Cladoceran Assemblages Research Articles

Long-term ecological changes in Mediterranean mountain lakes linked to recent climate change and Saharan dust deposition revealed by diatom analyses

Anthropogenic climate change and the recent increase of Saharan dust deposition has had substantial effects on Mediterranean alpine regions. We examined changes in diatom assemblage composition over the past ~180 years from high-resolution, dated sediment cores retrieved from six remote lakes in the Sierra Nevada Mountains of Southern Spain. In all lakes, changes in diatom composition began over a century ago, but were more pronounced after ~1970 CE, concurrent with trends in rising regional air temperature, declining precipitation, and increased Saharan dust deposition. Temperature was identified as the main predictor of diatom assemblage changes, whereas both Saharan dust deposition drivers, the Sahel precipitation index and the winter North Atlantic Oscillation, were secondary explanatory variables. Diatom compositional shifts are indicative of lake alkalinization (linked to heightened evapoconcentration and an increase in calcium-rich Saharan dust input) and reduced lake water turbulence (linked to lower water levels and reduced inflows to the lakes). Moreover, decreases in epiphytic diatom species were indicative of increasing aridity and the drying of catchment meadows. Our results support the conclusions of previous chlorophyll-a and cladoceran-based paleolimnological analyses of these same dated sedimentary records which show a regional-scale response to climate change and Saharan dust deposition in Sierra Nevada lakes and their catchments during the 20th century. However, diatom assemblages seem to respond to different atmospheric and climate-related effects than cladoceran assemblages and chlorophyll-a concentrations. The recent impact of climate change and atmospheric Saharan deposition on lake biota assemblages and water chemistry, as well as catchment water availability, will have important implications for the valuable ecosystem services that the Sierra Nevada provides.

Changes in Planktivory and Herbivory Regimes in a Shallow South American Lake (Lake Blanca Chica, Argentina) Over the Last 250 Years

Shallow lakes are vulnerable ecosystems impacted by human activities and climate change. The Cladocera occupy a central role in food webs and are an excellent paleoecological indicator of food web structure and trophic status. We conducted a paleolimnological study in Lake Blanca Chica (Argentina) to detect changes on the planktivory and herbivory regimes over the last 250 years. Generalized additive models were fitted to the time series of fish predation indicators (ephippial abundance and size, mucrone size, fish scales, and the planktivory index) and pheophorbide a concentration. The cladoceran assemblage changed from littoral-benthic to pelagic species dominance and zooplankton switched from large-bodied (Daphnia) to small-bodied grazers (Bosmina) ca. 1900 due to increased predation. The shift in planktivory regime (ca. 1920–1930), indicated by fish scales and the planktivory index, as well as herbivory (ca. 1920–1950), was triggered by eutrophication. Changes in planktivory affected the size structure of Bosmina, reducing its body size. This study describes the baseline for the lake as well as the profound changes in the composition and size structure of the zooplankton community due to increased predation and the shift in the planktivory regime. These findings will provide a reference status for future management strategies of this ecosystem.

Millennial‐to‐centennial scale lake system development in the mountains of tropical Mexico

Rapid degradation of freshwater ecosystems threatens water supply for human populations and natural landscapes. At diverse time scales, this process has been clearly associated with climatic and anthropogenic forcings. The question remains, however, how tropical lakes have responded to these two sources of variability. We present a multiproxy record from Lake San Lorenzo, Lagunas de Montebello National Park, tropical Mexico, spanning the last ~3400 years. We used multi‐elemental concentrations, and Cladocera and pollen assemblages along the record to reconstruct regional and local environmental variability, aiming to infer the factors and processes involved in the evolution of the lacustrine system. A principal component analysis on the pooled biological and geochemical evidence allowed the inference of the main changes in lake level and productivity. At millennial scales, the development of the lake system has been closely associated with regional moisture availability, with wetter (drier) time intervals associated with high (low) lake stands. According to Ti concentrations, from ~3400 to 1000 cal. a BP, regional conditions followed a trend towards drier conditions, with littoral cladoceran assemblages suggesting high lake productivity. The extreme regional droughts reportedly associated with the cultural collapse of the Maya civilization manifested in our study area through both high lake productivity and the lowest lake levels of the record. Through the last ~800 years, the regional moisture availability has increased, with the water body becoming deeper and larger. Overall, our record offers evidence of a highly variable system strongly coupled with regional climates, but also very sensitive to local disturbances associated with human occupation. Lake San Lorenzo has been highly resilient to external pressures and has previously recovered from conditions probably alike those associated with the ongoing modern deterioration process. Nevertheless, such recovery involves a complex network of interactions amongst natural and human factors.

Effects of environmental change on subfossil Cladocera in the subtropical shallow freshwater East Taihu Lake, China

East Taihu Lake (the south-eastern portion of Taihu Lake in China) suffers from eutrophication. The study of lacustrine subfossil zooplankton assemblages can be used to reconstruct the long-term evolution of lake water environments. In particular, the analysis of subfossil Cladocera can indicate historical changes in aquaticplants, water level, trophic states, and human disturbance in lakes. In this study, we correlated downcores changes in cladoceran assemblages with several geochemical proxies to identify the response of Cladocera to environmental change in East Taihu Lake over the past one hundred years. Redundancy analysis (RDA) and Pearson correlation analysis identified significant correlations between total phosphorus (TP) and Bosmina spp. (total), B. (E.) longispina, and Chydorus cf. sphaericus (correlation coefficients: −0.720 (P < 0.01), −0.646, and 0.667 (P < 0.05), respectively). We observed decreasing abundances of subfossil Bosminidae and increases in littoral cladoceran species and TP after the 1960s, coinciding with the introduction of land reclamation for fish and crab farming. These anthropogenic pressures exacerbated eutrophication, which led to the rapid growth of submerged vegetation and subsequently altered the zooplankton assemblage.

Spatiotemporal patterns of cladoceran community responses to water level variation in Haixi Lake, southwest China

ABSTRACT Hydrological regulation of lakes has been increasingly practiced around the world, with significant ecological consequences. However, little is known on how lake regulation affects community organization and succession. Crustacean zooplankton play a central role in energy transfer along lake food webs because of their intermediate trophic level. Haixi Lake, a mesotrophic deep-water reservoir in southwest China, was a shallow lake by nature but underwent dam construction and reinforcement in 1957 and 1987–1990, respectively. We applied the sediment records of cladoceran remains in Haixi to uncover the spatial and temporal changes of cladoceran assemblages along a gradient of water depth by combining a spatial survey of 27 surface sediment samples with a temporal survey of a well-dated sediment core covering the last 2 centuries. Lake depth was identified to be a paramount factor in driving the temporal and spatial variation of cladoceran assemblages, which was dominated by planktonic cladocerans such as Bosmina. With increasing water levels, a significant loss of benthic cladocerans and species diversity was noted, as well as a long-term decrease in antennule lengths of bosminids. Specifically, a threshold water depth of ∼8 m was found, possibly linked to lake water thermal stability and littoral habitat coverage. Our results highlight that water level serves as a significant factor in structuring zooplankton species composition and body sizes and should be considered for sustainable water management in regulated inland waters.

Response of Cladocera fauna to environmental change based on sediments from Shengjin Lake, a Yangtze River-connected lake in China

Shengjin Lake is a typical Yangtze River-connected lake, that is also a national nature reserve and a Wetland of International Importance. In order to evaluate the eco-environmental evolution of Shengjin Lake, a210Pb- and 137Cs-dated sediment core collected from the upper part of the lake was analyzed. Based on a biological indicator (subfossil cladoceran) and geochemical indicators (loss on ignition (LOI), total organic carbon (TOC), δ13C of bulk sediments (δ13Corg), total phosphorous (TP) and total nitrogen (TN)), we revealed the changes in the cladoceran assemblages and eco-environmental processes of Shengjin Lake. The results showed that there was a healthy ecological environment with low nutrient levels in Shengjin Lake before the 1980s. However, the increasing levels of the eutrophic species B. longirostris, nutrients (TN and TP) and organic matters (LOI and TOC), and the decreasing δ13Corg in recent decades indicated that the trophic state of Shengjin Lake has increased since the 1980s. This corresponded with increasing anthropogenic effects, including land reclamation, chemical fertilizer application, and sluice construction. In addition, the droppings of water birds also promoted increases in nutrient and organic matters levels in Shengjin Lake.

