Natural Beds Research Articles

Does Magnetic Reconnection Occur in the Near Lunar Surface Environment?

AbstractThe near lunar surface contains small‐scale magnetic field structures that provide a natural test bed for observing plasmas with a non‐zero Hall electric field, as well as potentially facilitating electron‐only reconnection. This study presents observational evidence of magnetized electrons as well as demagnetized ions when THEMIS‐ARTEMIS probe B reached an altitude of ∼15 km above the lunar surface. Additionally, observations suggest the presence of a field line topology change and traversal of a closed magnetic field structure containing solar wind electrons, suggestive of magnetic reconnection having occurred at some point between the solar wind interplanetary magnetic field and a lunar crustal magnetic field. Thus, the observations presented here are consistent with previous studies that predict prominent Hall electric fields near lunar crustal magnetic fields and further suggest that the solar wind interplanetary magnetic field may reconnect with lunar crustal magnetic fields, most likely via electron‐only reconnection.

Heterogeneous microgeographic genetic structure of the common cockle (Cerastoderma edule) in the Northeast Atlantic Ocean: biogeographic barriers and environmental factors.

Knowledge of genetic structure at the finest level is essential for the conservation of genetic resources. Despite no visible barriers limiting gene flow, significant genetic structure has been shown in marine species. The common cockle (Cerastoderma edule) is a bivalve of great commercial and ecological value inhabiting the Northeast Atlantic Ocean. Previous population genomics studies demonstrated significant structure both across the Northeast Atlantic, but also within small geographic areas, highlighting the need to investigate fine-scale structuring. Here, we analysed two geographic areas that could represent opposite models of structure for the species: (1) the SW British Isles region, highly fragmented due to biogeographic barriers, and (2) Galicia (NW Spain), a putative homogeneous region. A total of 9250 SNPs genotyped by 2b-RAD on 599 individuals from 22 natural beds were used for the analysis. The entire SNP dataset mostly confirmed previous observations related to genetic diversity and differentiation; however, neutral and divergent SNP outlier datasets enabled disentangling physical barriers from abiotic environmental factors structuring both regions. While Galicia showed a homogeneous structure, the SW British Isles region was split into four reliable genetic regions related to oceanographic features and abiotic factors, such as sea surface salinity and temperature. The information gathered supports specific management policies of cockle resources in SW British and Galician regions also considering their particular socio-economic characteristics; further, these new data will be added to those recently reported in the Northeast Atlantic to define sustainable management actions across the whole distribution range of the species.

Spatial distribution patterns of striped venus clam (Chamelea gallina, L. 1758) natural beds in the Gulf of Cádiz (SW Spain): Influence of environmental variables and management considerations

Spatial distribution of characteristic population parameters (density, biomass and mean size) of Chamelea gallina were analyzed from systematic survey data applying a geostatistical approach in the Gulf of Cádiz (SW Spain). The influence of static (depth and distance to inland outflows), dynamic (sediment and water column features) environmental variables on density, biomass and mean size was also investigated. The global estimations of kriged density mean was 8.30 ind m−2, biomass mean was 23.78 g m−2, and mean size was 18.71 mm, with the species heterogeneously distributed along the whole sandy subtidal strip of the coast of Huelva. The resulting kriged map shows the location and extension of the patches (5 NM range) in the study area; where the highest density and biomass hot-spots were observed near the river mouths, except for the Guadiana River. This species was present from 3 to 16 m, but preferred the depth window between 6-8 m, having a density and biomass peak at approximately 7 m depth. A negative and significant correlation was found between density/biomass and the coefficient of variation of mean size suggesting a density-dependent process. The most influential factors on density and biomass were depth, sediment characteristics (grain size and percentage of organic content), distance from river mouths and waste water treatment plants, and sea bottom temperature. This study, in addition to reporting on the current status of these natural beds and the influence of dynamic and static environmental variables on their distribution, proposes an additional approach to estimating several biological parameters in C. gallina that could be valuable for the spatial management of this commercial resource and highlight the role of marine protected areas.

Factors influencing structural characteristics of wetland bird communities in the middle Uzh River flow

Background. Long-term surveys of wetland bird communities of the Uzh mountain river in Zakarpattia region, along with an analysis of scientific data published over the past century enabled us to identify a set of anthropogenic factors that significantly influence the species and spatial structures of these communities. Two of the factors are specifically related to human disturbance of the riverbed and the floodplain. Namely, installation of hydraulic engineering structures aimed at water regulation and flood protection, as well as direct interventions in the river channel for smoothing the natural bed of the river bottom, removing small sedimentary islands and clearing the vegetation on the river banks. The factor of urbanization is favorable for species that tend to be synanthropic. For other wetland bird species, urbanization plays a positive role in winter. Materials and Methods. The studies were conducted in the middle Uzh River flow, which has a mountainous character. As the highest diversity of the wetland birds in the middle flow of the river is observed within the city of Uzhhorod, the main surveys were conducted right there. Birds were monitored all year round during the years 1994–2002 and 2020–2021. From 2003 to 2019, the studies were conducted sporadically. An annual cycle was subdivided into 6 periods: winter (November 20 – February 20), early spring (February 21 – April 10), breeding (April 11 – June 30), post-breeding (July), early autumn (August–September) and autumn (October – November 19). Results and Discussion. In the course of the monitoring activities on the Uzh River within the city of Uzhhorod, we identified 30 species of wetland birds belonging to 24 genera, 14 families and 10 orders. According to the pattern of their occurrence on the river throughout the year, they include resident nesting (3 species), wintering (3), migratory (4), wandering (4), summering (3) and occasional (13) bird species. Several of these species are new to the river in urban areas, while some others were not spotted there for the past 10–20 years due to a dramatic change in the habitat conditions. Numbers of certain species have also undergone significant changes due to the effects of various anthropogenic factors. The analysis of the results obtained over 30 years of studies allows us to identify 3 factors influencing the species and spatial structure of the wetland birds on the Uzh River. The first is urbanization, attracting numerous bird species. The second is water regulation, i.e. the construction of dams and water sto­rage facilities. This factor causes a negative impact on wetland birds by changing the river water dynamics, slo­wing the natural flow down, and raising the water level by retaining dams. The last one is a direct intervention into the river bed, which alters the river bottom, destroys riparian vegetation and alluvial islands that form additional micro-meanders in the riverbed, as well as shallow and deep water sections of the river. Conclusion. For the wetland bird species of the mountain rivers, it is crucial to keep the mosaic nature of their habitat. Interventions in the morphology of the riverbed, as well as alterations in the water dynamics of the river due to water management measures, adversely affect the species structure of wetland bird communities and the nature of their presence on the river. The cascades of retaining dams along the mountain rivers can substantially decrease the diversity of typical mountain river species and lead to a decline of these species’ population in the Carpathians. Cities, on the contrary, can serve as refuges for birds in critical winter periods.

Pathology, epidemiology, and phylogeny of mussel egg disease due to the microsporidian Steinhausia mytilovum (Field, 1924) in the Mediterranean mussel (Mytilus galloprovincialis)

Microsporidia are well known fungal pathogens of aquatic animals. However, the taxonomy of microsporidia is generally poorly resolved, which has consequently constrained our understanding of their pathology and epidemiology in marine animals. To date, microsporidia have been reported in both bivalves and gastropods, and microsporidia from mollusks have been classified in different genera. Despite ongoing work to better describe these genera, including detailed microscopic and ultrastructural images, so far we lack information on microsporidian phylogeny and pathogenicity of species within these genera. Here we investigate the microsporidian parasite Steinhausia mytilovum associated with the mussel, Mytilus galloprovincialis, in natural beds and farms along coast of southern Italy. A survey of M. galloprovincialis was conducted in 13 mussel farms and one natural bed between 2009 and 2020. We found the presence of S. mytilovum in 10 of the investigated farms, with a prevalence ranging between 14 and 100% of female mussels, depending on the population and season in which they were sampled. The parasite developed in the oocytes within a sporophorous vesicle (SV) where it produced 1–3 spores per cell, both in the cytoplasm and in the nucleus. Stenhausia mytilovum elicited an infiltrative (24.8%) or a strong capsular inflammatory response (43.4%) at gonadal follicles and surrounding vesicular connective tissue, in some cases accompanied by gonadal atresia (24.8%), leading to loss of gonadal architecture. In 7% of cases no reaction was observed. Ultrastructural observations revealed a mitochondrial re-organization to interact with all the phases of parasite development; the mitochondria were arranged outside the parasitophorous vesicle (PV) or directly interacting with the spore inside vesicle. There are five taxonomic clades of microsporidians as identified by SSU ribosomal gene sequence data. Maximum likelihood analysis assigned S. mytilovum within the Clade IV, defined as the Class Terresporidia, with closest genetic relationship (83.6% identity) to an undetermined invertebrate ovarian microsporidian. The constant presence, prevalence, and severity of S. mytilovum in coastline populations of M. galloprovincialis populations in southern Italy may indirectly reflect immunocompetence at both individual and population levels.

