Estuarine projects can change local topography and influence water transport and saltwater intrusion.The Changjiang(Yangtze)River estuary is a multichannel estuary,and four major reclamation projects have been impleme...Estuarine projects can change local topography and influence water transport and saltwater intrusion.The Changjiang(Yangtze)River estuary is a multichannel estuary,and four major reclamation projects have been implemented in the Changjiang River estuary in recent years:the Xincun Shoal reclamation project(RP-XCS),the Qingcao Shoal reclamation project(RP-QCS),the Eastern Hengsha Shoal reclamation project(RP-EHS),and the Nanhui Shoal reclamation project(RP-NHS).The effects of the four reclamation projects and each project on the saltwater intrusion and water resources in the Changjiang River estuary were simulated in a 3D numerical model.Results show that for a multichannel estuary,local reclamation projects change the local topography and water diversion ratio(WDR)between channels and influence water and salt transport and freshwater utilization in the estuary.During spring tide,under the cumulative effect of the four reclamation projects,the salinity decreases by approximately 0.5in the upper reaches of the North Branch and increases by 0.5-1.0 in the middle and lower reaches of the North Branch.In the North Channel,the salinity decreases by approximately 0.5.In the North Passage,the salinity increases by 0.5-1.0.In the South Passage,the salinity increases by approximately 0.5 in the upper reaches and decreases by 0.2-0.5 on the north side of the middle and lower reaches.During neap tide,the cumulative effects of the four reclamation projects and the individual projects are similar to those during spring tide,but there are some differences.The effects of an individual reclamation project on WDR and saltwater intrusion during spring and neap tides are simulated and analyzed in detail.The cumulative effect of the four reclamation projects favors freshwater usage in the Changjiang River estuary.展开更多
Hildenbrandia is an early diverged lineage in Florideophyceae,Rhodophyta.The species diversity of this genus is still unresolved due to the simple morphology and limited molecular information.The mitochondrial genome ...Hildenbrandia is an early diverged lineage in Florideophyceae,Rhodophyta.The species diversity of this genus is still unresolved due to the simple morphology and limited molecular information.The mitochondrial genome of freshwater H.jigongshanensis was determined in this study.The freshwater H.jigongshanensis had a larger mitochondrial genome than the marine H.rubra and GC content was higher.Collinear alignment structure was observed between the mitochondrial genomes of H.jigongshanensis and H.rubra,except for one block that was encoded on the complement strand.More introns were found in mitochondrial genome of H.jigongshanensis than in H.rubra,and H.jigongshanensis shares the common feature with Bangiophyceae that two introns were distributed in cox1.Comparison of mitochondrial genome organization suggests that H.jigongshanensis preserves characters that could be hypothetically more similar to the ancestor of Bangiophyceae and Florideophyceae,which differ with previous studies based on chloroplast,and nuclear markers.More mitochondrial genomes and phylogenetic analyses combing nuclear,chloroplast and mitochondrial genomes are needed to clarify this discrepancy.Mitochondrion-based phylogeny in this study resulted in better solution at both the deep and recent derived nodes than single-gene phylogenies.Most protein-coding genes between H.jigongshanensis and H.rubra were identical except atp8,which was present in H.jigongshanensis while absent from H.rubra.This finding follows the trend that high Ka/Ks ratio genes are more frequently lost than low Ka/Ks ratio ones in red algae.展开更多
DEAR EDITOR,The introduction of freshwater fish into areas outside their native range has impacted freshwater ecosystems worldwide.In China,the non-native Alligator gar(Atractosteus spatula)fish has attracted attentio...DEAR EDITOR,The introduction of freshwater fish into areas outside their native range has impacted freshwater ecosystems worldwide.In China,the non-native Alligator gar(Atractosteus spatula)fish has attracted attention due to its widespread occurrence and destructive effects on local fish populations,signaling a high potential of invasiveness.展开更多
DEAR EDITOR,Syngnathidae species commonly inhabit ocean environments.However,some have adapted to live exclusively in freshwater over long-term adaptive evolution but continue to retain physiological adaptations to sa...DEAR EDITOR,Syngnathidae species commonly inhabit ocean environments.However,some have adapted to live exclusively in freshwater over long-term adaptive evolution but continue to retain physiological adaptations to saltwater environments.The genetic basis underlying the adaptive strategies and molecular regulation of freshwater syngnathids to freshwater and saltwater remains unclear.Here,we investigated the molecular characteristics and core gene expression in freshwater belly pipefish(Hippichthys heptagonus)embryos and juveniles through salinity stress experiments and transcriptome analysis.Results showed that embryonic exposure to salinity at a concentration of 30‰down-regulated cell cycle-associated genes vital to embryonic development.Retinol metabolism,neuroactive receptor interaction,and peroxisome proliferator-activated receptor signaling pathways were significantly enriched in up-regulated genes in the embryos.Notably,there was no significant change in the expression of ion transport and energy metabolism genes.Conversely,juvenile exposure to 30‰salinity up-regulated ion transport-related genes and significantly enriched immune-related signaling pathways,including lysosome,phagosome,autophagy,and mitophagy signaling pathways.Carbohydrate metabolism genes were also up-regulated,whereas oxidative phosphorylation genes were significantly down-regulated.These results suggest that brood pouch protection during the embryonic stage and salinity adaptation plasticity in juveniles may be strategic adaptations in freshwater pipefish.展开更多
Objective:To investigate the epidemiological situation of cercarial trematodes infection in freshwater snails from different water resources in Chiang Mai province,Thailand.Methods:The snail specimens were collected f...Objective:To investigate the epidemiological situation of cercarial trematodes infection in freshwater snails from different water resources in Chiang Mai province,Thailand.Methods:The snail specimens were collected from 13 districts of Chiang Mai province during April 2008 to February 2012.The prevalence of cercarial infection in snails was investigated using the crushing method.The drawing was done with the help of a camera lucida for the morphological study.Results:A total of 2479 snail individuals were collected and classified into 7 families,11 genera,and 14 species,Among them,8 snails species were found to be infected with an overall prevalence of 17.27%(428/2479),which infected with nine groups of cercariae;gymnocephalous cercaria,strigea cercaria,megalurous cercaria,monostome cercaria,parapleurolophocercous cercaria(Haplorchis cercaria),pleurolophocercous cercaria,furcocercous cercaria(Transversotrema cercaria),xiphidiocercaria,and virgulate cercaria.The parapleurolophocercous cercaria was found to be the dominant type among the cercarial infection in the snails(64.25%).Conclusions:The various species of snails found in the research location act as the intermediate hosts for the high prevalence of parasitic infection of many species of mammals.This work will provide new information on both the distribution and first intermediate host of trematodes.展开更多
Natural wetlands are known to store huge amounts of organic carbon in their soils. Despite the importance of this storage,uncertainties remain about the molecular characteristics of soil organic matter(SOM), a key fac...Natural wetlands are known to store huge amounts of organic carbon in their soils. Despite the importance of this storage,uncertainties remain about the molecular characteristics of soil organic matter(SOM), a key factor governing the stability of soil organic carbon(SOC). In this study, the molecular fingerprints of SOM in a typical freshwater wetland in Northeast China were investigated using pyrolysis gas-chromatography/mass-spectrometry technology(Py-GC/MS). Results indicated that the SOC, total nitrogen(TN),and total sulfur contents of the cores varied between 16.88% and 45.83%, 0.93% and 2.82%, and 1.09% and 3.79%, respectively. The bulk δ^13C and δ^15N varied over a range of 9.85‰, between –26.85‰ and –17.00‰, and between –0.126‰ and 1.002‰, respectively. A total of 134 different pyrolytic products were identified, and they were grouped into alkyl(including n-alkanes(C:0) and n-alkenes(C:1),aliphatics(Al), aromatics(Ar), lignin(Lg), nitrogen-containing compounds(Nc), polycyclic aromatic hydrocarbons(PAHs), phenols(Phs), polysaccharides(Ps), and sulfur-containing compounds(Sc). On average, Phs moieties accounted for roughly 24.11% peak areas of the total pyrolysis products, followed by Lg(19.27%), alkyl(18.96%), other aliphatics(12.39%), Nc compounds(8.08%), Ps(6.49%), aromatics(6.32%), Sc(3.26%), and PAHs(1.12%). Soil organic matter from wetlands had more Phs and Lg and less Nc moieties in pyrolytic products than soil organic matters from forests, lake sediments, pastures, and farmland.δ^13 C distribution patterns implied more C3 plant-derived soil organic matter, but the vegetation was in succession to C4 plant from C3 plant. Significant negative correlations between Lg or Ps proportions and C3 plant proportions were observed. Multiple linear analyses implied that the Ar and Al components had negative effects on SOC. Alkyl and Ar could facilitate ratios between SOC and total nitrogen(C/N), while Al plays the opposite role. Al was positively related to the ratio of dissolved organic carbon(DOC) to SOC. In summary, SOM of wetlands might characterize by more Phs and lignin and less Nc moieties in pyrolytic products. The use of Pyrolysis gas-chromatography/mass-spectrometry(Py-GC/MS) technology provided detailed information on the molecular characteristics of SOM from a typical freshwater wetland.展开更多
A series of numerical experiments are carried out to study the tropical upper ocean response to combined momentum and buoyancy forcing, with emphasis on the three-dimensional thermohaline structure in the western Paci...A series of numerical experiments are carried out to study the tropical upper ocean response to combined momentum and buoyancy forcing, with emphasis on the three-dimensional thermohaline structure in the western Pacific warm pool. In response to climatological winds, heat fluxes and freshwater input, the model is able to simulate the salient dynamic and hydrographic features of the tropical Pacific Ocean and their seasonal variability. In response to idealized episodic westerly wind bursts and rainfall, the simulated upper ocean conditions compare favorably with available observations, thus enabling us to identify important physical processes involved. Local forcing, vertical mixing and meridional advection dominate the salt and heat budgets in the warm pool on short time scales, but it is necessary to include the saline water coming from the east with the South Equatorial Current to close the salt budget on seasonal and longer time scales. Strong westerly wind bursts generate a swift eastward equatorial jet and a pair of meridional circulation cells with convergence at the equator. This results in an equatorward advection of relatively fresh water from the north and a depression of the thermocline at the equator. Heavy rainfall reduces the surface mixed layer depth by creating a shallow halocline, thus trapping the momentum and heat inputs near the surface. The remote influences of the episodic momentum and buoyancy fluxes are very different. Westerly wind bursts can generate large downstream disturbances in both dynamic and thermal fields through the propagation of equatorial waves, while the effect of rainfall is mostly confined to the forcing area.展开更多
Model studies point to enhanced warming and to increased freshwater ?uxes to high northern latitudes in response to global warming. In order to address possible feedbacks in the ice-ocean system in response to such ch...Model studies point to enhanced warming and to increased freshwater ?uxes to high northern latitudes in response to global warming. In order to address possible feedbacks in the ice-ocean system in response to such changes, the combined e?ect of increased freshwater input to the Arctic Ocean and Arctic warming—the latter manifested as a gradual melting of the Arctic sea ice—is examined using a 3-D isopycnic coordinate ocean general circulation model. A suite of three idealized experiments is carried out: one control integration, one integration with a doubling of the modern Arctic river runo?, and a third more extreme case, where the river runo? is ?ve times the modern value. In the two freshwater cases, the sea ice thickness is reduced by 1.5–2 m in the central Arctic Ocean over a 50-year period. The modelled ocean response is qualitatively the same for both perturbation experiments: freshwater propagates into the Atlantic Ocean and the Nordic Seas, leading to an initial weakening of the North Atlantic Drift. Furthermore, changes in the geostrophic currents in the central Arctic and melting of the Arctic sea ice lead to an intensi?ed Beaufort Gyre, which in turn increases the southward volume transport through the Canadian Archipelago. To compensate for this southward transport of mass, more warm and saline Atlantic water is carried northward with the North Atlantic Drift. It is found that the increased transport of salt into the northern North Atlantic and the Nordic Seas tends to counteract the impact of the increased freshwater originating from the Arctic, leading to a stabilization of the North Atlantic Drift.展开更多
There are reports on the use of chemicals like sodium tri polyphosphate (STPP) and foreign materials like pearl tapioca (locally called ‘sagu’), jelly (litchi) to adulterate freshwater prawn (Macrobrachium rosenberg...There are reports on the use of chemicals like sodium tri polyphosphate (STPP) and foreign materials like pearl tapioca (locally called ‘sagu’), jelly (litchi) to adulterate freshwater prawn (Macrobrachium rosenbergii) prior to freeze processing to increase their weight. Studies were, therefore, undertaken to determine the changes in product quality on the use of different concentrations of STPP, sagu and litchi under ice storage condition. Percent weight gain of prawn was 5.46, 18.87 and 23.50 when dipped in 2%, 4% and 6% STPP solution, respectively. In all cases maximum water uptake by prawn muscle was during the first 6 h with fastest weight gain with STPP solutions containing tap water compared to those of ice and tap water. Organoleptic quality of the STPP treated samples became brown and spongy after 8 h of dipping treatment under iced condition. Quality assessment studies conducted after injecting sagu and litchi in prawn muscle showed little or no difference with those of control samples during the first 6 h, which turned whitish and swollen with severe drip loss after 24 h of ice stored condition, indicating characteristics for easy identification of the injected shrimps by organoleptic method.展开更多
Objective: To investigate the prevalence of cercarial trematode infection in snails and to examine the reconstruction of the phylogenetic relationship to explain the molecular system of cercarial stage trematodes to e...Objective: To investigate the prevalence of cercarial trematode infection in snails and to examine the reconstruction of the phylogenetic relationship to explain the molecular system of cercarial stage trematodes to estimate the infection rate of in the definite host from the Chao-Phraya Basin.Methods: The snails were collected from 10 provinces of the Chao-Phraya Basin,Thailand by stratified sampling method. The snails were examined for cercarial infection by the crushing method. All DNA specimens were amplified with internal transcribed spacer 3(ITS3) and ITS4 primer based on PCR technique. The sequence data were aligned and used to reconstruct the phylogenetic tree by unweighted pair-group method with arithmetic means with 10 000 bootstraps.Results: The overall rate of cercarial infection was found to be 5.90%(122/2 067). Snails in the family Thiaridae were found to be in the highest prevalence followed by Lymnaeidae, Bithyniidae, Planorbidae, Viviparidae, and Ampullariidae, respectively, while the Buccinidae family(Clea helena) did not reveal any infections. The frequently found species of cercariae were parapleurolophocercous cercariae, cercariae and megarulous cercariae. The monophyletic tree separated the snails into five groups comprised of Heterophyidae, Strigeidae, Lecithodendriidae, Philophthalmidae and Echinostomatidae using the sequence of Angiostrongylus cantonensis as an out-group.Conclusions: This study was the first to report on cercarial infection in the Chao-Phraya Basin, Thailand. This revealed that a high variety of freshwater snails were infected by cercariae stage trematodes with a high prevalence. The sequence data of ITS2 can be used to investigate the phylogenetic relationships of trematodes at the family level and in each clade of different families separated by the definitive hosts.展开更多
Seawater greenhouse(SWGH)is a technology established to overcome issues related to open field cultivation in arid areas,such as the high ambient temperature and the shortage of freshwater.It adopts the humidification-...Seawater greenhouse(SWGH)is a technology established to overcome issues related to open field cultivation in arid areas,such as the high ambient temperature and the shortage of freshwater.It adopts the humidification-dehumidification concept where evaporated moisture from a saline water source is condensed to produce freshwater within the greenhouse body.Various condenser designs are adopted to increase freshwater production in order to meet the irrigation demand.The aim of this study was to experimentally investigate the practicality of using the packed-type direct contact condenser in the SWGH to produce more freshwater at low costs,simple design and high efficiency,and to explore the impact of the manipulating six operational variables(inlet air temperature of the humidifier,air mass flowrate of the humidifier,inlet water temperature of the humidifier,water mass flowrate of the humidifier,inlet water temperature of the dehumidifier and water mass flowrate of the dehumidifier)on freshwater condensation rate.For this purpose,a direct contact condenser was designed and manufactured.Sixty-four full factorial experiments were conducted to study the effect of the six operational variables.Each variable was operated at two levels(high and low flowrate),and each experiment lasted for 10 min and followed by a 30-min waiting time.Results showed that freshwater production varied between 0.257 and 2.590 L for every 10 min.When using Minitab statistical software to investigate the significant variables that contributed to the maximum freshwater production,it was found that the inlet air temperature of the humidifier had the greatest influence,followed by the inlet water temperature of the humidifier;the former had a negative impact while the latter had a positive impact on freshwater production.The response optimizer tool revealed that the optimal combination of variables contributed to maximize freshwater production when all variables were in the high mode and the inlet air temperature of the humidifier was in the low mode.The comparison between the old plastic condenser and the new proposed direct contact condenser showed that the latter can produce 75.9 times more freshwater at the same condenser volume.展开更多
DEAR EDITOR,Bellamya purificata(Gastropoda:Caenogastropoda;Architaenioglossa;Viviparidae:Bellamyinae;Sinotaia),a homotypic synonym of S.purificata,is widely distributed in freshwater habitats in Asia.It is an economic...DEAR EDITOR,Bellamya purificata(Gastropoda:Caenogastropoda;Architaenioglossa;Viviparidae:Bellamyinae;Sinotaia),a homotypic synonym of S.purificata,is widely distributed in freshwater habitats in Asia.It is an economically important edible snail and plays a vital function in freshwater wetland ecology.However,genomic resources for this snail are lacking and no reference genome has been released.In this study,we constructed the first chromosome-level genome of B.purificata using PacBio long-read sequencing and high-throughput chromosome conformation capture(Hi-C)technology.展开更多
Freshwater is recharged mainly by rainfall and stored inland for a period of time,which is directly affected by its storage capability.The storage capability of river basins has different spatiotemporal features that ...Freshwater is recharged mainly by rainfall and stored inland for a period of time,which is directly affected by its storage capability.The storage capability of river basins has different spatiotemporal features that are important for the predictability of freshwater resources.However,the estimation of freshwater storage capability(FSC)remains a challenge due to the lack of observations and quantification indices.Here,we use a metric that characterizes hydrological“inertia”after rainfalls to analyze FSC over the 194 largest global major river basins based on satellite observations from the Gravity Recovery and Climate Experiment(GRACE)and simulations from the Community Land Model version 5(CLM5).During 2003–16,the global land was observed to retain 28%of precipitation after one month based on GRACE observations,and the simulation depicts that the retained proportions decrease from 42%after one day to 26%after one month,with smaller FSC partly attributed to wetter conditions and higher vegetation densities.The root zone contributes about 40%to the global land FSC on daily to monthly time scales.As the time scale increases,the contribution from the surface soil decreases from 26%to 14%,while the contribution from the deep soil increases from 4%to 10%.Snow contributes over 20%of land FSC,especially over high latitudes.With six decades of CLM5 long-term simulations,it is revealed that the change of FSC in most basins is related to internal climate variability.The FSC of river basins which displays the proportion of precipitation retained on land is worthy of further attention regarding the predictability of water resources.展开更多
As important freshwater resources in alpine basins,glaciers and snow cover tend to decline due to climate warming,thus affecting the amount of water available downstream and even regional economic development.However,...As important freshwater resources in alpine basins,glaciers and snow cover tend to decline due to climate warming,thus affecting the amount of water available downstream and even regional economic development.However,impact assessments of the economic losses caused by reductions in freshwater supply are quite limited.This study aims to project changes in glacier meltwater and snowmelt of the Urumqi River in the Tianshan Mountains under future climate change scenarios(RCP2.6(RCP,Representative Concentration Pathway),RCP4.5,and RCP8.5)by applying a hydrological model and estimate the economic losses from future meltwater reduction for industrial,agricultural,service,and domestic water uses combined with the present value method for the 2030 s,2050 s,2070 s,and 2090 s.The results indicate that total annual glacier meltwater and snowmelt will decrease by 65.6%and 74.5%under the RCP4.5 and RCP8.5 scenarios by the 2090 s relative to the baseline period(1980-2010),respectively.Compared to the RCP2.6 scenario,the projected economic loss values of total water use from reduced glacier meltwater and snowmelt under the RCP8.5 scenario will increase by 435.10×10^(6) and 537.20×10^(6) CNY in the 2050 s and 2090 s,respectively,and the cumulative economic loss value for 2099 is approximately 2124.00×10^(6) CNY.We also find that the industrial and agricultural sectors would likely face the largest and smallest economic losses,respectively.The economic loss value of snowmelt in different sectorial sectors is greater than that of glacier meltwater.These findings highlight the need for climate mitigation actions,industrial transformation,and rational water allocation to be considered in decision-making in the Tianshan Mountains in the future.展开更多
Objective:To investigate the prevalence of cercarial infections in freshwater snails from several water sources in Nakhon Nayok,Nonthaburi,and Pathum Thani provinces of Central Thailand,and to reconstruct a phylogenet...Objective:To investigate the prevalence of cercarial infections in freshwater snails from several water sources in Nakhon Nayok,Nonthaburi,and Pathum Thani provinces of Central Thailand,and to reconstruct a phylogenetic tree for improved understanding of the relationships in the cercarial stage.Methods:The snail specimens were collected from 34 total sampling sites and investigated for cercarial infections using the crushing method.The cercarial specimens were classified and used for the phylogenetic tree analysis using the Internal Transcribed Spacer 2(ITS2).Results:A total of 1921 snail specimens were classified into five families and seven species.The results showed that four snail species were identified as intermediate hosts of the larval stages of trematodes,with an overall prevalence of infection of 2.45%(47/1921).The infected snail specimens included five groups of the cercarial type:cercariaeum cercariae,echinostome cercaria,megalurous cercaria,parapleurolophocercous cercaria,and xiphidiocercariae.This is particularly true of xiphidiocercariae,which was found to be the dominant type among cercarial infections in bithyniid snails by approximately 38.00%.With regard to molecular identification,the phylogenetic tree was reconstructed using the neighbor-joining method with 10000 bootstraps and separated the trematodes into three clades:Echinostomatoidea,Microphalloidea and Opisthorchioidea.Conclusions:The study reveals a high prevalence of cercarial infection for each cercarial type and maturation into a definite trematode genus and delineates morphological characteristics and evolutionary trends among each larval trematode in Nakhon Nayok,Nonthaburi and Pathum Thani provinces.In addition,the ITS2 sequence data of cercariae could be used to examine classification of these species at the family level.展开更多
It has been reported recently that the simulated Atlantic meridional overturning circulation(AMOC) using the coupled Bergen climate model(BCM) showed initial intensity declines followed by gradual recoveries over a 15...It has been reported recently that the simulated Atlantic meridional overturning circulation(AMOC) using the coupled Bergen climate model(BCM) showed initial intensity declines followed by gradual recoveries over a 150-year enhanced freshwater input experiment.Stratification-dependent oceanic diapycnal mixing has been hypothesized as a reason for the simulated recovery of the AMOC.This study investigated the role of diapycnal mixing in transient responses of simulated AMOCs.Our results showed that stratification-dependent diapycnal mixing can cause stronger upwelling of deep water in the tropical Atlantic than that produced under conditions of fixed diapycnal mixing.Moreover,simulated AMOCs were more sensitive to active stratification-dependent diapycnal mixing than fixed mixing.However,stratification-dependent diapycnal mixing cannot be conclusively singled out as the critical cause of the recoveries of simulated AMOCs under enhanced-freshwater inputs.展开更多
Due to the rapid economic growth and the continuous increase of human, ecosystem disturbances and habitat destructions, the biodiversity of freshwater ecosystems in China is rapidly declining. This issue is gradually ...Due to the rapid economic growth and the continuous increase of human, ecosystem disturbances and habitat destructions, the biodiversity of freshwater ecosystems in China is rapidly declining. This issue is gradually gaining the government’s attention as its environmental policy becomes more and more equally-weighed on both “pollution prevention and control” and “ecological conservation” issues while only the former was emphasized in the past. However, some unsolved issues still exist with regard to aquatic biodiversity monitoring and management in China. For example, there are functional overlaps among governmental departments; regional ecological function divisions are not clarified; biodiversity is usually neglected or not emphasized in environmental impact assessment for construction projects; and so on. In our opinion, the following areas should be emphasied: (a) enhancing the cooperation among governmental departments; (b) setting up mechanisms to allow ecological watershed management; (c) establishing the biodiversity conservation and ecological restoration planning for local freshwater ecosystem; (d) clarifying the ecological function divisions; (e) enhancing the biodiversity monitoring and management for freshwater ecosystem in environmental impact assessment studies for industrial construction and rural development projects; (f) establishing a technical regulatory framework for related monitoring and management activities which includes an index system for monitoring and assessment; (g) studying and establishing the related biological criteria for formulating assessment standards; and (h) paying attention to aquatic vegetation, fishes, benthic macro-invertebrates and other key aquatic assemblages.展开更多
We surveyed the distribution, composition and diversity of freshwater fish in Hong Kong, China from 2002 to 2004. Sites surveyed were mainly streams, marshes and estuaries. There are ponds for aquaculture and reservoi...We surveyed the distribution, composition and diversity of freshwater fish in Hong Kong, China from 2002 to 2004. Sites surveyed were mainly streams, marshes and estuaries. There are ponds for aquaculture and reservoirs in Hong Kong but no large natural water bodies. From the 220 sites surveyed, 114 species of 37 families were found. Gobiidae (with 24 species) and Cyprinidae (21 species) were the dominant families. This survey has increased the number of freshwater fish species recorded in Hong Kong to 167. Among these, 71 (42.5%) are primary freshwater fish, 44 are brackish and 46 are vagrants. The remaining 6 species are diadromous. In Hong Kong, freshwater fish are conserved by a combination of measures. About 38% of Hong Kong’s land area is designated as country parks and/or special areas, and is managed for nature conservation and educational purposes. In addition, another 5% of land area is zoned for conservation in the statutory land use zoning system to protect them from development and incompatible land uses. Major development projects have to go through the statutory environmental impact assessment process to ensure that they will not have adverse impact as far as practicable. There are conservation action plans for important species. For example, captive-bred individuals of the endemic Hong Kong Paradise Fish Macropodus hongkongensis have been released to suitable and secure sites inside country parks and their populations are regularly monitored. Other measures such as wetland creation, restoration and enhancement programmes are also implemented for freshwater fish conservation.展开更多
Antarctica’s marginal seas are of great importance to atmosphere-ocean-ice interactions and are sensitive to global climate change.Multiple factors account for the freshwater budget in these regions,including glacier...Antarctica’s marginal seas are of great importance to atmosphere-ocean-ice interactions and are sensitive to global climate change.Multiple factors account for the freshwater budget in these regions,including glacier melting,seasonal formation/decay of sea ice,and precipitation.Hydrogen(H)and oxygen(O)isotopes represent useful proxies for determining the distribution and migration of water masses.We analyzed the H and O isotopic compositions of 190 seawater samples collected from the Amundsen Sea during the 34th Chinese Antarctic Research Expedition in 2017/2018.The upper-oceanic structure(<400 m)and freshwater(meteoric water and sea ice melt)distribution in the Amundsen Sea were identified based on conductivity-temperature-depth data and the H and O isotopic composition.Antarctic Surface Water,characterized as cold and fresh with low H and O isotopic ratios,was found distributed mainly in the upper~150 m between the Antarctic Slope Front and Polar Front,where it had been affected considerably by upwelled Upper Circumpolar Deep Water(UCDW)between 68°S and 71°S.A three-endmember(meteoric water,sea ice melt,and Circumpolar Deep Water)mixing model indicated that waters with relatively high proportions(>3%)of freshwater generally lie in the upper~50 m and extend from Antarctica to~65°S in the meridional direction(anomalously low freshwater proportion occurred between 68°S and 71°S).Winter Water mainly occupied the layer between 50 and 150 m south of 71°S in the western Amundsen Sea.The water structure and spatial distribution of freshwater in the upper Amundsen Sea were found influenced mainly by the rates of basal and surficial melting of ice shelves,seasonal alternation of sea ice melt/formation,wind forcing,and regional bathymetry.Owing to the distance between heavy sea ice boundary(HSIB)and ice shelves is much shorter in the western HSIB than the east HSIB,the western part of the heavy sea ice boundary includes a higher proportion of freshwater than the eastern region.This study,which highlighted the distribution and extent of freshwater derived from ice(ice shelves and sea ice)melt,provides important evidence that the offshore drift pathway of cold and fresh Antarctic continental shelf water is likely interrupted by upwelled UCDW in the Amundsen Sea.展开更多
基金Supported by the Science and Technology Commission of Shanghai Municipality(No.21JC1402500)。
文摘Estuarine projects can change local topography and influence water transport and saltwater intrusion.The Changjiang(Yangtze)River estuary is a multichannel estuary,and four major reclamation projects have been implemented in the Changjiang River estuary in recent years:the Xincun Shoal reclamation project(RP-XCS),the Qingcao Shoal reclamation project(RP-QCS),the Eastern Hengsha Shoal reclamation project(RP-EHS),and the Nanhui Shoal reclamation project(RP-NHS).The effects of the four reclamation projects and each project on the saltwater intrusion and water resources in the Changjiang River estuary were simulated in a 3D numerical model.Results show that for a multichannel estuary,local reclamation projects change the local topography and water diversion ratio(WDR)between channels and influence water and salt transport and freshwater utilization in the estuary.During spring tide,under the cumulative effect of the four reclamation projects,the salinity decreases by approximately 0.5in the upper reaches of the North Branch and increases by 0.5-1.0 in the middle and lower reaches of the North Branch.In the North Channel,the salinity decreases by approximately 0.5.In the North Passage,the salinity increases by 0.5-1.0.In the South Passage,the salinity increases by approximately 0.5 in the upper reaches and decreases by 0.2-0.5 on the north side of the middle and lower reaches.During neap tide,the cumulative effects of the four reclamation projects and the individual projects are similar to those during spring tide,but there are some differences.The effects of an individual reclamation project on WDR and saltwater intrusion during spring and neap tides are simulated and analyzed in detail.The cumulative effect of the four reclamation projects favors freshwater usage in the Changjiang River estuary.
基金Supported by the National Natural Science Foundation of China(No.31800172 to F.R.NAN,No.32170204 to S.L.XIE)。
文摘Hildenbrandia is an early diverged lineage in Florideophyceae,Rhodophyta.The species diversity of this genus is still unresolved due to the simple morphology and limited molecular information.The mitochondrial genome of freshwater H.jigongshanensis was determined in this study.The freshwater H.jigongshanensis had a larger mitochondrial genome than the marine H.rubra and GC content was higher.Collinear alignment structure was observed between the mitochondrial genomes of H.jigongshanensis and H.rubra,except for one block that was encoded on the complement strand.More introns were found in mitochondrial genome of H.jigongshanensis than in H.rubra,and H.jigongshanensis shares the common feature with Bangiophyceae that two introns were distributed in cox1.Comparison of mitochondrial genome organization suggests that H.jigongshanensis preserves characters that could be hypothetically more similar to the ancestor of Bangiophyceae and Florideophyceae,which differ with previous studies based on chloroplast,and nuclear markers.More mitochondrial genomes and phylogenetic analyses combing nuclear,chloroplast and mitochondrial genomes are needed to clarify this discrepancy.Mitochondrion-based phylogeny in this study resulted in better solution at both the deep and recent derived nodes than single-gene phylogenies.Most protein-coding genes between H.jigongshanensis and H.rubra were identical except atp8,which was present in H.jigongshanensis while absent from H.rubra.This finding follows the trend that high Ka/Ks ratio genes are more frequently lost than low Ka/Ks ratio ones in red algae.
基金supported by the National Natural Science Foundation of China(32022009)。
文摘DEAR EDITOR,The introduction of freshwater fish into areas outside their native range has impacted freshwater ecosystems worldwide.In China,the non-native Alligator gar(Atractosteus spatula)fish has attracted attention due to its widespread occurrence and destructive effects on local fish populations,signaling a high potential of invasiveness.
基金supported by the National Natural Science Foundation of China(42176120,41825013,42006109)Key Deployment Project of Centre for Ocean Mega-Research of Science,Chinese Academy of Sciences(COMS2020Q14)+1 种基金Science and Technology Planning Project of Guangdong Province,China(2020B1212060058)South Sea New Star of SCSIO,Chinese Academy of Sciences(NHXX2018ST0201)。
文摘DEAR EDITOR,Syngnathidae species commonly inhabit ocean environments.However,some have adapted to live exclusively in freshwater over long-term adaptive evolution but continue to retain physiological adaptations to saltwater environments.The genetic basis underlying the adaptive strategies and molecular regulation of freshwater syngnathids to freshwater and saltwater remains unclear.Here,we investigated the molecular characteristics and core gene expression in freshwater belly pipefish(Hippichthys heptagonus)embryos and juveniles through salinity stress experiments and transcriptome analysis.Results showed that embryonic exposure to salinity at a concentration of 30‰down-regulated cell cycle-associated genes vital to embryonic development.Retinol metabolism,neuroactive receptor interaction,and peroxisome proliferator-activated receptor signaling pathways were significantly enriched in up-regulated genes in the embryos.Notably,there was no significant change in the expression of ion transport and energy metabolism genes.Conversely,juvenile exposure to 30‰salinity up-regulated ion transport-related genes and significantly enriched immune-related signaling pathways,including lysosome,phagosome,autophagy,and mitophagy signaling pathways.Carbohydrate metabolism genes were also up-regulated,whereas oxidative phosphorylation genes were significantly down-regulated.These results suggest that brood pouch protection during the embryonic stage and salinity adaptation plasticity in juveniles may be strategic adaptations in freshwater pipefish.
基金Supported by National Research Council of Thailand(NRCT)(Grant No.2555A10402010)
文摘Objective:To investigate the epidemiological situation of cercarial trematodes infection in freshwater snails from different water resources in Chiang Mai province,Thailand.Methods:The snail specimens were collected from 13 districts of Chiang Mai province during April 2008 to February 2012.The prevalence of cercarial infection in snails was investigated using the crushing method.The drawing was done with the help of a camera lucida for the morphological study.Results:A total of 2479 snail individuals were collected and classified into 7 families,11 genera,and 14 species,Among them,8 snails species were found to be infected with an overall prevalence of 17.27%(428/2479),which infected with nine groups of cercariae;gymnocephalous cercaria,strigea cercaria,megalurous cercaria,monostome cercaria,parapleurolophocercous cercaria(Haplorchis cercaria),pleurolophocercous cercaria,furcocercous cercaria(Transversotrema cercaria),xiphidiocercaria,and virgulate cercaria.The parapleurolophocercous cercaria was found to be the dominant type among the cercarial infection in the snails(64.25%).Conclusions:The various species of snails found in the research location act as the intermediate hosts for the high prevalence of parasitic infection of many species of mammals.This work will provide new information on both the distribution and first intermediate host of trematodes.
基金Under the auspices of the National Key R&D Program of China(No.2016YFC0500404)the National Natural Science Foundation of China(No.41671087,41671081,41771103)the Youth Innovation Promotion Association,Chinese Academy of Sciences(No.2018265)
文摘Natural wetlands are known to store huge amounts of organic carbon in their soils. Despite the importance of this storage,uncertainties remain about the molecular characteristics of soil organic matter(SOM), a key factor governing the stability of soil organic carbon(SOC). In this study, the molecular fingerprints of SOM in a typical freshwater wetland in Northeast China were investigated using pyrolysis gas-chromatography/mass-spectrometry technology(Py-GC/MS). