Recovery of crustacean zooplankton communities from acidification in Killarney Park,Ontario, 1971-2000: pH 6 as a recovery goal

Despite reductions in atmospheric SO4(2-) deposition and resultant decreases in surface water acidity, widespread biological recovery from acidification has not yet been documented. Temporal trends in crustacean zooplankton species richness (number of species) and composition were examined between 1971-2000 in 46 Killarney Park lakes, Ontario, Canada, to assess the degree of biological recovery in lakes with significant water quality improvements, i.e. pH now > 6, compared to 2 other groups: i) lakes which never acidified; and ii) lakes which are still acidified (pH < 6). Time trends in species richness could not be distinguished among the 3 groups of lakes, nor did changes in species richness indicate recovery. In contrast, the zooplankton community composition of lakes in which the pH increased to above 6, as measured by a multivariate index of species abundances, changed from a "damaged" state to one typical of neutral lakes. Some recovery in composition was also documented for the acidic lakes. While still acidic, the pH levels of these lakes have risen. The extent and pace of recovery in Killarney Provincial Park bodes well for the future of other acidified regions in North America and Europe.     

Decreased acid deposition and the chemical recovery of Killarney,Ontario, lakes

Lakes in Killarney Park near Sudbury, Ontario, Canada, have shown dramatic water quality changes including general increases in pH and alkalinity, and decreases in SO4(2-), base cations and metals. While some lakes have recovered to pH > 6.0, many are still highly acidic despite decades of improvement. Very high historical S deposition related to emissions from the Sudbury metal smelters dominated the acidification process in this region. However, since the implementation of substantial S emission controls (90%) at the smelters, the Sudbury emissions are no longer the major source of S deposition in the Sudbury area. Wet deposition of SO4(2-) and SO4(2-) concentrations in lakewaters at Killarney now approach values in the Dorset, Ontario, area, about 200 km from Sudbury. This suggests that the S deposition to the Killarney area is now primarily from long-range transport, not from local sources. Studies of Killarney lakes are revealing the complex nature of the chemical recovery process. As lake acidity decreases, other changes including decreased Ca2+ concentrations, increased transparency, and altered thermal regimes may potentially affect some of these ecosystems. It is clear that continuing assessments of the recovery of Killarney lakes, within a multiple-stressor framework, are needed.     

Resilience of epilithic algal assemblages in atmospherically and experimentally acidified boreal lakes

Algal assemblages can be highly responsive to environmental changes in recovering acidified lakes. We compared epilithic algal assemblages in boreal lakes during chemical recovery from atmospheric (Killarney Park, Ontario) and experimental (Lake 302S, Experimental Lakes Area, Ontario) acidification to assess the impact of spatial and temporal scale of severe acidification on taxonomic resilience (i.e. recovery rate). Resilience was measured as the distance traveled by lakes in ordination space during pH recovery based on canonical correspondence analysis. Resilience was relatively negligible in the Killarney lakes, suggesting that eight years of experimental acidification in Lake 302S had less impact on biological recovery than did decades of regional acidification. Increases in dissolved organic carbon, dissolved inorganic carbon, and calcium best explained temporal variance of epilithic species abundances in the recovering acidified lakes. In Lake 302S, contrasting trajectories of taxonomic resilience and resistance, i.e. displacement from reference conditions following a perturbation, indicated that ecological factors affecting epilithon differed at corresponding pH levels during recovery and acidification. Our findings reveal that modeling of ecosystem recovery from severe acidification must account for the spatial and temporal scale of the perturbation, and biological delay responses that result in differences between recovery and acidification trajectories.     

Use of rehabilitation experiments to understand the recovery dynamics of acid-stressed fish populations

We used rehabilitation experiments involving the stocking of 2 native sportfish, lake trout (Salvelinus namaycush) and smallmouth bass (Micropterus dolomieu), in combination with recent fish community surveys, to study the recovery dynamics of fish populations in acid-stressed lakes near Sudbury and Killarney, Ontario, Canada. Population recovery rates differed between the 2 species. Introduced lake trout did poorly in species-rich lakes and exhibited slower growth, lower survival and delayed recruitment. Smallmouth bass, in contrast, readily colonized species-rich lakes. The biomass of natural smallmouth bass recruits increased to reference lake levels within 5 years following water quality recovery and spawning by stocked fish, whereas the biomass of natural lake trout recruits remained well below reference levels 5-15 years after water quality recovery and spawning by adults occurred. We document introductions by anglers of smallmouth bass into acid-damaged lake trout lakes, including some lakes that did not contain bass prior to acidification. This range expansion of a warm-water species (bass) that can alter food-web structure and reduce the growth of a cold-water species (trout), illustrates the potential for the combination of climate warming and species introductions to greatly alter the biological recovery endpoints in acid-stressed lakes.     

Dynamic modelling of recovery from acidification of lakes in Killarney Park,Ontario, Canada

During much of the 1900s, the lakes in Killarney Provincial Park have been exposed to high levels of acid deposition due to sulfur emissions from the nearby metal smelters in Sudbury. The sulfur emissions from this large point source have decreased to about 10% of what they were in the 1960s. Lake water quality in Killarney Park has greatly changed in response to reduced emissions, with noticeable declines in sulfate, aluminum and calcium concentrations. Here we apply the dynamic acidification model MAGIC to 3 lakes in Killarney Park. The lakes, which have different buffering capacities and response times, were selected to represent fast, intermediate and slow recovery from acidification. The model was calibrated to match observed data for the lakes and 4 different forecast scenarios for future sulfur deposition reductions were applied. The results indicate that there is still a large potential for improvement in the water quality in Killarney. The recovery time for the different lakes varies greatly. For the lake having the slowest response time several decades are needed for the chemistry to stabilize after implementation of deposition reductions.     

Assessing the recovery of lakes in southeastern Canada from the effects of acidic deposition

Reductions in North American sulfur dioxide (SO2) emissions promoted expectations that aquatic ecosystems in southeastern Canada would soon recover from acidification. Only lakes located near smelters that have dramatically reduced emissions approach this expectation. Lakes in the Atlantic provinces, Quebec and Ontario affected only by long-range sources show a general decline in sulfate (SO4(2-)) concentrations, but with a relatively smaller compensating increase in pH or alkalinity. Several factors may contribute to the constrained (or most likely delayed) acidity response: declining base cation concentrations, drought-induced mobilization of SO4(2-), damaged internal alkalinity generation mechanisms, and perhaps increasing nitrate or organic anion levels. Monitoring to detect biological recovery in southeastern Canada is extremely limited, but where it occurs, there is little evidence of recovery outside of the Sudbury/Killarney area. Both the occurrence of Atlantic salmon in Nova Scotia rivers and the breeding success of Common Loons in Ontario lakes are in fact declining although factors beyond acidification also play a role. Chemical and biological models predict that much greater SO2 emission reductions than those presently required by legislation will be needed to promote widespread chemical and latterly, biological recovery. It may be unrealistic to expect that pre-industrial chemical and biological conditions can ever be reestablished in many lakes of southeastern Canada.     

Recolonization of acid-damaged lakes by the benthic invertebrates Stenacron interpunctatum,Stenonema femoratum and Hyalella azteca

The recolonization of acid-damaged lakes in Killarney Park, Canada is described for 3 species of benthic invertebrates; 2 mayflies (Stenonema femoratum, Stenacron interpunctatum) and an amphipod (Hyalella azteca). Synoptic surveys of 119 lakes for amphipods and 77 lakes for mayflies were conducted between 1995 and 1997 and defined pH thresholds of 5.6 for S. femoratum and H. azteca and pH 5.3 for S. interpunctatum. In an intensive study of 2 acid-damaged lakes and 2 reference lakes from 1997 to 2002, reestablishment of S. interpunctatum, S. femoratum and H. azteca occurred, when timing of the events could be estimated, less than 4-8 years after pH thresholds for specific taxa were reached. Dispersal of S. interpunctatum to all habitat patches within a lake was completed 3 years after recolonization was detected in the smallest lake (11 ha). It is anticipated that dispersal throughout the largest lake (189 ha) will take much longer. The time lag from estimated pH recovery to reestablishment and subsequent dispersal of mayflies to all suitable habitats within a lake was as much as 11 to 22+ years. The density of S. interpunctatum increased in the recovering lakes to levels higher than in reference lakes, but stable endpoints have not yet been reached during 6 years of monitoring.     

