The meiofauna distribution in correlation with environmental characteristics in 5 Mekong estuaries, Vietnam

Meiofauna assemblages in 5 estuaries of the Mekong river system (Cua Tieu, Cua Dai, Ba Lai, Co Chien and Dinh An) were sampled for community analysis in March 2009, the dry season. The objectives of this research were to provide the first base line survey of meiofauna assemblages in the 5 Mekong estuaries, and to understand how environmental characteristics affect the densities, diversity and structure of the meiofauna. In each estuary, three to four sampling stations were chosen along the salinity gradient from the river mouth to the fresh water part. Besides the meiofauna also sediment- and water column-related environmental characteristics were identified such as dissolved oxygen, pH, salinity, temperature, median grain size, density of coliform bacteria, nutrient and pigment concentrations. Twenty-three major taxa of meiofauna were recorded over the 19 sampling stations. Nematoda, Copepoda, Turbellaria and Oligochaeta dominated with varying densities, but without any clear correlation with the salinity gradient present along the estuaries. The densities of the meiofauna ranged from 105 to 3678 ind.10 cm-2 on average. Nematodes were always dominant with relative abundances ranging from 40-98% of the total meiofauna. Meiofauna densities were significantly correlated with sediment pigment concentrations but also other factors may play a role. Diversity showed a positive correlation with dissolved oxygen in the overlying water. The observed densities of the intertidal meiofauna in the Mekong delta are high compared to other estuaries worldwide

Nematodes from sandy beaches of Guanabara Bay, Rio de Janeiro, Brazil

This work assessed the nematode composition in three sandy beaches located at Guanabara Bay, Rio de Janeiro, Brazil (22°24’ and 22°57’S; 42°33’ and 43°19’W). These microtidal, sheltered sandy beaches (Bica, Bananal and Coqueiros) were surveyed on January and June 2001, during the low tide. Samples were taken using a PVC core of 10cm2. Nematodes were extracted using the sugar-flotation methodology. The sediment of these beaches was mainly composed of sand and showed a variation between medium to very coarse sediments. In total 6312 specimens were identified up to the genus level or when possible to species level. At the three beaches, 62 genera were found, belonging to 25 families and distributed along of 8 orders. Chromadoridae was the most abundant family in terms of genera. All the families found have also been recorded from previously studied beaches. Amongst the genera found, four of them (Deontolaimus, Dracograllus, Phanodermella and Subsphaerolaimus) were for the first time recorded for Brazilian’s coastline. The number of genera occurring on the Guanabara beaches (31 for Bica, 39 for Bananal and 46 for Coqueiros) is more or less similar to another Brazilian sandy beach whereas these values showed higher variation concerning worldwide tropical and non-tropical beaches. The first occurrence of four genera for the Brazilian coastline suggest the possibility to discover new species in this bay, therefore to the need for further development of nematode taxonomy in Brazil

Studie van het meiobenthos van een dumpingsgebied van titaandioxide-afval in de Nederlandse kustwateren periode 1988

In 1988 and 1989~ 4 extra stations situated west of the TiO2-dumping site, were sampled for reason of getting adequate reference stations out of possible influence of the dutch and belgian dumping grouds.According to the sediment analysis, these stations are comparable to the stations within the dumping area and can be regarded as reference stations.The vertical distribution of the meiobenthos was investigated for 10 stations, 5 situated within the dumping area and 5 situated westwards. Nematoda, Capepoda, Gastrotricha and Turbellaria did occur until 20 cm deep; Tardigrada, Hydrozaa, Ostracoda, Halacarida and Rotifera were confined to the upper 15 cm. At least the upper 10 cm of the sediment was oxigenated.Within the dumping area the highest percentage of meiofauna occured in the 5-10 cm layer, whereas in the reference area the highest percentages occured in the layers 0-2 cm and 2-5 cm.There was a significant difference between the dumping area and the reference area for the parameter mean density of the total meiafauna, the nematods, the copepods and the turbellarians af the uppermost 10 cm layers (0-2 cm, 2-5 cm, 5-10 cm; nematods only in 0- 2 cm)

Influence of the ratio of planktonic to benthic diatoms on lacustrine organic matter δ13C from Erlongwan maar lake, northeast China

Carbon isotope ratio (δ13Corg) values of organic matter in lake sediments are commonly used to reconstruct environmental change, but the factors which influence change are varied and complex. Here we report δ13C values for sediments from Erlongwan maar lake in northeast China. In this record, changes in δ13C cannot be explained by simple changes in aquatic productivity. Instead, values were likely influenced by differences in the ratio between planktonic and benthic algae, as indicated by the remains of diatoms. This is because the variation of δ13Corg in algae from different habitats is controlled by the thickness of the diffusive boundary layer, which is dependent on the turbulence of the water. Compared with benthic algae, which grow in relatively still water, pelagic algae are exposed to greater water movement. This is known to dramatically reduce the thickness of the boundary layer and was found to cause even more severe δ13C depletion. In Erlongwan maar lake, low values were linked to the dominance of planktonic diatoms during the period commonly known as the Medieval Warm Period. Values gradually increased with the onset of the Little Ice Age, which we interpret as being driven by an increase in the proportion of benthic taxa, due to effect of the colder climate. The increase in planktonic diatoms at the end of the Little Ice Age, linked to higher temperature and a reduction in ice cover, resulted in a further decline in δ13Corg

Clinical and genetic spectrum of SCN2A-associated episodic ataxia

Background: Pathogenic variants in SCN2A are associated with various neurological disorders including epilepsy, autism spectrum disorder and intellectual disability. Few reports have recently described SCN2A-associated episodic ataxia (EA). Our study identifies its broader clinical and genetic spectrum, and describes pharmacological approaches. Results: We report 21 patients with SCN2A-associated EA, of which 9 are unpublished cases. The large majority of patients present with epileptic seizures (18/21, 86%), often starting within the first three months of life (12/18, 67%). In contrast, onset of episodic ataxia ranged from 10 months to 14 years of age. The frequency of EA episodes ranged from brief, daily events up to 1-2 episodes per year each lasting several weeks. Potential triggers include minor head traumas and sleep deprivation. Cognitive outcome is favorable in most patients with normal or mildly impaired cognitive development in 17/21 patients (81%). No clear genotype-phenotype correlations were identified in this cohort. However, two mutational hotspots were identified, i.e. 7/21 patients (33%) harbor the identical pathogenic variant p.A263V, whereas 5/21 (24%) carry pathogenic variants that affect the S4 segment and its cytoplasmic loop within the domain IV. In addition, we identified six novel pathogenic variants in SCN2A. While acetazolamide was previously reported as beneficial in SCN2A-associated EA in one case, our data show a conflicting response in 8 additional patients treated with acetazolamide: three of them profited from acetazolamide treatment, while 5/8 did not. Conclusions: Our study describes the heterogeneous clinical spectrum of SCN2A-associated EA, identifies two mutational hotspots and shows positive effects of acetazolamide in about 50%. (C) 2019 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.Peer reviewe

First circumpolar assessment of Arctic freshwater phytoplankton and zooplankton diversity : Spatial patterns and environmental factors

Arctic freshwaters are facing multiple environmental pressures, including rapid climate change and increasing land-use activities. Freshwater plankton assemblages are expected to reflect the effects of these stressors through shifts in species distributions and changes to biodiversity. These changes may occur rapidly due to the short generation times and high dispersal capabilities of both phyto- and zooplankton. Spatial patterns and contemporary trends in plankton diversity throughout the circumpolar region were assessed using data from more than 300 lakes in the U.S.A. (Alaska), Canada, Greenland, Iceland, the Faroe Islands, Norway, Sweden, Finland, and Russia. The main objectives of this study were: (1) to assess spatial patterns of plankton diversity focusing on pelagic communities; (2) to assess dominant component of beta diversity (turnover or nestedness); (3) to identify which environmental factors best explain diversity; and (4) to provide recommendations for future monitoring and assessment of freshwater plankton communities across the Arctic region. Phytoplankton and crustacean zooplankton diversity varied substantially across the Arctic and was positively related to summer air temperature. However, for zooplankton, the positive correlation between summer temperature and species numbers decreased with increasing latitude. Taxonomic richness was lower in the high Arctic compared to the sub- and low Arctic for zooplankton but this pattern was less clear for phytoplankton. Fennoscandia and inland regions of Russia represented hotspots for, respectively, phytoplankton and zooplankton diversity, whereas isolated regions had lower taxonomic richness. Ecoregions with high alpha diversity generally also had high beta diversity, and turnover was the most important component of beta diversity in all ecoregions. For both phytoplankton and zooplankton, climatic variables were the most important environmental factors influencing diversity patterns, consistent with previous studies that examined shorter temperature gradients. However, barriers to dispersal may have also played a role in limiting diversity on islands. A better understanding of how diversity patterns are determined by colonisation history, environmental variables, and biotic interactions requires more monitoring data with locations dispersed evenly across the circumpolar Arctic. Furthermore, the importance of turnover in regional diversity patterns indicates that more extensive sampling is required to fully characterise the species pool of Arctic lakes.Peer reviewe

Dust inputs and bacteria influence dissolved organic matter in clear alpine lakes

Remote lakes are usually unaffected by direct human influence, yet they receive inputs of atmospheric pollutants, dust, and other aerosols, both inorganic and organic. In remote, alpine lakes, these atmospheric inputs may influence the pool of dissolved organic matter, a critical constituent for the biogeochemical functioning of aquatic ecosystems. Here, to assess this influence, we evaluate factors related to aerosol deposition, climate, catchment properties, and microbial constituents in a global dataset of 86 alpine and polar lakes. We show significant latitudinal trends in dissolved organic matter quantity and quality, and uncover new evidence that this geographic pattern is influenced by dust deposition, flux of incident ultraviolet radiation, and bacterial processing. Our results suggest that changes in land use and climate that result in increasing dust flux, ultraviolet radiation, and air temperature may act to shift the optical quality of dissolved organic matter in clear, alpine lakes

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter