Alona Affinis Research Articles

Гіллястовусі раки Львівщини (Crustacea: Cladocera) у гідробіологічних дослідженнях Б. Дибовського та М. Гроховського (за матеріалами круглого столу екологічної комісії наукового товариства ім. Шевченка)

49 taxa of Cladocera were registered in the reservoirs of Lviv region according to the materials of B. Dybovskyi and M. Grohovskyi. From the point of view of faunal diversity, the studied locations can be divided into two groups. The first group of locations (registered 10 or more taxa each): Pelchynsky pond, Yanivsky pond, Big Golosko. The second group of locations (up to 5 taxa are registered): Kilinsky Park, Sobka pond, Small Golosko, Zboishcha, Snopkiv, Horodok, Zhydachiv. The largest number of Cladocera taxa was registered in the Janivsky pond (21 taxa). The smallest number (1 taxon) was registered in the location Zboyishcha. Taking into account the frequency of occurrence, 4 groups of taxa were distinguished. The first group has a frequency of 10 % (34 taxa), the second – 21 % (10 taxa), the third – 30 % (4 taxa), the fourth – 50 % (1 taxa). The most common taxa with a frequency of 30 % include Alona affinis, Leydig., Ceriodaphnia polonica, nob., Peracantha truncata, O. Fr. Müll., Sida crystallina, O. Fr. Müll. The frequency of occurrence of 50 % is characteristic of Simocephalus vetulus, O. F. Müll. The measure of pairwise similarity of the Cladocera fauna of reservoirs of various locations, calculated by the Jaccard index and the Sørensen index, has the same trends. 23 pairs of water bodies do not have common species. For them, the Jaccard index and the Sørensen index are equal to zero. The highest coefficient of similarity of fauna between the reservoirs of the locations Kilinsky Park and Zboiyshche (Jaccard’s index – 33 %, Sørensen’s index – 50 %). The lowest rate was registered for the locations Yaniv – Zhidachiv and Small Golosko – Yaniv (Jaccard’s index – 4 %, Sørensen’s index – 8 %). The Jaccard index is characterized by a larger amplitude of the calculated indicators and gives better differentiation at high and average indicators of similarity. With low indicators of similarity, the Sørensen index is preferred. The conducted research is of particular interest in view of the faunal analysis of Cladocera groups and the comparative characteristics of indicators identifying long periods of time. Such materials are one of the key aspects on which the issue of hydroecological monitoring is based.

Human impacts on the cladoceran community of Jili Lake, arid NW China, over the past century

Deterioration of aquatic ecosystems, as a consequence of human-induced disturbances, is a critical global concern. To fully understand the responses of aquatic systems to anthropogenic impacts, it is crucial to assess long-term changes in lakes. The water quality of Jili Lake, a large water body in northwest China, has deteriorated recently, owing to the growing impacts of regional warming and human activities. Thus, Jili Lake was a prime candidate for evaluation of historical multi-stressor impacts. Meteorological data, historical documents, and assemblages of cladoceran microfossils in the sediments of Jili Lake were employed to investigate changes in the cladoceran community over the past century, and to evaluate the response of that aquatic community to human activities. From the 1920s to the 1950s, species richness of the cladoceran community was high, which reflected conditions of relatively low human impact. From the 1960s to 1970s, a sharp decrease in Bosmina longirostris, a planktonic cladoceran species, suggested a decrease in water level as a result of dam construction and intensified water exploitation. Since the 1980s, the water level in the lake has been restored, but increased fish farming and construction of a water storage facility caused salinisation and eutrophication of Jili Lake. Accordingly, the cladoceran community displayed distinct signs of a regime shift, with a gradual transition to dominance of B. longirostris and a sharp decrease in littoral species (e.g. Leydigia leydigi, L. acanthocercoides, Alona quadrangularis, Alona affinis). Our results suggest that human-induced disturbances were the main factor that drove changes in the cladoceran community since about the mid-20th century.

