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Spring pH and Alkalinity Depressions in Lake Superior Tributaries
J. Great Lakes Res. 9(3):425~429 Internat. Assoc. Great Lakes Res., 1983
NOTE SPRING pH AND ALKALINITY DEPRESSIONS IN LAKE SUPERIOR TRIBUTARIES
W. Keller Ontario Ministry of the Environment 199 Larch Street Sudbury, Ontario P3E 5P9
ABSTRACT. Between October 1980 and October 1981. the pH and alkalinity of 21 Canadian Lake Superior tributaries were measured. All tributaries studied exhibited reductions in pH and alkalinity during the spring runoffperiod of 1981; two showed pH minima of near 5.0 and an additional five showed pH minima in the range of 5.5 to 6.0. Since most of these waters constitute valuable fishery resources. particularly for salmonids. the observed pH depressions prompt concern over possible effects on fish populations. ADDITIONAL INDEX WORDS: Acid rain. trout. salmon. fish management.
INTRODUCTION Episodic depressions in stream pH associated with spring snowmelt have been identified in Scandinavia (Gjessing et al. 1976, Hultberg 1977), the U.S.A. (Schofield 1977), and Canada (Jeffries et al. 1979, Scheider, et al. 1979). In the Muskoka-Haliburton area of Ontario, Jeffries et al. (1979) documented springtime declines in the pH of tributary streams, lake surface and littoral waters, and lake outflows. They also expressed concern over the potential effects of such low pH periods on acid-sensitive fish species. Despite the obvious importance of flowing waters as spawning and nursery areas for many fish species, little information is available on the influence of acidic spring runoff on the chemistry of streams and rivers in other areas of Ontario. During 1980-81, water quality investigations were carried out on tributaries to Lake Superior between Sault Ste. Marie, Ontario, and Wawa, Ontario. Emphasis was placed on documenting the pH and alkalinity of these waters through the spring runoff period of 1981. Work was focused on this area because most of the waters involved constitute valuable fishery resources, particularly for salmonids (M. Powell, Ontario Ministry of Natural Resources, Sudbury, Ontario, personal communication), and limited sampling in 1979
(Keller, unpublished data) had suggested sensitivity to acidic precipitation. The study area falls within the region of Ontario considered geologically susceptible to surface water acidification (Kramer 1977). The mean annual precipitation pH in the area (measured at a collector"" 45 km north of Sault Steo Marie) ranged from 4.25 to 4.52 during the period 1976 to 1979 (Kelso et al. 1982). During the winter of 1981, snowpack samples collected throughout the Sault Ste. Marie District (n =58) were consistently acidic (average pH =4.7; J. R. M. Kelso, Canadian Department of Fisheries and Oceans, Sault Ste. Marie, Ontario, unpublished data). Many of the tributaries studied have historically supported spawning runs of rainbow trout (Salmo gairdneri (Richardson» and resident populations of brook trout (Salvelinus fontinalis (Mitchill». More recently, some have also become spawning grounds for introduced pacific salmon, including the coho (Oncorhynchus kisutch (Walbaum», pink (Oncorhynchus gorbuscha (Walbaum», and chinook (Oncorhynchus tshawytscha (Walbaum». METHODS In total, 21 tributaries (Fig. 1) were sampled between 9 October 1980 and 24 October 1981. 425
w.
426
KELLER grab samples were collected at the same point slightly upstream of the Highway 17 crossing. Samples were retained in clean, sample-rinsed 500 mL polystyrene bottles for analyses of pH and total inflection point alkalinity. Analyses were completed at the Sudbury Ministry of the Environment laboratory on the day following collection (after overnight refrigeration) using a Radiometer model PHM 64 pH meter (standardized and checked against five buffers) interfaced with an automatic titration system (Radio Shack TRS80 desk top calculator coupled to a Radiometer ABU13 autoburette). The normality of the acid (0.020 N H 2S04) used in titrations was checked before running each series of samples. All samples and buffers were at room temperature (rv 22°C) during measurements.
a:: o a::
LU
0-
::>
Cf)
20 Kilometers
FIG. 1. The study area, showing the locations of the watercourses sampled.
Sampling intensity varied somewhat between sites; however, in most cases, sites were visited weekly from late March to early June and about monthly during other periods. During each visit, surface
RESULTS AND DISCUSSION All tributaries, even those with high buffering capacity during most sampling periods, showed substantial reductions in pH and alkalinity during spring runoff. Recorded minima for these parameters (Table 1) were associated with high spring flows while maxima were associated with low flow periods, primarily in late summer. In most tributaries the degree of pH depression observed was not extreme (i.e., 14 did not show pH < 6.0); however, two (Speckled Trout Creek and the Barrett River) exhibited low minimum pH (5.09 and 5.00, respectively) and an additional five showed pH minima in the range of 5.5 to 6.0 (Table 1). Although the weekly sampling frequency did not provide a temporally complete picture (i.e., conditions more acidic than recorded could have occurred between sampling events), it is interesting to observe the apparent pattern of pH depression in the two most seriously affected waters. Both Speckled Trout Creek and the Barrett River showed substantial reductions in pH for three consecutive weekly samplings (2 April to 14 April 1981) after the onset of substantial spring snowmelt (Fig. 2). Following the period of major snowmelt in early April, pH increased briefly until a second short pH depression event occurred in early May (Fig. 2), coincident with heavy rains. Snowfall during the winter of 1980-81 (284 and 268 cm at Sault Ste. Marie and Wawa, respectively; Environment Canada 1981, 1982a) approached annual averages for the area (306 and 278 cm, respectively, at the same stations; Environment Canada 1982b) for winters between 1951 and 1980.
427
SPRINGTIME STREAM pH DEPRESSIONS
TABLE 1. Locations, number of samplings (n), and ranges in pH and alkalinityfor Lake Superior tributaries sampled October 1980 to October 1981. Tributary Agawa River Alona Creek Barrett River Batchawana River Chippewa River Coldwater River East Baldhead River Goulais River Harmony River Magpie River Michipicoten River Montreal River Old Woman River Old Woman Tributary #1 Old Woman Tributary #2 Old Woman Tributary #3 Pancake River Sand River South Baldhead River Speckled Trout Creek Stokely Creek
Long. 47°21' 47°08' 47°24' 46°56' 46°56' 46°56' 47°28' 47°31' 46°44' 46°51' 47°55' 47°14' 47°46' 47°47' 47°46' 47°45' 46°58' 47°26' 47°36' 47°19' 46°49'
Alkalinity
wa
84°38' 84°42' 84°42' 84°32' 84°24' 84°24' 85°47' 84°48' 84°21' 84°22' 84°48' 84°39' 84°54' 84°53' 84°51' 84°49' 84°39' 84°44' 84°49' 84°36' 84°24'
n
pH
(mgj L as CaC03)b
14 16 17 10 12 17 17 II 12
5.77-7.32 6.64-7.60 5.00-6.76 6.50-7.48 6.85-7.57 5.74-7.25 5.98-6.90 6.82-7.40 6.16-7.24 7.21-8.05 6.92-7.52 6.81-7.28 6.54-7.44 6.57-7.12 6.54-7.42 6.25-6.81 6.65-7.25 5.57-7.30 5.71-7.17 5.09-7.20 6.76-7.54
0.69-20.12 5.25-27.24 -0.50-6.83 3.81-25.53 6.80-23.84 0.49-10.77 1.00-5.16 6.01-26.58 1.59-16.22 25.61-65.36 I I.l8-29.40 12.88-23.96 5.44-25.80 4.18-12.32 3.63-26. 17 2.56-21.53 5.64-17.61 0.33-11.65 0.95-18.09 -0.35-11.88 6.70-49.05
II
12 12 15 15 16 11 12 14 17 18 9
"at crossing of Highway 17 btotal inflection point alkalinity
In addition, based on personal observations, much of the accumulated snowpack was lost in a February thaw which resulted in some depression of stream pH (Fig. 2). Thus, the spring melt period of 1981 may not reflect worst-case conditions which would likely occur in years of maximum snowfall with a single period of rapid spring snowmelt. The potential impact of spring pH depression on fish populations in the waters studied is difficult to estimate because in situ fish responses to low pH are not well defined and laboratory toxicity results often show little agreement with findings in the field (Muniz and Leivestad 1980). Based on field observations, declines in natural salmonid populations seem to appear at about pH 5.0 to 5.5 (Haines 1981). A particularly important aspect to consider is the timing of reproductive activity in relation to observed pH depressions. Rainbow trout in general seem especially sensitive to acid stress (Grande et 01. 1978). However, because they are spring spawners with hatching and emergence usually occurring in late spring or early summer (Scott and Crossman 1973), the highly vulnerable (Schofield 1976, Harvey et 01. 1981) early life stages may not
occur in these tributaries until worst conditions, from a pH viewpoint, have passed. During the present study, pH minima occurred in early spring
7.0
SPECKLED TROUT ().
.d
- --
Q
" " \
6
tf
d
BARRETT - - -
~ 6.0
5.0
OCT
NOV
1980
DEC
JAN
f(8
IWl
APR
~AY
JUN
JUL
AUG
S!P
OCT
1981
FIG. 2. Temporal pH variation in Speckled Trout Creek and the Barrett River, October 1980 to October 1981.
428
W. KELLER
(April and early May). Brook trout are regarded as one of the salmonids more tolerant to low pH (Grande et al. 1978); however, due to behavior (i.e., fall spawning, hatching and alevin emergence in late winter! early spring) the most sensitive stages may coincide with worst-case water quality. Offspring of fall-spawning pacific salmon may be similarly susceptible. At present, adverse effects on fish have not been documented in the study area; however, data on these fish communities are scarce. Electroshocking surveys in late August 1982 did show that even the waters with the greatest observed pH depressions in this study (Speckled Trout Creek and the Barrett River) contained abundant young-of-the-year rainbow trout and coho salmon (M. Powell, Ontario Ministry of Natural Resources, personal communication).
CONCLUSIONS Sampling during 1980-81 demonstrated that at least some Lake Superior tributaries are subjected to substantial pH depressions coinciding with snowmelt and spring rains, similar to observations in south-eentral Ontario (Jeffries et al. 1979). Although adverse effects on fish populations in the study area have not been documented, concern over possible influences is warranted because these waters exhibit generally high sensitivity to acidic inputs and most constitute valuable fishery resources. The data provide a further indication that, as previously suggested by Harvey et al. (1981), the phenomenon of short-term surface water acidification may be widespread in geologically sensitive areas of Canada. They also suggest that fish populations, in areas of the Great Lakes not usually considered sensitive to inputs of acidic precipitation, could potentially be affected through acidification of tributaries.
ACKNOWLEDGMENTS I wish to thank P. Gale and M. Brideau for assistance in the field and laboratory, R. Labbe for help with the graphics, E. W. Piche, M. Powell, and N. Conroy for support, and N. D. Yan for encouragement. The comments of W. S. Gardner and an anonymous reviewer were greatly appreciated.
REFERENCES Environment Canada. 1981. Monthly records-meteorological observations in eastern Canada. Vol. 65, nos. 9- 12. Atmospheric Environment Service, Downsview, Ontario. _ _ _ _ . 1982a. Monthly records-meteorological observations in eastern Canada. Vol. 66, nos. 1-5. Atmospheric Environment Service, Downsview, Ontario. _ _ _ _ . 1982b. Canadian climate normals 19511980. Atmospheric Environment Service, Downsview, Ontario. Gjessing, E. T., Henriksen, A., Johannessen, M., and Wright, R. F. 1976. Effects of acid precipitation on freshwater chemistry. In Impact of acid precipitation on forest and freshwater ecosystems in Norway, ed. F. Braekke, pp. 64-85. SNSF Res. Rept. 6/76. Grande, M., Muniz, I. P., and Andersen, S. 1978. Relative tolerance of some salmonids to acid waters. Int. Assoc. Theor. Appl. Limnol. Proc. 20:2076-2084. Haines, T. 1981. Acidic precipitation and its consequences for aquatic ecosystems-a review. Trans. Am. Fish. Soc. 110:669-707. Harvey, H. H., Pierce, R. c., Dillon, P. J., Kramer, J. R., and Whelpdale, D. M. 1981. Acidification in the Canadian aquatic environment. Publication NRCC No. 18475. Environmental Secretariat. National Research Council of Canada, Ottawa, Ontario. Hultberg, H. 1977. Thermally stratified acid water in late winter-a key factor inducing self-accelerating processes which increase acidification. Water Air Soil Pollut. 7:279-294. Jeffries, D. S., Cox, C. M., and Dillon, P. J. 1979. Depression of pH in lakes and streams in central Ontario during snowmelt. J. Fish. Res. Board Can. 36:640-646. Kelso, J. R. M., Love, R. J., Lipsit, J. H., and Dermott, R. 1982. Chemical and biological status of headwater lakes in the Sault Ste. Marie District, Ontario. In Proc. Conf. on Acid precipitationeffects on ecological systems, ed. F. D'itri, pp. 165-207. Ann Arbor, Michigan. Kramer, J. R. 1977. Geochemical factors and terrain response to environmental contaminants. UnpubIished report, Department of Geology. McMaster University, Hamilton, Ontario. Muniz, I. P., and Leivestad, H. 1980. Acidificationeffects on freshwater fish. In Ecological impact of acid precipitation, ed. D. Drablos and A. Tollan, pp. 84-98. Proc. Int. Conf. Ecol. Impact of Acid Precipitation. Sandefjord, Norway. Scheider, W. A., Jeffries, D. S., and Dillon, P. J. 1979. Effects of acidic precipitation on Precambrian freshwaters in southern Ontario. J. Great Lakes Res. 5:45-51.
SPRINGTIME STREAM pH DEPRESSIONS Schofield, C. L. 1976. Acid precipitation: effects on fish. Ambio 5:228-230. _ _ _ _ . 1977. Acid snow-melt effects on water quality andfish survival in the Adirondack Mountains of New York. State Res. Proj. Techn. Compl. Rept.
429
Project A-072-NY. Cornell University, Ithaca, New York. Scott, W. B., and Crossman, E. J. 1973. Freshwater fishes of eastern Canada. Bull. 184 Fish. Res. Board Can., Ottawa, Ontario.
NOTE SPRING pH AND ALKALINITY DEPRESSIONS IN LAKE SUPERIOR TRIBUTARIES
W. Keller Ontario Ministry of the Environment 199 Larch Street Sudbury, Ontario P3E 5P9
ABSTRACT. Between October 1980 and October 1981. the pH and alkalinity of 21 Canadian Lake Superior tributaries were measured. All tributaries studied exhibited reductions in pH and alkalinity during the spring runoffperiod of 1981; two showed pH minima of near 5.0 and an additional five showed pH minima in the range of 5.5 to 6.0. Since most of these waters constitute valuable fishery resources. particularly for salmonids. the observed pH depressions prompt concern over possible effects on fish populations. ADDITIONAL INDEX WORDS: Acid rain. trout. salmon. fish management.
INTRODUCTION Episodic depressions in stream pH associated with spring snowmelt have been identified in Scandinavia (Gjessing et al. 1976, Hultberg 1977), the U.S.A. (Schofield 1977), and Canada (Jeffries et al. 1979, Scheider, et al. 1979). In the Muskoka-Haliburton area of Ontario, Jeffries et al. (1979) documented springtime declines in the pH of tributary streams, lake surface and littoral waters, and lake outflows. They also expressed concern over the potential effects of such low pH periods on acid-sensitive fish species. Despite the obvious importance of flowing waters as spawning and nursery areas for many fish species, little information is available on the influence of acidic spring runoff on the chemistry of streams and rivers in other areas of Ontario. During 1980-81, water quality investigations were carried out on tributaries to Lake Superior between Sault Ste. Marie, Ontario, and Wawa, Ontario. Emphasis was placed on documenting the pH and alkalinity of these waters through the spring runoff period of 1981. Work was focused on this area because most of the waters involved constitute valuable fishery resources, particularly for salmonids (M. Powell, Ontario Ministry of Natural Resources, Sudbury, Ontario, personal communication), and limited sampling in 1979
(Keller, unpublished data) had suggested sensitivity to acidic precipitation. The study area falls within the region of Ontario considered geologically susceptible to surface water acidification (Kramer 1977). The mean annual precipitation pH in the area (measured at a collector"" 45 km north of Sault Steo Marie) ranged from 4.25 to 4.52 during the period 1976 to 1979 (Kelso et al. 1982). During the winter of 1981, snowpack samples collected throughout the Sault Ste. Marie District (n =58) were consistently acidic (average pH =4.7; J. R. M. Kelso, Canadian Department of Fisheries and Oceans, Sault Ste. Marie, Ontario, unpublished data). Many of the tributaries studied have historically supported spawning runs of rainbow trout (Salmo gairdneri (Richardson» and resident populations of brook trout (Salvelinus fontinalis (Mitchill». More recently, some have also become spawning grounds for introduced pacific salmon, including the coho (Oncorhynchus kisutch (Walbaum», pink (Oncorhynchus gorbuscha (Walbaum», and chinook (Oncorhynchus tshawytscha (Walbaum». METHODS In total, 21 tributaries (Fig. 1) were sampled between 9 October 1980 and 24 October 1981. 425
w.