Littoral microcrustacean (Cladocera and Copepoda) indicators of acidification in Canadian Shield lakes

We identify littoral microcrustacean indicators of acidification in 2 surveys of Canadian Shield lakes conducted 10 years apart. We found a total of 90 cladoceran and copepod species with richness increasing severalfold from acidic to nonacidic lakes. The fauna of the nonacidic lakes differed between the surveys. The 1987 survey employed activity traps, and caught more littoral taxa than the more recent, net-haul-based survey. Similar faunas were identified in the acidified lakes in both surveys, and several good indicator species were identified. For example, Acanthocycops vernalis was restricted to lakes with pH < 6. Sinobosmina sp. was very common but only in lakes with pH > 4.8. Tropocyclops extensus, Mesocyclops edax, and Sida crystallina were commonly found but only at pH > 5, and Chydorus faviformis only at pH > 5.9. These indicators showed promise in gauging the early stages of recovery from acidification in 3 lakes that were included in both surveys.     

Contemporary (1979-1988) and inferred historical status of headwater lakes in North Central Ontario, Canada

Fifty-six headwater Canadian Shield lakes were repetitively sampled from 1979 to 88 to determine their response to changes in acidic deposition of the period. Annual wet sulphate loadings varied between 38 and 83 meq m(-2), with highest deposition in the late 1970s followed by somewhat lower but variable deposition in the 1980s. Median pH of the lakes increased 0.42 pH units from 1979 to 1985 and decreased by 0.15 units between 1985 and 1988. Short water renewal times (x=1.1 y) promoted rapid equilibration. Since lake were so responsive to changes in SO4(2-) inputs, they were at or near steady state at all times. Comparison of predicted original pH and ANC with 1979 data indicate a median decline of 0.45 pH units and a loss of 34 microeq litre(-1). ANC. Four of 9 lakes were found to be historically fishless, based on the continued presence of Chaoborus americanus in sediment cores. The remaining five lakes historically had fish populations, but fish were not collected in 1979 when pH ranged betwen 4.6 and 5.3. By 1987, fish species were found in five of these lakes where pH had increased on average by 0.9 pH units. Our data indicate that water quality improvements could allow for the reinvasion or resumption of recruitment for a significant number of Ontario lakes.     

Anthropogenic oligotrophication via liming: Long-term phosphorus trends in acidified,limed, and neutral reference lakes in Sweden

Restoration of acidified lakes by liming does not, in many cases, improve productivity to a pre-acidified state. We hypothesize that the poor recovery detected in many of these lakes is due to constrained in-lake phosphorous (P) cycling caused by enhanced precipitation of metals in higher pH, limed waters. Long-term (1990–2012) data for 65 limed, circum-neutral (pH 6–8), and acidified lakes in Sweden were analyzed to determine trends for P and potential drivers of these trends. Limed lakes not only had lower mean values and stronger decreasing trends for total P than non-limed lakes, but they also had the highest percentage of decreasing trends (85 %). A P release factor (Hypolimnetic P/Epilimnetic P) was developed to elucidate differences in internal P cycling between lake groups. Consistently, lower P release factors in limed lakes show limitation of internal P cycling during summer months that may be a factor limiting P bioavailability and thus productivity of these systems.     

Challenges in assessing biological recovery from acidification in Swedish lakes

Since the 1980s, Swedish lakes have in general become less acidified. Assessment of biological recovery is, however, hampered by poor pre-acidification data, confounding effects of climate change, and few lakes with annual sampling of fish and other organisms. Only three critically acidified, but non-limed, lakes had two decades of fish monitoring. The lakes had not yet recovered to pre-industrial chemical targets. Fish had low species richness compared to other organism groups. Roach (Rutilus rutilus) and/or European perch (Perca fluviatilis) were the dominant fish species, and the acid-sensitive roach had been lost from one of the lakes. Calcium decreased, possibly approaching pre-acidification concentrations, but exceeded minimum levels needed to sustain some Daphnia species. High or increasing levels of total organic carbon, likely due to reduced acidification and climate change, might influence the biological communities in unexpected ways, for example, facilitating more frequent occurrence of the invasive algae Gonyostomum semen.     

Effects of experimental acidification on mobilisation of metals from sediments of limed and non-limed lakes

In order to study the influence of pH on the mobilisation of metals from lake sediments, intact sediment cores with overlying water were sampled from one lime treated lake and one acidified lake. The overlying water of two cores from each lake was successively acidified to pH 4.2 over a period of 3 months. In the acid treated samples from the limed lake, the initial concentrations of Al, Cd, Mn, Pb and Zn in the overlying water were generally lower and the final concentrations were higher than in the acid treated samples from the acidified lake. The labile inorganic fraction of Al (Al(i)) was increasingly dominating as pH decreased. Redox potential and pH in the sediment indicated that the upper two centimetres were involved in the exchange reactions. The experiment showed that mobilisation of metals from sediments can occur and the results indicated that mobilisation could contribute to increased concentrations of metals in lake water during reacidification of formerly lime treated lakes.     

Biomass and production of amphipods in low alkalinity lakes affected by acid precipitation

Population biomass and production of the amphipod Hyalella azteca (Saussure) were found to be related to alkalinity (ranging from 0.2 to 58.1 mg liter(-1)) in 10 Canadian Shield lakes in south-central Ontario. Biomass and production of amphipods in the two lakes characterized by spring depressions of pH below 5.0 were found to be lower than those for populations inhabiting lakes that did not experience such acid pulses. The proportional biomass of amphipods in relation to the total littoral zoobenthos community was lower in lakes of low alkalinity than in circumneutral or hardwater lakes. Because production in these amphipod populations is known to depend closely on population abundance, the labour-intensive derivation of production rates yields relatively little information for biomonitoring that cannot be obtained from abundance data alone.     

Acid and aluminum effects on freshwater zooplankton: an in situ Mesocosm study

An in situ mesocosm experiment was performed to evaluate the role of aluminum toxicity in determining zooplankton community responses to take acidification. Large plastic enclosures were suspended in East Twin Lake, Ohio, USA, and duplicates were either untreated controls (pH 8.8), acidified to pH 4.5 over a 23 day period, or acidified and also spiked with incremental additions of Al, to produce a final inorganic monomeric Al level of 180 microg/liter at pH 4.5. Zooplankton abundance and species richness declined in both acid treatments, relative to the control, as numerous acid-sensitive species were eliminated. All of the acid-sensitive species were also Al-sensitive, declining in abundance more rapidly in the acid plus Al treatment than in the acid-alone treatment. Only two small cladocerans (Bosmina longirostris and Chydorus sphaericus) were acid tolerant. Both were also tolerant of elevated Al levels.     

Towards a model of acidification effects on waterfowl in Eastern Canada

Data from 212 lakes in central Ontario were used to examine the relationship between presence of breeding waterfowl and loons and the following lake characteristics: pH, presence of fish, lake area, dissolved organic carbon (DOC) and total phosphorus (TP) concentration. In univariate analyses, the two fish-eating species preferred large, high pH lakes with fish, while insectivorous species showed little consistent pattern of lake association. Logistic regression analyses confirmed that large lake size and presence of fish were important determinants of presence of piscivores, though the residual effect of pH differed between the two species. Broods of three of the four insectivorous species avoided lakes with fish, and independently showed a positive response to pH. By calculating the probability that fish will be present on a lake of given area and pH, it is possible to estimate the net effect of pH change on these waterfowl. Relationships such as those presented here can, with some assumptions, be linked to models of lake acidification to estimate response of waterfowl to predicted changes in acidic deposition.     

Factors affecting trace-metal bioaccumulation in Finnish headwater lakes

Fourteen unpolluted Finnish headwater lakes with pH values varying from 4.8 to 7.0 were studied for trace-metal concentrations in water, sediment, aquatic plants (Nuphar luteum L., Sparganium sp.), aquatic insect larvae (Limnophilus sp., Phryganea sp.) and fish (Esox lucius L., Perca fluviatilis L., Coregonus sp., Salvelinus fontinalis L., Salmo trutta L.). Trace-metal deposition was estimated by analysing the snowpack. Non-parametric correlation analysis was carried out between trace metal concentrations in biota and pH, ANC, TOC, CA + Mg concentration in water and a given metal concentration in water and sediment. Bioaccumulation of several trace metals increased with increasing acidity and decreasing ANC in water. This was especially true for Pb and Cd. Aquatic plants were, in general, the best indicator group concerning differences in trace-metal bioaccumulation in lakes with different acidity. There was some evidence that a higher concentration of TOC in water may reduce bioaccumulation of Pb, Cd and Zn in aquatic plants and fish. The copper concentration in sediment was the only background variable explaining Cu concentration in aquatic insects. Multivariate analysis of the whole background data gave comparable preliminary results. Over 80% of the trace metal concentrations in biota of different lakes was explained by the background variables. In general, elevated concentrations of most of these trace metals can be expected to occur in the biota of acidified low calcareous lakes.     

Effects of reduced nitrogen and sulphur deposition on the water chemistry of moorland pools

To assess changes as a result of reduced acidifying deposition, water chemistry data from 68 Dutch moorland pools were collected during the periods 1983-1984 and 2000-2006. Partial recovery was observed: nitrate- and ammonium-N, sulphur and aluminium concentrations decreased, while pH and alkalinity increased. Calcium and magnesium concentrations decreased. These trends were supported by long term monitoring data (1978-2006) of four pools. Increased pH correlated with increases in ortho-phosphate and turbidity, the latter due to stronger coloration by organic acids. Increased ortho-phosphate and turbidity are probably the result of stronger decomposition of organic sediments due to decreased acidification and may hamper full recovery of moorland pool communities. In addition to meeting emission targets for NO_x, NH_x and SO_x, restoration measures are still required to facilitate and accelerate recovery of acidified moorland pools.     

Environmental effects of one thousand years of copper production at Falun, central Sweden

Copper production in Falun, central Sweden, has emitted sulfur dioxide (SO2) and metals to the air during at least 1000 years. Emissions peaked in the 17th century when Falun produced 2/3 of the world's copper supply. This area offers unique opportunities to study long-term effects of acid deposition and metal pollution, including recovery following the three centuries of decreasing SO2 and metal deposition. Here we present a 1000-yr perspective on local emissions of SO2, estimated air concentrations and dry deposition of SO2, as well as results on acidification and metal pollution of soils and lakes. Despite a long period when deposition of SO2 exceeded the critical load, soil acidification is limited to the most heavily polluted area 12 km NW and SE from the mine. According to diatom analyses of take sediments, only 8 of 14 lakes have become acidified (0.4-0.8 pH units). None of these lakes show recovery from acidification, probably due to large amounts of sulfate still accumulated in the soils and changes in land use.     

Effects of pH on the toxicity of cadmium, copper, lead and zinc to Folsomia candida Willem, 1902 (Collembola) in a standard laboratory test system

EC₅₀s for cadmium, copper, lead and zinc were determined for juvenile production of Folsomia candida at pH6.0, 5.0 and 4.5 in a standard laboratory test system. In contrast to most previous studies where metal toxicity was increased at low pHs, in our experiments there was no clear relationship between soil acidity and EC_{50-reproduction} in this species. The EC_{50-reproduction} values (μg g⁻¹) for cadmium and zinc were similar at all three pHs (pH6.0: Cd 590, Zn 900; pH5.0: Cd 780, Zn 600; pH4.5: Cd 480, Zn 590). In contaminated field sites adjacent to primary zinc smelters, zinc is invariably present in soils at concentrations of at least 50 times that of cadmium Thus deleterious effects of mixtures of these metals on populations of Collembola in such sites can be attributed to zinc rather than cadmium.     

Lethal effects on different marine organisms, associated with sediment�Cseawater acidification deriving from CO2 leakage

CO(2) leakages during carbon capture and storage in sub-seabed geological structures could produce potential impacts on the marine environment. To study lethal effects on marine organisms attributable to CO(2) seawater acidification, a bubbling CO(2) system was designed enabling a battery of different tests to be conducted, under laboratory conditions, employing various pH treatments (8.0, 7.5, 7.0, 6.5, 6.0, and 5.5). Assays were performed of three exposure routes (seawater, whole sediment, and sediment elutriate). Individuals of the clam (Ruditapes philippinarum) and early-life stages of the gilthead seabream, Sparus aurata, were exposed for 10?days and 72?h, respectively, to acidified clean seawater. S. aurata larvae were also exposed to acidified elutriate samples, and polychaete organisms of the specie Hediste diversicolor and clams R. philippinarum were also exposed for 10?days to estuarine whole sediment. In the fish larvae elutriate test, 100?% mortality was recorded at pH?6.0, after 48?h of exposure. Similar results were obtained in the clam sediment exposure test. In the other organisms, significant mortality (p?相似文献