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1.
Ecological and toxicological data from field studies on acidic rivers of Nova Scotia were examined to review the effects of low pH on Atlantic salmon (Salmo salar) populations in waters rich in organic acids where noexchangeable forms of Al dominate at all times. There were no survival of salmon past the dry stage at pH <4.7, and survival rates for salmon from egg to smolt only increased at pH >4.9. Annual production of juvenile salmon and potential yield of smolts were lower at pH 4.7 to 5.4 than at pH 5.6 to 6.3 because of reduced densities attributable to the high mortality of fry at pH ≤5.0. However, acidity episodes to pH <4.7 also resulted in mortality of parr, reducing densities and often completely eliminating year-classes. The physiological responses of juvenile salmon to chronic acid conditions and to acute acidity typical of episodic events were also reviewed in relation to toxicity. Decreased in plasma Na and Cl were well correlated with ambient pH, but not with exchangeable Al concentrations in rivers. These plasma electrolytes provided reliable indicators of the thresholds for sublethal effects on ionoregulatory mechanisms. There was no morphological evidence of damage or lesions in gill epithelia, indicating that accumulation of Al in the gills of parr was not a significant factor in the lethal effects observed in acidic rivers. High organic matter content in the water apparently protected gills from adverse Al effects. Toxicity was considered to result from the effect of low ambient pH on branchial ionoregulatory mechanisms.  相似文献   

2.
An important consequence of acidification is the mobilization of Al from the edaphic to the aquatic environment. Elevated Al levels in acidic waters may be toxic to fish. Eggs, larvae, and postlarvae of white suckers (Catostomus commersoni) and brook trout (Salvelinus fontinalis) were exposed in laboratory bioassays to pH levels 4.2 to 5.6 and inorganic Al concentrations of 0 to 0.5 mg l?1. Aluminum toxicity varied with both pH and life history stage. At low pH levels (4.2 to 4.8), the presence of Al (up 0.2 mg l?1 for white suckers; 0.5 mg l?1 for brook trout) was beneficial to egg survival through the eyed stage. In contrast, Al concentrations of 0.1 mg l?1 (for white suckers) or 0.2 mg l?1 (for brook trout) and greater resulted in measurable reductions in survival and growth of larvae and postlarvae at all pH levels (4.2 to 5.6). Aluminum was most toxic in over-saturated solutions at pH levels 5.2 to 5.4. The simultaneous increase in Al concentration with elevated acidity must be considered to accurately assess the potential effect of acidification of surface waters on survival of fish populations.  相似文献   

3.
Southwestern Nova Scotia receives acidic precipitation (average pH 4.5 to 4.6), and there are many waterbodies that are susceptible to acidification. This study characterizes the physical and chemical features of three remote, oligotrophic lakes and their watersheds in this region, in order to provide baseline information against which assessments can be made of changes caused by atmospheric depositions. Two of the lakes are small (<0.5 km2) and on headwater watersheds: Beaverskin Lake has an almost completely forested watershed and is moderately acidic and clear (pH 5.3, 5 Hazen units), while the watershed of Pebbleloggitch Lake is about 2/3 forested and 1/3 covered by a Sphagnum-heath bog, and its water is very acidic and highly colored (pH 4.3, 87 Hazen units). Kejimkujik Lake is much larger, its watershed is mostly forested but also contains some boggy terrain, its water is intermediate in acidity and color (pH 4.9, 65 Hazen units), and because it drains a much larger area of watershed it has relatively large concentrations of Ca, Mg, Na, Cl, and SO4.  相似文献   

4.
Mature male and female rainbow trout were treated with low pH (Av. 4.5) sulfuric acid water for 1 or 2 weeks. Percentage of eyed embryos in eggs from control, 1-week-treated and 2-week-treated females were 100%, 80% and 0%, respectively. Low pH exposure of male trout induced 11% deformation in embryos fertilized with their sperm. In order to clarify the physiological mechanism of the effects of low pH exposure, sex hormone levels were compared. In female fish, plasma sex hormones levels showed no difference among the groups, but egg contents of 1720-dihydroxy-4-pregnen-3-one, which induces oocyte maturation, were significantly lower in low pH exposed groups. Acidified male fish showed higher plasma levels of the spermiation inducing hormone, 11-ketotestosterone. Effects on eggs were manifested under pH lower than 5. Under continual rearing of land-locked sockeye salmon in acid water, the effects on the oocyte were observed in those adult females which were exposed to acidic condition for more than 1 week before the timing of ovulation. These results suggest that low pH affects oocyte maturational events occurring just 1 week before ovulation, and that acid stress affects the endocrinological mechanisms of final maturation in fish gametocytes. Thus, acidification of the aquatic environment may reduce the reproductive activity of fish at rather low acidity levels.  相似文献   

5.
Duis  K. 《Water, air, and soil pollution》2001,132(3-4):373-388
Following abandonment of lignite mines, many acidic hardwaterlakes have formed in eastern Germany. Even after neutralisation,a risk of reacidification remains. In view of plans to use thepost-mining lakes for fisheries, acid tolerance of early life stages of tench, Tinca tinca, was determined using reconstituted post-mining lake water. Two experimental serieswere compared: A) incubation of the embryonic stages in Petri dishes and transfer of the larvae to aquaria, and B) incubationin aquaria throughout the experiment. All tench embryos exposedto pH 3.50–4.75 died prior to hatch. At pH 5.00, no (series B) or very few embryos (series A) hatched. The latter died shortly after hatching. At pH 5.50, the hatching percentage in series A did not differ significantly from that in the pH 7.40 control, whereas that in series B was reduced to halfof the control value. Transition to exogenous feeding was impaired in both series and mortality gradually increased.Consequently, overall survival at pH 5.50 only amounted to 4% in series A and 3% in series B. Reacidification to pH ≤ 5.50 would, thus, most probably pose a threat to earlylife stages of tench.  相似文献   

6.
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.  相似文献   

7.
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.  相似文献   

8.
Abstract

Crop growth in Oxisols is known to be limited by high soil acidity and low levels of basic cations. Five greenhouse experiments were conducted to evaluate the effects of soil pH on the growth and nutrient uptake of upland rice (Oryza sativa L.), wheat (Triticum aestivum L.), corn (Zea mays L.), common bean (Phaseolus vulgaris L.), and cowpea (Vigna unguiculata L. Walp.). Six levels of soil pH (4.1, 4.7, 5.3, 5.9, 6.6, and 7.0) were achieved by addition of various levels of CaCO3. Crop species responded differently to pH, reflecting the genetic diversity among species. Higher dry matter accumulation in roots and tops of rice, corn, and cowpea was observed at acidic pH ranges indicating that these species are tolerant to soil acidity. However, increasing soil pH enhanced dry matter accumulation in roots and tops of wheat and common bean, reflecting their intolerance to soil acidity. In all of the crop species, uptake of calcium (Ca) and magnesium (Mg) decreased with a decrease in soil pH. Overall uptake of zinc (Zn), manganese (Mn), and iron (Fe) in all species increase with a decrease in soil pH. Higher pH in an Oxisol might induce micronutrient deficiencies; therefore, one has to avoid overliming. In general, increasing soil pH decreased the uptake of nitrogen (N), phosphorus (P), and potassium (K) in rice, but uptake of these elements increased in wheat, corn, and common bean. In order to achieve the full genetic potential of any given species on an Oxisol, one needs to consider the species tolerance to soil acidity and its nutrient demand.  相似文献   

9.
Shenandoah National Park receives more atmospheric sulfate loading than any other USA national park. pH has been gradually declining in low-ANC streams for more than 10 years. We have completed four 1-to-3 month-long field bioassays in three streams differing in acid neutralizing capacity (ANC), using a total of 18,000 hatchery brook trout eyed-eggs through fry. In three of the four bioassays, embryos/fry showed poorer survivorship in the low-ANC stream, compared to the high-ANC stream. Substantial mortalities occurred under different hydrological conditions, including steady rain plus significant rain events (fall 1992), low rainfall followed by a significant rain event (spring 1993), and steady light rain and snowmelt with no large rain events (spring 1994). In a fourth bioassay (fall 1993), poor survivorship occurred in all three streams due to drought conditions. Trout placed in the intermediate-ANC stream showed variable survivorship, in two bioassays as high as in the high-ANC stream, and in one bioassay as poor as in the low-ANC stream. Baseflow ANC in the intermediate-ANC stream is 40–100 ueq/L, and pH never falls below 6.0. However, during episodes, pH in this stream sometimes fluctuates rapidly in the range of 6.0 to 7.0, and this fluctuation itself may be a source of physiological stress.  相似文献   

10.
Vegetation and soil acidity of a mangrove swamp in southeastern Nigeria   总被引：1，自引：0，他引：1  
Abstract. The relationships between vegetation and acid properties of soils from a mangrove swamp in southeastern Nigeria were examined. Field moist soils were moderately acidic with pH ranging from 5.3 to 6.8. Air dry pH ranged from 2.9 to 4.9 indicating strong acidity; the values increased with profile depth and were related to decreasing fibrous root content. Less acidic conditions (air dry pH 4.3–4.9) were associated with the less fibrous soils under Avicennia africana and Pandanus candelabrum ; more acidic conditions (air dry pH 2.9–3.8) occurred in the more fibrous Rhizophora spp. and Nypa fruticans soils. Species occurrences and levels of aluminium and sulphate in the profiles were related, suggesting that hydrogen ions, aluminium and sulphate were the main contributors to exchangeable acidity. Unless crops are known to tolerate very acidic conditions, the fibrous Rhizophora and Nypa soils should not be drained for cultivation.  相似文献   