426
KELLER grab samples were collected at the same point slightly upstream of the Highway 17 crossing. Samples were retained in clean, sample-rinsed 500 mL polystyrene bottles for analyses of pH and total inflection point alkalinity. Analyses were completed at the Sudbury Ministry of the Environment laboratory on the day following collection (after overnight refrigeration) using a Radiometer model PHM 64 pH meter (standardized and checked against five buffers) interfaced with an automatic titration system (Radio Shack TRS80 desk top calculator coupled to a Radiometer ABU13 autoburette). The normality of the acid (0.020 N H 2S04) used in titrations was checked before running each series of samples. All samples and buffers were at room temperature (rv 22°C) during measurements.
a:: o a::
LU
0-
::>
Cf)
20 Kilometers
FIG. 1. The study area, showing the locations of the watercourses sampled.
Sampling intensity varied somewhat between sites; however, in most cases, sites were visited weekly from late March to early June and about monthly during other periods. During each visit, surface
RESULTS AND DISCUSSION All tributaries, even those with high buffering capacity during most sampling periods, showed substantial reductions in pH and alkalinity during spring runoff. Recorded minima for these parameters (Table 1) were associated with high spring flows while maxima were associated with low flow periods, primarily in late summer. In most tributaries the degree of pH depression observed was not extreme (i.e., 14 did not show pH < 6.0); however, two (Speckled Trout Creek and the Barrett River) exhibited low minimum pH (5.09 and 5.00, respectively) and an additional five showed pH minima in the range of 5.5 to 6.0 (Table 1). Although the weekly sampling frequency did not provide a temporally complete picture (i.e., conditions more acidic than recorded could have occurred between sampling events), it is interesting to observe the apparent pattern of pH depression in the two most seriously affected waters. Both Speckled Trout Creek and the Barrett River showed substantial reductions in pH for three consecutive weekly samplings (2 April to 14 April 1981) after the onset of substantial spring snowmelt (Fig. 2). Following the period of major snowmelt in early April, pH increased briefly until a second short pH depression event occurred in early May (Fig. 2), coincident with heavy rains. Snowfall during the winter of 1980-81 (284 and 268 cm at Sault Ste. Marie and Wawa, respectively; Environment Canada 1981, 1982a) approached annual averages for the area (306 and 278 cm, respectively, at the same stations; Environment Canada 1982b) for winters between 1951 and 1980.
427
SPRINGTIME STREAM pH DEPRESSIONS
TABLE 1. Locations, number of samplings (n), and ranges in pH and alkalinityfor Lake Superior tributaries sampled October 1980 to October 1981. Tributary Agawa River Alona Creek Barrett River Batchawana River Chippewa River Coldwater River East Baldhead River Goulais River Harmony River Magpie River Michipicoten River Montreal River Old Woman River Old Woman Tributary #1 Old Woman Tributary #2 Old Woman Tributary #3 Pancake River Sand River South Baldhead River Speckled Trout Creek Stokely Creek
Long. 47°21' 47°08' 47°24' 46°56' 46°56' 46°56' 47°28' 47°31' 46°44' 46°51' 47°55' 47°14' 47°46' 47°47' 47°46' 47°45' 46°58' 47°26' 47°36' 47°19' 46°49'
Alkalinity
wa
84°38' 84°42' 84°42' 84°32' 84°24' 84°24' 85°47' 84°48' 84°21' 84°22' 84°48' 84°39' 84°54' 84°53' 84°51' 84°49' 84°39' 84°44' 84°49' 84°36' 84°24'
n
pH
(mgj L as CaC03)b
14 16 17 10 12 17 17 II 12
5.77-7.32 6.64-7.60 5.00-6.76 6.50-7.48 6.85-7.57 5.74-7.25 5.98-6.90 6.82-7.40 6.16-7.24 7.21-8.05 6.92-7.52 6.81-7.28 6.54-7.44 6.57-7.12 6.54-7.42 6.25-6.81 6.65-7.25 5.57-7.30 5.71-7.17 5.09-7.20 6.76-7.54
0.69-20.12 5.25-27.24 -0.50-6.83 3.81-25.53 6.80-23.84 0.49-10.77 1.00-5.16 6.01-26.58 1.59-16.22 25.61-65.36 I I.l8-29.40 12.88-23.96 5.44-25.80 4.18-12.32 3.63-26. 17 2.56-21.53 5.64-17.61 0.33-11.65 0.95-18.09 -0.35-11.88 6.70-49.05
II
12 12 15 15 16 11 12 14 17 18 9
"at crossing of Highway 17 btotal inflection point alkalinity
In addition, based on personal observations, much of the accumulated snowpack was lost in a February thaw which resulted in some depression of stream pH (Fig. 2). Thus, the spring melt period of 1981 may not reflect worst-case conditions which would likely occur in years of maximum snowfall with a single period of rapid spring snowmelt. The potential impact of spring pH depression on fish populations in the waters studied is difficult to estimate because in situ fish responses to low pH are not well defined and laboratory toxicity results often show little agreement with findings in the field (Muniz and Leivestad 1980). Based on field observations, declines in natural salmonid populations seem to appear at about pH 5.0 to 5.5 (Haines 1981). A particularly important aspect to consider is the timing of reproductive activity in relation to observed pH depressions. Rainbow trout in general seem especially sensitive to acid stress (Grande et 01. 1978). However, because they are spring spawners with hatching and emergence usually occurring in late spring or early summer (Scott and Crossman 1973), the highly vulnerable (Schofield 1976, Harvey et 01. 1981) early life stages may not
occur in these tributaries until worst conditions, from a pH viewpoint, have passed. During the present study, pH minima occurred in early spring
7.0
SPECKLED TROUT ().
.d
- --
Q
" " \
6
tf
d
BARRETT - - -
~ 6.0
5.0
OCT
NOV
1980
DEC
JAN
f(8
IWl
APR
~AY
JUN
JUL
AUG
S!P
OCT
1981
FIG. 2. Temporal pH variation in Speckled Trout Creek and the Barrett River, October 1980 to October 1981.
428
W. KELLER
(April and early May). Brook trout are regarded as one of the salmonids more tolerant to low pH (Grande et al. 1978); however, due to behavior (i.e., fall spawning, hatching and alevin emergence in late winter! early spring) the most sensitive stages may coincide with worst-case water quality. Offspring of fall-spawning pacific salmon may be similarly susceptible. At present, adverse effects on fish have not been documented in the study area; however, data on these fish communities are scarce. Electroshocking surveys in late August 1982 did show that even the waters with the greatest observed pH depressions in this study (Speckled Trout Creek and the Barrett River) contained abundant young-of-the-year rainbow trout and coho salmon (M. Powell, Ontario Ministry of Natural Resources, personal communication).
CONCLUSIONS Sampling during 1980-81 demonstrated that at least some Lake Superior tributaries are subjected to substantial pH depressions coinciding with snowmelt and spring rains, similar to observations in south-eentral Ontario (Jeffries et al. 1979). Although adverse effects on fish populations in the study area have not been documented, concern over possible influences is warranted because these waters exhibit generally high sensitivity to acidic inputs and most constitute valuable fishery resources. The data provide a further indication that, as previously suggested by Harvey et al. (1981), the phenomenon of short-term surface water acidification may be widespread in geologically sensitive areas of Canada. They also suggest that fish populations, in areas of the Great Lakes not usually considered sensitive to inputs of acidic precipitation, could potentially be affected through acidification of tributaries.
ACKNOWLEDGMENTS I wish to thank P. Gale and M. Brideau for assistance in the field and laboratory, R. Labbe for help with the graphics, E. W. Piche, M. Powell, and N. Conroy for support, and N. D. Yan for encouragement. The comments of W. S. Gardner and an anonymous reviewer were greatly appreciated.
REFERENCES Environment Canada. 1981. Monthly records-meteorological observations in eastern Canada. Vol. 65, nos. 9- 12. Atmospheric Environment Service, Downsview, Ontario. _ _ _ _ . 1982a. Monthly records-meteorological observations in eastern Canada. Vol. 66, nos. 1-5. Atmospheric Environment Service, Downsview, Ontario. _ _ _ _ . 1982b. Canadian climate normals 19511980. Atmospheric Environment Service, Downsview, Ontario. Gjessing, E. T., Henriksen, A., Johannessen, M., and Wright, R. F. 1976. Effects of acid precipitation on freshwater chemistry. In Impact of acid precipitation on forest and freshwater ecosystems in Norway, ed. F. Braekke, pp. 64-85. SNSF Res. Rept. 6/76. Grande, M., Muniz, I. P., and Andersen, S. 1978. Relative tolerance of some salmonids to acid waters. Int. Assoc. Theor. Appl. Limnol. Proc. 20:2076-2084. Haines, T. 1981. Acidic precipitation and its consequences for aquatic ecosystems-a review. Trans. Am. Fish. Soc. 110:669-707. Harvey, H. H., Pierce, R. c., Dillon, P. J., Kramer, J. R., and Whelpdale, D. M. 1981. Acidification in the Canadian aquatic environment. Publication NRCC No. 18475. Environmental Secretariat. National Research Council of Canada, Ottawa, Ontario. Hultberg, H. 1977. Thermally stratified acid water in late winter-a key factor inducing self-accelerating processes which increase acidification. Water Air Soil Pollut. 7:279-294. Jeffries, D. S., Cox, C. M., and Dillon, P. J. 1979. Depression of pH in lakes and streams in central Ontario during snowmelt. J. Fish. Res. Board Can. 36:640-646. Kelso, J. R. M., Love, R. J., Lipsit, J. H., and Dermott, R. 1982. Chemical and biological status of headwater lakes in the Sault Ste. Marie District, Ontario. In Proc. Conf. on Acid precipitationeffects on ecological systems, ed. F. D'itri, pp. 165-207. Ann Arbor, Michigan. Kramer, J. R. 1977. Geochemical factors and terrain response to environmental contaminants. UnpubIished report, Department of Geology. McMaster University, Hamilton, Ontario. Muniz, I. P., and Leivestad, H. 1980. Acidificationeffects on freshwater fish. In Ecological impact of acid precipitation, ed. D. Drablos and A. Tollan, pp. 84-98. Proc. Int. Conf. Ecol. Impact of Acid Precipitation. Sandefjord, Norway. Scheider, W. A., Jeffries, D. S., and Dillon, P. J. 1979. Effects of acidic precipitation on Precambrian freshwaters in southern Ontario. J. Great Lakes Res. 5:45-51.
SPRINGTIME STREAM pH DEPRESSIONS Schofield, C. L. 1976. Acid precipitation: effects on fish. Ambio 5:228-230. _ _ _ _ . 1977. Acid snow-melt effects on water quality andfish survival in the Adirondack Mountains of New York. State Res. Proj. Techn. Compl. Rept.
429
Project A-072-NY. Cornell University, Ithaca, New York. Scott, W. B., and Crossman, E. J. 1973. Freshwater fishes of eastern Canada. Bull. 184 Fish. Res. Board Can., Ottawa, Ontario.