Biological and geochemical indicators of climatic oscillations during the Last Glacial Termination, the Kaniewo palaeolake (Central Poland)

• Bølling-Allerød complex shows climatic heterogeneity and includes cold events. • Deglaciation passed 3 cold (GS-2a, GI-1d, GS-1) and 2 warm periods (GI-1e, GI-1a-c) • Traces of cold oscillation (GI-1b) within the Allerød were found. This study presents the results and interpretations of biological (floral and faunal) and geochemical (isotopic and chemical element composition) investigations of the Late Glacial and Holocene sediment accumulated in the Kaniewo palaeolake. These data allowed us to determine the indicators of environmental changes in this lake ecosystem, such as zooplankton and vegetation development, trophic state, water temperature, and water level. We documented the three cold periods (Oldest, Older, and Younger Dryas) separated by two warm periods (Bølling, Allerød). Additionally, we found traces of cold oscillations within the Allerød, lasting approximately 150 years, probably the Intra-Allerød-Gerzensee oscillation, recorded in western and southern Europe. Our data show that sediment accumulation began at the end of the Oldest Dryas period before ca. 13,900 yr cal BP. The top of the studied sediments represented the transition from the Late Glacial to the early Holocene (Preboreal period, ca.10,500 yr cal BP). The lithology of the sediments changed from silty sands at the bottom, then calcareous detritus gyttja partially interbedded by lake marl to peat at the top. Organic matter occurring in the deposits reflects algae and terrestrial sources. In the cold periods, small number of both Cladocera individuals and species (e.g. Bosmina (E.) longispina , Chydorus sphaericus , Alona affinis ), corroborate the unfavourable conditions for the development of zooplankton. Cladocera species indicated the initial oligotrophic status of the lake and the subsequent increase in trophic status. Plant and animal macrofossils indicate initial shallow lake ecosystem. Chara meadow developed at the bottom of the lake with a belt of vascular plants ( Carex sp., Hippuris vulgaris , Scirpus sp . ) in the littoral zone of the lake. Rich shallow vegetation was accompanied by animals, such as Mollusca (e.g. Valvata piscinalis, Pisidium obtusale, Bithynia tentaculata ) and Oribatidae sp., Cristatella mucedo , and Plumatella type.

Subfossil cladoceran assemblages in the sediment core from the Arctic Lake Arkto-Pimberto of the Pechora Delta (Nenets Autonomous Okrug, Russia)

This paleoecological investigation is based on the analysis of bottom sediment columns sampled during a summer research expedition in 2018 from the Arctic Lake Arkto-Pimberto, which is located within the Pechora River delta in the Nenets State Nature Reserve. Lake Arkto-Pimberto is of great interest for research due to several reasons: it is round in shape and small in diameter; its depth is less than 2 m (9 m); the lake has not been subjected to any anthropogenic influence. Our investigation shows that the cladoceran communities of the studied lake are diverse and abundant. In total, 16 Cladocera taxa were found in the samples. Most of the identified taxa belong to the Chydoridae family. The Bosminidae family includes only two species. Bosmina longispina was the absolute dominant among the subfossil remains of Cladocera. The subdominants were represented by Chydorus cf. sphaericus, Alona affinis, and Rhynchotalona falcata. The Shannon diversity index varied from 0.86 to 1.85. According to the PantleBuck saprobity index modied by Sladecek, the lake is mesosaprobic.

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.

The Eemian/Early Vistulian development of the Solniki paleolake (north-eastern Poland) as shown by subfossil Cladocera

<p>This work presents results of a paleolimnological study focussed on subfossil Cladocera analysis and on different aspects of the evolution of the Solniki paleolake during the Eemian/Early Vistulian period. The study aimed at the reconstruction of the long-term dynamics of this paleoecosystem and at defining the conditions (<em>e.g</em>., water level, trophic status and water temperature) of the ancient lake. Paleolacustrine deposits of ca. 10 m thickness were discovered at Solniki during cartographic works for the Trześcianka sheet of the Detailed Geological Map of Poland. This archives recorded one full-interglacial sequence (Eemian Interglacial), one interstadial warming (Brørup) and two stadial coolings (Herning and Rederstall) stages, which were confirmed by palynological analyses. The subfossil Cladocera fauna from the Solniki paleolake consisted in 17 species belonging to the families Bosminidae, Chydoridae, Sididae and Daphniidae. Littoral species were dominant (52%), the most frequent of which were <em>Alona affinis</em> and <em>Camptocercus rectirostris</em>. The most abundance pelagic species were <em>Eubosmina coregoni</em> and <em>Bosmina longirostris</em>. The sediment species composition was quite similar to that of contemporary Central European lakes. The early and the late stages of Eemian Interglacial were likely the most favourable periods for the Cladocera development in the paleolake, in relation to higher water level, moderate water temperature and the mesotrophic state of water. A further ecologically favourable period was the Brørup Interstadial. The highest species richness, abundance, and diversity during the whole paleolake existence were recorded during these three periods. Surprisingly, the middle of the Middle Eemian Interglacial climate optimum appeared as an unfavourable period for the Cladocera growth as it was associated with decreasing water level and pronounced climate fluctuations. This sequence was also recorded by other studies of Eemian lakes in Central Europe.</p>

Role of terrestrial carbon in aquatic UV exposure and photoprotective pigmentation of meiofauna in subarctic lakes

Summary Aquatic organisms are adversely influenced by ultraviolet radiation (UV) and utilise photoprotective strategies, including pigmentation. We examined UV‐protective melanin pigmentation of aquatic meiofauna (Cladocera) in relation to the UV exposure across 25 tree line lakes in Finland to address the potential effects of increased UV and altered input of UV‐screening terrestrial dissolved organic carbon (DOC) on aquatic organisms. Bio‐optical parameters, including concentration of DOC, the coloured dissolved organic matter (CDOM) fraction, a suite of carbon quality indices and chlorophyll a, were analysed from lake water, and their role in controlling underwater UV environment (measured as diffuse UV attenuation coefficient Kd at 305 and 340 nm) was examined. Cladoceran (Alona affinis) carapaces were extracted from the surface sediments, and their melanisation was assessed with spectroscopic UV‐visible light absorbance measurements. DOC, CDOM and specific UV absorbance (SUVA) had strong positive relationships with the attenuation of UV in the lakes, suggesting that terrestrial organic carbon controls underwater UV exposure in the examined lakes. The absorbance measurements indicated the presence of melanin in the cladoceran carapaces, the degree of melanisation varying strongly among the lakes. Melanisation had significant relationships with SUVA and fluorescence index (FI). It was higher in lakes with low SUVA and high FI, indicating that cladocerans exhibit strong melanisation in lakes with low contribution of UV‐attenuating allochthonous DOC (i.e. high UV exposure). The results suggest that cladoceran meiofauna respond to UV by utilising photoprotective pigmentation and that the degree of pigmentation is affected by site‐specific underwater UV exposure, which is ultimately controlled by UV‐attenuating DOC of terrestrial origin. Although cladoceran meiobenthos are able to adapt to varying underwater UV doses, climate change with its multiple consequences on hydrology, limnology and catchment vegetation in the tree line zone may cause major changes in underwater UV environment for the organisms to adapt.

Sedimentary cladoceran assemblages and their functional attributes record late Holocene climate variability in southern Finland

We examined long-term relationships between Cladocera and limnogeological and climate variables in a late Holocene lake sediment sequence to assess cladoceran responses to climate change and reconstruct past climate variations in southern Finland, near the Baltic Sea coast. Elemental composition, organic matter, and inferred water quality variables were used to constrain paleoenvironmental (until 4500 cal BP) conditions and human impact. Fossil Cladocera assemblages, ephippia, and body size trends were utilized to estimate mean July air temperature (TJul) variability, open-water season length, and water-temperature regimes. Results revealed stable cladoceran communities, dominated by Eubosmina, until 500 cal BP, followed by major assemblage changes including increases in Chydorus cf. sphaericus, Alonella spp., and Bosmina longirostris. Pb and Cu concentrations were associated temporally with increasing human impact and warming climate during the past few centuries, and were the most significant factors in explaining cladoceran community changes, based on redundancy analysis. A Cladocera-based TJul reconstruction estimated elevated temperatures for the end of the Holocene Thermal Maximum, a cooler period during ~3000–2000 cal BP, slightly increased temperatures during 1200–800 cal BP corresponding to the Medieval Climate Anomaly (MCA), and lower temperatures during the Little Ice Age (LIA), 800–200 cal BP. The reconstruction also suggests that significant climate warming took place during the twentieth century. Cladocerans mostly associated with warm periods included B. longirostris and Pleuroxus uncinatus, whereas Alona affinis, A. quadrangularis, and C. cf. sphaericus were associated with colder climate. Compared to a reference Chironomidae-inferred TJul reconstruction from the same region, discrepancies were apparent in amplitude of temperature change, as the temperature variability in the cladoceran-based record was muted until ~200 cal BP. During the LIA, increased ephippia and body size agreed with the temperature reconstruction, but suggested a severely shorter open-water season and reduced water temperatures compared to the preceding late Holocene episodes, even though the cladoceran TJul showed quite similar temperatures for these periods. Our results suggest that fossil cladoceran assemblages, ephippia, and morphological attributes respond sensitively to long-term climate fluctuations and this record reflects well the major climate events of the late Holocene and provides realistic paleoclimatic estimates for maritime southern Finland.

Niche separation by littoral-benthic Chydoridae (Cladocera, Crustacea) in a deep lake - potential drivers of their distribution and role in littoral-pelagic coupling

Niche separation of 22 species of benthic Chydoridae was examined in a depth gradient in the littoral zone of a deep Lake Piaseczno (eastern Poland), by using a trap sampler. Individual species showed high segregation across the littoral zone according to depth, macrophyte biomass, total organic carbon (TOC), conductivity and pH, of which the depth turned out to be the most important. The species Acroperus harpae, Alona affinis, Alonella nana, Leydigia acanthocercoides, Pseudochydorus globosus, Pleuroxus trigonellus and Pleuroxus aduncus were found in the whole littoral zone, but the remaining Chydoridae species displayed clear spatial distribution, e.g. Coronatella rectangula, Acroperus elongatus, Alona guttata, Alonella excisa, Alonella exigua, Rhychotalona falcata, Monospilus dispar and Pleuroxus truncatus settled the shallower parts of the littoral, whereas Eurycercus lamellatus, Camptocercus rectirostris, Pleuroxus laevis, Graptoleberis testudinaria, Alona costata, Pleuroxus uncinatus and Alona intermedia were found mainly in areas located 3-6 m deep. To find out the role of Chydoridae in littoral-pelagic food web coupling, the contribution of chydorids to total number of Cladocera in the guts of fish was estimated showing that they are an important intervening link in nutrient movement from the littoral to the pelagic zone, as their contribution to the total cladoceran number found in guts of fish caught in the pelagic zone was even as high as 98%. This study provides more insight into the nature of constraints associated with littoral-benthic cladocerans’ habitat preferences and their importance in littoral-pelagic coupling.

English

Taxonomic survey of the crustacean community was conducted at five study sites in Wular Lake. Plankton samples were collected on monthly basis from September 2010 to August 2011 and identified in the laboratory under different magnifications using the Olympus microscope. Of the 42 taxa identified, 23 were Cladocera, 16 were Copepoda and only three were Ostracoda. Among the Copepoda, one taxa namely Cyclops latipes seems to be a new addition which was previously unreported in Kashmir. Cladocera dominated Copepoda followed by Ostracoda in the community throughout the study. However, the species more frequently found in the samples were Chydorus sphaericus, Alona affinis, Bryocamptus minutus and Cyclops bicolor. As per the species composition of crustaceans, Lake Wular is still enjoying the infancy stage of eutrophication. Key words: Taxonomy, Cladocera, Copepoda, distribution, trophic status, Kashmir.

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.

Cladocerans of Alona affinis group (Cladocera: Anomopoda: Chydoridae) from North America.

Cladocera of Alona affinis group from North America preserved in the collection of Professor D. G. Frey were investigated. A new subspecies of Alona ossiani Sinev, 1998 is described. Alona ossiani herricki ssp. nov. differs from the nominative subspecies in presence of 2-3 marginal denticles on postanal angle of male postabdomen, no differences between subspecies were revealed in the female morphology. An obscure taxon Alona lepida Birge,1892 was shown to be a valid species of affinis-group and is redescribed. A. lepida shares characteristic features of the group, but differs from all other species in the body shape, by postabdominal claw with basal spine almost parallel to the claw itself, and by IDL seta 1 being not claw-like. Morphology, relationships and distribution of studied taxa are discussed.

Some crustacean zooplankton of Wular lake in Kashmir Himalaya

In a taxonomic survey of crustacean zooplankton collected from Wular lake of Kashmir, a pictorial key was developed. Thirty-six (36) pictures of 25 species of crustacean zooplankton, out of which 21 represented 16 Cladocera taxa belonging to Chydoridae ( Alona affinis, A. rectangula and A. monacantha, Chydorus sphaericus and C. ovalis ), Daphnidae (Daphnia magna, D. catawba, D. magna, D. pulex; D. rosea, D. galeata, D. retrocurva and Moinodaphn ia), Polyphemidae (Polyphemus pediculus ) and Sididae ( Sida crystallina) and 15 pictures of Copepoda belonged to 9 species being represented by three families viz Cyclopidae ( Cyclops scutifer, C. bicuspidatus, C. vernalis, C. panamensis, Eucyclops agilis, Megacyclops viridis) , Canthocamptidae ( Bryocamptus hiemalis ) and Diaptomidae (Diaptomus sp. ). Key words : Crustacean, Cladocera, Copepoda, taxonomy, Wular lake.

Spatio‐temporal distribution of sedimentary Cladocera (Crustacea: Branchiopoda) in relation to climate

AbstractAimSpatial and temporal variations in the composition of freshwater invertebrate assemblages may be useful indicators of past climate change and help us to predict species responses to future climate change. The objective of this study was to understand the relationship between climate variables and fossil Cladocera assemblages in lake sediments along a contemporary climate gradient from hemiboreal to subarctic ecoregions in Finland and throughout the Holocene climate succession.LocationSeventy‐three small shallow lakes across a climate gradient from hemiboreal (60° N) to subarctic (70° N) Finland and a case study lake, Lake Arapisto, in south boreal Finland.MethodsFossil cladoceran assemblages were analysed from the surface sediments of 73 lakes to investigate their association with climate, using ordination techniques (detrended correspondence analysis and redundancy analysis) and generalized linear modelling (GLM). The long‐term variation of the abundance of specific climate‐sensitive cladoceran species was then analysed in a sediment core from a boreal lake and compared with a chironomid‐based Holocene temperature reconstruction from an adjacent lake.ResultsMean July air temperature was identified as a significant variable in explaining species distribution across the spatial climate gradient. This result, together with GLMs that recognized several climate‐sensitive species, indicates that certain cladoceran taxa may be useful indicators of climate. For example, the planktonic Bosmina longirostris and the phytophilous Graptoleberis testudinaria were more abundant in the warm southern lakes, in contrast to the benthic Alona affinis and Alona intermedia, which were typical for the cold northern lakes. The surface‐sediment inferences were supported by the core analysis from Lake Arapisto, because species associated with cold lakes increased in abundance during the cold early Holocene, and species associated with warm lakes thrived during the Holocene Thermal Maximum and Anthropocene.Main conclusionsThe spatio‐temporal distribution of Cladocera is regulated by regional climate, and therefore the species–climate relationships in space and time can be used to interpret past, present and future distributional patterns under a changing climate.

Sedimentary chydorid (Cladocera) ephippia in relation to lake ecological quality in the Austrian Alps

Research on chydorid (Crustacea: Cladocera: Chydoridae) reproduction is scarce and very little is known about the dynamics of parthenogenetic (asexual) and gamogenetic (sexual) reproduction modes in these cyclical parthenogens. The paleolimnological approach has a lot to offer to this research since chydorid carapaces (indicative of asexual reproduction) and ephippia (indicative of sexual reproduction) are identifiable in lake sediments. In the current study, we examined historical changes in chydorid reproduction patterns in an Austrian Alpine lake with the objective to explore reproductive shifts under limnological variability and with the hypothesis that sexual reproduction intensifies under unfavourable environmental conditions. For this, we utilised subfossil remains from a sediment sequence covering the past ~300 years in a high Alpine lake, lake Oberer Landschitzsee. The results suggested that in-lake processes likely changed as a response to post-Little Ice Age (LIA) climate warming. Indeed, the benthic quality – indicated by the chironomidbased benthic quality index (BQI) – deteriorated, and the productivity – indicated by organic matter in the sediment – increased. The chydorid community exhibited dramatic shifts in the post-LIA section of the core, around 1850-1950 AD, when the two dominant species Alona (A.) affinis and A. quadrangularis were outcompeted by Acroperus harpae, Alonella excisa, and Chydorus (C.) sphaericus-type and their reproduction gradually shifted towards the dominance of sexual reproduction. The community shift and prevalence of sexual reproduction coincided with the period of unfavourable limnological conditions, evidenced by low BQI values and higher organic content. Therefore, we suggest that the intensified sexual reproduction was a local response to deteriorated benthic conditions and a vigorous adaptive mechanism to ensure successful diapause and genetic variability under environmental change. The results give reason to suggest that fossil chydorid assemblages and ephippia indicate the ecological quality of lake ecosystems and, thus, they can be used as additional proxies in future assessments of the lake ecological status.

Response of subfossil Cladocera in Gerzensee (Swiss Plateau) to early Late Glacial environmental change

Sub-fossil Cladocera were studied in a core from Gerzensee (Swiss Plateau) for the late-glacial periods of Oldest Dryas, Bølling, and Allerød. Cladocera assemblages were dominated by cold-tolerant littoral taxa Chydorus sphaericus, Acroperus harpae, Alonella nana, Alona affinis, and Alonella excisa. The rapid warming at the beginning of the Bølling (GI-1e) ca. 14,650yr before present (BP: before AD 1950) was indicated by an abrupt 2‰ shift in carbonate δ18O and a clear change in pollen assemblages. Cladocera assemblages, in contrast, changed more gradually. C. sphaericus and A. harpae are the most cold-tolerant, and their abundance was highest in the earliest part of the record. Only 150–200years after the beginning of the Bølling warming we observed an increase in less cold-tolerant A. excisa and A. affinis. The establishment of Alona guttata, A. guttata var. tuberculata, and Pleuroxus unicatus was delayed by ca. 350, 770, and 800years respectively after the onset of the Bølling. The development of the Cladocera assemblages suggests increasing water temperatures during the Bølling/Allerød, which agrees with the interpretation by von Grafenstein et al. (2013-this issue) that decreasing δ18O values in carbonates in this period reflect increasing summer water temperatures at the sediment–water interface. Other processes also affected the Cladocera community, including the development and diversification of aquatic vegetation favourable for Cladocera. The record is clearly dominated by Chydoridae, as expected for a littoral core. Yet, the planktonic Eubosmina-group occurred throughout the core, with the exception of a period at ca. 13,760–13,420yr BP. Lake levels reconstructed for this period are relatively low, indicating that the littoral location might have become too shallow for Eubosmina in that period.

Faunal (Chironomidae, Cladocera) responses to post-Little Ice Age climate warming in the high Austrian Alps

Present climate warming strongly affects limnological and ecological properties of lakes and may cause regime shifts that alter structure and function in the water bodies. Such effects are especially pronounced in climatologically extreme areas, e.g. at high altitudes. We examined a sediment core from Lake Oberer Landschitzsee, Austrian Alps, which spans the period from the Little Ice Age (LIA) to present. We investigated whether post-LIA climate warming altered aquatic invertebrate communities and limnological status in this sensitive high Alpine lake. Fossil Cladocera (Crustacea) and Chironomidae (Diptera) and organic matter in the core were analyzed. Chironomids were used to assess the lake’s benthic quality (i.e. oxygen availability). An instrumental Alpine temperature record was used to assess whether changes in the biotic assemblages correspond to post-LIA temperature trends. The planktonic and macro- and microbenthic invertebrate communities exhibit almost complete and simultaneous species turnover after the LIA, from about AD 1850 onward, when Sergentia coracina-type replaced oxyphilous Micropsectra contracta-type as the dominant macrobenthic taxon, and phytophilous Acroperus harpae outcompeted Alona affinis and Alona quadrangularis in the microbenthos. These directional community shifts corresponded with a period of reduced benthic quality, higher sediment organic content, and progressive climate warming, superimposed on Alpine land-use changes, until the early twentieth century. Detected changes suggest increased productivity and lower benthic oxygen availability. Faunal shifts were even more pronounced during the late twentieth century, simultaneous with enhanced warming. A new planktonic Cladocera species, Bosmina longirostris, typically absent from high Alpine lakes, colonized the lake and gradually became dominant toward the core top. Results show that post-LIA climate warming, coupled with increasing benthic and planktonic production, substantially altered the limnological and ecological status of this remote Alpine lake. Observed faunal turnovers provide evidence that temperature-driven ecological thresholds, whether associated directly or indirectly with greater human activity, have been crossed. Species abundances and distributions have changed in response to post-LIA and late twentieth century climate warming.

Paleolimnological reconstruction of the trophic state in Lake Balaton (Hungary) using Cladocera remains

The sediment of Lake Balaton (Hungary) provides important information about the lake’s history, particularly with regard to eutrophication. In this study, we used fossil pigment analysis and subfossil Cladocera remains preserved in a dated sediment core to identify trophic stages from ~250 bc to present. Dates of the most recent eutrophic events are in good agreement with previously published data. In general, the abundance and diversity of the Cladocera community increased with eutrophication and decreased with oligotrophication. The sediments of Lake Balaton were characterised by Chydoridae remains, of which Alona species were the most abundant. Of these, Alona quadrangularis and Alona affinis accounted for 40 and 20% of the total Cladocera remains, respectively. The trophic state of Lake Balaton varied between mesotrophic and eutrophic regimes. Seven different trophic periods were identified in Lake Balaton on the basis of Sedimentary Pigment Degradation Unit (SPDU) content of the sediment. Eutrophic states were (1) from ~250 to ~30 bc, (3) between ~300 and ~590 ad, (5) between 1834 and 1944 and (7) from the 1960s until present. Mesotrophic states were (2) ~30 bc to ~300 ad, (4) 590–1834, (6) 1944–1960s. Discriminant analysis of the cladoceran data confirmed these historic events, except for the short mesotrophic episode between 1944 and 1960. The first stage of eutrophication of Lake Balaton (~250 to ~30 bc) was characterised by extensive macrophyte vegetation, as indicated by the increasing abundance of vegetation-associated Cladocera species (Eurycercus lamellatus, Sida crystallina, Pleuroxus sp.). Intensification of eutrophication was identified since the 1980s, reflected by a high abundance of Bosmina species. The most significant planktivorous fish of Lake Balaton was the Sabre carp (Pelecus cultratus), and when its number decreased, the abundance of Bosmina species increased. This study shows that Cladocera are responsive to trophic state changes, underlining their importance as a tool for the assessment of lake eutrophication.

Cladocera response to Late Glacial to Early Holocene climate change in a South Carpathian mountain lake

This study explores changes in cladoceran composition in a high mountain lake of the Retezat (Lake Brazi), the South Carpathian Mountains of Romania, during the Late Glacial–Early Holocene (14,500–11,600 cal. yr. bp) transition using a paleolimnological approach. The lake had a species poor cladoceran community throughout this period. Daphnia longispina, Chydorus sphaericus and Alona affinis were the most common, showing marked fluctuations in their relative abundances through time. Distinct faunal response to warming at the Younger Dryas (YD)/Preboreal transition was recorded by increasing fossil densities and distinct community composition change: Alona affinis became dominant while numbers of Chydorus sphaericus dramatically decreased. In the Early Holocene, the productivity of Lake Brazi seem to have increased as reflected by higher numbers of Cladocera due to appearance of new species (Alona rectangula, A. quadrangularis and A. guttata) which are common in productive waters. Significant negative correlation was found between average dorsal length of daphnid ephippia and the NGRIP δ18O isotope values. Given the absence of fish predation, changes in Daphnia ephippia size were taken to indicate climatic change: larger ephippium size inferred cold conditions during the Late Glacial, while smaller size reflected climate warming during the Early Holocene. We conclude that Cladocera fossils are good indicators of climatic change that happened during the transition from the Late Glacial to the Holocene. We found that climatic conditions can be tracked either by size distribution of Daphnia ephippia (larger ephippium size under colder climate) and/or by community change of cladocerans.

The Afromontane Cladocera (Crustacea: Branchiopoda) of the Rwenzori (Uganda–D. R. Congo): taxonomy, ecology and biogeography

The timely characterization of high-altitude freshwater habitats allows an assessment of the diversity of its biota and provides the basis for monitoring community change. In this study, we investigate the Cladocera fauna of 29 water bodies (pools, freshwater lakes, and surrounding swamps sampled at various occasions between 2005 and 2009) in the Rwenzori Mountains (Uganda, D. R. Congo), which are part of the East African Sky Island Complex. All sites except one are located above 3700 m altitude. We include notes on the morphology, taxonomy, distribution, and ecology of each recorded taxon and describe a new species of the Alona rustica-group (Alona sphagnophila n.sp.; Chydoridae). We found 11 species of which seven are restricted to Lake Mahoma, the lowest lake in our study area (2990 m) (Alona affinis barbata, A. intermedia, Alonella exisa, Alonella nana, Daphnia cf. obtusa, Pleuroxus aduncus) and/or Lake Bujuku (Daphnia cf. curvirostris, P. aduncus) (3900 m). Two taxa (Ilyocryptus cf. gouldeni, A. sphagnophila n.sp.) are restricted to Carex/Sphagnum bogs surrounding lakes in the afroalpine zone. Pigmented populations of Chydorus cf. sphaericus occur in all the sites. It is the only cladoceran species surviving the extreme alpine and nival conditions in the Rwenzori. The species is joined by A. guttata at locations at lower altitudes (ca. 3000–4000 m), present in about half of the sites. The Rwenzori Cladocera fauna is characterized by a strong extratropical temperate component and a low level of speciation/endemism. Harboring an impoverished boreal cladoceran community, Lake Mahoma is given closer attention. At 2990 m, the lake is a cold-temperate aquatic island in the tropics and may function as a stepping stone for Palaearctic taxa. We introduce a new term for high-altitude, cold-water habitats in the tropics, which act as climatic islands for extratropical freshwater faunas, Loffler Islands, in honor of Dr Heinz Loffler. In comparison to surveys in 1961, we list five new records in Lake Mahoma, which could indicate cladoceran community changes over the past few decades at ca. 3000 m in the Rwenzori. Since the species distributions correlate to temperature and catchment properties of the lakes, the Rwenzori cladoceran fauna can be expected as sensitive indicators for local changes.