11.
Results from surveys of low-ANC lakes (high elevation, and seepage lakes), and of surface waters in dystrophic, acidic bogs, indicate that acidic precipitation and organic acidity are each generally necessary, but not solely sufficient, for chronically acidic status in Maine lakes. Acidic, low DOC (ANC < 0; DOC < 5 mg L-1) lakes of all hydrologic types are acidic due largely to acidic deposition; high DOC (DOC > 30 mg L-1) acidic seepage lakes are acidic due largely to organic acidity, and high DOC drainage lakes are acidic due to a combination of both factors. No low DOC drainage lakes are known with pH less than about 5.0, suggesting that organic acidity is necessary to depress lake pH values to below 5 in Maine at current deposition loadings,The dominant anion of low DOC, acidic waters is sulfate. Acidic waters with intermediate concentrations of DOC (5 to 30 mg L-1), may be dominated by S04 and/or organic acidity. Seepage-input lakes were the only group to include both organically-dominated (37% of the acidic lakes) and S04-dominated members (63% of the acidic lakes). High DOC systems are typically low pH bogs, and are all organic acid-dominated.  相似文献   

12.
Surveys of fish populations were conducted on 74 lakes of the Outaouais hydrographic region during the summers of 1985 and 1986 to assess the potential impact of acidity on ichtyologic fauna. Results show that species diversity declined with the increasing acidity. The color of water does not seem to mitigate the adverse effects of acidity. On the contrary, the number of species decreased similarly in both brown lakess (>30 Hazen) and clear lakes (≤30 Hazen) with the increase of acidity. The species tolerance threshold levels to acidity show that 72% of fish species are no longer captured when pH reaches 5.0, compared to 32% at pH ≤5.5. The pH range 5.0 to 5.5 can possibly be regarded as the break point for the occurrence of most fish species in this area. Analysis of the size frequency distributions show that recruitment failures have occurred in acidic waters for walleye and lake trout. We have estimated that anthropogenic acidification is responsible for the loss of more than 10000 fish populations in the Outaouais area.  相似文献   

13.
During the latter decades extensive fish kills have been observed in the mountainous areas of southernmost Norway. These kills have been attributed to the increased acidity of the river-water. The increased acidity is generally assumed to be caused by acid precipitation. However, the relationship between precipitation and runoff quality is very complex. The present paper is concerned with the relationship between chemical composition of simulated rain and that of runoff from bare granitic rock, partly covered by lichens. When supplying simulated rain with a pH value of approximately 5 the very first runoff had pH values between 4.1 and 4.3. However, the pH in the runoff increased rapidly and leveled out at values between 4.6 and 4.7. When supplying simulated rain with pH approximately 3.5, the pH in the first runoff varied between 3.8 and 3.6. The pH then gradually decreased to the same values as those in the simulated rain. Runoff from ‘rain’ with pH 4.3, obtained the same pH value as that of the ‘rain’. The pH of the runoff was dependent not only on the rain acidity, but also on its content of neutral salts.  相似文献   

14.
The effects of low pH on upstream migratory behavior in land-locked sockeye salmon Oncorhynchus nerka were examined using 2-way flow-through channels. Homing mature salmon captured at the mouth of their native stream were used. When neutral (pH 6.7) hatchery water of the same origin as native stream water was allowed to flow through both channels, fish showed active swimming into both channels during a 48 hrs period. When water pH in one channel was lowered by the addition of sulfuric acid, salmon completely ceased upstream swimming behavior into areas of pH lower than 6.0, and swam up into only neutral areas. In the lower pond of the 2-way channels, fish also avoided acidic areas even when average pH was 6.2. Since it has been reported that extremely slight changes in pH such as in the pH 6 range inhibits spawning behavior in this species, it is suggested that land-locked sockeye salmon have a sensitive ability to perceive even slight acidity, and avoid environments which may be deleterious to their offspring.  相似文献   

15.
We studied the effects of acidification on female sexual behavior in brown trout (Salmo trutta) and compared the results with those in hime (land-locked sockeye) salmon (Oncorhynchus nerka) (Kitamura and Ikuta, 2000). The results were similar to those of sockeye salmon. Spawning brown trout were extremely sensitive to the acidity of ambient water, and nest-digging behavior was severely inhibited (p<0.05) by very slight acidification (pH below 6.4). However, there were some differences between the two species. Female trout and salmon showed almost no digging below pH 5.0 and 6.0 (Kitamura and Ikuta, 2000), respectively. When the ambient water was returned to nearly neutral (pH6.6) conditions, digging in hime salmon reappeared in 4 of the 6 fish tested (Kitamura and Ikuta, 2000), whereas digging in brown trout reappeared in all 6 fish tested. The above-mentioned differences in behavioral response between the two species appear to reflect the species difference in terms of vulnerability to acidification (Ikuta et al., 1992). Avoidance of slightly acidic water in selection of spawning site or cessation of spawning behavior in weakly acidic environments may be the most potent cause of the reduction of salmonid populations in the early stages of acidification.  相似文献   

16.
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, Ali = 240 μg L?1) and a limed control (pH = 5.70, Ali = 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.  相似文献   

17.
The hatchery environment often favours completely different traits than natural selection in the wild. Consequently, hatchery-reared fish are usually larger and more aggressive than their wild counterparts. Increased growth rate and aggression are predicted to be beneficial in feeding competition in hatcheries, but not necessarily in nature, where food resources are spatially and temporally more variable. We compared the growth, condition and mortality of landlocked Atlantic salmon (Salmo salar L.) juveniles in a common hatchery environment and when feeding on natural prey in semi-natural channels. We found that the growth and survival probability of the fish in the hatchery was negatively associated with their performance in the semi-natural channels. Furthermore, we found tendencies for directional selection (linear selection differential and gradient: P < 0.1, in both cases) against large body size in semi-natural channels, but not in the hatchery. Therefore, good performance during hatchery rearing may indicate reduced performance in food-limited natural conditions, where selection may favour smaller individuals that have a lower standard metabolic rate (higher growth efficiency). If our results are also valid in fully natural conditions, they suggest that selective stocking of the most successful hatchery phenotypes may not be an optimal strategy to conserve endangered natural salmonid populations.  相似文献   

18.
The headwater lakes in peat-rich areas in Finland commonly have high organic matter concentrations and are surrounded by soils and bedrock poor in bases. As a result the organic acid load on the watercourses is generally high. The significance of the organic vs anthropogenic acidity in 78 moderately acid lakes (pH range 4.3 to 7.1, TOC range 0.6 to 33.9 mg L?1) was evaluated in areas receiving different levels of acid deposition. The lakes were sampled during autumn overturn, and their water quality (mean TOC = 10.9 mg L?1, mean pH = 5.9) represents rather well the average water quality in small lakes in Finland. According to the correlation and regression analyses, TOC is a better predictor of pH than non-marine sulfate. Base cation concentrations are important in determining the sensitivity of the lakes to organic and anthropogenic acidity. The highest minerogenic acid contribution is found in high-deposition areas, while the percent organic acid contribution is greater in low deposition areas although TOC levels are comparable in both areas. It would appear that the pH of humic lakes is determined to a greater extent by individual watershed characteristics than by their geographical location at the present atmospheric loadings received in Finland.  相似文献   

19.
Lime (calcium oxide), animal manure and crop straw soil treatments have been shown to ameliorate soil acidity, yet their effectiveness at concurrently enhancing soil fertility status and improving crop yields is less well understood. In this study, an acidic nutrient deficient red soil (Ferralic Cambisol) received these treatments at various dosage rates (% of DW soil) in pot experiments with maize plants. Lime was applied at four dosage rates (0.05%, 0.10%, 0.15% and 0.20%), pig manure at three rates (0.50%, 1.00% and 1.50%), maize straw or milk vetch at two rates (0.50% and 1.00%) and combinations of lime (0.10% or 0.15%) with maize straw (0.50%) and/or pig manure (0.50%). Soils treated with and without chemical fertilizers were also included as controls. Measurements of soil pH, exchangeable acidity, plant available nutrients and maize shoot biomass were recorded. Maize shoot biomass increased by 4.7–7.6 times under pig manure treatments, 1.1–1.6 times under milk vetch, 0.4–1.5 times under lime and 1.1–6.2 times under combination treatments, compared with the control. Soil pH increased by 0.5–0.9 units under lime, by 0.2–0.4 units under pig manure and by 0.7 pH units under the combination treatment relative to the control. Variance partitioning analysis showed that on an individual basis, soil acidity amelioration (pH, exchangeable H+ and Al3+) or nutrient input (C, N, P, K, Ca, Mg, Zn) explained only 4.3% and 5.6% of improved maize growth, respectively. Whereas, their interaction explained 85.9% of the variation. We also report that the over-application of pig manure could lead to P saturation and negative impacts on aquatic systems in the wider environment. Therefore, we recommend a combination of lime, pig manure and straw provides an optimal solution for addressing soil acidity and limiting P saturation in acid soils.  相似文献   

20.
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.  相似文献   

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