Acidification and the structure of crustacean zooplankton in mountain lakes: The Tatra Mountains (Slovakia,Poland)

Species composition of planktonic Crustacea in 102 lakes in the West and High Tatra Mountains, studied during the peak of anthropogenic acidification (1978–1996), is presented in this work. Zooplankton of the Tatra lakes have been studied since the middle of the 19^th century, which later enabled the recognition of lake acidification and the assessment of its effect on the plankton community of lake ecosystems. In the pre-acidification period, the distribution of zooplankton was determined namely by the lake altitude and orientation (north vs. south) and by the catchment character. Crustacean zooplankton in larger lakes consisted of a limited number of species, with Acanthodiaptomus denticornis and Daphnia longispina dominating lakes in the forest zone, and Arctodiaptomus alpinus, Cyclops abyssorum, Daphnia longispina, Daphnia pulicaria, and Holopedium gibberum dominating lakes in the alpine zone. Ceriodaphnia quadrangula, Daphnia obtusa, Daphnia pulex, and Mixodiaptomus tatricus occurred in lakes with high concentrations of dissolved organic matter and in strongly acidified waters. Anthropogenic acidification has caused drastic changes in both the chemistry and biology of the Tatra lakes. Based on their status during the acidification peak, lakes were divided into three categories: non-acidified (with no change in the species composition of crustacean zooplankton due to the acidification), acidified (planktonic Crustacea disappeared in lakes with meadow-rocky catchments), and strongly acidified lakes where original Crustacea in meadow-rocky catchment lakes disappeared and were replaced by populations of the acid-tolerant littoral species Acanthocyclops vernalis, Chydorus sphaericus, and Eucyclops serrulatus. The acidification-induced processes of oligotrophication and toxicity of aluminium played a key role in the extinction of species. Despite the first signs of biological recovery observed in the early 2000s, acidification remains the most important factor governing the structure of plankton in the Tatra lakes.     

Littoral benthic macroinvertebrates of mountain lakes in the Tatra Mountains (Slovakia,Poland)

Littoral benthic macroinvertebrates of 45 mountain lakes in the Tatra Mountains were sampled using a semi-quantitative method in September 2000. A total of 32,852 specimens were identified to 93 taxa belonging to 14 higher taxonomic groups. Multivariate statistics (CCA, RDA) and nine biotic metrics (AQEM/STAR) were used to explain relationships between macroinvertebrate assemblages and environmental variables. Up to 57% of the ecological position of littoral macroinvertebrate assemblages were explained by variance of environmental variables divided into chemical, trophic, physical, catchment and location. Five types of Tatra lakes were recognized using CCA: A — strongly acidified lakes (small catchment, low pH, high concentration of TP, DOC, highest amount of POM in littoral); B — alpine acidified lakes (low amount of POM, low values of biotic metrics); C — alpine non-acidified lakes (high value of diversity index, predominance of Diptera); D — subalpine acidified lakes (high values of biotic metrics: number of families, proportion of crenal and rhithral taxa/total taxa); E — subalpine non-acidified lakes (high values of biotic metrics: number of families, number of genera, BMWP score, number of taxa and abundance of EPT taxa). RDA was used to design five levels of macroinvertebrate taxa acidification tolerance. The Tatra Acidification Index (TAI) was established to assess the acidification status of the lakes in the Tatra Mts.     

Epilithic diatoms of mountain lakes of the Tatra Mountains (Slovakia)

In the framework of the international project EMERGE, species composition of epilithic diatoms of 34 selected high mountain lakes of Slovak part of the Tatra Mountains were investigated. In all, 127 taxa of diatoms belonging to 26 genera were recorded. Comparison of the epilithic assemblages of the investigated lakes showed differences both in relative abundance and taxa present in the individual lakes. On the basis of species composition and relative abundance of epilithic diatoms using hierarchical cluster analysis, two main groups of lakes were created. The first group includes 4 lakes which can be classified as strongly acidified and 9 lakes which are acidified or threatened by acidification. In this group, acidophilous species such as Achnanthes helvetica, A. marginulata, Aulacoseira distans and Tabellaria flocculosa prevailed. The second group includes 19 non-acidified lakes. The most common diatoms in these lakes were Achnanthes minutissima, A. helvetica, Cymbella minuta and Denticula tenuis which occur practically in all these lakes but with different abundances. The division of lakes due to their diatom species composition mostly confirmed the status of these lakes as judged from their water chemistry.     

How many fish populations in Finland are affected by acid precipitation?

Synopsis The number of fish populations affected or lost from small lakes in southern and central Finland due to acid precipitation is estimated. Tolerance limits (pH and labile aluminum) of common fish species were obtained from a fish status survey of 80 lakes. These tolerance values were used to estimate the proportion of affected lakes from the water chemistry data of 783 statistically selected lakes. The proportion of anthropogenically acidified lakes was estimated by calculating pre-acidification pH and aluminum concentrations of the lakes, using a steady-state model based on water chemistry. The number of fish populations for which acidification has affected growth or population structure was estimated at between 2200 and 4400. Out of these, the number of fish populations that have disappeared due to acid precipitation would be about 1000–2000. Almost 60% of the affected or lost populations are roach, Rutilus rutilus, the most sensitive of the common fish species in small lakes in southern and central Finland. Less than 15% of the damaged population is European perch, Perca fluviatilis, the most common species. This is due to the substantially higher tolerance of perch to acidified water in comparison with roach.     

Macrozoobenthos of two different catchment areas of the tatra mountain lakes with a special reference on the effects of acidification

The structure of macrozoobenthos of two different high-mountain Tatra lakes, namely Starolesnianske pleso (strongly acidified) and Ni?né Terianske pleso (reference site) is described. The latter is characterised by a large catchment and total area, and is relatively deep with strong inlet and outlet. It is not affected by acidification. Univoltine species of mayflies, stoneflies and caddisflies dominate in the littoral, mainly scrapers. Predators are represented by stoneflies. Shredders dominate in the lake outlet. From the zoogeographic point of view, Carpathian endemites and Central European species prevail. Forty percent of species are sensitive to acidification. The former has a smaller catchment and total area, and is relatively shallow, without inlet. It is strongly affected by acidification. Semivoltine species, mainly predators (beetles) and shredders prevail. From the zoogeographic point of view Palaearctic species dominate. Species sensitive to acidification are missing. Emergence of water insects has two peaks during spring and fall circulation.     

Subfossil chironomids (Diptera,Chironomidae) in three Tatra Mountain lakes (Slovakia) on an acidification gradient

Three lakes were studied in the High Tatra Mountains at altitudes from 2000 to 2157 m a.s.l., which represent three categories of acidity status recognised in the Tatra lakes in the 1980s: non-acidified, acidified, and strongly acidified. Subfossil chironomid remains from dated sediment cores covering ca. throughout 200 years were analysed. The chironomid thanatocoenoses of all cores layers reflected ultra-oligotrophic non-acidified conditions in L’adové pleso. Nevertheless, the finding of the acid-tolerant species Zalutschia tatrica in littoral samples in 1980s indicates that the littoral zone was more influenced by acidification than deeper areas of the lake. Three stages of lake developmental history can be distinguished in the acidified lake Vy?né Wahlenbergovo pleso based on the chironomid subfossil record: the pre-acidification stage before the 1920s, the anthropogenic acidification stage between the 1920–1980s, and the recovery of the lake from the end of the 1980s. The period of acidification was accompanied by a decline in chironomid numbers, while chironomid fauna composition was unchanged during the whole investigated history of the lake. None of the chironomid taxa present prior to the acidification period disappeared during the peak of acidification. The most apparent change in the sediment record taken from the strongly acidified lake Starolesnianske pleso was recognised in the layers corresponding to the period 1960–1980. It is characterised by the disappearance of the dominant acid-sensitive Tanytarsus lugens group and the dominance of acidtolerant Tanytarsus gregarius group. The most recent chironomid assemblage probably benefits from the amount of food resources as a result of increased lake productivity induced by acidification.     

Benthic macroinvertebrate fauna of two alpine lakes over the last century: The value of historical data for interpreting environmental changes

Data on benthic macroinvertebrate assemblages of two alpine lakes in the Tatra Mts (Slovakia) collected in 1914, 1933, 1979–1982, 1993–1997, and 2000 were collated and analysed in an attempt to define their relationship to major environmental events affecting these alpine lakes over the last century. The oldest data were considered an important background before the onset of acidification in one of the lakes in the 1950s, while the most current contain possible information on biological recovery. Results show that data from the 1910s are insufficient to characterize the macroinvertebrate fauna. Deep zone assemblages of both studied lakes have remained stable since the 1930s. Changes in the density of dominant species over time were found in the acidified lake, suggesting a connection between an increase in phosphorus and chlorophyll-a concentration. The composition of the littoral assemblages in the acidified lake in the 1930s indicates that the lake was not strongly acidified at that time. A stable composition since the 1980s reflects the ongoing acid stress. Incomplete species data on the non-acidified lake did not allow us to detect possible changes in the littoral fauna related to acidification. Single findings of species indicating a recovery process need longer-term data to confirm such a trend. Results from this study suggest that historical datasets consist of valuable information that can supplement palaeolimnological analyses in the reconstruction of lake ontogeny.     

Classification of the Tatra Mountain lakes (Slovakia) using chironomids (Diptera,Chironomidae)

Chironomid assemblages in thirty-three mountain lakes situated above tree line in the Slovakian part of the Tatra Mountains were studied during 2000–2002. Chironomid species/taxa, collected as pupal exuviae, were correlated with physical, chemical, and lake morphometry variables of 22 lakes. Two-way indicator species analysis (TWINSPAN) was used to classify the lakes into four distinct groups: higher situated alpine lakes, lower situated alpine lakes, subalpine lakes and acidified lakes. Presence/absence of eight taxa was identified as indicative for this classification. In discriminant function analysis, pH, dissolved organic carbon, altitude and lake area were the most significant variables reflecting differences among groups of lakes. This model of four variables allowed 77% success in the prediction of group membership. A multiple regression model with lake area, concentration of magnesium and total phosphorus accounted for 37% of the variance in taxa richness. Lakes with greater area contained more chironomid taxa than smaller ones. Lakes with higher alkalinity and higher trophic status tend to support more taxa. Canonical correspondence analysis (CCA) indicated that most variation in the composition of chironomid assemblages was related to pH and to altitude. The results can be used as reference data for long-term monitoring of the Tatra lakes, especially in connection with a recovery from acidification and global climatic change.     

Humic substances: remediation option for anthropogenically acidified waterways

The acidification of waterways through anthropogenic means is a global problem. Treatment options for anthropogenically acidified waterways are currently limited. This review proposes the use of humic substance (HS) to treat waterways acidified via anthropogenic means such as those affected by acid rain, acid mine drainage and acid sulphate soils. In laboratory settings, HS have been shown to successfully remove metals from solutions. HS also have the added benefit of being present in all natural waters and have been shown to positively influence aquatic organism’s survival to acidification, metals and the combined stressors of low pH and metal mixtures commonly associated with anthropogenically acidified waters. Comparative food webs of waterways affected by natural and anthropogenic acidification are provided along with a third conceptual food web showing the potential benefits of adding HS to an affected system. HS may represent a sustainable remediation option as it may be locally sourced from environmentally friendly options such as green waste. However, if such options are to be fully developed and utilised, the specific requirements for treating anthropogenically acidified waters with different HS sources (e.g. treatment volumes and efficacy) will require further study.     

Studies on zooplankton in two acidified high mountain lakes in the Alps

Being located in remote areas, alpine lakes are good indicators of regional and global pollution, and are particularly sensitive to atmospheric depositions. When situated in areas where acidic rocks dominate, they are sensitive to acidification. In the framework of an international project partially funded by the EU, a two-year study on zooplankton was carried out on two lakes, Lake Paione Inferiore (LPI) and Lake Paione Superiore (LPS), selected because of their susceptibility to acidification. In particular, LPS is permanently acidified, with pH ranging between 5.3 and 6.2, and LPI is acidified during the ice melt, when pH drops to 6.1 units. In addition, LPI is subjected to further anthropogenic interference, since fish (Onchorynchus mykiss) have been repeatedly introduced into the lake during the last thirty years. Literature information is available on the species composition and the seasonal dynamics of the zooplankton communities of the two lakes before these anthropogenic disturbances took place. Previously, the two lakes had a similar species composition and abundant zooplankton. An analysis of the present-day situation reveals significant changes compared to the past. Both acidification and the introduction of fish are responsible for the marked alterations observed. By reconstructing of the past cladocera assemblages and by analysing the literature on lakes with different impacts of the two factors (pH and fish), we can estimate the relative importance of the two different anthropogenic disturbances on species composition and abundance of the zooplankton communities of the two lakes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Are Chaoborus larvae more abundant in acidified than in non-acidified lakes in Central Canada?

Eriksson et al (1980) hypothesized that the abundance of certain macroinvertebrate predators, such as larvae of the phantom midge Chaoborus , should increase in acidified lakes because of the elimination of fish. To examine the influence of pH and presence of fish on Chaoborus abundance, we surveyed Chaoborus populations in 33 lakes in Ontario, Canada which ranged in pH from 4.5 to 7.4. Chaoborus larvae were not more abundant in the acidified lakes that were devoid of fish than in the remaining lakes. Therefore, we concluded that pH and presence of fish are not prime determinants of total Chaoborus abundance in Canadian Shield lakes. We hypothesized that significant increases in Chaoborus abundance should only be anticipated when fish populations are eliminated by acidification of relatively nutrient rich lakes.     

Chlorophyll-phosphorus relationship in acidified lakes of the High Tatra Mountains (Slovakia)

Concentrations of total phosphorus (TP) and chlorophyll a (CHLA) were measured in 28 lakes in the High Tatra Mountains (Slovakia) from 1983 to 1990. The relationship between log CHLA and log TP in the Tatra lakes is similar to relationships developed for lakes in other regions, but variation is higher. A part of this variation is caused by acidification of the lakes. In the lakes with pH between 4.9 and 6.3 the CHLA concentrations are often extremely low while TP concentrations decreased, but not as drastically.     

Restructuring of Fish Assemblages in Swedish Lakes Following Amelioration of Acid Stress through Liming

A large-scale liming program was initiated in Sweden in the mid-1970s to ameliorate the effects of acidification and to restore acidified lakes and rivers to conditions present before acidification. I compared the fish fauna composition and biomass among limed, acidified, and consistently circumneutral lakes. The study focused on (1) recolonization and fish assemblage development and (2) fish biomass and assemblage composition. Time-series data from 14 limed, 5 acid, and 10 circumneutral lakes, and a data set of 323 limed and 346 nonlimed circumneutral lakes, are analyzed. Long-term monitoring revealed that fish species richness increased after liming and was of the same magnitude in limed lakes as in nonlimed circumneutral lakes after 10–20 years. Species proportions differed between limed and nonlimed lakes, and the relative biomass of Perca fluviatilis (Eurasian perch) was in general higher, whereas cyprinid and pelagic species were less important in the limed lakes than in the nonlimed circumneutral lakes. Recolonization of fish species was found to be a crucial factor for the development of the fish assemblages after liming, and in several limed lakes the reintroduction of fish species has accelerated the recovery of pre-acidification fish assemblages.     

Biological recovery of the Bohemian Forest lakes from acidification

A limnological survey of eight small, atmospherically acidified, forested glacial lakes in the Bohemian Forest (?umava, Böhmerwald) was performed in September 2003. Water chemistry of the tributaries and surface layer of each lake was determined, as well as species composition and biomass of the plankton along the water column, and littoral macrozoobenthos to assess the present status of the lakes. The progress in chemical reversal and biological recovery from acid stress was evaluated by comparing the current status of the lakes with results of a survey four years ago (1999) and former acidification data since the early 1990s. Both the current chemical lake status and the pelagic food web structure reflected the acidity of the tributaries and their aluminium (Al) and phosphorus (P) concentrations. One mesotrophic (Ple?né jezero) and three oligotrophic lakes (?erné jezero, ?ertovo jezero, and Rachelsee) are still chronically acidified, while four other oligotrophic lakes (Kleiner Arbersee, Prá?ilské jezero, Grosser Arbersee, and Laka) have recovered their carbonate buffering system. Total plankton biomass was very low and largely dominated by filamentous bacteria in the acidified oligotrophic lakes, while the mesotrophic lake had a higher biomass and was dominated by phytoplankton, which apparently profited from the higher P input. In contrast, both phytoplankton and crustacean zooplankton accounted for the majority of plankton biomass in the recovering lakes. This study has shown further progress in the reversal of lake water chemistry as well as further evidence of biological recovery compared to the 1999 survey. While no changes occurred in species composition of phytoplankton, a new ciliate species was found in one lake. In several lakes, this survey documented a return of zooplankton (e.g., Cladocera: Ceriodaphnia quadrangula and Rotifera: three Keratella species) and macrozoobenthos species (e.g., Ephemeroptera and Plecoptera). The beginning of biological recovery has been delayed for ～20 years after chemical reversal of the lakes.     

Contrasts between dystrophic and clearwater lakes in the long‐term effects of acidification on cladoceran assemblages

1. Most studies on zooplankton responses to acidification have focused on clearwater lakes with a dramatic acidification history. The role of dissolved organic carbon (DOC) in moderating zooplankton responses to acidification in naturally acidic, dystrophic lakes is less well understood and is partially impeded by a lack of baseline data. 2. Cladocera leave identifiable remains preserved in lake sediments that can be used to provide information on pre‐industrial species assemblages and their responses to environmental stressors such as acidification. Therefore, we used palaeolimnological approaches to track cladoceran assemblage responses to acidification since c.1850 (inferred from sedimentary diatom assemblages) in three acidified lakes in Kejimkujik National Park (Nova Scotia, Canada) that differ markedly in DOC content. These include two highly dystrophic lakes (Kejimkujik and Pebbleogittch lakes), and one clearwater lake (Beaverskin Lake). 3. In dystrophic Pebbleogittch Lake, an increase in the acid‐tolerant, jelly‐clad, pelagic taxon Holopedium glacialis occurred coincident with diatom‐inferred pH (DI‐pH) declines, but no other notable cladoceran assemblage shifts occurred. Similarly, Cladocera assemblages did not appear to respond to lakewater acidification in dystrophic Kejimkujik Lake. 4. In contrast, in the clearwater Beaverskin Lake, several observed shifts in cladoceran assemblage corresponded to DI‐pH declines, including an increase in the proportion of littoral taxa and an increase in Hill’s N2 species diversity. This may indicate increased water clarity as a result of acidification‐related decreases in DOC, which may have enhanced growth of emergent aquatic macrophytes and improved visibility for planktivorous fish, leading to increased predation on pelagic taxa. Species shifts within the littoral assemblage of Beaverskin Lake may reflect the differing tolerances of littoral taxa to low pH and aluminium toxicity. 5. Overall, our results suggest that cladoceran assemblages in naturally acidic, dystrophic lakes may be resilient against additional pH declines related to industrial emissions of acidifying agents, as dystrophic lakes are less vulnerable to increased aluminium toxicity and acidification‐induced increases in water clarity and often have a pre‐industrial cladoceran assemblage already adapted to acidic conditions.     

Mallomonadacean (Chrysophyceae) Scales: Early biotic paleoindicators of lake acidification

17 subfossil mallomonadacean species have been detected in the acidified Kleiner Arbersee. The most abundant one is M. crassisquama. In the top most layers, it is replaced by acid tolerant Synura spp. and several acidophilic and acidobiontic Mallomonas spp. Mallomonadaceae respond to acidification (and alkalinization) of lakes prior to benthic diatoms. Mallomonadaceae live euplanktically and mainly in spring, when most of the annual acid loading enters the lakes.     

Acidification of small mountain lakes in the High Tatra Mountains,Poland

A hydrochemical investigation was carried out on eight small High Tatra mountain lakes (Poland). When comparing recent data with those from the period 1935–1965, a constant process of acidification of the lakes is found. The average pH of precipitation is 4.8 in the study area, but the lakes are in two stages of acidification: weak (pH 6.0–6.5) and intermediate (pH 5.5–5.8). The differences are due to differences in water sources.     

Responses of insects,especially Chironomidae (Diptera), and mites to 130 years of acidification in a Scottish lake

About 130 years of anthropogenic acidification of Round Loch of Glenhead, SW Scotland, has resulted in successively decreased stability, diversity, productivity and survival rate of the non-biting midge (Diptera: Chironomidae) fauna. Similar trends have also been observed among mayflies, caddis-flies and water mites. The first effects of anthropogenic acidification on the insect and mite fauna, as evidenced by palaeolimnological analyses of²¹⁰Pb-dated sediment cores, occurred as early as around 1850, i.e. earlier than in any other lake hitherto studied. The drop in the lake's pH was first indicated by decreased stability and changes in species composition of chironomids and mayflies in the littoral zone. Major changes in the profundal chironomid fauna did not take place until about 1950, when mean lake pH dropped below 5.0. At the same time, the littoral insect fauna became even more unstable and the first significant elimination of species occurred. Comparison with insect fauna of other lakes suggests that a pH of less than 5 might be critical for the ecological conditions in many acidified lakes. None of the twelve most common chironomid species present prior to the acidification of the lake had disappeared after 120–130 years of considerable acidification, and they are all common in oligotrophic lakes with a pH of 6.5–7.0. This is in contrast to the effects of heavy acidification on other aquatic animal groups. Chironomids are probably more sensitive to lake trophic status than lake acidity.     

Macroinvertebrate indicators of lake acidification: analysis of monitoring data from UK, Norway and Sweden

Although the acid sensitivity of many invertebrate species in lakes is well known, methods for assessment of lake acidification based on macroinvertebrate samples are less developed than for rivers. This article analyses a number of existing metrics developed for assessment of river acidification, and evaluates their performance for assessment of lake acidification. Moreover, new species-based indicators of lake acidification were developed and tested. The selected dataset contains 668 samples on littoral macroinvertebrates from 427 lakes with almost 60% of the samples from Sweden and the rest from UK and Norway. Flexible, non-parametric regression models were used for explorative analyses of the pressure–response relationships. The metrics have been assessed according to their response to pH, the degree of non-linearity of the response and the influence of humic compounds. Acid-sensitive metrics often showed a threshold in response to pH between 5.8 and 6.5. Highly acid-tolerant metrics were typically dominant across the whole pH range. Humic level had a positive effect for most acid-sensitive metrics. Generally, most metrics showed a more non-linear response pattern for the humic lakes than for clear lakes. The significant relationship between these macroinvertebrate metrics and acidification shows that there is a potential for developing further the assessment systems for ecological quality of lakes based on these metrics, although the metrics explained a low % of the variation (<30%). In order to improve the predictive power of the biotic metrics across the acidified part of Europe, further harmonization and standardisation of sampling effort and taxa identification are needed.