Aerobic Exercise Does Not Promote Significant Adaptations in Cardiac Mitochondrial Respiration

A sediment core was obtained from Moira Lake to study the legacy of contamination and remediation at the Deloro industrial site which includes 95-years of operations involving gold mining, mineral processing, and arsenic-based pesticide production resulting in high levels of arsenic, cobalt, and nickel. A timeline for the sediment core was established by 210Pb dating and used to evaluate the geochemical record and the impact on primary production and subfossil cladocerans. In the early 1800s, there was an initial increase in the arsenic, cobalt and nickel concentrations due to industrial development. By the 1850s, the rate of enrichment increased due to the conglomeration of small-scale operations. In the 1960s, the concentrations of those metal(loid)s decreased following the cessation of the industrial activity at Deloro and the initiation of a clean-up effort. Primary production, inferred by chlorophyll-a concentrations, initially decreased as the metal(loid)s concentrations increased. This was followed by a recovery of the chlorophyll-a concentrations and further increases in production to higher levels than recorded prior to the Deloro years. Secondary production, inferred by cladoceran assemblage structure, was initially dominated by bosminids. The assemblage then changed to one dominated by chydorids and daphnids with the change occurring contemporaneous with the change in chlorophyll-a. However, the changes in primary and secondary production occurred during the period of accelerated metal(loid) enrichment, suggesting limited impact of contamination on primary and secondary producers. Loss on ignition results revealed that during the period of accelerated arsenic enrichment, the carbonate content of the sediments increased while the percent organic content decreased. This work contributes to ongoing research to establish the environmental legacy of historical industrial activities within complex ecosystems. Furthermore, the combination of geochemical (i.e. 210Pb, ICP-OES, XANES) and ecological analysis provides a more complete picture of the complex interactions that have occurred in Moira Lake.

Cladoceran assemblage distribution in shallow alpine lakes of Sierra Nevada (Spain) and its relationship with environmental variables

Subfossil cladoceran assemblages were studied in surface sediments from 17 shallow alpine lakes in the Sierra Nevada (Spain) to evaluate relationships between species assemblages and environmental variables. Factors associated with the presence of Daphnia were also investigated. Chydorids predominated in the cladoceran assemblages. Redundancy analyses (RDA) revealed that the distribution of cladoceran assemblages was mainly associated with morphometric variables (extent of catchment vegetation in basin, lake depth and size, and the presence of inlets and outlets in basin). The explanatory power of chemical parameters was lower, with total nitrogen (TN) being the most influential variable. The relative abundances of Alona quadrangularis and Chydorus sphaericus showed a significant negative relationship in the lake set, suggesting the adaptation of these species to diverging lakes conditions in Sierra Nevada. More favorable conditions for species growth (warmer waters and increased input of material from the catchment in small, open-basin lakes surrounded by alpine meadows) were observed in lakes with higher abundance of A. quadrangularis than in those with higher abundance of C. sphaericus. Our results agree with those from previous paleolimnological studies in Sierra Nevada which show an abrupt increase in the relative abundance of A. quadrangularis at the expense of C. sphaericus since 1970 associated with more favorable conditions for growth as a result of climate change. Positive relationships were also observed between the relative abundance of Daphnia pulex gr. and closed, deep basins.

Cladoceran (Crustacea) Niches, Sex, and Sun Bathing—A Long-Term Record of Tundra Lake (Lapland) Functioning and Paleo-Optics

Under fundamental ecosystem changes in high latitude lakes, a functional paleolimnological approach may increase holistic understanding of lake responses and resilience to climate warming. A ~2000-year sediment record from Lake Loažžejávri in the tundra of northern Finnish Lapland was examined for fossil Cladocera assemblages to examine long-term environmental controls on aquatic communities. In addition, cladoceran functional attributes, including functional diversity (FD), UV absorbance (ABSUV) of Alona carapaces, and sexual reproduction (ephippia) in Bosmina and Chydoridae were analyzed. Cladoceran communities responded to a major change in benthic habitat quality, reflected as elevated (increasingly benthic) sediment organic matter δ13C signal since the 17th century. FD fluctuations showed association with climate oscillation, FD being generally higher during warm climate periods. These ecological changes were likely attributable to diversification of littoral-benthic consumer habitat space. ABSUV, irrespective of increases during the Little Ice Age (LIA) due to higher UV transparency of lake water, was lower under increasing autochthony (benthic production) suggesting establishment of physical UV refugia by the benthic vegetative substrata. Bosmina ephippia exhibited a decreasing trend associated with increasing benthic production, indicating favorable environmental regime, and, together with chydorid ephippia, transient increases during the climate cooling of the LIA driven by shorter open-water season.

Response of Cladocera Fauna to Heavy Metal Pollution, Based on Sediments from Subsidence Ponds Downstream of a Mine Discharge (S. Poland)

Mining is recognized to deeply influence invertebrate assemblages in aquatic systems, but different invertebrates respond in different ways to mining cessation. Here, we document the response of the cladoceran assemblage of the Chechło river, S. Poland (southern Poland) to the cessation of Pb-Zn ore mining. The aquatic system includes the river and associated subsidence ponds in the valley. Some ponds were contaminated during the period of mining, which ceased in 2009, while one of the ponds only appeared after mining had stopped. We used Cladocera to reveal how the cessation of mine water discharge reflected on the structure and density of organisms. A total of 20 Cladocera taxa were identified in the sediment of subsidence ponds. Their density ranged from 0 to 109 ind./1 cm3. The concentrations of Zn, Cd, Cu and Pb were much higher in sediments of the ponds formed during peak mining than in the ponds formed after the closure of the mine. Statistical analysis (CCA) showed that Alonella nana, Alona affinis, Alona sp. and Pleuroxus sp. strongly correlated with pond age and did not tolerate high concentrations of heavy metals (Cu and Cd). This analysis indicated that the rate of water exchange by the river flow and the presence of aquatic plants, affect species composition more than pond age itself.

Geochemical and ecological changes within Moira Lake (Ontario, Canada): A legacy of industrial contamination and remediation.

A sediment core was obtained from Moira Lake to study the legacy of contamination and remediation at the Deloro industrial site which includes 95-years of operations involving gold mining, mineral processing, and arsenic-based pesticide production resulting in high levels of arsenic, cobalt, and nickel. A timeline for the sediment core was established by 210Pb dating and used to evaluate the geochemical record and the impact on primary production and subfossil cladocerans. In the early 1800s, there was an initial increase in the arsenic, cobalt and nickel concentrations due to industrial development. By the 1850s, the rate of enrichment increased due to the conglomeration of small-scale operations. In the 1960s, the concentrations of those metal(loid)s decreased following the cessation of the industrial activity at Deloro and the initiation of a clean-up effort. Primary production, inferred by chlorophyll-a concentrations, initially decreased as the metal(loid)s concentrations increased. This was followed by a recovery of the chlorophyll-a concentrations and further increases in production to higher levels than recorded prior to the Deloro years. Secondary production, inferred by cladoceran assemblage structure, was initially dominated by bosminids. The assemblage then changed to one dominated by chydorids and daphnids with the change occurring contemporaneous with the change in chlorophyll-a. However, the changes in primary and secondary production occurred during the period of accelerated metal(loid) enrichment, suggesting limited impact of contamination on primary and secondary producers. Loss on ignition results revealed that during the period of accelerated arsenic enrichment, the carbonate content of the sediments increased while the percent organic content decreased. This work contributes to ongoing research to establish the environmental legacy of historical industrial activities within complex ecosystems. Furthermore, the combination of geochemical (i.e. 210Pb, ICP-OES, XANES) and ecological analysis provides a more complete picture of the complex interactions that have occurred in Moira Lake.

Long-term change of the assemblages and abundance of cladocerans in different ecotypes of Lake Taihu

枝角类作为淡水湖泊生态系统中的初级消费者之一，对生存环境的改变极为敏感.本文分析了太湖西、中和东部等湖区的钻孔沉积物、表层沉积物以及春夏秋季活体枝角类的组成与丰度.结果表明：活体枝角类组成以象鼻溞（Bosmina spp.）为优势种，秋季枝角类属种数量最多.太湖不同生态型湖区表层沉积物枝角类组成均以象鼻溞为优势种，其中西部与中心湖区的枝角类组成与丰度较为相似，种类单一，枝角类绝对丰度高；东部湖区枝角类属种较为丰富，绝对丰度低，优势种由浮游种象鼻溞以及沿岸种圆形盘肠溞（Chydorus sphaericus sl）和西方笔纹溞（Graptoleberis testudinaria）等种属构成.百年以来，太湖枝角类组成与丰度随着营养水平增加而改变，富营养指示种（Bosmina longirostris）丰度的增加与贫营养指示种（Bosmina longispina）丰度的下降，响应了湖区生态环境的演变过程.1970s末期，太湖西部与中心湖区在进入富营养化阶段，枝角类组成单一，象鼻溞占有绝对优势，与东部湖区相比，沿岸种、底栖种稀少.东部湖区在1960s以后，枝角类属种数量增加，但丰度下降，响应了1960s以来该区域营养水平提高、沉水植被生物量增加以及沼泽化加剧的环境过程.;Cladoceran, as one of the primary consumers in freshwater lake ecosystem, is sensitive to environmental change. So far, fruitful researches of subfossil cladocerans have been applied in many fields, such as paleoclimate reconstruction, food web, and nutritional changes and so on. However, most of studies focused on the lakes in boreal, temperate and subarctic zones, especially the alpine and deep lakes. Few works paid attention to freshwater shallow lakes in the middle and low latitudes of subtropics in Asia. Lake Taihu, located in the south of the Yangtze River Delta, is a large shallow lake covering over 2000 km² area which is also the third largest freshwater lake in China. Lake Taihu is ecologically divided into different basins. The west and north parts of Lake Taihu are observed increase of nutrient which has led to the emergence of non-N₂ fixing Microcystis sp. cyanobacterium causing serious cyanobacterial blooms and reduced biodiversity. The eastern part of Lake Taihu is also a mild eutrophic lake under the condition of growing large number of submerge plants. Those changes had influence on cladoceran composition and abundance. In this paper, we analysed the composition and abundance of cladoceran assemblages from cores and surface sediments and modern waters in spring, summer and autumn of the western, central and eastern parts of Lake Taihu. The results showed that Bosmina spp. was the dominant cladoceran of the sediments and water in different ecotypes of Lake Taihu. The composition of modern cladoceran was basically the largest number of cladoceran species in autumn. The cladoceran composition was single but with a high-level abundance in the western and central Lake Taihu. The cladoceran species in the eastern Lake Taihu were relatively rich but with a low-level abundance. The dominant species in the east part of Lake Taihu were composed of several species such as Bosmina spp., Chydorus sphaericus sl and Graptoleberis testudinaria. Over the past century, the composition and abundance of cladoceran in Lake Taihu had changed with the change of ecological environment. Especially, the change of the relative proportion of the eutrophic species (Bosmina longirostris) and the poor nutrient species (Bosmina longispina) indicated the evolution process of the eutrophication in Lake Taihu. At the end of 1970s, the western and central regions of Lake Taihu entered the eutrophication stage. The composition of cladoceran assemblages was single with a high-level abundance of Bosmina spp. and scarce littoral and benthic species compared with the eastern Lake Taihu. After 1960s, the cladoceran community in eastern Lake Taihu became relatively abundant but with a decrease of the abundance of cladocerans, which responded to the expansion of submerged vegetation biomass, swampiness and the aggravating eutrophication since 1960 AD.

Paleoecological assessment of cladoceran community dynamics in two subarctic peatlands

Crustacean community structure and dynamics are very well studied in lakes, rivers and oceanic systems but wetlands, where moisture conditions fluctuate, have not received equal attention in research. For example, cladoceran communities in peatland systems in the subarctic region have not been fully investigated. We used paleolimnological and paleoecological methods to study plant and cladoceran assemblages and the community dynamics in two subarctic peatlands, which differ in their hydrological characteristics. At the first site, Iitto, river floods introduce planktonic species to fen pools and the steep topography of the catchment induces rapid but relatively short flooding periods. Fluctuating environmental conditions result in a high amount of cladoceran resting stages in the samples. At the other site, Kaamanen, the cladoceran assemblage goes through clear directional changes, which could be attributed to changes in fen hydrology and ultimately to climatic changes during the past two millennia.

Cladoceran assemblage changes across the Eastern United States as recorded in the sediments from the 2007 National Lakes Assessment, USA

Cladoceran zooplankton subfossils have been widely applied as indicators of lake health and used to infer past environmental change. However, our understanding of how the environment controls the abundance and distribution of Cladocera, as recorded in lake sediments, is still developing; only a few large landscape studies have been conducted in temperate North American lakes. Here we examine cladoceran remains from across 72 lakes and through time by analysing sediments that were collected as part of the US Environmental Protection Agency 2007 National Lakes Assessment. Using both taxonomic and functional-trait approaches, we related both taxonomic and functional-trait subfossil cladoceran assemblages to a suite of biological, chemical, and physical variables of lake health by applying Redundancy Analyses and Multivariate Regression Trees. Primary gradients identified as predictors of the cladoceran assemblages were: calcium and pH, depth and measures associated with pelagic and littoral habitat, and climate. Notably, calcium was identified as the primary driver of the Bosminidae, with greater relative abundances of Bosmina longirostris at concentrations ≥3.99 mg L−1, and with Eubosmina spp. associated with lower concentrations. Comparison of surface and pre-industrial sediments on a northern (temperate) lake subset suggested that the primary agents of change were localized, as we did not detect consistent directional shifts in Cladocera. In particular, the quality and complexity of the littoral habitat were associated with changes in key cladoceran groups through time. Overall, our study identified insightful relationships between cladoceran subfossil assemblages and environmental variables across spatial and temporal gradients, which are critical for refining the utility of Cladocera as ecological indicators in paleolimnological studies.

