Water Flow Environment Research Articles

Fish community dynamics following the low-head dam removal and newly installed fish passage in a headstream tributary of Jinsha River, Southwest China

Low-head dams and small hydropower developments are widely distributed in global rivers because of their high cost-efficiency and smooth implementation. However, these installations have great ecological impacts on native fish communities due to the loss of longitudinal river connectivity. Although dam removal and fishway construction are effective measures to mitigate river fragmentation, research on their effects on fish communities remains limited to date. In this study, we investigated fish community dynamics in a mountainous tributary of the Jinsha River–Heishui River following dam removal, fishway construction, and fishway renovation. Our fish sampling data from 2018 to 2023 yielded 6137 fish belonging to 25 species, 12 families, and 3 orders. The native fish community predominantly represented the typical fish fauna of the Qinghai-Tibetan Plateau, primarily including the genus Schizothorax and the families Sisoridae and Nemacheilidae. Representative fish species in the Heishui River demonstrate notable adaptations to cold water, high altitude, and rapid flow environments. After removing the Laomuhe Dam, upstream fish abundance increased sharply, but species richness slightly decreased in the short term. Fishway construction significantly enhanced species richness and abundance and reduced the difference between the upstream and downstream fish communities from the Songxin Dam. However, the subsequent fishway renovation altered the dominance of fish species, with marginal changes in community structure and abundance. Variations in fish community dynamics in the river channel and fishway structure can be attributed to differences in ecological guilds (e.g., flow preference and thermal regime) and environmental factors (e.g., flow discharge, water temperature, and water depth). The present study provides insight into the significance of mitigation measures for the impact of dams on mountainous rivers in southwest China through ecological assessment and guides for decision-making in the conservation and restoration of specific fish communities.

Arsenic removal adsorbent using limonite-polyethersulfone composite fiber via continuous flow column process.

This research introduces an enhanced limonite-based composite fiber adsorbent for arsenic (As) removal. The modification involves creating polyethersulfone (PES)-limonite composite fibers loaded with 60 wt% limonite powders, designed to be applicable in water flow environments. The fibers were prepared using a wet-spinning process based on phase inversion, with varying concentrations (10, 20, and 30 wt%) of PES in NMP solution. The composite fiber with 10wt% NMP exhibited a porous structure and demonstrated efficient absorption of both As(III) and As(V). Adsorption followed the Langmuir model, with qm values of 1.5mg/g for As(III) and 3.2mg/g for As(V) at pH6. In column experiments, As removal rates increased with contact time, attributed to decreased flow rates (1mL/min). Moreover, increasing fiber column height led to enhanced removal rates, as indicated by the Adams-Bohart model. The mechanism for As(V) removal involved the formation of an inner-sphere complex through ion exchange between α-FeOOH and HAsO4 - and H2 AsO4 2- in an aqueous solution at pH6.8. PRACTITIONER POINTS: Changing the polyethersulfone ratio in the composite leads to variations in the appearance of limonite within each composite fiber. Limonite composite fibers effectively remove As(III) and As(V) at neutral pH. The adsorption behavior follows Langmuir kinetic model, the qm of 1.5mg/g for As(III) and 3.2mg/g for As(V). Longer columns and contact times enhance arsenic (As) removal in practical water treatment systems. Adam-Bohart model aids in predicting breakthrough and saturation time in As adsorption column design.

Enhancing performance of triboelectric nanogenerator by accelerating the charge transfer strategy

Developing high-performance triboelectric nanogenerators (HP-TENGs) is paramount for expanding their commercial utility. Presently, HP-TENGs predominantly concentrate on augmenting surface charge density. Here, we introduce an innovative strategy, denoted ACT-TENG (Accelerated Charge Transfer TENG), which markedly enhances TENG's performance by effectively accelerating charge transfer between materials, all while preserving the original charge density. We substantiate the feasibility of this approach through systematic investigations, employing magnetic field modulation and bidirectional rotation mode to verify the gain effect of ACT-TENG. Notably, compared to conventional free-standing TENG (FS-TENG), ACT-TENG achieves a 4-fold increase in charge transfer rate and a remarkable 14.6-fold enhancement in output power. This leads to an impressive average power density of 499.05 mW m-² Hz-¹ , showcasing superior performance compared to previously reported FS-TENG designs. Furthermore, ACT-TENG exhibits exceptional characteristics when deployed in a water flow environment, generating the power of 10.76 mW at a flow rate of 180 L min−1. Finally, we utilize ACT-TENG to harvest energy from water flow, constructing a self-powered Internet of Things (IoT) system within the underground pipeline gallery. This study addresses existing limitations in TENG technology and offers valuable insights into further advancements in enhancing TENG's performance.

A Horizontal Distribution Model of Static Ice Cover Generated by Static and Dynamic Water Considering the Heat Transfer of Riverbanks

The thermal factor is the main reason for winter ice cover with a low Froude number flow, and the heat transfer to narrow and deep river banks accelerates ice cover formation and ice thickness change. The freezing of water flow to freezing thickening is a nonisothermal-flow phase transition process coupled with the water flow temperature, environment and riverbank. Here, the Nusselt number and viscous dissipation are used to consider the flow velocity influence on icing, and a thermodynamic model of static ice cover horizontal distribution considering riverbed heat transfer is established. The initial ice time, freezing time and static ice cover thickness formed by static and dynamic water calculated by the model were consistent with measured data. The model reflects the horizontal growth process of the static ice cover, which was significant for narrow and deep channels. The horizontal distribution of the static ice cover was thin in the center and thick on both sides. The maximum horizontal thickness difference of −20 °C indoor freezing for 24 h reached 15% of the central ice thickness. Compared with the degree-day method for calculating ice thickness, the numerical model and dimensionless formula better reflect the growth law and horizontal distribution characteristics of static ice cover and provide a theoretical basis for safe water conveyance under ice cover in winter and ice cover formation in reservoirs and lakes in cold regions.

Structural load monitoring of floating mooring column and its application on optimal regulation for water conveyance system operation of sea shiplock

Due to the sea water intrusion and the development trend of using large-scale ships, more stringent requirements are put forward for the safety of water delivery process and the mooring equipment operation for the sea shiplock. The maximum loads for the mooring equipment of sea shiplock, i.e., floating mooring column (FMC), are generally occurred at the end of water delivery. The superimposed effect of turbulent flow and marine corrosive environment can accelerate the failure of the floating mooring column structure for the sea shiplock, which leads to the safety incidents, including the structural damage of FMC and the breakage of mooring lines for the ship, etc. The safety of the FMC is mostly influenced by three factors, including the ship’s tonnage, the water flow environment of the locked room, and the lock operation technologies; among these, the water flow environment can be considered the most significant. In practice, because the mooring load of an FMC due to water delivery from the shiplock is very complicated, there is currently no mature approach to condition monitoring. This investigation aims to address a large sea shiplock, and the optimal regulation approach for water delivery of shiplock is established based on a load monitoring methodology for FMCs. The detection accuracy of the FMC mooring loads is controlled by simulation verification with errors less than 10%. During the optimized water delivery process, the exerted loads on the FMCs are noticeably reduced to be lower than the maximum design rating. The innovative approach is essentially based on an inversion calculation of the load response model for obtaining the mooring loads of FMCs, with the monitored load results used to regulate and optimize the water delivery process of the shiplocks. The research results can fill a part of the research gap of FMC mooring load condition monitoring method in shiplock water delivery, and provide technical support for the safety of shiplock water delivery process and mooring equipment operation.

Influence of reef structure and its flow field effect on the spatial behavior of Sebastes schlegelii adults

Sebases schlegelii is an important economic reef fish in northern China. Its distribution in the reef area is affected by the reef structure and flow field. To evaluate the effects of differently shaped artificial reefs with distinct flow field properties on the distribution of adult S. schlegelii, four types of artificial reefs (cubic (CAR), pyramidal (PAR), star-shaped (SAR) and tubular (TAR) artificial reef) and the related flow regimes were experimentally examined. The mean gathering rate (MGR) and wavelet analysis were adopted to analyze the distribution patterns of S. schlegelii adults around reef bodies in three representative environmental conditions (static water (FE1), 40 Hz water flow environment (FE2), and 50 Hz water flow environment (FE3)). The significant gathering behaviors around the artificial reefs were depicted through the MGR of adult fish during physical observations. For FE1, the MGR of adult fish showed a decrease in the order PAR > CAR > SAR > TAR. With increasing incoming velocities, the MGR changed such that the quantity of adult fish in the CAR gradually increased more than that in the PAR, but no significant differences were observed between them (P>0.05). Wavelet analysis showed that the fluctuations in the gathering behaviors of adults decreased with increasing flow velocities. Based on the two-factor analysis of variance, the reef structural characteristics had a more significant impact than the flow velocities on the gathering behavior of adult fish. In summary, the PAR and CAR are recommended to restore the habitats of S. schlegelii in marine ranches given their dominant aggregation effects on S. schlegelii.

Numerical investigation of the lateral response of pile groups in sand under local scour conditions

Bridge foundations located in a water flow environment commonly experience scour, which can lead to significant drops in the soil elevation immediately surrounding the foundation. This has significant ramifications for lateral bearing capacity as well as the integrity of the supported superstructure. While pile groups are one of the most foundation systems for bridges, current research on scouring effects has been largely limited to single piles. This paper fills this gap through the use of 3D finite element (FE) analysis, validated using centrifuge tests reported elsewhere in the literature. Results from a parametric analysis is described exploring the effects of the scour hole geometry, defined by the depth and slope angle, on the lateral behavior of pile groups. In particular, the influences on the load–displacement and bending moment and soil resistance distributions with depth for each pile within the group are considered. The results show that scour can have a significant detrimental influence on the lateral response of a pile group. An increase in the length of the pile group is also shown to significantly reduce the sensitivity of the lateral bearing capacity of the group to scour.

Adaptive effects of parental and developmental environments on offspring survival, growth and phenotype

Abstract Phenotypic adjustments to environmental variation are particularly relevant to cope with putative environmental mismatches often imposed by natal dispersal. We used an intergenerational cross‐transplant field‐based experiment to evaluate the morphological and physiological effects of parental and postsettlement water flow environments on the orange‐fin anemonefish Amphiprion chrysopterus through ontogeny (at pre‐ and postsettlement stages). Offspring born from parents under high water flow had an 18% higher caudal fin aspect ratio (a compound measure of shape) at the presettlement stage, 10% slower growth after settlement, and 55% lower survival after settlement compared to offspring from low water flow parents. At the presettlement stage, caudal fin length was determined by parental caudal fin length. At the postsettlement stage, fish survived equally well with similar phenotypes in both high and low developmental flow environments. However, results suggest potential developmental phenotypic plasticity in caudal fin length, which increases more under low water flow during development. After settlement, growth was the only morphological or physiological trait that was associated with parental water flow, which was lower from parents under high flow, as was survival. These results give important insights into the parental contribution, both genetic and nongenetic, in determining early offspring phenotype and subsequent growth and survival. Our results also suggest that offspring may possess flexibility to cope with a wide range of local environments including those different from their parents. Overall, the findings of this study show the fitness consequences of living in different environments and the likely trade‐offs between parental and offspring fitness in a wild population. Read the free Plain Language Summary for this article on the Journal blog.

Research on the Depth Control Strategy of an Underwater Profiler Driven by a Mixture of Ocean Thermal Energy and Electric Energy

Marine resources are rich and contain an enormous amount of energy. The exploration of marine resources and the effective use of ocean energy have gradually become the research focus of scholars all over the world. A profiler driven by ocean thermal energy can monitor the vertical profile of the surrounding sea area for a long time. To realize the levitation at a fixed water depth on the premise of saving energy, in this paper, a new buoyancy regulation system driven by the mixture of ocean thermal energy and electric energy is designed, and a new depth control strategy for the hybrid drive is proposed. Compared with the traditional profiler, the new profiler, in which the main energy required for buoyancy regulation is provided by ocean thermal energy, can reduce electrical energy consumption. Simulations of SMC (sliding mode control) and conventional PID control were conducted, and the results showed that the SMC method has advantages in terms of response speed, overshoot, and energy saving. A lake test was conducted and the results showed that the new control method can make the equipment reach the fixed water depth position; however, due to the complex water flow environment, the precision and stability of the controller need to be improved in the future.

Monitoring Inflow Dynamics in a Multipurpose Dam Based on Travel-time Principle

Understanding inflow dynamics in a dam lake forms the basis for optimal dam operation and management practices. However, methods pertaining to adequately determining negative inflows and addressing them, as well as quantifying uncertainties in dam inflow, have been scarcely investigated. In this study, the inflow was observed using two pairs of fluvial acoustic tomography (FAT) systems placed diagonally in a dam lake, forming a crossed-shaped pattern. The “travel-time” principle is the primary approach for measuring the inflow by FAT. The novelty of this study is in discussing the inflow characteristics within a slow water-flow environment monitored by FAT. Based on the reciprocal sound transmission, we upgraded an equation to estimate the flow direction; this newly proposed generalized equation can be used in a fluctuating flow environment. We also discussed the sound propagation characteristics for slow flow velocities. Finally, we demonstrated that a small inaccuracy in the acoustic signal, even by a sub-millisecond, can cause significant errors in measurements. One of the novel findings of this study is the detection of internal waves using the improved flow direction equation and acoustic travel-time records. Overall, this study presents a promising approach for inflow measurements under extremely slow flow conditions.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11269-022-03161-w.

Lotic Environment Affects Morphological Characteristics and Energy Metabolism of Juvenile Grass Carp Ctenopharyngodon idella

This study investigated the effect of a lotic environment on morphological characteristics and energy metabolism in juvenile grass carp Ctenopharyngodon idella. The fish were stocked in the lotic environment and forced to swim for 12 h per day for 4 weeks at three water current velocities of 0.5, 2, and 4 body length s−1 (Bl s−1). The control fish were stocked in the lentic environment with water current velocities of 0 Bl s−1. The results showed that lotic environment significantly increased body weight, body length, and condition factor of grass carp. The first principal component (PC1) characterized by measured overall body size suggested that fish in a lotic environment had body stoutness and wider tail stalk. Standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic swimming performance (Ucrit) were elevated with the increased water flow and positively correlated with PC1. The 4 Bl s−1 group showed significantly decreased contents of serum glucose and muscular glycogen, and a significantly increased level of serum lactic acid. The mRNA expression levels of AMP-activated protein kinase-phosphorylate PPAR γ coactivator 1 α-nuclear respiratory factor 1 (AMPK-PGC1α-NRF1) pathway-related genes were significantly upregulated in red muscle of grass carp in the lotic environment. Water flow environment at 4 Bl s−1 significantly increased ratios of metabolic enzymes (lactate dehydrogenase/citrate synthase) and cytochrome c oxidase/citrate synthase) in the muscle. The relationship between morphological characteristics and metabolic capacity suggested that the body size of grass carp in a lotic environment was shaped to promote energy metabolism. The study identified the evidence of the mechanism and relationship of the trade-off between energy and morphology in grass carp.

The moving vibration source perception using bionic lateral line system and data-driven method

In recent years, the application scope of artificial lateral line sensor (ALLS) systems is mainly limited to the perception of water flow environment and dipole source. In order to expand the application scope, an ALLS based on a pressure sensor array is proposed in this work to recognize the shape and size parameters of moving vibration sources. First of all, the pressure sensor array is appropriately installed in the underwater vehicle with the help of sensor topology optimization. Then, a numerical simulation model of the ALLS is established and its validation is verified by experimental tests. Subsequently, the information of the moving vibration sources with different parameters is collected by the simulations and experiments to generate training data sets. Lastly, two typical data-driven methods (i.e., the random forest algorithm and support vector machine) are trained to identify the shape and size parameters of the moving vibration sources. The analysis results demonstrate that the developed ALLS is effective in vibration source perception, which enhances the function of underwater vehicles.

Multi-Step Combined Control Technology for Karst and Fissure Water Inrush Disaster During Shield Tunneling in Spring Areas

Shield tunneling in highly fractured karst water-rich conditions easily results in water inrush disaster or even causes the roof of the karst caves to collapse. Severe water inrush disasters have occurred during the EPB (earth pressure balance) shield machine of the Jinan Metro Line R1 advanced through a karst and fissure groundwater-rich limestone ground in the spring area. To cope with the extreme water inrush risk, a multi-step combined control technology was put forward. First, a detailed geological exploration was carried out by ahead geophysical prospecting using high-density resistivity method, geological radar, etc., and geological borehole drilling was conducted from the ground surface before excavation. As a result, the distribution orientation, size, fissure development degree, and water inflow channel within the surrounding rock of the karst caves were detected. Second, multi-step grouting was performed to reinforce the surrounding rock, including pre-grouting treatment and filling rock blocks to the big karst caves from the ground surface, multiple grouting with a small amount of inert slurry each time inside the tunnel, and secondary circumferential hoop grouting at the shield tail. Third, the tunneling process was optimized, including optimizing the tunneling parameters, making full use of the air-pressurized tunneling technology of the EPB to press bentonite into the fractures around the excavation cabin to seal the fissure water, and using the drainage system of EPB and muck improvement technology to reduce the water inrush disaster. Meanwhile, shield protection slurry technology is applied to cutter inspection and replacement in the pressurized chamber under dynamic water flow environment of the spring terrain. The practice shows that the water inrush on the tunnel face is obviously alleviated after the shield machine advanced into the grouting area. According to statistics, the water inflow on the tunnel face decreases from about 4 m3/h before treatment to less than 0.3 m3/h after the abovementioned control, and the water seepage between the segmental linings reduces to almost zero. The average advance rate increased from 3 m/day without stopping or even zero when the shield machine needs to shut down 2–3 days for drainage to about 6 m/day. In addition, the treatments prevented the shield machine from jamming and the head descending disaster. This study provided a reliable control method for shield tunneling through the karst and fissure water-rich area and played an essential role in protecting the spring water.

A validated protocol for fish farm monitoring using environmental DNA

Sea-based fish farms are associated with strong benthic enrichment gradients and routine monitoring is usually required by regulation. Internationally a wide range of approaches exist for measuring the degree of benthic deterioration around fish farming activities, ranging from simple visual or odour assessments to the calculation of secondary indices that combine multiple biological and/or physico-chemical metrics (e.g., AZTI Marine Biotic Index; Invertebrate Species Index; Norwegian Quality Index; Infauna Trophic Index). In New Zealand, the health of marine benthic ecosystems around coastal salmon farms is currently measured using an Enrichment State (ES) index. This index incorporates physico-chemical (redox, organic matter, sulphates, etc.) and benthic macrofaunal measurements, which requires taxonomic expertise, is time consuming and expensive. Supported by a range of private/government agencies and industry partners, we have developed and tested the robustness of bacterial, eukaryotic, and multi-trophic Metabarcoding Biotic Indices (b-MBI, e-MBI, and mt-MBI, respectively) using a molecular Eco-Group approach. The indices were calculated via automatic computer pipelines using data collected over a period of nine years from a range of high- and low-flow salmon farms (12 farms and 60 stations) from three distinct regions in New Zealand. The MBIs were compared against the established ES index. All MBIs yielded strong and highly significant relationships with the ES index. The strongest relationships (R2 > 0.9) were obtained with the b-MBI. A refinement of the b-MBI (2019-2020) was supported by highly prolific microbes throughout the ES spectrum, and in particular in the upper end of the organic enrichment scale where traditional benthic indices tend to fail. This resulted in ES values of both (molecular-based versus morphology-based) indices to follow a near one-to-one relationship, performing consistently across water flow environments and considered sub-regions. Station-averaged results were also used to compare regulated compliance outcomes between the two indices, based on the current key compliance criteria for farms within each flow regime. Of the 67 seabed monitoring stations that were subsequently classified as compliant or non‑compliant, 62 stations had identical compliance outcomes (i.e. 92% of instances). Furthermore, the b-MBI showed consistently narrower (~50%) confidence interval bands when compared to the traditional ES index. The b-MBI offers unprecedented precision for determining subtle changes along enrichment gradients, constituting a valuable asset for triggering timely management responses and improving compliance. The protocols developed in this project enable rapid, standardised, and cost-effective eDNA isolation and extraction, followed by automatic b-MBI calculation. The affordability and versatility of the b-MBI tool suggests that it could be immediately integrated into current monitoring strategies as the primary benthic assessment tool for assessing benthic impacts of salmon farms in New Zealand.

Study on the influence of ecological vegetation revetment on river flow and sediment environment

AbstractThis paper studied the influence of vegetation cover on the river water flow environment and on sediment suspended load movement environment, closely combining the development and construction of new ecological water conservancy projects such as ecological embankments and ecological wetlands with ecological vegetation revetment cultivated on river bank slopes. The glass flume experiment was carried out in the vegetation-water flow-sediment environment. In the experiment, natural straight holly in the early growth stage was selected as the experimental vegetation, and erect type vegetation with uniform distribution of the upper and lower branches and leaves was simulated, and a total of 14 experimental groups were set in different combinations with fixed bed, movable bed, submerged and non-submerged conditions. The measured data of flow quantity, flow velocity and suspended load concentration were achieved in the experiment. The experimental results show that: (1) as to the influence of vegetation on the water flow environment, the vegetation canopy density directly affects the turbulent environment of the water flow, and the greater the density, the greater the disturbance to the water flow environment, and the flow velocity near the canopy will be decreased sharply; (2) in the fixed bed, under submerged conditions, the maximum turbulence intensity appears near z/h = 0.6; under non-submerged conditions, the turbulence intensity near the water surface is largest. In the movable bed, under submerged conditions, the maximum turbulence intensity reaches the maximum in the top and upper locations of the top of the plant, and the turbulence intensity reaches the maximum at the top of the plant under non-submerged conditions. (3) In terms of the influence of vegetation on the sediment suspended load movement environment, the concentration of suspended sediment decreases with the increase of plant height, the sediment content in the tail of the plant belt is reduced to some degree. When the relative water depth is z/h > 0.5, almost no suspended sediment exists. And the sediment-retaining effect under non-submerged conditions is better than that under submerged conditions.

Study on Aeration Optimization and Sewage Treatment Efficiency of a Novel Micro-Pressure Swirl Reactor (MPSR)

This study developed a new type of micro-pressure swirl reactor (MPSR) for treating rural domestic sewage with variable water volume in northern China. The transformation of a traditional aeration tank to MPSR was mainly divided into three steps. Firstly, the aeration device was installed on one side of the aeration tank. Secondly, most of the top cover plate was sealed. Finally, the liquid level-lifting zone was set to achieve micro-pressure. The study measured the flow velocity and dissolved oxygen (DO) distribution in the main reaction zone of MPSR, studied the effects of MPSR sewage treatment in continuous operation mode and sequential batch operation mode, and analyzed the main microbial species. The experimental results showed that a stable circular circle flow and a spatial DO gradient in MPSR were formed when the aeration rate of MPSR was 0.2 m3/h. Through the MPSR sewage treatment experiment in two operation modes, it could meet the current requirements of rural environmental pollution controlled in China. Analysis of the types of microorganisms showed that microorganisms with different functions gathered in different zones of the MPSR due to the different dissolved oxygen environment and water flow environment, which further improved the ability of MPSR to simultaneously remove nitrogen and phosphorus.

Multi-plate structured triboelectric nanogenerator based on cycloidal displacement for harvesting hydroenergy

Hydroenergy is a widely distributed renewable energy source. Triboelectric nanogenerators (TENGs) have recently been extensively studied as a powerful approach for harvesting mechanical energy. In this paper, a multi-plate structured triboelectric nanogenerator (MPS-TENG) based on cycloidal displacement is proposed for harvesting hydroenergy. The MPS-TENG consists simply of a transmission component, the core components of which are a wave plate and a power generation component that has a multi-plate structure working in contact-separation mode. Rotational motion driven by water flow is converted into linear reciprocating motion by the design of the wave plates. The impact of the transmission process is reduced or eliminated by the wave plate surface design, and high contact-separation motion frequency is obtained by setting the number of waves on the wave plate. The power generation component is a multi-plate structure that improves power generation performance. The peak output power of the MPS-TENG is about 225 μW. The MPS-TENG is tested in a simulated water flow environment to verify its practical application. The 106 light-emitting diodes (LEDs) can be lighted up by the MPS-TENG using the rectifier circuit at a water flow rate of 55 L/min. The MPS-TENG can power a commercial sensor by a rectifier circuit with capacitors connected in parallel, using the same water flow rate. The MPS-TENG has the capacity to harvest energy for self-powered sensors from the environment.

Experimental investigation of natural gas hydrate production characteristics via novel combination modes of depressurization with water flow erosion

Depressurization is considered the most efficient method for natural gas hydrates (NGHs) exploitation. However, ice formation, hydrate reformation, and insufficient decomposition driving forces in the later stages of depressurization are the main issues to be solved. In this study, a more effective combination of depressurization with water flow erosion for the production of NGHs was investigated to promote efficient exploitation of methane hydrate (MH) by using in-situ magnetic resonance imaging. Three different MH decomposition modes were used, and water flow erosion was employed to eliminate the problem of incomplete MH decomposition in the later stages of depressurization, which is caused by insufficient driving forces and slower heat and mass transfer due to lower decomposition pressure and the protection effect of water films. The promotion of MH decomposition by water flow erosion was experimentally confirmed. Depressurization could decrease water-phase permeability in the sediment core and further optimize the water flow environment. Water flow erosion could greatly accelerate heat and mass transfer and provided extra driving force by increasing the chemical potential difference in the later stages of depressurization. In addition, the phenomenon of ice formation caused by sudden depressurization could be relieved by water flow erosion, which improved the ambient heat transfer, further changing the MH decomposition characteristics. The mutual promotion of MH decomposition by water flow erosion and depressurization was clearly demonstrated in this study.

A Low-Diversity Microbiota Inhabits Extreme Terrestrial Basaltic Terrains and Their Fumaroles: Implications for the Exploration of Mars.

A major objective in the exploration of Mars is to test the hypothesis that the planet hosted life. Even in the absence of life, the mapping of habitable and uninhabitable environments is an essential task in developing a complete understanding of the geological and aqueous history of Mars and, as a consequence, understanding what factors caused Earth to take a different trajectory of biological potential. We carried out the aseptic collection of samples and comparison of the bacterial and archaeal communities associated with basaltic fumaroles and rocks of varying weathering states in Hawai‘i to test four hypotheses concerning the diversity of life in these environments. Using high-throughput sequencing, we found that all these materials are inhabited by a low-diversity biota. Multivariate analyses of bacterial community data showed a clear separation between sites that have active fumaroles and other sites that comprised relict fumaroles, unaltered, and syn-emplacement basalts. Contrary to our hypothesis that high water flow environments, such as fumaroles with active mineral leaching, would be sites of high biological diversity, alpha diversity was lower in active fumaroles compared to relict or nonfumarolic sites, potentially due to high-temperature constraints on microbial diversity in fumarolic sites. A comparison of these data with communities inhabiting unaltered and weathered basaltic rocks in Idaho suggests that bacterial taxon composition of basaltic materials varies between sites, although the archaeal communities were similar in Hawai‘i and Idaho. The taxa present in both sites suggest that most of them obtain organic carbon compounds from the atmosphere and from phototrophs and that some of them, including archaeal taxa, cycle fixed nitrogen. The low diversity shows that, on Earth, extreme basaltic terrains are environments on the edge of sustaining life with implications for the biological potential of similar environments on Mars and their exploration by robots and humans.

Mechanical properties of the wave-swept kelp Egregia menziesii change with season, growth rate and herbivore wounds.

The resistance of macroalgae to damage by hydrodynamic forces depends on the mechanical properties of their tissues. Although factors such as water-flow environment, algal growth rate and damage by herbivores have been shown to influence various material properties of macroalgal tissues, the interplay of these factors as they change seasonally and affect algal mechanical performance has not been worked out. We used the perennial kelp Egregia menziesii to study how the material properties of the rachis supporting a frond changed seasonally over a 2year period, and how those changes correlated with seasonal patterns of the environment, growth rate and herbivore load. Rachis tissue became stiffer, stronger and less extensible with age (distance from the meristem). Thus, slowly growing rachises were stiffer, stronger and tougher than rapidly growing ones. Growth rates were highest in spring and summer when upwelling and long periods of daylight occurred. Therefore, rachis tissue was most resistant to damage in the winter, when waves were large as a result of seasonal storms. Herbivory was greatest during summer, when rachis growth rates were high. Unlike other macroalgae, E. menziesii did not respond to herbivore damage by increasing rachis tissue strength, but rather by growing in width so that the cross-sectional area of the wounded rachis was increased. The relative timing of environmental factors that affect growth rates (e.g. upwelling supply of nutrients, daylight duration) and of those that can damage macroalgae (e.g. winter storms, summer herbivore outbreaks) can influence the material properties and thus the mechanical performance of macroalgae.