Showing papers in "Journal of Limnology in 2013"
TL;DR: The continental core of Southeast (SE) Asia, Sundaland, was assembled from Gondwana fragments by the Early Mesozoic as mentioned in this paper, and continental blocks rifted from Australia in the Jurassic [South West (SW) Borneo, East Java-West Sulawesi-Sumba], and the Woyla intraoceanic arc of Sumatra, were added toSundaland in the Cretaceous.
Abstract: The continental core of Southeast (SE) Asia, Sundaland, was assembled from Gondwana fragments by the Early Mesozoic. Continental blocks rifted from Australia in the Jurassic [South West (SW) Borneo, East Java-West Sulawesi-Sumba], and the Woyla intraoceanic arc of Sumatra, were added to Sundaland in the Cretaceous. These fragments probably included emergent areas and could have carried a terrestrial flora and fauna. Sarawak, the offshore Luconia-Dangerous Grounds areas, and Palawan include Asian continental material. These probably represent a wide accretionary zone at the Asia-Pacific boundary, which was an active continental margin until the mid Cretaceous. Subduction ceased around Sundaland in the Late Cretaceous, and from about 80 Ma most of Sundaland was emergent, physically connected to Asia, but separated by deep oceans from India and Australia. India moved rapidly north during the Late Cretaceous and Early Cenozoic but there is no evidence that it made contact with SE Asia prior to collision with Asia. One or more arc-India collisions during the Eocene may have preceded India-Asia collision. The arcs could have provided dispersal pathways from India into SE Asia before final suturing of the two continents. During the Late Cretaceous and Early Cenozoic there was no significant subduction beneath Sumatra, Java and Borneo. At about 45 Ma Australia began to move north, subduction resumed and there was widespread rifting within Sundaland. During the Paleogene east and north Borneo were largely submerged, the Makassar Straits became a wide marine barrier within Sundaland, and West Sulawesi was separated from Sundaland but included land. By the Early Miocene the proto-South China Sea had been eliminated by subduction leading to emergence of land in central Borneo, Sabah and Palawan. Australia-SE Asia collision began, eliminating the former deep ocean separating the two continents, and forming the region now known as Wallacea. The microplate or terrane concept of slicing fragments from New Guinea followed by multiple collisions in Wallacea is implausible. Neogene subduction drove extension and fragmentation of Wallacea that caused both subsidence of deep marine basins and elevation of land; bathymetry changed very rapidly, especially during the Pliocene, but the detailed palaeogeography of this region remains uncertain.
189 citations
TL;DR: This paper proposes the Tardigrada Register, a free, comprehensive, and standardised online data repository for tardigrade taxonomy, and describes the idea, structure and works of the service and discusses challenges it may face.
Abstract: In this paper we present the Tardigrada Register (www.tardigrada.net/register): a free, comprehensive, and standardised online data repository for tardigrade taxonomy. We outline key problems of the modern tardigrade systematics and we propose the Register as a potential solution to some of them. We then describe the idea, structure and works of the service and discuss challenges it may face. However, most importantly, we hope to convince fellow Tardigradologists that sharing their data via the Register will benefit the entire community of the contemporary and future tardigrade researchers.
128 citations
TL;DR: This review gives an overview of the most abundant prokaryotic populations by grouping them in specific ecological guilds based on their life strategies, reflected in a distinct seasonality of the freshwater bacterioplankton.
Abstract: Lakes and ponds harbour a high number of diverse planktonic microorganisms that are centrally involved in biochemical cycles and aquatic food webs. Although the open water body (pelagial) seems to be a uniform and unstructured environment, ecological niche separation of coexisting microbial taxa might be triggered by limiting resources (bottom-up control) and mortality factors (top-down control), leading to distinct spatial and temporal distribution patterns of different microbes. This review gives an overview of the most abundant prokaryotic populations by grouping them in specific ecological guilds based on their life strategies. Defense specialists such as very small actinobacteria or big filamentous bacteria mostly occur at times of highest grazing pressure by heterotrophic nanoflagellates, the main consumers of bacteria. Oligotrophic ultramicrobacteria , on the other hand, seem to be mostly adapted to nutrient depleted water layers during summer stratification, while opportunistic bacteria profit from material released during short-living algal blooms. Seasonal changes in abiotic and biotic factors may be the main causes for periodic reoccurring density maxima of different prokaryotes populations in the pelagial of temperate lakes, reflected in a distinct seasonality of the freshwater bacterioplankton.
81 citations
TL;DR: In this article, the authors presented an overview of optical remote sensing techniques applied to lake water monitoring, and showed the temporal trend of chlorophyll-a (chl-a), suspended particulate matter (SPM), coloured dissolved organic matter (CDOM), and the z90 signal depth, as estimated from the images acquired by the Medium Resolution Imaging Spectrometer (MERIS) in the pelagic area of the lake from 2003 to 2011.
Abstract: Optical satellite remote sensing represents an opportunity to integrate traditional methods for assessing water quality of lakes: strengths of remote sensing methods are the good spatial and temporal coverage, the possibility to monitor many lakes simultaneously and the reduced costs In this work we present an overview of optical remote sensing techniques applied to lake water monitoring Then, examples of applications focused on lake Maggiore, the second largest lake in Italy are discussed by presenting the temporal trend of chlorophyll-a (chl-a), suspended particulate matter (SPM), coloured dissolved organic matter (CDOM) and the z90 signal depth (the latter indicating the water depth from which 90% of the reflected light comes from) as estimated from the images acquired by the Medium Resolution Imaging Spectrometer (MERIS) in the pelagic area of the lake from 2003 to 2011 Concerning the chl-a trend, the results are in agreement with the concentration values measured during field surveys, confirming the good status of lake Maggiore, although occasional events of water deterioration were observed ( eg , an average increase of chl-a concentration, with a decrease of transparency, as a consequence of an anomalous phytoplankton occurred in summer 2011) A series of MERIS-derived maps (summer period 2011) of the z90 signal are also analysed in order to show the spatial variability of lake waters, which on average were clearer in the central pelagic zones We expect that the recently launched ( eg , Landsat-8) and the future satellite missions ( eg , Sentinel-3) carrying sensors with improved spectral and spatial resolution are going to lead to a larger use of remote sensing for the assessment and monitoring of water quality parameters, by also allowing further applications ( eg , classification of phytoplankton functional types) to be developed
55 citations
50 citations
TL;DR: The fish kill in lake Peipsi (Estonia/Russia) during the extraordinarily hot summer of 2010 evoked an investigation into the effects of environmental extremes and long-term eutrophication on the fish community of the lake as discussed by the authors.
Abstract: The fish kill in lake Peipsi (Estonia/Russia) during the extraordinarily hot summer of 2010 evoked an investigation into the effects of environmental extremes and long-term eutrophication on the fish community of the lake. Current data on lake Peipsi indicate that temperature extremes and synergistic interactions with eutrophication have led to a radical restructuring of the fish community. Commercial landings of lake smelt, Osmerus eperlanus eperlanus m. spirinchus (Pallas), the previous dominant species of the fish community, have decreased dramatically since the 1930s, these declines being coupled with summer heat waves coinciding with low water levels. Gradual decline in smelt stock and catches was significantly related to a decline of near-bottom oxygen conditions and to a decrease in water transparency. The first documented fish kill in 1959 occurred only in the southern, most shallow and eutrophic lake (lake Pihkva). Recently, summer fish kill have become more frequent, involving larger areas of the lake. In addition to the cold-water species, e.g. smelt and vendace Coregonus albula (L.), the abundance of bottom-dwelling fishes such as ruffe Gymnocephalus cernuus (L.) and juvenile fish have significantly decreased after the 2010 heat wave probably due to hypoxia and warm water temperatures. This study showed that fish community structure in large shallow lakes may be very vulnerable to water temperature increases, especially temperature extremes in combination with eutrophication.
43 citations
TL;DR: Generally, the cladoceran faunas of SE Asia are poorly known and only continuous extensive taxonomic studies would improve this situation.
Abstract: The history of Cladocera studies in South-East Asia is reviewed, beginning from the early start of explorations in the end of the 19 th century by J. Richard and T. Stingelin. In the first half of the 20 th century, extensive research was carried out by V. Brehm, who investigated material collected by the Wallacea-Expedition and the Deutschen Limnologischen Sunda-Expedition. Later, in the 1970-1980s, C.H. Fernando and collaborators, besides a few other researchers, provided a new series of regional studies of the cladoceran faunas together with the systematic revisions of some taxa from tropical Asia. Then and up to present, investigations of the Cladocera have concentrated in Thailand and many species have been revised and described as new to science. In total, 298 taxa of species rank have been recorded in SE Asia but only comparatively few of them (67 taxa; 22.5%) can be regarded good species, of which the valid status has been confirmed by recent studies, while others are synonyms (68; 22.8%) or taxa of uncertain taxonomic status, including those which definitely represent complexes of species (163; 54.7%). Most total taxa of species level and good species are known from Thailand (155 and 54, respectively), followed by Malaysia (plus Singapore), Indonesia, Philippines, Vietnam, and Cambodia in this respect (70-119 total taxa and 23-33 good species respectively). Laos, Burma (Myanmar) and Brunei remain practically unexplored. Only good species were used for the zoogeographic analysis. Of them, about a quarter is known only in SE Asia but more species are distributed in tropical/subtropical/temperate Asia and Australia, others in tropics/subtropics of the eastern hemisphere (17.9%) or even wider. Tropical species, constituting the primary part of the cladoceran fauna of SE Asia, can penetrate the neighboring subtropical and southern temperate zones to a different degree. Only a small fraction of species (7 or 10.5%) here are of more or less northern origin, the are distributed predominantly in the subtropical/southern temperate or in the northern boreal latitudes. Few species are suggested to penetrate SE Asia from the north using the Mekong river and its tributaries. Generally, the cladocerans of SE Asia are poorly known and only continuous extensive taxonomic studies would improve this situation.
40 citations
TL;DR: The period of water permanence in rice fields resulted to be only one of the factors influencing the community of benthic macroinvertebrates, and the role of the water chemical-physical parameters was emphasised.
Abstract: Rice fields can be considered man-managed temporary wetlands Five rice fields handled with different management strategies, their adjacent channels, and a spring were analysed by their benthic macroinvertebrate community to i) evaluate the role of rice agroecosystem in biodiversity conservation; ii) find indicator species which can be used to compare the ecological status of natural wetlands with rice agroecosystems; and iii) find the influence of environmental variables on biodiversity Different methods of data analysis with increasing degree of complexity – from diversity index up to sophisticated multivariate analysis – were used The investigation provided a picture of benthic macroinvertebrates inhabiting rice agroecosystems where 173 taxa were identified, 89 of which detected in rice paddies Among them, 4 phyla (Mollusca, Annelida, Nematomorpha, and Arthropoda), 8 classes (Bivalvia, Gastropoda, Oligochaeta, Hirudinea, Gordioida, Insecta, Branchiopoda, and Malacostraca), 24 orders, 68 families, 127 genera and 159 species have been found Ten threatened and 3 invasive species were detected in the habitats examined The information obtained by the different methods of data analysis allowed a more comprehensive view on the value of the components of rice agroecosystems Data analyses highlighted significant differences between habitats (feeding channel and rice field), with higher diversity observed in channels, and emphasised the role of the water chemical-physical parameters The period of water permanence in rice fields resulted to be only one of the factors influencing the community of benthic macroinvertebrates The presence of rare/endangered species allowed characterising some stations, but it was less informative about management strategies in rice paddies because most of these species were absent in rice fields
39 citations
TL;DR: In this paper, the distribution of Branchinecta orientalis, B. ferox and Chirocephalus carnuntanus was assessed in the natural and semi-natural astatic soda pans of the Carpathian basin.
Abstract: The distribution of Branchinecta orientalis, B. ferox and Chirocephalus carnuntanus was assessed in the natural and semi-natural astatic soda pans of the Carpathian basin. In Europe, these habitats are exclusively restricted to Hungary (Great Hungarian Plain), Austria (Seewinkel) and Serbia (Vojvodina). The present research is the first comprehensive large-scale study – covering an area of approximately 125,000 km2 – on these three fairy shrimp species in the region, and it is important especially in the case of Branchinecta spp., due to former taxonomical uncertainties. The local, land use and spatial effects on the species distribution were also analysed. The three anostracans were found to adopt different strategies, mainly according to the salinity of the pans. The apparently halophilous B. orientalis tolerated higher salinities than the other species, which can be regarded as habitat-generalist halotolerants, showing a high preference for soda waters in Central Europe. The density of the species was significantly affected only by local factors, while their occurrence was influenced also by pan isolation. Land use did not explain a significant amount of variation in either case. In conclusion, soda pans with a wide range of different salinities constitute a suitable habitat for all the three species. Also, protected areas with high number of pans – as Seewinkel (in Austria) or Kiskunsag (in Hungary) – can play an essential role in the long-term conservation of these anostracans. Finally, we suggest that these species should be legally protected, primarily because the number of their habitats in the basin is seriously declining.
38 citations
TL;DR: The diversity and succession pattern of cyanob bacteria, particularly picocyanobacteria and bloom-forming cyanobacteria, were examined monthly in a eutrophic lake in China using a combination of light microscopy and 16S ribosomal RNA (rRNA) sequence analysis, and it was revealed that picocianobacteria (mainly Synechococcus -like) are also important cyanobacterial members in lake Chaohu.
Abstract: The diversity and succession pattern of cyanobacteria, particularly picocyanobacteria and bloom-forming cyanobacteria, were examined monthly in a eutrophic lake (lake Chaohu) in China using a combination of light microscopy and 16S ribosomal RNA (rRNA) sequence analysis. The results showed that both picocyanobacteria and bloom-forming cyanobacteria have high levels of diversity. Microcystis and Anabaena were the two predominant bloom-forming genera, and two obvious shifts occurred between them from spring to winter. Anabaena was dominant in spring, then it was rapidly replaced by Microcystis in summer and became dominant again in late autumn and early winter. Apart from water temperature, three forms of dissolved nitrogen (NO3-N, NO2-N, and NH4-N) were important driving factors for their seasonal succession, as demonstrated by redundancy analysis. Clone libraries and sequence analysis revealed that picocyanobacteria (mainly Synechococcus -like) are also important cyanobacteria members in lake Chaohu. All 8 picocyanobacterial phylotypes belonged to the Cyanobium clade. The phylotypes could be further grouped into at least 7 distinct clusters, and 4 of these clusters do not belong to any of the previously described clusters. Picocyanobacteria accounted for more than 70% (percentage in the clone library) in March and April but only accounted for less than 10% from June to October during the Microcystis bloom. The relative abundance of picocyanobacteria was positively correlated with the mass ratio of dissolved inorganic nitrogen and phosphorus (r=0.965, P<0.01, n=10) and ammonium concentration (r=0.721, P<0.05, n=10).
38 citations
TL;DR: It is proposed that a comparison with biogeographical hypotheses of plants, may provide useful analogies when studying anomopod biogeography, because ephippia, the propagules for dispersal, functionally act as minute aquatic plant seeds.
Abstract: Tropical Amphi-Pacific and trans-Pacific disjunctions are among the most controversial distribution patterns in biogeography. A disjunct distribution pattern between SE Asia (in fact, Indochina-Assam) and the Neotropics is rarely investigated in freshwater invertebrates. In the following, we give the first review on potential tropical Amphi-Pacific disjunctions in the Cladocera (Crustacea: Branchiopoda), a group of freshwater microcrustaceans. As a case study, we examine the littoral-benthic freshwater genus Leydigiopsis Sars, 1901 (Cladocera: Anomopoda: Chydoridae). The lineage has four known species in the Neotropics and we examine the status of Leydigiopsis records from Indochina and Assam (India). Our morphological study shows that the Oriental Leydigiopsis is not a humanmediated introduced species from South America. The populations belong to a distinct species, which we describe as new from Thailand and Vietnam. We discuss the biogeography of Leydigiopsis and examine possible hypotheses underlying the observed distribution pattern (e.g. transoceanic long-distance dispersal, boreotropical migration scenario, African extinction scenario). Our case study shows that a boreotropical origin seems the most plausible scenario for the current distribution of this tropical chydorid lineage. In the absence of a good fossil record, we propose that a comparison with biogeographical hypotheses of plants, may provide useful analogies when studying anomopod biogeography, because ephippia, the propagules for dispersal, functionally act as minute aquatic plant seeds. We list other examples of potential tropical Amphi-or trans-Pacific disjunctions in the Cladocera, based on phenotypes and we provide an updated key to the Leydigiopsis species of the world. Undersampling, taxonomical bias, the absence of molecular data and a poor fossil record, remain the most important obstacles for studying biogeography in non-planktonic tropical freshwater zooplankton.
TL;DR: The Sunda region was the scene of widespread rifting during the mid-Cenozoic, resulting in the development of numerous large lake-filled rifts, analogous in scale to the rift valley system of East Africa as mentioned in this paper.
Abstract: The Sunda region was the scene of widespread rifting during the mid-Cenozoic, resulting in the development of numerous large lake-filled rifts, analogous in scale to the rift valley system of East Africa. The Tonle Sap in Cambodia forms the closest modern analogue for these lakes in the Southeast Asian region. Many of the palaeolakes were long lived, continuing uninterrupted as open lakes for several millions of years during the Oligocene. Smaller rift systems infilled with fluvial sediments, but the larger ones remained as lakes, and with Late Oligocene subsidence, were transformed by brackish, and in the earliest Miocene, by marine incursion, into large inland seas. These seas reached their greatest extent at the time of the mid Miocene thermal maximum. This paper describes the development and eventual demise of these lakes following marine transgression, and, based on their rich content of pollen and spores, illustrates the variety of fresh and brackish water swamp communities which developed around their margins. The marginal swamps can be divided into: i) seasonally inundated swamps, mainly during the Oligocene, characterised by Barringtonia , Lagerstroemia and grasses/sedges; ii) fern swamps and iii) from the Late Oligocene onward alluvial swamps, often characterised by Pandanus; and iv) peat swamps. The latter can be differentiated into kerapah peat swamps, first occurring during the Oligocene, and basinal peat swamps, becoming widespread from the Early Miocene onward.
TL;DR: The first faunistic report on the Laotian Cladocera from diverse habitats in Vientiane province, Central Laos counted a total of 70 species, belonging to 37 genera, which is realistically close to an estimated 77 species.
Abstract: We present the first faunistic report on the Laotian Cladocera from diverse habitats in Vientiane province, Central Laos. We counted a total of 70 species, belonging to 37 genera, which is realistically close to an estimated 77 species. The five most common species were Diaphanosoma excisum , Ephemeroporus cf. barroisi , Anthalona harti , Macrothrix spinosa and Chydorus cf. eurynotus . The fauna is typically Oriental/Southeast (SE) Asian, showing a strong similarity with neighbouring countries and especially Thailand. We discussed the current taxonomical status of the species and provided illustrations of the main taxa for future comparison. There are no surprising faunistic elements, except for a few new records for SE Asia ( Matralona freyi , Ilyocryptus thailandensis ). Our data is preliminary, as the fauna of Laos remains insufficiently studied. As for SE Asia as a whole, a significant number of taxa is in need of taxonomical revision.
TL;DR: It is shown that so-called low endemism in this region is mainly attributed to the authors' limited state of knowledge of the local cladoceran fauna, and there are no specific primitive morphological characters in comparison to congeners (within their respective genus/species group) and the morphology mainly suggests strong isolation.
Abstract: We review the current state of knowledge and patterns of distribution in the endemic Cladocera (Crustacea: Branchiopoda) of Southern Africa and describe two species of the Western Cape, of which one is new to science. Frey (1993), Korovchinsky (2006) and Smirnov (2008) previously suggested that South Africa harbours few endemics in the Cladocera. In the current study, we show that so-called low endemism in this region is mainly attributed to our limited state of knowledge of the local cladoceran fauna. Many of the South African taxa are ignored and revisions are lacking, as we briefly discuss for the genus Daphnia . We list known Southern African endemic Cladocera with notes on their status, map the distributions of well-studied taxa, and discuss the importance of temporary freshwater rockpools. We confirm that Southern Africa is a region of endemism for the group. We recognise three categories of endemics: i) Montane endemics in the East ( e.g. Drakensberg mountains); ii) endemics of the Western Cape (lowlands); iii) South African endemics, widely distributed in the region, both in the mountains and the lowlands. South African endemics have previously been regarded as relicts (Korovchinsky 2006), yet for the two taxa explored in detail in this study, there are no specific primitive morphological characters in comparison to congeners (within their respective genus/species group) and the morphology mainly suggests strong isolation. The two species belong to the Chydoridae and the Eurycercidae, respectively, and are used here as case studies for the investigation of Western Cape endemics. The first, Alona capensis Ruhe, 1914 (Anomopoda: Chydoridae: Aloninae), is redescribed based on the type material. We discuss the affinities of this enigmatic species for the first time. Morphology of the habitus and the postabdomen parallel that of members of the Alona affinis -complex. The disconnected head pores and limb characters, on the other hand, place A. capensis in the Alona pulchella -group, a different lineage in the Aloninae subfamily. The specific postabdomen shape of A. capensis and a unique, inflated rostrum, diverge from the main A. pulchella -morphotype and illustrate the significant morphological isolation of A. capensis within its group. The second species, Eurycercus (Eurycercus) freyi s p.nov. (Eurycercidae), is described based on material from the collection of the late Prof. Dr. David G. Frey. It is an E. lamellatus -like taxon that is easily differentiated from the two related species ( E. lamellatus and E. microdontus ) by a strong indentation (with depth larger than head pore diameter) behind the head pores. E. freyi sp.nov. seems to be the closest relative of E. lamellatus . The small clade of just two species is supported by two synapomorphies: i) the rostrum is long; and ii) the spine situated on the proximal segment of the exopod of antenna II is longer than the second segment, in contrast to E. microdontus .
TL;DR: Anhydrobiotic organisms seem to apply two main strategies to cope with the danger of oxygen toxicity, namely an increased efficiency of antioxidant defences and a metabolic control of both energy-production and energy-consuming processes.
Abstract: Although the evolution of life has turned oxygen into a vital chemical for aerobic organisms, this element can also have deleterious effects on living systems through the production of oxidative stress This is a process resulting from an imbalance between the excessive production of Reactive Oxygen Species (ROS) and the limited action of antioxidant defences It is a particularly harmful health risk factor, involved in the development of several chronic human pathologies and believed to play a major role in the ageing process Consequently aerobic metabolism needs a stringent control of ROS Water too is essential for life, but some organisms widespread throughout nature have the ability to survive complete desiccation by entering an anhydrobiotic state The loss of water induces changes in metabolism, cell membrane organization, and molecular composition In the anhydrobiotic state, high temperatures, high humidity, light exposure, and high oxygen partial pressure negatively affect organism survival and directly influence the time required to reactivate the metabolism after a period of desiccation These abiotic factors induce damages that are accumulated in proportion to the time spent in the desiccated state, potentially leading to organism death Oxidative stress seems to be one of the most deleterious damages due to water depletion, therefore anhydrobiosis also needs a stringent control of ROS production Anhydrobiotic organisms seem to apply two main strategies to cope with the danger of oxygen toxicity, namely an increased efficiency of antioxidant defences and a metabolic control of both energy-production and energy-consuming processes Experimental studies provide evidence that antioxidant defences such as ROS scavenging enzymes ( eg peroxidases, catalases, superoxide dismutase, glutathione peroxidases) and other molecules ( eg glutathione, carotenoids, vitamins C and E) represent a key group of molecules required for desiccation tolerance in anhydrobiotic organisms The action of these molecules emphasises the need for redox balancing in anhydrobiotic organisms including tardigrades and chironomid larvae
TL;DR: The fossil diatom records revealed shifts in the communities in the three Lakes Annecy, Bourget and Geneva over time, most of which were changes typically associated with nutrient enrichment, which limits the study ability to set accurate TP reference conditions below this threshold.
Abstract: Like many lakes worldwide, French sub-alpine lakes (lakes Annecy, Bourget and Geneva) have suffered from eutrophication in the mid-20 th century. Although restoration measures have been undertaken and resulted in significant reductions in nutrient inputs and concentrations over the last 30 years in all three lakes, the limnological monitoring does not extend back far enough to establish the reference conditions, as defined by the European Water Framework Directive. The over-arching aim of this work was to reconstruct, using a paleolimnological approach, the pre-eutrophication levels and subsequent temporal changes in the lakes trophic status over the last century. The objectives were three-fold: i) to test whether fossil diatoms archived in deep sediment cores adequately reflect past changes in the planktonic diatom communities for these deep sub-alpine lakes based on data from lake Geneva; ii) to investigate changes in the diatom communities over the last 150 years in the three lakes; and iii) to infer the past total phosphorus (TP) concentrations of the lakes from a diatom based transfer function. Annual paleolimnological and limnological diatom countings for lake Geneva were strongly correlated over the last 30 years. Most notable differences essentially resulted from both taphonomic and depositional biases, as evidenced by the underestimation of thin skeleton species such as Asterionella formosa and Diatoma tenuis in the paleolimnological dataset and the presence of many benthic taxa. The fossil diatom records revealed shifts in the communities in the three lakes over time, most of which were changes typically associated with nutrient enrichment. Indeed, in all three lakes, the proportion of Cyclotella spp. was very high before the 1950s, but these species were then replaced by more eutrophic taxa, such as Stephanodiscus spp, by the mid-20 th century. From the 1980s, some but not all diatom species typical of re-oligotrophicated conditions ( i.e. Cyclotella sp.) re-appeared in all three lakes. Yet, not all changes that occurred in the diatom communities since then may be attributed to decreasing TP. TP concentrations inferred from weighted averaging with classical deshrinking in lake Annecy and lake Geneva and weighted averaging with inverse deshrinking in Lake Bourget were very close to the monitored values. Comparisons of diatom-inferred TP concentrations to other paleo-proxies for trophic status revealed though that the transfer functions were rather insensitive to changes occurring below 10 µg L –1 , which limits the study ability to set accurate TP reference conditions below this threshold. However, current diatom community compositions arestill rather different from the pre-eutrophication ones, suggesting that reference conditions are still not achieved.
TL;DR: It is shown that swamps harbour underestimated Cladocera diversities in South East (SE) Asia, and two new paludal species of the Chydoridae are described, restricted to inland swamps in S Thailand.
Abstract: Freshwater surveys in the tropics have high potential for revealing new taxa if a wide range of habitats is included. Tropical inland swamps are ignored during most zooplankton sampling campaigns. We show that swamps harbour underestimated Cladocera diversities in South East (SE) Asia, illustrated here for Southern (S) Thailand. According to our preliminary data, based on 22 swamp sites in ten provinces, the cladoceran diversity of swamp habitats is high (about 73 taxa), i.e. a species richness of about 85% of the cladoceran taxa recorded in S Thailand. The Chydoridae are the most diverse group, about 66% of the total (48 out of 73 species), followed by the Macrothricidae (12%; 9 species) and the Sididae (11%; 8 species). Daphniidae only occupy a small proportion of the total species in these sites (5%; 4 species). Besides rare taxa, the SE Asian tropical swamps contain new records, even new species. We discuss the importance of tropical swamp habitats as hotspots of cladoceran diversity, which are being destroyed through agricultural and urban development in SE Asia. As an example, we describe two new paludal species of the Chydoridae (Crustacea: Branchiopoda: Cladocera), restricted to inland swamps in S Thailand. The new taxa have conspicuous morphologies within their respective genera (Karualona Dumont and Silva-Briano, 2000 and Notoalona Rajapaksa and Fernando, 1987), compared to their common sister species in the region. Karualona serrulata n.sp. is separated from congeners by i) divided denticles on the posteroventral corner of the valves and ii) single setules on the anterior face of the first limb (instead of groups of setules, as in the majority of the Aloninae). We include notes on the other, common Karualona sp. populations from S Thailand. These animals show similarities with K. iberica and K. karua, yet belong to neither; we discuss the variability of characters in these populations and in the genus. The second new taxon, Notoalona pseudomacronyx n.sp., is a small species with a postabdomen strongly resembling that of Alona macronyx Daday, 1898, recently allocated to Celsinotum. It seems closest in morphology to an African, yet undescribed species of Notoalona. We included pictorial keys to all the species of these two chydorid genera, which have their main distribution in the circumtropics.
TL;DR: Diversity and distribution of SE Asian inland water sponges is reported on the basis of available literature and a recent biodiversity assessment of the Lower Mekong basin, with the highest diversity recorded from Indonesia, Philippines, Thailand, and Myanmar.
Abstract: Despite the fact that South East (SE) Asia is considered as a biodiversity hotspot, knowledge of sessile invertebrates such as freshwater sponges (Porifera: Haplosclerida: Spongillina) in this region is poor and scarcely reported. For this synopsis, diversity and distribution of SE Asian inland water sponges is reported on the basis of available literature and a recent biodiversity assessment of the Lower Mekong basin. A diagnostic key of families/genera from SE Asia is provided together with Light Microscopy and Scanning Electron Microscopy protocols to prepare the basic spicular complement for taxonomic identification. So far, SE Asian freshwater sponges consist of widespread and/or endemic species belonging to the families Metaniidae, Potamolepidae, and Spongillidae. The highest diversity is recorded from Indonesia, Philippines, Thailand, and Myanmar, respectively. Data from the other countries are necessary for our understanding of their diversity and distribution. Biodiversity in SE Asia is strongly underestimated, as indicated by recent new records and the discovery of new species of freshwater sponges in Thailand. Further investigations should reveal higher values of taxonomic richness, highlighting biogeographic patterns at the family/genus/species levels. A cooperative network involving Thai, Laotian and Italian researchers, was set up to contribute and fulfil knowledge on taxonomy, ecology and biotechnological potentialities of these neglected filter feeders, playing a key role in water purification and biomass production in both lentic and lotic ecosystems in the tropics.
TL;DR: In this paper, seasonal changes in the carbon stable isotope composition of phytoplankton and related environmental factors were determined in karst reservoirs from the Wujiang river basin, China.
Abstract: In order to systematically understand the mechanisms controlling the carbon stable isotope composition of phytoplankton (δ13CPHY)in freshwater ecosystems, seasonal changes in δ13CPHY and related environmental factors were determined in karst reservoirs from the Wujiang river basin, China. Substantial and systematic differences within seasons and reservoirs were observed for δ13CPHY, which ranged from -39.2‰ to -15.1‰. An increase in water temperature triggered fast growth of phytoplankton which assimilated more dissolved inorganic carbon (DIC), resulting in the increase of δ13CPHY, δ13CDIC and pH. When the concentration of dissolved carbon dioxide (CO2) was less than 10 mmol L–1, phytoplankton shifted to using HCO3– as a carbon source. This resulted in the sharp increase of δ13CPHY. The carbon stable isotope composition of phytoplankton tended to decrease with the increase of Bacillariophyta, which dominated in January and April, but tended to increase with the increase of Chlorophyta and Dinophyta, which dominated in July. Multiple regression equations suggested that the influence of biological factors such as taxonomic difference on δ13CPHY could be equal or more important than that of physical and chemical factors. Thus, the effect of taxonomic differences on δ13CPHY must be considered when explaining the δ13C of organic matter in lacustrine ecosystem.
TL;DR: In this article, the authors reviewed the ecology of present day ombrotrophic, rheotrophic and brackish mangrove peat swamps, and their pattern and timing of development during the Holocene and latest Pleistocene based on palynological studies.
Abstract: Tropical peat swamps are more widespread in Sundaland than in any other equatorial region. Also, Cenozoic deposits from the area are rich in coals. The developmental pattern of present day peat swamps from the region has often been used to help clarify that of coals in the geological record. This paper initially reviews the ecology of present day ombrotrophic, rheotrophic and brackish mangrove peat swamps, and their pattern and timing of development during the Holocene and latest Pleistocene based on palynological studies. Then, it attempts to examine the developmental pattern of the peats which led to the formation of Cenozoic coals across the region, based on both published and unpublished datasets generated during the course of hydrocarbon exploration programmes. It is concluded that Cenozoic coals reflect a greater variety of peat forming settings than occurs in the region today. Extensive brackish water peats formed during the Middle and Late Eocene and Middle and Late Miocene, these often being laterally very extensive. Rheotrophic peats also formed widely through most of the Cenozoic. Ombrotrophic kerapah type peats are first recognised in the Late Oligocene, based on their content of common Casuarina type and Dacrydium pollen, and were particularly common during the Early and Late Miocene in the Sunda shelf region. Kerapah peats sometimes developed great thickness. Basinal peats, on the other hand, increased in representation during the course of the Miocene. No convincing evidence for doming in Cenozoic peats has yet been noted, but on the other hand, no really thick coals, which may have been formed from basinal peats, have so far been studied. As a consequence, examples of doming in the rock record from this area are probably yet to be found.
TL;DR: It is demonstrated that generations of daphniids from the Sulejow reservoir had more effective antioxidant systems protecting them against the accumulation of cyanobacterial toxins; thereby, they are less susceptible to toxic effects than the daphNIids from lake Biale.
Abstract: Microcystins (MCs), the main group of cyanotoxins, can induce oxidative stress in the cells of aquatic animals. This study evaluated the sensitivity of daphniids – from two ecosystems characterised by different trophic states and habitat levels of cyanobacteria abundance – to microcystin toxicity by analysing oxidative stress parameters and MC detoxification ability. As a study site, we chose the eutrophic Sulejow reservoir, which has regular annual toxic cyanobacterial blooms, and the mesotrophic lake Biale, where low abundances of cyanobacteria have only recently appeared. We found much higher accumulations of MCs in tissues of Daphnia spp. in lake Biale, despite low toxin concentrations in this ecosystem compared with the Sulejow reservoir. Simultaneously, high levels of lipid peroxidation (LPO) and a significant decrease in glutathione (GSH) were observed in daphniid cells in lake Biale, while LPO levels were generally lower and GSH concentration more stable in the Sulejow reservoir. Catalase activity, which reflects more efficient oxidative protection, was always significantly higher in the reservoir than in lake Biale. These results demonstrate that generations of daphniids from the Sulejow reservoir had more effective antioxidant systems protecting them against the accumulation of cyanobacterial toxins; thereby, they are less susceptible to toxic effects than the daphniids from lake Biale. However, the presence of conjugate forms of microcystins (MC-GSH and MC-Cys) in tissues of the studied animals indicated the ability for MC detoxification by daphniids from the Sulejow reservoir and lake Biale. Nevertheless, the high effectiveness of antioxidant systems in daphniids coexisting with cyanobacteria for a long time in the Sulejow reservoir indicates the importance of a selective pressure exerted by toxic cyanobacterial strains that favours the most resistant daphniid genotypes.
TL;DR: Whether the observations on a small population from temporary pools could be considered part of a diversified bet-hedging strategy is discussed, as well as the effect of conductivity and thermal regimes on other traits like recruitment from egg bank, voltinism and sex ratio.
Abstract: The persistence of crustacean populations in ephemeral ponds requires appropriate adaptations in life history strategies (e.g. in hatching phenology). Organisms take advantage of pond filling when it occurs and hedge their bets for the possibility to complete one or more life cycles or to produce resting stages that ensure that the population will not go extinct. We carried out laboratory experiments to investigate the dynamics of a sexual population of Heterocypris barbara from a vernal pool in Lampedusa Island (Sicily). Experimental organisms were obtained hydrating sediments from Aria Rossa temporary pond. Recruitment from resting eggs, voltinism, mean body size and sex ratio were observed in microcosms at different conductivities (high 2.0-2.7 mS cm-1, intermediate 1.0-1.1 mS cm-1 and low 0.5-0.6 mS cm-1). Microcosms were kept in laboratory controlled conditions: constant (24°C 12:12 L:D and 16°C 10:14 L:D photoperiod) or fluctuating thermal regimes. The experiment lasted 7 months. Resting and non-resting egg production and up to a bivoltine life cycle were observed. Recruitment events from egg bank and voltinism varied by thermal regime and conductivity. A prolonged recruitment phase occurred in conditions that could be considered a proxy of a rainy season (16°C, 10:14 L:D and low conductivity) or of long hydroperiods (spring thermal fluctuating regime and intermediate conductivity). At 24°C, age at reproduction of females from resting eggs almost doubled at low conductivity (in comparison with high conductivity). Low conductivity also reduced hatching time of resting eggs while it increased development time and age at maturity. In thermal fluctuating regime, degree-days to reproduction were about double than at constant 24°C. Males, observed in all microcosms, reached maturity faster and had a shorter life span than females. Males initially outnumbered females, but later in the experiments females became dominant. We also evaluated the effect of conductivity and thermal regimes on other traits like recruitment from egg bank, voltinism and sex ratio. We discuss whether our observations on a small population from temporary pools could be considered part of a diversified bet-hedging strategy.
TL;DR: A checklist of the freshwater Rotifera recorded from Thailand, based on a review of available literature, finds that most Thai rotifers are cosmopolitan followed by Trichocerca, Lepadella and Brachionus, and the most diverse genus is Lecane.
Abstract: We provide a checklist of the freshwater Rotifera recorded from Thailand, based on a review of available literature. Approximately 398 species of rotifers are recorded. The rotifer fauna of Thailand has been investigated quite comprehensively and these studies focus on four main parts of the country: the northern, north-eastern, central and southern. The number of rotifers on record is the highest in the north-eastern part (275), followed by the southern part (261), the central part (182) and the northern part (115). The majority of Thai Rotifera belongs to family Lecanidae (24.4%), Lepadellidae (11.3%), Brachionidae (11.1%), Trichocercidae (9.0%) and Flosculariidae (9.0%). The most diverse genus is Lecane followed by Trichocerca, Lepadella and Brachionus. Although most Thai rotifers are cosmopolitan, there are a number of Oriental endemics, including some strict Thai or regional endemics. Illoricate rotifers and bdelloids are understudied, while experimental and molecular approaches promise to add most to our knowledge and understanding of the role of rotifers in ecosystem functioning.
TL;DR: The limited distributions of these few taxa suggest that this region has a distinct branchiopod fauna, and four of the five native fairy shrimp species are endemic to SE Asia.
Abstract: The large branchiopod crustaceans (fairy shrimp, tadpole shrimp and clam shrimp) of South East (SE) Asia have only recently been examined with scientific vigor. Although more than 70 species have been reported for Asia and Indonesia, only six native taxa and one introduced species are known from SE Asia. The majority of records are from Thailand, with fewer than three records each from Laos, Myanmar, Malaysia, Cambodia, Vietnam, and Singapore. Eleven genera reported from adjacent regions may potentially occur in SE Asia. Spinicaudatan clam shrimp have been collected from Thailand and Cambodia, but have not been identified beyond genus. Four of the five native fairy shrimp species are endemic to SE Asia. The limited distributions of these few taxa suggest that this region has a distinct branchiopod fauna. In addition, we present new species and records of clam shrimp from Thailand. Future survey efforts will undoubtedly reveal additional taxa.
TL;DR: In this article, the distribution of subfossil chironomid larval head caspules in a suite of surface sediment samples from a large deep subtropical lake, i.e. Lugu lake, located in southwest China, was analyzed.
Abstract: The present study analysed the distribution of subfossil chironomid larval head caspules in a suite of surface sediment samples from a large deep subtropical lake, i.e. Lugu lake, located in southwest China. In order to identify the relationships between environmental variables and the chironomid assemblages ordination methods were used. A total of 41 chironomid taxa were found across the 46 samples, 21 of which had a minimum abundance >1% and were present in more than one site. The samples were dominated by 12 taxa, which together accounted for 97% of the fauna. Redundancy analysis (RDA) revealed that the predominant drivers of chironomid distribution within Lugu lake were bottom water temperature, water depth, loss-on-ignition (LOI) and water total phosphorus (TP) concentration. Abrupt changes in chironomid assemblages occurred at 10 m of water depth, which is closely related to the macrophyte distribution and the position of the thermocline. The chironomid assemblages became uniform below a water depth of ca. 15 m, and the anthropogenic impact on the chironomid fauna was then limited to the edge of Lugu lake. The depth-related faunal shifts primarily reflect the dominant controls of temperature and macrophyte distribution on the chironomids in Lugu lake. This is the first within-lake subfossil chironomid study from this region and the understanding of key environmental influences on contemporary faunas within the lake will aid interpretations of palaeolimnological datasets to reconstruct past trends and magnitude of environmental change over a range of timescales.
TL;DR: A species of tardigrade from moss samples collected from Langhovde and Skarvsnes, near Syowa station, East Antarctic, is isolated, identical to that of Acutuncus antarcticus from King George island, South Shetland islands, and Morphological analyses via both light and scanning electron microscopy show general agreement with characteristics of A. antarctica.
Abstract: We isolated a species of tardigrade from moss samples collected from Langhovde and Skarvsnes, near Syowa station, East Antarctic, from which we cultured a parthenogenetic strain in Petri dishes with co-occurring cyanobacteria or green algae. This culture was maintained at both 4 and 10oC, though the latter proved more suitable for growth. Eggs were laid free, rather than in exuviae. We isolated the 18S rRNA sequences from this tardigrade, identical to that of Acutuncus antarcticus from King George island, South Shetland islands. Morphological analyses via both light and scanning electron microscopy also show general agreement with characteristics of A. antarcticus : dorsal and ventral apophyses for the insertion of stylet muscles and dorsal longitudinal thickening on the anterior part of buccal tube; presence of pharyngeal apophyses, two macroplacoids and absence of a microplacoid; the surface structure of egg; and claw shape. Peribuccal lamellae were absent, but six oval swellings surrounded the mouth opening. An additional study of moss pillars from lake Hotoke-ike, Skarvsnes, proved the existence of the same tardigrade taxon living at the bottom of the lake.
TL;DR: Cladocera of Cat Tien National Park, South Vietnam, and the surrounding agricultural area, were surveyed during the spring of 2009 and autumn 2010 (end of the wet season), and the studied water bodies included two large lakes (Bau Sau and Bau Chim), small lakes and ponds, temporary pools, rivers and streams, as well as rice fields and ponds in an agricultural area beyond the boundaries of the National Park.
Abstract: Cladocera of Cat Tien National Park, South Vietnam, and the surrounding agricultural area, were surveyed during the spring of 2009 (onset of the wet season) and autumn 2010 (end of the wet season) The studied water bodies included two large lakes (Bau Sau and Bau Chim), small lakes and ponds, temporary pools, rivers and streams, as well as rice fields and ponds in an agricultural area beyond the boundaries of the National Park Fifty three species of Cladocera were found, 18 of them new for Vietnam Distribution and taxonomical status of the species are discussed Of the recorded species, 585% (31) were found only in the National Park, 34% (18) both in the National Park and the agricultural area, and only 75% (4) exclusively in the agricultural area Of the 20 species new for Vietnam, only one was found both in the National Park and the agricultural area, all others were found in the National Park only Such a difference can be directly attributed to the loss of natural habitats (forest ponds and streams) in agricultural areas and to the pollution by pesticides Our study shows the importance of surveys in pristine and protected areas, for the full evaluation of regional microcrustacean richness
TL;DR: This work explores and discusses some ideas relating to the likelihood of parallel phenotypic evolution through similar (parallel) vs .
Abstract: Population genetic theory predicts that effective population size and gene flow can strongly influence the levels and patterns of genetic variability, and thereby also the likelihood, pace and direction of evolutionary transformations. Given that levels and patterns of genetic variability in lakes and ponds often differ from those observed in continuous marine environments, it follows that the dynamics of adaptation and evolution in freshwater habitats are also likely to differ from those in marine habitats. Here, I explore and discuss some ideas relating to the likelihood of parallel phenotypic evolution through similar (parallel) vs . different (convergent) genetic changes with particular focus on freshwater isolates. I will review and discuss the available genetic data with particular focus on freshwater fish populations, and outline possible avenues for future work in which ponds and small lakes could serve as useful model systems to study genetic parallelism and convergence, as well as molecular adaptation in general. Conservation issues related to genetics of isolated pond and lake populations are also addressed.
TL;DR: Ten shallow lakes in the Pampean region were studied in 2009 and 2010 winters, and in 2010 summer in order to assess the abundance, size and biomass of zooplankton and the density of flamingoes populations.
Abstract: The lowland saline shallow lakes in the Pampa de las Lagunas (Argentina), constitute an important habitat for flamingoes Phoenicopterus chilensis Molina and Phoenicoparrus andinus (Philippii) . Little is known about the zooplankton communities of these systems, and their relationships with the temporal and spatial distribution of flamingoes. Ten shallow lakes in the Pampean region were studied in 2009 and 2010 winters, and in 2010 summer in order to assess the abundance, size and biomass of zooplankton and the density of flamingoes populations. Zooplankton was represented by 28 species. Copepods and cladocerans were dominant when salinity was lower (winter and summer of 2010). Seasonal changes were recorded in composition and mean abundance of zooplankton. Significant differences were observed in mean size of zooplankton showing a negative relationship with the abundance of P. chilensis , which can be interpreted as a consequence of the selective flamingoes zooplanktophagy feeding upon the largest members of this community. Other community parameters, such as abundance, biomass, diversity and composition, did not show an apparent direct relationship with the presence or abundance of flamingoes.
TL;DR: A limnological study of the Merja Sidi Boughaba in 2009 has shown that there are many common features between the physico-chemical and biological conditions of this site and previous data reported from some of the wetlands of the Donana National Park (South-West Spain).
Abstract: Addressing the underlying common processes within aquatic systems located in the same geographical region has long been used as a tool for the advancement of limnology. A limnological study of the Merja Sidi Boughaba in 2009 has shown that there are many common features between the physico-chemical and biological conditions of this site and previous data reported from some of the wetlands of the Donana National Park (South-West Spain). Both are Ramsar sites located on extensive dune systems of the Atlantic coast with a Mediterranean climate. They have a common palaeoenvironmental history that is largely responsible for their similar hydrology and water composition. Oceanic influence has probably produced a slight disproportion of Mg 2+ over Ca 2+ through airborne sea salt deposition and the surface evaporation of groundwater feeding these wetlands during annual flood and drought cycles. The wide spectrum of environmental conditions encountered in the Donana wetlands is epitomised by the Merja Sidi Boughaba, where water and sediment gradually change in the same water body from north to south: from humic-coloured waters and a sandy substrate to a calcium-rich substrate with turbid and silted waters which eventually dry out. As a consequence, the community of submersed macrophytes is very rich and dominated by dense charophyte beds. The high primary production coupled with high biodiversity found in the Merja Sidi Boughaba is also shared by the Donana wetlands. The high conservation status of both sites enables a useful comparison to be made of the water quality of shallow aquatic systems at a regional scale which, contrary to the trophic classifications developed for deep stratified lakes in temperate regions, is not based on regressions between the concentrations of chlorophyll and total phosphorus (Tot-P) but on the proportions of dissolved and particulate P pools. In these Mediterranean sites, nutrients are more efficiently recycled through the sediment (whether deposited at the bottom or suspended in the water column) while seasonal fluctuations of the water level are stronger than in deep stratified lakes and, hence, no significant correlation was found between chlorophyll and either total or particulate P in our study.