Spatial distribution of cladoceran assemblages in surface sediments of shallow lakes in Yunnan.

Shallow lakes, sensitive to environmental changes due to low environmental carrying capacity, generally experience decreases in ecosystem function and even regime shifts after over-exploitation. Surface sediments of 18 shallow lakes in Yunnan were collected and analyzed to identify the spatial pattern and the influencing factors of cladoceran communities. The results showed that there was significant heterogeneity in the spatial distribution of cladocera in those lakes. For example, the cladoceran community was generally dominated by benthic taxa in alpine lakes, while there was a clear replacement of benthic cladocerans by planktonic ones with increasing nutrient levels across lakes from Southeast Yunnan. Altitude and total phosphorus were the main driving factors, which independently explained 22.0% and 7.7% of the change in cladocera communities, respectively. The altitude gradient and related changes in climate and catchment features were the main factors in structuring cladocerans for shallow lakes of Yunnan, while the anthropogenic impacts on cladoceran distribution was significant via the processes such as catchment development, pollutant input and macrophyte changes. Meanwhile, the interaction between elevation and total phosphorus explained 26.3% of the total variance in cladoceran community shift, indicating that the increase in human activity intensity in lakes at lower altitudes would have stronger impact on cladocerans through anthropogenic nutrient inputs.

Cladocera in shallow lakes from the Ecuadorian Andes show little response to recent climate change

Lakes of the Andean paramo are critical water reservoirs for millions of people. Paramo ecosystems have experienced anthropogenic warming faster than the global average. Recent paleolimnological work from Cajas National Park (southern Ecuador) revealed striking shifts in diatoms and Cladocera linked to climate change. However, the impacts on shallow lakes (< 5 m deep), which are numerically dominant on the landscape, remain poorly understood. Here, we use paleolimnology to investigate cladoceran species changes and responses to climate change in three shallow waterbodies from Cajas. Each system supported abundant littoral Cladocera. The deepest site (~ 4 m) contained the highest proportion of pelagic taxa, while the shallowest (~ 0.3 m) contained almost exclusively littoral taxa. Cladoceran assemblages in these shallow lakes reflect littoral habitat, likely partly influenced by shifting precipitation, and in one site, construction of a small rock dam. The cladoceran assemblage shifts do not align with regional temperature increases and reduced wind speeds, contrasting the ecological responses previously recorded in nearby deeper lakes. Although these polymictic, ice-free shallow systems are not immune to climate-related change, algal and cladoceran assemblages in nearby deeper lakes are responding earlier and more sensitively to recent climate changes, largely through changes to lake thermal stratification regimes.

Faunal diversity of Cladocera (Crustacea: Branchiopoda) with notes on biogeographically important species in the floodplain wetlands of the Subansiri river basin, India

The plankton samples collected from the Subansiri floodplain wetlands revealed a rich Cladocera assemblage of 55 species belonging to 30 genera and 7 families. The species richness represents 42% and 75% of the total amount of fresh water species reported from India and Assam, respectively. Chydoridae was the most speciose family, with 31 species, while Ilyocryptidae was represented by a single species. Sididae, Daphniidae, Bosminidae, Moinidae and Macrothricidae were represented by four, five, three, two and four species, respectively. The faunal composition is represented by cosmopolitan, tropical and oriental elements. The documentation ofDiaphanosoma dubium,Latonopsis australis,Simocephalus mixtus,Chydorus sphaericus,Chydorus parvus,Chydorus ovalis,Alonella clathratula,Pleuroxuscf.denticulatus,Picripleuroxus quasidenticulatus,Celsinotummacronyx,Coronatella anodontaandKurzia (Rostrukurzia) brevilabrishas biogeographic importance. We provide brief geographical distributional remarks about these 12 species from the collected samples. This was a preliminary study, as the fauna from the Indian subcontinent is poorly documented, and requires a taxonomic revision as a whole. The faunistic diversity of cladocerans comprises a clear representation of a tropical cladoceran assemblage.

Subfossil Cladocera from surface sediment reflect contemporary assemblages and their environmental controls in Iberian flatland ponds

Cladoceran subfossils from surface sediments have been recognized as useful and reliable ecological indicators in freshwater ecosystems. Nevertheless, investigations concerning the relationships between contemporary and sedimentary assemblages are scarce in the Mediterranean region and no studies are available from Iberian flatland ponds. Here, we explore the concordance between present-day Cladocera assemblages and their sedimentary remains from 25 ponds distributed across a vast heterogeneous region in the Iberian Plateau. Overall, this study aims at identifying sediment biological proxies with good capacity to track long-term changes in Iberian flatland ponds. We found a total of 15 and 18 taxa in the contemporary and sedimentary samples, respectively, with daphniids dominating water column samples whereas the majority of the remains recovered from surface sediments were from chydorids. In accordance with previous work, we found that subfossil Cladocera properly reflect the contemporary assemblages from which they are derived. Similarly, our results showed not only analogous environmental controls structuring contemporary and sedimentary assemblages (mainly pH and soluble reactive phosphorous), but also a similar proportion of explained variance in the two. Although there were several taxa occurring only in contemporary samples (Diaphanosoma brachyurum, Moina rosea, Macrothrix hirsuticornis, Scapholeberis sp. and Simocephalus sp.), we found that subfossil assemblages were significantly more rich, diverse, equitable and heterogeneous, indicating that an integrated sample of surface sediment from each pond may supply enough information for assessing cladoceran composition and the numerous drivers controlling their assemblage structure.

The usefulness of subfossil Cladocera remains in Younger Dryas climatic reconstructions in central Poland

Abstract Cladoceran-based paleotemperature estimates for the Younger Dryas for ten sections of paleo-oxbow lakes, valley mires, and lacustrine sediments from central Poland are presented, and their potential usefulness to climatostratigraphy is described. Most of the changes observed in the cladoceran assemblages are responses to climate changes. The cladoceran-based temperature reconstructions reflect cold conditions during the Younger Dryas (YD) and allow a division of this period into two phases: an older colder phase, between 12,800 and 12,000 cal yrs BP, and a younger, warmer phase, between ca. 12,000 and 11,500 cal yrs BP. The geomorphological features of the study sites and local environmental forces are also taken into consideration. The cladoceran-inferred summer temperature estimates from all of the study sites correspond closely with the available climate reconstruction for the YD in central Europe.

Climate change and Saharan dust drive recent cladoceran and primary production changes in remote alpine lakes of Sierra Nevada, Spain.

Recent anthropogenic climate change and the exponential increase over the past few decades of Saharan dust deposition, containing ecologically important inputs of phosphorus (P) and calcium (Ca), are potentially affecting remote aquatic ecosystems. In this study, we examine changes in cladoceran assemblage composition and chlorophyll-a concentrations over the past ~150years from high-resolution, well-dated sediment cores retrieved from six remote high mountain lakes in the Sierra Nevada Mountains of Southern Spain, a region affected by Saharan dust deposition. In each lake, marked shifts in cladoceran assemblages and chlorophyll-a concentrations in recent decades indicate a regional-scale response to climate and Saharan dust deposition. Chlorophyll-a concentrations have increased since the 1970s, consistent with a response to rising air temperatures and the intensification of atmospheric deposition of Saharan P. Similar shifts in cladoceran taxa across lakes began over a century ago, but have intensified over the past ~50years, concurrent with trends in regional air temperature, precipitation, and increased Saharan dust deposition. An abrupt increase in the relative abundance of the benthic cladoceran Alona quadrangularis at the expense of Chydorus sphaericus, and a significant increase in Daphnia pulex gr. was a common trend in these softwater lakes. Differences in the magnitude and timing of these changes are likely due to catchment and lake-specific differences. In contrast with other alpine lakes that are often affected by acid deposition, atmospheric Ca deposition appears to be a significant explanatory factor, among others, for the changes in the lake biota of Sierra Nevada that has not been previously considered. The effects observed in Sierra Nevada are likely occurring in other Mediterranean lake districts, especially in softwater, oligotrophic lakes. The predicted increases in global temperature and Saharan dust deposition in the future will further impact the ecological condition of these ecosystems.