed water. In the acid water, no mortality occurred on any stage of brown trout or brook trout. Among the migratory and landlocked salmon, however, 5% of the alevins died after 49 and 70 hr, respectively. All smolts of both the landlocked and the migratory salmon died after 83 and 35 hr, respectively, the co responding loss rate of plasma chloride was ?0.76 and ?1.26 meq Cl hr^?1. Brook trout, however, increased plasma ion concentration during the experimental period, and hence showed no stress.     

Chemical effects of spring and summer alum additions to a small,Northwestern Ontario Lake

Aluminum was added as aluminum sulfate (alum) to Lake 114, a small, shallow lake of the Experimental Lakes Area, northwestern Ontario, in spring and summer point-source additions. Aluminum and H⁺ gradients were established during the additions, with high Al and low pH (about 1000 μg L^?1 Al, pH 4.7) near the alum sources, and background conditions (< 50 μg L^?1 Al, pH 5.7) further from the sources. Approximately 80% of the added Al was lost from the water column in two weeks. Phosphorus concentrations remained unchanged during the additions, whereas lake alkalinity decreased and sulfate increased close to the sources. Dissolved organic carbon (DOC) concentrations decreased slightly (from 540 μM L^?1 to about 500 μM L^?1) near the alum source during the summer addition.     

Airborne transport of sulphur: Impacts on chemical composition of rivers on north shore of the St. Lawrence River (Québec)

The St. Lawrence North Shore region (Québec) is subject to acid precipitation entailing sulphate deposition (17 to 22 kg SO₄ ^2? ha^?1 yr^?1) which poses a threat to sensitive aquatic ecosystems. Physicochemical surveys conducted in 1982–1983 revealed the extreme sensitivity of the region owing to weak mineralization of the waters (mean alkalinity of 55 μeq L^?1 and conductivity of 17 μS cm^?1). Calculation of the annual loads of S discharged from 21 rivers throughout the region shows atmospheric deposition as the principal source of sulphate. A decreasing west-east gradient in the concentration is interpreted in terms of the impact of long-range airborne transport, although certain local sources of S emission are not to be overlooked. Analysis of the seasonal variation in the sulphate load balance, conducted in a small drainage basin (40 km²), revealed that the sulphate anion plays a part in lowering the water pH in spring. The spring pH depression is apparently intensified by an additional input of sulphate stemming from the release of this element subsequent to accumulation in the drainage basin during summer and fall. Organic acids play a measurable role in the chemical equilibrium of surface waters in the region, particularly in the eastern sector where there is less S fallout. Low pH levels in this sector (5.5 to 6.0) point to some degree of organic acidification.     

Effects of Acidity and Aluminum on the Physiology and Migratory Behavior of Atlantic Salmon Smolts in Maine, USA

Atlantic salmon, Salmo salar, smolts of hatchery origin were held for 5 to 16 days in ambient (pH 6.35, labile Al = 60 µg L^?1), limed (pH 6.72, labile Al = 58.4 µg L^?1), or acidified (pH 5.47, labile Al=96 µg L^?1) water from the Narraguagus River in Maine, USA. Wild smolts were captured in the same river in rotary traps and held for up to two days in ambient river water. Osmoregulatory ability was assessed by measuring Na⁺/K⁺ ATPase activity, hematocrit, and blood Cl concentration in freshwater, and after 24-hr exposure to seawater. Hatchery smolts exposed to acidic water and wild smolts displayed sub-lethal ionoregulatory stress both in fresh and seawater, with mortalities of wild smolts in seawater. Using ultrasonic telemetry, hatchery-reared ambient and acid-exposed, and wild smolts were tracked as they migrated through freshwater and estuarine sections of the river. The proportion of wild smolts migrating during daylight hours was higher than for hatchery-reared smolts. Wild smolts remained in the freshwater portions of the river longer than either group of hatchery smolts, although survival during migration to seawater was similar for all three treatments. Acid-exposed hatchery-origin and wild Narraguagus River smolts were both under ionoregulatory stress that may have affected their migratory behavior, but not their survival for the time and area in which we tracked them.     

Field and laboratory studies of exposures of brown trout to acid waters

Some recent work on the effects of acid waters on brown trout are presented. Laboratory bioassay experiments have demonstrated that yearling trout are relatively insensitive to pH >4.3. Aluminium is demonstrated to be extremely toxic with suppression of growth occurring at concentrations above 20 μg L^?1 at pH 4.4 to 5.2. Aluminium toxicity is reduced at high pH (5.9 and 6.3). Field studies carried out on 61 acidic and circumneutral streams in upland areas of England and Wales showed a strong relationship between water quality and standing crop of 1+ brown trout. Measured pH levels per se were too high to be directly toxic. On the other hand, heavy metal and Al concentrations could account for low or zero brown trout biomass in the more acidic streams. A mobile bioassay laboratory has been developed to allow controlled bioassay experiments to be carried out in the field. Natural and synthesised waters can be tested concurrently in multi-factorial experiments with in situ determinations of pH, Ca, Al (total and monomeric) and other water quality characteristics.     

Physiological response of brown trout (Salmo trutta) spawners and postspawners to acidic alminum-rich stream water

High immediate postspawning mortality due to inferior autumn water quality has been hypothesized to cause juvenilization in some brown trout populations in acidified areas. We exposed male and female spawners and female postspawners from a juvenile-dominated brown trout population to acidic streamwater (pH = 4.83, Al_i = 240 μg L^?1) and a limed control (pH = 5.70, Al_i = 55 μg L^?1) for 28 days in November and December, 1984. Water chemistry was monitored at least bi-daily, and physiological stress was assessed by analysis of plasma chloride, osmolality and haematocrit. Neither pronounced physiological stress nor mortality was observed at the control site. At the exposure site trout showed significant but moderate stress responses and 15 % died. The results are discussed in terms of potential population effects and physiological mechanisms, e.g., plasma volume reduction.     

Liming acid streams: Aluminium toxicity to fish in mixing zones

Liming to neutralize acidic surface waters involves a possible risk of toxicity to fish due to precipitation or changes in speciation of Al. We report the response of captive brown trout to the experimental liming of an acid stream rich in Al. Within 15 m of lime dosing 0.22 µm filterable Al fell from 580 to 230 µg L^?1, and to 120 jig L^?1, within 30 m, though total Al was unchanged. After 24 hr, fish mortality was 100% at untreated acidic sites, 80% up to 30 m downstream of liming, declining to zero within 100 m. Mortality was 70% at 15 m below the confluence of an acidic tributary with the limed stream, despite little change in pH or total Al concentration. Mortalities were significantly correlated with concentrations of Al and Fe in gill tissues, and with 0.22 µm filterable Al and Fe in the water, but not with particulate Al or Fe. AI(OH)₄ ^?, precipitating A1 or polymeric hydrolysis products are all possible causes of the observed toxicity. Iron may have also have contributed, but the stream concentrations of this metal were relatively low. The practical conclusion is that changes in Al chemistry, where waters of differing acidity mix, may be important in some circumstances where river systems are limed selectively.     

Implications of natural acidification for mitigation strategies in northern Sweden

Northern Sweden has been regarded as unaffected by acid deposition, but many surface waters in the region fall within the definition of acid surface water (pH < 6.0, alkalinity < 50 mmol_c m^?3) permanently or during episodes. Approximatly 100 MSEK in spent annually on liming in northern Sweden. This paper summarizes our conclusions from a workshop on natural versus anthopogenic acidification held in February 1995. It was shown that organic substances have a key role in determining the acidity of surface waters in the region, although anthropogenic effects are documented in some coastal systems and in the southern mountain range. Sulfide oxidation occurs by the coast. It appears clear that many surface waters that were naturally acidic have been limed to unnatural pH levels. New criteria to screen liming candidates should be developed, and one such model based on water chemistry data is proposed.     

Changes in the fish community of a limed lake near sudbury,Ontario: Effects of chemical neutralization or reduced atmospheric deposition of acids?

Nelson Lake, a moderately acidic (pH 5.7), metal-contaminated (Cu 22 μg L^?1; Zn 18 ug L^?1) lake, 28 km from the smelters at Sudbury, had a degraded fish community in the early 1970's, with lake trout (Salvelinus namaycush) scarce, smallmouth bass (Micropterus dolomieui) extinct, and the littoral zone dominated by the acid-tolerant yellow perch (Perca flavescens). Liming of the lake in 1975–76 increased pH to 6.4, and decreased metal concentrations. Chemical conditions have remained relatively stable in the 10 yr following base addition. Initially, it appeared that neutralization produced dramatic changes in the resident fish community. Yellow perch abundance declined rapidly after neutralization, lake trout abundance increased to the extent that 3.26 kg ha^?1 were caught in the winter of 1980, and reintroduced smallmouth bass reproduced and established a large population. However, these changes in the fish community can not be directly attributed to liming, as water quality and the sport fisheries of an unlimed nearby lake also improved. Reduced emissions from Sudbury smelters were responsible for improvements in the untreated lake. Recovery of the lake trout population in Nelson Lake appears to have begun prior to liming. Of the lake trout sampled during the 1980 winter fishery, 65.8% were present prior to the chemical treatment. Predation by lake trout was the likely cause of the perch decline. Our results suggest that chemical conditions producing population level responses in fish have abrupt thresholds and that neutralization of lakes above these thresholds may not produce distinguishable effects.     

Chronic effects of low ph and elevated aluminum on survival,maturation, spawning and embryo-larval development of the fathead minnow in soft water

Fathead minnows (Pimephales promelas) were exposed to a range of pH and A1 concentrations in soft water (8 mg Ca L^?1) to determine effect levels at various life stages. The tested pH levels ranged from 8.0 through 5.2 and inorganic monomeric Al from 15 through 60 μg L^?1. Reproductive processes including spawning, embryogenesis and early larval survival were more sensitive to acid stress than were juvenile growth and survival. Juvenile survival was significantly reduced at pH 5.2 + 60 μg Al L^?1 (P <0.05). Spawning success was reduced at pH 6.0 and 5.5 (P <0.10) and failed completely at pH 5.2, regardless of Al concentration. An apparant beneficial effect of added Al was observed during spawning at pH 7.5 + 35 μg Al L^?1, but this effect was not significantly greater than at pH 7.5 + 15 μg Al L^?1. A significant (P <0.05) decrease in larval survival occurred at pH 6.0 + 15 μg Al L^?1 and lower compared to the survival at pH 7.5 + 15 μg Al L^?1. Aluminum at 30 μg L^?1 provided protection resulting in short term increased embryo-larval survival at pH 5.5. The effect of parental exposure on progeny survival was assessed by an interchange of embryos from the spawning treatment to all tested exposure conditions. When reared at pH 8.0 + 15 μg Al L^?1 through 6.0 + 15 μg Al L^?1 or at pH 5.5 + 30 μg Al L^?1, parental exposure did not significantly influence progeny survival. However, survival was significantly reduced among progeny from brood fish reared at pH 5.5 + 15 μg Al L^?1 as compared to those spawned at pH 6.0 + 15 μg Al L^?1 and above, or at pH 5.5 + 30 μg Al L^?1 (P <0.05). Juvenile or 14 d larval growth effects were not detected under any exposure condition (P >0.05). Ultimately, fathead minnow young-of-the-year recruitment and production potential can be expected to diminish when environmental pH falls to 6.0, and to fail completely at 5.5 and lower.     

Response of lake trout (Salvelinus namaycush) and brook trout (S. fontinalis) to surface water acidification in Ontario

Netting surveys of lakes varying in pH (4.4–7.1) showed that lake trout (Salvelinus namaycush) populations fail to recruit at pH <5.5 and are lost from lakes with pH<5.2. Brook trout (S. fontinalis) were extirpated in lakes with pH <5.0. In regional chemical surveys of Ontario lakes, it was found that 2% of sampled brook trout lakes and 2.5% of lake trout lakes were acidified (alkalinity <0 uEq L^?1). Threshold pH levels determined from fisheries assessments were used to estimate that 1% of lake trout and brook trout populations have been lost due to acidification.     

Occurrence of acidic groundwater in precambrian crystalline bedrock aquifers,Southwestern Sweden

The pH and alkalinity of groundwater from 7651 wells drilled in the Precambrian crystalline bedrock of southwestern Sweden has been evaluated. The wells are generally less than 100 m deep. Analytical results were collected from different laboratories and authorities in the region. In areas with thin soil cover or coarse-grained deposits overlying the bedrock, alkalinity is normally less than 100 mg HCO₃ L^?1. Below the marine limit, where clayey sediments predominate, alkalinity sometimes even exceeds 200 mg HCO₃ L^?1. When comparing pH and alkalinity of groundwaters from Quaternary deposits with bedrock groundwaters, the latter always have higher pH and alkalinity values. The most acidic bedrock groundwaters are found in small areas close to the city of Göteborg due to additional factors of high acid loadings, high groundwater discharge and thin soil layers. A study of data from 1949 to 1985 in the province of Värmland suggests that no regional acidification of importance is in progress. However, results from public water supplies support the hypothesis that the groundwaters which are most sensitive to acidification are those where discharge from wells in small bedrock aquifers induces rapid groundwater recharge of acidic surficial water.     

Acidity status of surface waters in Massachusetts

The Massachusetts Acid Rain Monitoring project surveyed 80.5% of the state's 5294 named water bodies between 1983 and 1985. PH and acid neutralizing capacity (ANC) were measured monthly the first 14 mo and semi-annually afterwards. Sample collection and analysis were performed by volunteers. The majority of surface waters in Massachusetts were found to be sensitive to possible long term acidification, with 63% exhibiting ANC less than 200 μeq L^?1 and 22% with ANC less than 40 μeq L^?1. Seasonal patterns in ANC were observed, the median ANC being 384 μeq L^?1 in summer/fall and 134 μeq L^?1 in winter/spring. Geographical differences were also found across the state: the streams and lakes with lowest pH and ANC were located in the southeastern and north-central parts of the state, while the most alkaline surface waters were found in the western-most part of the state, which is the only area of the state with significant limestone deposits.     

Validating a Simple Equation to Predict and Analyze Organic Anion Charge in Swedish Low Ionic Strength Surface Waters

Acid neutralising capacity (ANC) is substituted by CBALK, a term that has been theoretically introduced in the early 1990s, to evaluate a simple pH equilibrium model used for Swedish surface waters. The CBALK approach with its simple three pK_a organic acid analogue is re-evaluated with a new data set of 900 stream water samples. End-point alkalinity and TOC suffice to predict air equilibrated pH in the range 4.5 to 7.5 within 0.08 pH units. This is equivalent to an error in the charge balance of about 5 ueq L^?1. In the studied pH range it renders more precise predictions than when using ANC. The model equations can be used to estimate the effect of organic carbon or carbon dioxide on ambient pH during episodes as well as for sample quality control.     

Growth and gas exchange of loblolly pine seedlings as influenced by drought and air pollutants

One-year-old loblolly pine seedlings were exposed to 0₃(≤0.025 or 0.10 μ L L^?1, 4 hr d^?1, 3 d wk^?1) in combination with simulated rain (pH 5.6 or 3.0, 1 hr d^?1, 2 d wk^?1, 0.75 cm hr^?1) for 10 wk. After the 10-wk treatment, the seedlings were submitted to two drought cycles, and water potential, net photosynthesis (Pn), and transpiration (Tr) were measured. Whole-plant fresh weight increment and relative growth rate were significantly increased in seedlings exposed to simulated rain at pH 3.0 compared to pH 5.6. An interaction between 0₃ and simulated rain occurred in height growth. Shoot height elongation was significantly less in seedlings exposed to 0.10 μL L^?1 0₃ + pH 5.6 than in any other pollutant combination after the 10-wk treatment period. There were no significant effects of 0₃ on Pn and Tr prior to the drought cycles; however, after the first drought cycle, Pn was significantly higher in seedlings pre-exposed to 0.10 μL L^?1 0₃ compared to the low 0₃ concentration. The 10-wk treatment with simulated rain at pH 3.0 significantly increased Pn and Tr. The relationship between gas exchange rates and needle water potential during the moisture stress period was affected by preexposure to pollutants. In general, Pn and Tr were more sensitive to decreasing needle water potential in seedlings exposed to pH 3.0 during the first drought cycle and to 0.10 μL L^?1 0₃ during second drought cycle.