Cladoceran Assemblages Research Articles

Long-term stability of cladoceran assemblages in small, shallow, Canadian Shield lakes experiencing marked calcium declines

A greater appreciation of biotic responses to environmental changes is warranted in small, shallow lakes because of the high number of these habitats, and their unique contributions to regional biodiversity. Furthermore, recent water chemistry monitoring data show that shallow lakes in Ontario are sensitive and have responded significantly to environmental stressors such as acid deposition and lake water calcium decline. Here, we use paleoecological techniques to examine cladoceran assemblages in modern and pre-industrial sediments of 30 shallow lakes to determine the key environmental gradients that influence present-day assemblages, and to assess how assemblage structure has changed since pre-industrial times (pre-1850s). Redundancy analysis of present-day cladoceran assemblages and key environmental variables identified lake surface area and Secchi depth as significant predictors of assemblage composition. In our data set, Secchi depth was not correlated to water clarity but rather to macrophyte cover, suggesting that cladoceran assemblages were highly influenced by habitat structure. In contrast to nearby, deeper lakes, where pelagic cladoceran taxa have changed significantly in relative abundance over time, cladoceran assemblages in present-day and pre-industrial sediments of shallow lakes did not differ significantly in composition. While the specific reasons for this muted response are unknown, we hypothesize that: (1) littoral taxa may be less sensitive to low Ca concentrations, or ecological thresholds have not yet been crossed or are lower for littoral taxa; (2) calcium availability may vary spatially within shallow lakes, and this is not captured in a single measure of water chemistry from the centre of the lake; and/or (3) habitat structure is more important than water chemistry as a predictor of assemblage composition in these study lakes, and this has not changed significantly over time.

Differences among modern-day and historical cladoceran communities from the “Ring of Fire” lake region of northern Ontario: Identifying responses to climate warming

The Ring of Fire in the Far North of Ontario (50 - 57° N, 79 - 94° W) is a region of growing economic and environmental interest due to recent mineral discoveries and the potential for resource development. Due to the remote location of the region, little baseline ecological information is available to distinguish any environmen- tal impacts of mine development from ongoing regional warming. Here, we compare modern and pre-industrial sedimentary cladoceran assemblages from 60 lakes centered on McFaulds Lake in the Ring of Fire to identify directional changes through time and compare the assemblages with prior paleolimnological cladoceran studies of Ontario lakes closer to the Hudson Bay coast, and further south in the Muskoka-Haliburton region. The cladoceran assemblages from the Ring of Fire contain diverse littoral assemblages relative to the other two regions; however, despite the shallow depth of these lakes, there have been significant increases in the relative abundances of pelagic taxa (e.g. Bosmina spp. and Daphnia spp.) since pre-industrial times; taxonomic shifts consistent with warming- induced changes in lake properties including a longer ice-free period and increased algal plankton production. This evidence of widespread changes within the cladoceran assemblages in the Ring of Fire prior to the onset of resource extraction provides lake managers and stewards with information to better monitor and evaluate future development projects.

Recent climate warming favours more specialized cladoceran taxa in western Canadian Arctic lakes

AbstractAimShifts in the distribution of freshwater algal communities as a result of climate‐related limnological changes are well documented; however, impacts on higher trophic levels have received less attention. For example, little is known about how Cladocera (Crustacea, Branchiopoda), often dominant invertebrates and key ecological indicators, have responded to recent warming on broad spatial and temporal scales. Here, we use lake sediment records to test the hypothesis that recent, intensive warming in the western Canadian Arctic has resulted in consistent shifts in the composition of cladoceran assemblages.LocationSmall, first‐order lakes in the Mackenzie Delta region of the western Canadian Arctic.MethodsSediment cores representing the recent past (approximately 150–200 years) were obtained from five lakes spanning a strong climatic gradient. Subfossil remains of Cladocera were identified and enumerated and overall primary production was inferred using spectroscopic techniques. The habitat preferences and feeding strategy of each taxon were compared. Detrended canonical correspondence analysis was used to estimate compositional turnover since 1850, and compared with that of three cladoceran assemblages from Nova Scotia, to place high‐latitude changes in context.ResultsCladoceran assemblage changes occurred coincident with the timing of known regional warming and were strongly linked to estimated changes in primary production. In the northern and deepest lakes, an increase in the planktonic, filter‐feeding taxon Bosmina spp. coincided with a decrease in the generalist littoral taxa Chydorus cf. brevilabris and Alona circumfimbriata. In the more southern lakes, an increase in macrophyte‐associated scrapers Acroperus harpae and Eurycercus spp. occurred concurrently with decreases in generalist taxa. In one lake, an increase in another specialist, an obligate mud‐dwelling taxon, was observed.Main conclusionsIn the western Canadian Arctic, warming has resulted in an increase in cladoceran taxa occupying more specialized feeding and habitat niches. Generalist taxa capable of occupying multiple habitats and employing diverse feeding strategies have been systematically replaced by more specialist species. This response is analogous to what has been inferred for algal communities across the Northern Hemisphere, and represents the first evidence of consistent cladoceran changes to recent climate warming in high‐latitude regions.

Ecosystem diversity of Cladocera (Crustacea: Branchiopoda) of the floodplain lakes of Majuli River Island, the Brahmaputra river basin, northeast India

Plankton and semi-plankton samples collected from twelve floodplain lakes (beels) of Majuli River Island of the Brahmaputra river basin, Upper Assam reveal rich Cladocera assemblage of 48 species belonging to 32 genera and 7 families. This report assumes biodiversity value as ~65.0% and ~37.0% of the species, and ~78.0% and ~72.0 of genera of the taxon known from Assam state of northeast India (NEI) and India, respectively. Picripleuroxus quasidenticulatus (Smirnov) is a new record from the Indian sub-region. Biogeographically important elements include one Australasian, three Indo-Chinese and two Oriental species. Total cladoceran richness in individual beels ranged between 16-38 (26 ± 6) species while monthly and seasonal richness in six beels each varied between 8 ± 3-13 ± 3 species and 11 ± 4-17 ± 3 species, respectively and showed lack of any pattern of temporal variations. The community similarities (40.1-86.5% vide Sorensen’s index) and the hierarchical cluster analysis affirm heterogeneity in Cladocera composition in different beels. Individual abiotic factors indicated insignificant influence on richness except for significant positive correlation with alkalinity only in Khorkhoria beel.

Synchronous changes in chironomid assemblages in two Arctic delta lake ecosystems after a major saltwater intrusion event

Low-lying Arctic coastal environments are threatened by marine storm surges, which are predicted to increase in frequency and intensity as a result of decreasing sea ice, rising sea levels and altered intensity and frequency of storm activity. The Mackenzie Delta of Canada’s Northwest Territories, a vast, low-lying wetland ecosystem, is particularly susceptible to such storm surges, because much of the outer alluvial plain is below 2-m elevation. A large storm-surge event in September 1999 flooded >13,000 ha of alluvial terrain and impacted the terrestrial and freshwater ecosystems of the region. Previous research on the limnological impacts of the storm surge recorded a shift from freshwater to brackish diatom taxa, and a change in cladoceran assemblages to more saline-tolerant species. We examined the remains of Chironomidae (Insecta, Diptera) in sediment cores from two lakes impacted by the 1999 saltwater inundation to determine whether the storm surge also affected benthic macroinvertebrate communities, which are particularly important to lake ecosystem function in Arctic regions. We observed an increase in the relative abundance of saline-tolerant taxa in the two impacted lakes, including Paratanytarsus and Cricotopus/Orthocladius, and decreases in saline-intolerant Sergentia and Corynocera oliveri-type, coincident with the 1999 storm. We observed no major assemblage changes after 1999 in a control lake located beyond the zone of inundation. The number of head capsules recovered from sediments of the impacted lakes increased after the 1999 storm, suggesting no negative impact on overall chironomid abundance as a result of the shift to brackish conditions. There has, however, been no recovery of the chironomid community to the pre-1999 composition. Earlier assemblage changes in both impacted lakes likely tracked regional climate warming in the region, known to have begun in the late nineteenth century.

Elevated metal concentrations inhibit biological recovery of Cladocera in previously acidified boreal lakes

Summary Lakes near Sudbury, Canada, have been exposed to intense acidification and metal contamination from nearby mining and smelting operations. Although lakewater pH improved substantially following the implementation of emission controls in the late 1960s, biological recovery continues to lag behind chemical recovery. We assessed the current state of biological recovery (relative to pre‐impact times) using multiproxy palaeolimnological records from two nearby lake districts (Sudbury and Killarney), both impacted by acidification but having experienced differences in metal contamination due to their respective distances from smelters. Twentieth century cladoceran shifts were most pronounced in the acidified and metal‐contaminated Sudbury lakes, with assemblage changes tracking industrial activity. Chydorus brevilabris increased markedly in dominance, largely at the expense of Bosmina spp. In contrast, the Killarney lakes, with similar changes in pH but lower Cu and Ni inputs than the Sudbury lakes, experienced minimal changes within their sedimentary cladoceran assemblages. These regional differences in cladoceran impact and recovery patterns are best explained by varying levels of Cu and Ni contamination, with concentrations of these metals still exceeding provincial water quality guidelines in the Sudbury lakes. Biological recovery in these systems appears to be inhibited by persistent high metal levels. Increased lake primary production and coincident shifts in cladoceran assemblages over the past approximately 40 years in all the study lakes suggest that climate impacts may be gaining prominence as drivers of ecological change, and therefore a return to the biotic structure of the pre‐smelter era is unlikely.

Relatedness between contemporary and subfossil cladoceran assemblages in Turkish lakes

Cladocerans are valuable indicators of environmental change in lakes. Their fossils provide information on past changes in lake environments. However, few studies have quantitatively examined the relationships between contemporary and sub-fossil cladoceran assemblages and no investigations are available from Mediterranean lakes where salinity, eutrophication and top-down control of large-bodied cladocerans are known to be important. Here we compared contemporary Cladocera assemblages, sampled in summer, from both littoral and pelagic zones, with their sub-fossil remains from surface sediment samples from 40 Turkish, mainly shallow, lakes. A total of 20 and 27 taxa were recorded in the contemporary and surface sediment samples, respectively. Procrustes rotation was applied to both the principal components analysis (PCA) and redundancy analysis (RDA) ordinations in order to explore the relationship between the cladoceran community and the environmental variables. Procrustes rotation analysis based on PCA showed a significant accord between both littoral and combined pelagic–littoral contemporary and sedimentary assemblages. RDA ordinations indicated that a similar proportion of variance was explained by environmental variation for the contemporary and fossil Cladocera data. Total phosphorus and salinity were significant explanatory variables for the contemporary assemblage, whereas salinity emerged as the only significant variable for the sedimentary assemblage. The residuals from the Procrustes rotation identified a number of lakes with a high degree of dissimilarity between modern and sub-fossil assemblages. Analysis showed that high salinity, deep water and high macrophyte abundance were linked to a lower accord between contemporary and sedimentary assemblages. This low accord was, generally the result of poor representation of some salinity tolerant, pelagic and macrophyte-associated taxa in the contemporary samples. This study provides further confirmation that there is a robust relationship between samples of modern cladoceran assemblages and their sedimentary remains. Thus, sub-fossil cladoceran assemblages from sediment cores can be used with confidence to track long-term changes in this environmentally sensitive group and in Mediterranean lakes, subjected to large inter-annual variation in water level, salinity and nutrients.

The dynamics of cladoceran assemblages in response to eutrophication and planktivorous fish introduction in Lake Chenghai, a plateau saline lake

Lake Chenghai, a brackish lake located in southwest China, has changed from oligotrophic to mesotrophic and finally eutrophic conditions since the 1990s. In the late 1990s, planktivorous icefish were introduced into the lake, which dramatically altered the fish population. A paleolimnological evaluation using the cladoceran remains was conducted in order to analyze the effects of increasing nutrient load and fish introduction on the cladoceran community of this lake. Our results showed that the dominant cladocerans were littoral species, with a low abundance of planktonic Bosmina in the sediment. Increasing eutrophication since the late 1990s greatly enhanced the abundance of cladoceran assemblages, especially for the species that prefer eutrophic conditions. Meanwhile, the species which prefer oligotrophic conditions were extirpated. The changes in Daphnia ephippium length suggested that the planktivorous icefish have varying effects on the body size of different species.

A paleolimnological perspective on aquatic biodiversity in Austrian mountain lakes

We assessed long-term aquatic biodiversity patterns, with a focus on functional diversity (FD), by using sedimentary Chironomidae and Cladocera assemblages in four mountain lakes in the Austrian Alps. The objectives were to detect whether the invertebrate communities exhibited similar recent diversity trends in climate-sensitive alpine lakes, to observe how lake-specific limnological shifts affect biodiversity, and to test the relationship between taxonomic diversity (TD) and FD for paleolimnological biodiversity evaluations. We applied traditional TD indices to the sedimentary assemblages and used an FD index that was based on functional traits of the encountered taxa of both invertebrate groups. There were some similar long-term trends in invertebrate FD and TD among the lakes; e.g. chironomid diversity increased in two lakes and cladoceran diversity in three lakes toward the twentieth and twenty-first century, but in general the diversity patterns were variable between lakes. Overall, FD had a positive relationship with TD suggesting that functionality can be used in paleolimnological studies as a measure of biodiversity. However, cladoceran taxon richness did not correlate with FD in two lakes suggesting that TD is not always a surrogate for FD. Furthermore, TD of chironomids tended to increase more pronouncedly than FD in the top core sections indicating that increasing TD does not necessarily enhance FD and that different taxonomic entities may play similar functional roles in ecosystems. Accordingly, when evaluating biodiversity and ecological redundancy, functionality of the species pool should be carefully considered and highlighted also in paleolimnological research.

Subfossil Cladocera from surface sediment in thermokarst lakes in northeastern Siberia, Russia, in relation to limnological and climatic variables

Subfossil Cladocera were sampled and examined from the surface sediments of 35 thermokarst lakes along a temperature gradient crossing the tree line in the Anabar-river basin in northwestern Yakutia, northeastern Siberia. The lakes were distributed through three environmental zones: typical tundra, southern tundra and forest tundra. All lakes were situated within the continuous permafrost zone. Our investigation showed that the cladoceran communities in the lakes of the Anabar region are diverse and abundant, as reflected by taxonomic richness, and high diversity and evenness indices (H = 1.89 ± 0.51; I = 0.8 ± 0.18). CONISS cluster analysis indicated that the cladoceran communities in the three ecological zones (typical tundra, southern tundra and forest-tundra) differed in their taxonomic composition and structure. Differences in the cladoceran assemblages were related to limnological features and geographical position, vegetation type, climate and water chemistry. The constrained redundancy analysis indicated that TJuly, water depth and both sulphate (SO4 2−) and silica (Si4+) concentrations significantly (p ≤ 0.05) explained variance in the cladoceran assemblage. TJuly featured the highest percentage (17.4 %) of explained variance in the distribution of subfossil Cladocera. One of the most significant changes in the structure of the cladoceran communities in the investigated transect was the replacement of closely related species along the latitudinal and vegetation gradient. The results demonstrate the potential for a regional cladoceran-based temperature model for the Arctic regions of Russia, and for and Yakutia in particular.

New Records of Cladocera (Crustacea: Anomopoda) from Laguna Navío Quebrado, La Guajira Department, Colombia

Zooplankton plays key roles in structuring interactions in aquatic communities but often remain undescribed in many water systems. This paper reports seventeen species of the Cladocera (Crustacea: Branchiopoda) from Laguna de Navio Quebrado, all of them new records for La Guajira Department, Colombia. The Cladocera assemblages include mostly the Neotropical taxa associated with vegetation. This paper also serves as the first compilation of the data on the Cladocera of this region and includes brief remarks, descriptions and illustrations of some species with additional notes on their distribution.

Diatoms indicate that calcium decline, not acidification, explains recent cladoceran assemblage changes in south-central Ontario softwater lakes

In recent decades, softwater lakes across Canada have experienced a wide array of anthropogenic influences, with acidification and climate warming of particular concern. Here, we compare modern and pre-industrial sedimentary diatom assemblages from 36 softwater lakes located on the Canadian Shield in south-central Ontario to determine whether lake acidification or reduced calcium availability was the main stressor responsible for recent declines in Ca-sensitive cladoceran taxa. Regional surveys of south-central Ontario water chemistry have identified the pH recovery of many formerly acidified lakes, and our fossil diatom-inferred pH analyses indicate that modern lakewater pH in the 36 study lakes is similar to (or higher than) pre-industrial levels, with diatom assemblages from both time periods dominated by taxa with similar pH preferences. In addition, modern diatom assemblages compared to pre-industrial assemblages contained higher relative abundances of planktonic diatom taxa (e.g. Asterionella formosa and the Discostella stelligera complex) and lower relative abundances of heavily silicified diatoms (e.g. Aulacoseira taxa) and benthic fragilarioid taxa. These taxonomic shifts are consistent with warming-induced changes in lake properties including a longer ice-free period, decreased wind speed and/or increased thermal stability. We conclude that recent changes observed within the cladoceran assemblages of these lakes are not a response to acidification, but are likely a consequence of Ca declines. In addition, our data suggest that regional climate warming is now responsible for the diatom changes observed in this region.

Abiotic predictors of faunal communities in an ombrotrophic peatland lagg and an open peat bog

Most ecological research has hitherto focused more on sea and lake ecosystems than on peatland habitats. The primary objectives of this paper were to analyse the ciliate, rotifer, cladoceran, copepod and insect assemblages in a horizontal lagg and an open peat bog, and to assess the influence of physical and chemical parameters on their communities. Sampling was done in a transitional bog from May to October 2012 in a transect comprising the lagg and the open peatbog. The first two axes of a principal component analysis accounted for 49.8% of the total variance in the composition of the faunal communities studied. The distribution of samples in ordination space suggested that the habitats are distributed along the gradient of water level and the gradients of total organic carbon and nutrients. Assemblages of all groups investigated showed a strong compositional gradient correlated with surface water and phosphates. However, species composition of ciliates and rotifers was explained by conductivity and/or chlorophyll-aconcentration. The results suggest that the lagg zone of a bog can function as an ecotone, with significantly greater species richness and abundance of faunal communities.

Effect of poor manageability and low nutritional value of cyanobacteria on Daphnia magna life history performance

Cyanobacteria may reduce Daphnia fitness through their toxicity, low nutritional value or poor manageability. In this study, the relative importance of the low nutritional value and poor manageability of cyanobacteria on Daphnia life history were determined. To separate these two aspects of cyanobacteria impact, short or long filaments of Cylindrospermopsis raciborskii were given as food to five clones of Daphnia magna either alone or together with the green alga Scenedesmus obliquus. Feeding with short cyanobacterial filaments caused reductions in growth rate (,45%) and fecundity (,60%) in some clones. The deleterious effects caused by cyanobacterial poor nutritional quality could be completely overcome by supplementation with highquality food. Long cyanobacterial filaments caused greater reductions in growth rate (,65%) and fecundity (,80%) in the most affected clones, and the addition of high-quality food only partially diminished the effects of poor filament manageability. In Daphnia fed with long filaments, there was no correlation between body size at maturity and fecundity, and the maximum fecundity was reached by individuals of intermediate size. Decreased body size may, thus, represent an adaptive mechanism against interference with food collection caused by long filaments. The pattern of responses to different food regimes was similar in all Daphnia clones, but they differed in the absolute values of the life history parameters affected. Differences in the fecundity of Daphnia caused by the presence of cyanobacteria may affect clonal composition of cladoceran assemblages, thus, cyanobacteria can shape microevolutionary changes in Daphnia populations.

Long-term Trends in Cladoceran Assemblages Related to Acidification and Subsequent Liming of Middle Lake (Sudbury, Canada)

In the mid-20th century, similar to many lakes in the vicinity of Sudbury, Canada, Middle Lake was severely acidified due to nearby smelting operations. However, this lake is of particular interest because it was limed in 1973, and later fertilized as part of a restoration effort. Here, we use paleolimnological methods to track cladoceran assemblage responses to acidification, liming, and subsequent recovery in a ∼250-year lake sediment record. Cladoceran assemblage changes, notably increases in Chydorus brevilabris, coincided with the late 1800s establishment of open-pit ore roasting in the region. As acidification progressed, the Daphnia pulex complex was replaced by the Daphnia longispina complex. At the height of acidification, and with similar timing to the liming, C. brevilabris increased abruptly in relative abundance in the sediment record, followed by a rapid decline. Invertebrate predation was investigated using Bosmina mucro length; however, no significant trends were evident. Our results suggest that complete biological recovery has not occurred. Specifically, species richness (rarefied) is ∼64 % lower after the onset of acidification, and many rare species present prior to the onset of acidification have not yet returned to pre-impact levels despite dispersal events of these rare taxa being observed during contemporary zooplankton monitoring. Factors impeding the complete biological recovery of the cladocerans in Middle Lake may include biotic resistance, ongoing metal contamination, and a warming climate.

A Multi-Trophic Exploratory Survey of Recent Environmental Changes using Lake Sediments in the Hudson Bay Lowlands, Ontario, Canada

A multi-proxy paleolimnological survey was performed on 13 lakes in the Hudson Bay Lowlands (HBL) of northern Ontario in order to provide a regional analysis of recent environmental changes in this poorly studied sub-Arctic region. In contrast to the amplified warming experienced by most of the circumpolar Arctic since the mid-19th century, the climate of the Hudson Bay (HB) region has remained relatively cool and stable for hundreds of years. However, since approximately the 1990s, the HBL has experienced rapid and large increases in air temperature and declines in sea ice. Diatom, cladoceran, and chironomid remains preserved in the recent (surface) and pre-1850 sediments of 13 lakes were used to examine whether this new climate regime has resulted in species assemblage changes across multiple trophic levels. Our results indicate clear limnological responses to warming among the freshwater biota of HBL lakes; however, the magnitude of this change varied among both biological indicators and sites. As expected, diatoms exhibited the greatest degree of change, closely followed by chironomids, with relatively little change observed among cladoceran assemblages. Planktonic diatoms were more common in modern assemblages, often including plankters that were previously not recorded in the bottom sediments, and in fact all indicator groups recorded a change in benthic/littoral taxa in the recent sediments indicative of warming-induced increases in habitat availability due to decreased lake ice cover.

Evaluation of a new sampling method for assessing Cladocera richness (Crustacea, Branchiopoda) in macrophyte-rich wetlands

The wetlands found in the Brazilian Cerrado are poorly studied environments regarding ecologi- cal aspects. Assessing the diversity of aquatic invertebrates in wetlands is a challenging task, since there are no standard sampling methods that minimize the spatial effects caused by macrophytes. The aim of this study was to evaluate the efficiency of a new sampling method for assessing Cladocera richness in macrophyte-rich wetlands of Brazilian Cerrado. In six wetlands, one transect was established which corresponded to a gradient of depth or change in aquatic vegetation. Samples containing cladocerans were collected using plankton net dragged among aquatic vegetation in the dry and rainy seasons. The species accumulation curves using non-parametric estimators and the overestimation of richness were used to determine the sampling efficiency. The species accumulation curves showed different asymptotic trends regarding the season and wetland stu- died. Especially in the rainy season, an asymptotic trend was not observed in two of the wetlands studied, which may reflect the influence of seasonality on Cladocera assemblage. Nevertheless, the overestimation of species richness showed that the method of sampling was able to find more than 60% of the estimated species richness, regardless of season or wetland studied. These results indicate that the method employed for sampling Cladocera in the Cerrado wetlands can be considered adequate.

Is there a bias between contemporary and subfossil cladoceran assemblages?

Is there a bias between contemporary and subfossil cladoceran assemblages? Sediment and water samples differ in both temporal and spatial resolution. In this study, we compare a set of contemporary cladoceran samples covering the past 30 years with a subfossil sedimentary sequence from a surficial core spanning the same period. More species were found in the sediment than in the water samples. This result reflects the accumulative and integrative consequences of sedimentation processes. For example, Alona quadrangularis, Alona affinis, Pleuroxus truncatus and Tretocephala ambigua were only found in the sedimentary sequence. In contrast, species occurring frequently in contemporary samples, such as Simocephalus vetulus, were not found in the sediment because their remains are poorly preserved. Ordination analyses (a CA for contemporary samples and a PCA for sediment samples) were performed to investigate the patterns and variation of cladoceran species abundances in both data sets. The application of a Procrustes rotation and PROTEST permutation test to the ordinations (CA and PCA) of these two sets of samples demonstrated that the two sets were significantly similar. However, the number of samples analysed to obtain the same integrating characterisation of the lake community must be much greater if we use live collections rather than sediment samples. This study evidenced the role of lake sediment as an important library for species information and highlighted the potential role of palaeolimnological approaches in biodiversity studies.

A multiproxy reconstruction of effective precipitation in the central Austrian Alps since the Little Ice Age

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 58:15-28 (2013) - DOI: https://doi.org/10.3354/cr01184 A multiproxy reconstruction of effective precipitation in the central Austrian Alps since the Little Ice Age Tomi P. Luoto1,2,*, Liisa Nevalainen1,3 1Research Institute for Limnology of the University of Innsbruck, Mondseestraße 9, 5310 Mondsee, Austria 2Department of Geosciences and Geography, PO Box 64, 00014 University of Helsinki, Finland 3Department of Environmental Sciences, University of Helsinki, Niemenkatu 73, 15140 Lahti, Finland *Email: tomi.luoto@helsinki.fi ABSTRACT: Lake levels can act as valuable proxy sources for long-term effective precipitation dynamics. In this study, lake-level fluctuations were reconstructed from the Little Ice Age (LIA) until the present using a multiproxy paleolimnological approach from Lake Moaralm (Moaralmsee) in the Niedere Tauern Alps, Austria. Quantitative lake level reconstruction techniques were applied to the sediment core data using intralake (Moaralmsee) calibration models based on fossil Chironomidae and Cladocera assemblages, and supplementary models based on oribatid mites and loss-on-ignition were used. The results showed that the inferred lake-level trends were strongly correlated among one another and also with the observed precipitation record from an adjacent weather station since 1860 AD. Periods of low lake level were reconstructed for ca. 1600-1650 AD and 1700-1900 AD, while high lake level periods occurred from ca. 1650-1700 AD and from ca. 1900 AD to the present. These results were in good agreement with previous records on lake level and precipitation patterns in the European Alps, though with some spatiotemporal differences. Our records of long-term patterns of effective moisture, combined with the previously established temperature variability since the 17th century, suggested that a period of high effective moisture occurred between ca. 1650 and 1700 AD during the LIA, after which moisture levels decreased. High temperatures during the last century were accompanied by increasing moisture, and the lake levels are now at a 400-yr maximum. This study provides a new proxy for spatiotemporal moisture patterns that is invaluable for improved understanding of synoptic climate variability for periods prior to the observational records. KEY WORDS: Chironomidae · Cladocera · Lake sediments · Loss-on-ignition · Oribatida · Paleoclimate · Precipitation Full text in pdf format PreviousNextCite this article as: Luoto TP, Nevalainen L (2013) A multiproxy reconstruction of effective precipitation in the central Austrian Alps since the Little Ice Age. Clim Res 58:15-28. https://doi.org/10.3354/cr01184 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 58, No. 1. Online publication date: November 19, 2013 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2013 Inter-Research.

How does the Taquari River influence in the cladoceran assemblages in three oxbow lakes?

This study examined the cladoceran assemblages in three oxbow lakes of the Taquari River floodplain, near the transition between the plateau and the plain. We sought to answer the following questions: does the Taquari River function as a geographical barrier or dispersal corridor for Cladocera? Can different degrees of connection induce different structures in the assemblages in each lake? Cladocerans and limnological variables were sampled every other month for one year. Forty-one species were recorded, four of which were common to all the lakes. Our results indicated that the different degrees of connection between the river and the oxbow lakes favoured environmental heterogeneity and diversification in the cladoceran assemblages. The greatest dissimilarity between the two lakes connected with the river indicates that in this case the river functions better as a barrier than a dispersal corridor.