Concise review of genus Lessonia Bory

Abstract Lessonia (order Laminariales) is a kelp genus restricted to the temperate southern hemisphere, where species form dense forests from the low intertidal to 25 m depth at wave exposed sites. Lessonia spp. are among the most harvested kelps globally due to their importance in providing raw materials for food, cosmetics, bioactive and biomedical industries. Over-harvesting of natural beds can negatively affect Lessonia populations and the many species that depend on these habitats, including commercially important fish and molluscs, but good harvest management plans reduce these impacts on natural Lessonia stocks. However, the increasing demand for raw materials will likely only be met by aquaculture for which Lessonia shows high potential in pilot scale studies undertaken in Chile, New Zealand, and Australia. In this concise review, we highlight the current knowledge of Lessonia spp. taxonomy and distribution, life history, ecology and ecosystem services, wild harvest, aquaculture, and commercial applications. We discuss future research directions.

Chromosome-Level Genome Assembly of the Blue Mussel Mytilus chilensis Reveals Molecular Signatures Facing the Marine Environment.

The blue mussel Mytilus chilensis is an endemic and key socioeconomic species inhabiting the southern coast of Chile. This bivalve species supports a booming aquaculture industry, which entirely relies on artificially collected seeds from natural beds that are translocated to diverse physical-chemical ocean farming conditions. Furthermore, mussel production is threatened by a broad range of microorganisms, pollution, and environmental stressors that eventually impact its survival and growth. Herein, understanding the genomic basis of the local adaption is pivotal to developing sustainable shellfish aquaculture. We present a high-quality reference genome of M. chilensis, which is the first chromosome-level genome for a Mytilidae member in South America. The assembled genome size was 1.93 Gb, with a contig N50 of 134 Mb. Through Hi-C proximity ligation, 11,868 contigs were clustered, ordered, and assembled into 14 chromosomes in congruence with the karyological evidence. The M. chilensis genome comprises 34,530 genes and 4795 non-coding RNAs. A total of 57% of the genome contains repetitive sequences with predominancy of LTR-retrotransposons and unknown elements. Comparative genome analysis of M. chilensis and M. coruscus was conducted, revealing genic rearrangements distributed into the whole genome. Notably, transposable Steamer-like elements associated with horizontal transmissible cancer were explored in reference genomes, suggesting putative relationships at the chromosome level in Bivalvia. Genome expression analysis was also conducted, showing putative genomic differences between two ecologically different mussel populations. The evidence suggests that local genome adaptation and physiological plasticity can be analyzed to develop sustainable mussel production. The genome of M. chilensis provides pivotal molecular knowledge for the Mytilus complex.

Shedding light on variation in reproductive success through studies of population genetic structure in a Southeast Pacific Coast mussel.

Phylogeography often focuses on the spatial dimension of genetic diversity, rarely including the temporal dynamics occurring interannually among local populations, which can provide insight into past variations in reproductive success. Currently, there is an intense aquaculture industry of Mytilus spp. on the Southeast Pacific Coast which depends entirely on the spat released by natural populations forming a relevant and sensitive social-ecological system. Temporal and spatial spat variability from natural mussel beds could be related to interannual reproductive dynamics with variable reproductive success and recruitment, which leave genetic signatures. Temporal and spatial genetic structure was evaluated in six natural beds in the Southeast Pacific (from 39°25'S to 43°07'S) on the most abundant and widespread Mytilus lineage detected, Mytilus cf. chilensis, in 4 consecutive years. Analyses included data from >180 individuals per year, with a total of 751 (mitochondrial COI) and 747 (nuclear H1) individuals, respectively. Overall, both markers showed high haplotype diversity and low spatial and temporal genetic differentiation. Likely, the high dispersal capacity of Mytilus cf. chilensis maintains population homogeneity and prevents diversity erosion. The slight differences in genetic variance of COI were better explained by differences among sites (space), and conversely, the H1 genetic variance was better explained by interannual (temporal) comparisons, which could explain temporal variability in spat availability. This study highlights the important insights achieved with the evaluation of both temporal and spatial population genetic structures in marine species with high reproductive output, which can condition the success and sustainability of the relevant social-ecological system.

Comparison of invertebrate assemblages between concrete and natural beds in lowland streams.

Comparison of invertebrate assemblages between concrete and natural beds in lowland streams.

Correction to: Experimental Study of Natural Bed Roughness Effect on Hydraulic Condition and Energy Dissipation Over Chutes

Correction to: Experimental Study of Natural Bed Roughness Effect on Hydraulic Condition and Energy Dissipation Over Chutes

Trophic Assessment of an Artificial Kelp Eisenia bicyclis Bed Off the Eastern Coast of Korea Based on Stable Isotope Analyses

Effective trophic assessment of restoration success after the creation of an artificial habitat is essential for ecological management. In this study, to evaluate the ecological trophic function of restored kelp beds of artificial macroalgal reefs (AMRs) attached with the kelp species Eisenia bicyclis, we compared carbon and nitrogen stable isotope ratios of organic matter sources and macrobenthic consumers and isotopic indices of functional feeding groups between artificial and reference (natural bed and barren ground, respectively) habitats. There were no significant differences in isotopic values of consumer feeding groups (except for carnivores) and their potential food sources between the artificial and natural sites, suggesting that resource diversity and resource use by consumers was similar across all sites. The isotopic data also exhibited similar or relatively higher trophic niches of feeding groups at the artificial site compared to those at the natural site, indicating that the artificial kelp bed can play important roles in similar ecological functions and services as a natural counterpart. In addition, the present study revealed that the isotopic ranges and niche indices of feeding groups were significantly wider at the artificial and natural kelp beds compared to those at the barren ground, suggesting the trophic importance of macroalgal-derived organic matter to consumer nutrition in coastal ecosystems. Overall, our results support the conclusion that the creation of an Eisenia bicyclis kelp bed by the AMRs may lead to the restoration success of the macroalgae habitat through the recovery of the ecological function of a natural food web structure.

Effect of the alveolate parasite Perkinsus olseni infection on sexual maturation and spawning efficiency of the clam Ruditapes decussatus.

The effect of Perkinsus olseni infection on the reproduction ability of clams has been underestimated so far. Although some studies found evidence of reduction of egg production and delay in gonad maturation after infection, the total effect of the infection is still unclear. In this study, Ruditapes decussatus clams from a naïve population were injected with two different doses of P. olseni parasites, a low dose leading to a light infection and a high dose leading to a heavy infection. Clams were maintained during 2 months for maturation, and at the end of the experiment, the spawning was induced, the number of larvae release and mortality were evaluated. During the maturation period, infection level, gonadal stage, condition index, gross biochemical composition and oxidative status of progenitors were evaluated at days 0, 30 and 60 post-injection. The effects of P. olseni infection on clams showed alterations on biochemical parameters, namely lipid peroxidation, a significant mortality and a delayed gonad maturation, with a greater effect in the highly infected individuals. The reproductive capacity of the clams was impaired in both infected groups showing a lower production and a higher mortality rate of larvae. Finally, this study indicates that the production of natural beds with a high prevalence of P. olseni could be compromised by a deregulation of the natural reproduction cycle and a decrease in larvae production by infected animals, probably due to a combination of lower egg production and lower lipid reserves in larvae from infected clams.

Seaweed restocking along the Chilean coast: History, present, and inspiring recommendations for sustainability

Several seaweed species are commercialized worldwide both due to high demand for food and feed and as a raw material for the extraction of phycocolloids such as agar, carrageenan, and alginates that are used broadly in the food, cosmetic, and pharmaceutical industries. Chile is the world’s leading marine seaweed biomass producer when it comes to the exploitation of natural kelp beds. This extraction pressure has persisted for decades and has resulted in a reduction in natural stocks along the benthic ecosystems of the Chilean coast. Over the last three decades, several strategies aimed at restoring seaweed stocks have been implemented (i.e., sexual and asexual reproduction, the use of spore-type propagules or fragments of thalli, and entire thallus transplants). Success rates have varied, but the biological feasibility of such strategies has been demonstrated for several species. However, technological improvements must be achieved to move from small-scale, pilot experiments to cost-effective restocking strategies that are easy to transfer to fisher communities and another end-user, scalable to marine field conditions, and socio-ecologically sustainable. Researchers in other geographic areas have explored similar pathways for developing kelp restocking strategies and have tackled the research gaps regarding its massification. This work summarizes the research activities carried out in recent decades in the search for sustainable strategies to restore algal stocks in Chile.

Establishing construction of clarifiers for managing turbid sediments in flood reservoirs in mountain areas

The article presents the results of field research conducted in the Langar flood reservoir in the Kashkadarya region. Accumulation of large amounts of muddy sediments occurred in flood reservoir basins. The useless dead volume of the anchor flood reservoir is completely filled with silty sediments. As a result, storing the required volume of water in the flood reservoir is impossible when the flood flows occur. Therefore, building a two-chamber filter in the water-bearing basin of the flood reservoir is advisable. A two-chamber clarifier built in the catchment basin allows for the temporary settling of turbid sediments and improves the operational conditions of the flood reservoir. The construction of the flood reservoir is placed in the river bed of the flood reservoir. The 2nd chamber is connected to the first chamber, the length L2 = 200 m, the width b2 = 80 m, it is 1.25 times larger than the width of the natural bed, and the depth h2 = 1.5 m. Both cameras are assumed to have the same longitudinal slope i1 = i2. Preliminary recommendations on the safety assessment of flood reservoirs have been developed.

A Hotspot of TTX Contamination in the Adriatic Sea: Study on the Origin and Causative Factors.

Tetrodotoxins (TTXs), the pufferfish venom traditionally associated with Indo-Pacific area, has been reported during last decades in ever wider range of marine organisms and ever more geographical areas, including shellfish in Europe. Wild mussels (Mytilus galloprovincialis) grown in the Marche Region (N Adriatic Sea, Italy) were shown to be prone to TTX contamination during the warm season, with a suspected role of Vibrio alginolyticus characterized by non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS)-encoding genes. This work aimed to deepen the knowledge about the toxin's origin and the way through which it accumulates in mussels. A two-year study (spring-summer 2020-2021) confirmed the recurrent presence of TTX (11-68 µg kg-1) in the official monitored natural mussel beds of the Conero Riviera. During 2021, a supplementary nonroutine monitoring of a natural mussel bed in the same area was carried out weekly from June until August for TTXs and/or the presence of V. alginolyticus. Biotic (mussels, mesozooplankton, worms and phytoplankton); abiotic (water and sediment) matrices and phytoplankton assemblage characterizations were studied. Mussels showed relevant TTX contamination levels (9-296 µg kg-1) with extremely rapid TTX accumulation/depletion rates. The toxin presence in phytoplankton and its distribution in the different mussel tissues supports its possible exogenous origin. The V. alginolyticus count trend overlaps that of TTX contamination in mussels, and similar trends were reported also for some phytoplankton species. The role of V. alginolyticus carrying NRPS or PKS genes as a possible TTX source and of phytoplankton as a "potential vector" should therefore be further investigated.

Gonad development and recruitment pattern of the oysters Crassostrea ariakensis and Crassostrea sikamea in a subtropical bay in China

The extent of oyster stocks and their habitat loss experienced on the Chinese coasts suggests that oyster restoration will be necessary to rebuild direct fisheries and recover lost ecosystem services. Limited understanding of oyster biology and ecology is among the potential barriers to successful restoration along the Chinese coasts. At a natural oyster bed in Jiantiao Bay, Sanmen County, China, the study compared gonad development and spawn duration of the Sumonie oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikamea through histological sections from May 2020 to March 2021. Their temporal and vertical recruitment patterns were simultaneously observed along an increasing tidal elevation gradient (0.1 m, 0.6 m, 1.1 m, 1.6 m, 2.1 m). The gonad index did not differ between the oysters (P>0.05), with the maximum values in June–August, but C. sikamea had a longer spawning duration (May–December) than C. ariakensis (May–October). Crassostrea ariakensis recruited to only the lower 3 tidal zones (0.1 m, 0.6 m, 1.1 m), and its recruits varied linearly and significantly as an inverse function of tidal elevation. Significant 2nd degree polynomial fits best described the relationships for C. sikamea recruits and tidal elevation. The greatest recruits were commonly observed at the mid intertidal zones (0.6 m, 1.1 m and 1.6 m). An evident vertical settlement pattern emerged for C. sikamea at both 1-day and 3-day experiments; the greatest settlement rates occurred in the 1.6 m tidal zone, intermediate rates occurred in the 1.1 m and 0.6 m, the lowest rates occurred in the 0.1 m and 2.1 m. The study concluded that C. sikamea sustained longer spawning and recruitment durations than C. ariakensis, and a strong zonation pattern in recruitment emerged; C. sikamea achieved its maximum recruits in the mid-tidal zone, while the recruits of C. ariakensis linearly decreased with increasing tidal elevation.

Molecular Typing of Bacterial Pathogens Isolated from Air, Non-Living Surfaces and Clinical Sources in Diyala Governorate Using MLST Technique

The study aimed to isolate and diagnose bacterial species from clean room air samples for caesarean sections, natural childbirth, sterile preterm infants halls and the sub-corridors leading to these halls and main corridors of the hospital and from the air outside hospital building with isolation and diagnosis of bacterial species from non- living surface and clinical samples that were withdrawn from inside Al-Zahra Hospital for Women and Children in AL-Muqdadiya district in Diyala Governorate – Iraq that extends at latitudes (-3.33 and -36.6) north and longitudes (-44.22 and 45.56) east, during the period from 25 December 2021 to 19 February 2022 in light of the lack of studies that are concerned with this aspect, as 192 air samples were taken distributed to the hospital halls, such as the surgery hall and its sub-corridor leading to it, the delivery hall and its sub-corridor leading to it, the sterile preterm infant unit and its sub-corridor leading to it, the main corridor of these halls, and the air outside the hospital environment, where the air samples distributed into two groups, the first included 96 samples collected in the morning before the start of work at 8 am and the second also included 96 samples collected during Work (noon) at 12 noon ; also, 208 different swabs were collected from patients included 85 swabs after surgeries (caesarean section after suture lift after 7-10 days after delivery), 60 vaginal swabs from patients inside the delivery hall and 63 swabs from newborns lying inside the sterile preterm hall. Also, swabs were collected from non-living surfaces amounting to 100 swabs withdrawn from the natural delivery bed, caesarean section, floors, ventilation outlets, anesthesia device, fluid withdrawal device, incubators for preterm infants, ventilator and dressing cart. The total number of samples withdrawn by the effective method using the SAS air sampling device was 192, with 24 samples for each site, of which 172 samples were given a positive growth rate of 89.5%, the gram-positive bacteria constituted 69%, while the gram-negative bacteria formed an isolation rate of 31%. Sixty vaginal swabs were collected from women in the delivery hall during the examination before the birth began, 33 swabs gave a positive growth rate of 55%, of which 33 were bacterial isolated, the gram negative bacteria formed the isolates by 69.7%. 63 swabs were taken from newborns in the neonatal unit (either normal or caesarean section), those who were admitted to the preterm care hall as a result of complications during childbirth (suffering from shortness, rapid breathing and high bile in the first place, and from inflammation of the respiratory tract and urinary tract infection in the second degree), 38 swabs gave a positive growth rate of 63.3%, of which 38 bacterial isolates were mostly gram-negative bacteria. 85 swabs were taken from caesarean section wounds (7-10 days after caesarean section when the suture is lifted), 29 swabs gave a positive growth rate of 34%, the majority of which were 75.7% gram-negative bacteria. Twenty-six surface swabs gave a positive growth with a rate of 26%, of which 26 different bacterial isolates. The data of the bacterial typing analysis of the three strains of E. coli (multi-resistant bacteria) used in the molecular study by using MLST technique by using housekeeping genes showed that they are globally registered strains on the site of the Institute Pasteur in France, as the results showed that two bacterial isolates, which bear numbers (17,119) of air samples and clinical samples respectively, belong to the same strain (sequence type (ST)=741), while isolates No. (72) of surface samples belong to a different strain (ST=390). Molecular typing (MLST) was performed on three isolates of K. pneumonia (multi-resistant bacteria) where housekeeping genes were used for the purpose of testing. The strains obtained are new strains that have not been isolated before in Iraq, which means that our isolates are not registered in the MLST database at the Institute Pasteur in France.

The local energy flux surrogate in turbulent open-channel flows

We present a local analysis of turbulence in open-channel flows, using time-series velocity measurements. The method is based on a local form of the Kolmogorov “4/3-law” of homogeneous turbulence for the third-order moment of velocity increments. Following the Duchon and Robert [“Inertial energy dissipation for weak solutions of incompressible Euler and Navier–Stokes equations,” Nonlinearity 13, 249 (2000)] idea, which envisions turbulence dissipation as a lack of smoothness of the Navier–Stokes solutions, we estimate the local energy flux in a laboratory experiment with natural bed flows. Taking advantage of one-dimensional filtering techniques, under reasonable hypothesis, simple expressions of a surrogate of the energy flux are provided. The local energy flux surrogate reveals that, independently of the geometry, turbulence dissipation is highly intermittent. Among a variety of eddies that populate turbulence, dissipative singularities appear in sheet-like, tube, and filament structures, with large amplitude variations and rotations. This simplified technique can be applied to any measurement of hydrodynamic turbulence.

Chromosomal assembly of the flat oyster (Ostrea edulis L.) genome as a new genetic resource for aquaculture.

The European flat oyster (Ostrea edulis L.) is a native bivalve of the European coasts. Harvest of this species has declined during the last decades because of the appearance of two parasites that have led to the collapse of the stocks and the loss of the natural oyster beds. O.edulis has been the subject of numerous studies in population genetics and on the detection of the parasites Bonamia ostreae and Marteilia refringens. These studies investigated immune responses to these parasites at the molecular and cellular levels. Several genetic improvement programs have been initiated especially for parasite resistance. Within the framework of a European project (PERLE 2) that aims to produce genetic lines of O.edulis with hardiness traits (growth, survival, resistance) for the purpose of repopulating natural oyster beds in Brittany and reviving the culture of this species in the foreshore, obtaining a reference genome becomes essential as done recently in many bivalve species of aquaculture interest. Here, we present a chromosome-level genome assembly and annotation for the European flat oyster, generated by combining PacBio, Illumina, 10X linked, and Hi-C sequencing. The finished assembly is 887.2Mb with a scaffold-N50 of 97.1Mb scaffolded on the expected 10 pseudochromosomes. Annotation of the genome revealed the presence of 35,962 protein-coding genes. We analyzed in detail the transposable element (TE) diversity in the flat oyster genome, highlighted some specificities in tRNA and miRNA composition, and provided the first insight into the molecular response of O.edulis to M.refringens. This genome provides a reference for genomic studies on O.edulis to better understand its basic physiology and as a useful resource for genetic breeding in support of aquaculture and natural reef restoration.

Experimental Study on the Impact of Pulsed Flow Velocity on the Scouring of Benthic Algae from a Mountainous River

The decrease in periodic scouring of pulsed flows in regulated rivers can result in algal communities dominated by filamentous algae, not available as food sources for fish and macroinvertebrates. To study the pulsed flow velocity required to scour benthic algae from natural river beds, the removal effects on the algal biomass and resistances of different species were tested in a laboratory flume at different velocities of 0.8, 1.1, 1.4, 1.7, and 2.0 m/s. The removal of total algal biomass showed a significant positive relationship with increasing velocities, which reached 22% at 2.0 m/s. The biomass removal of green algae and diatoms was higher than that of blue–green algae. The flow velocity at 1.4 m/s had a clear removal effect on filamentous algae. The velocity higher than 1.7 m/s caused a significant increase in the removal percentage of total biomass dominated by diatoms and blue–green algae. To reduce the filamentous algae and retain the diatoms and blue–green algae, a range of near bed flow velocity was suggested to be 1.4–1.7 m/s. This range could serve as a reference for required pulsed flow velocity to reduce the growth of excessive or nuisance periphyton.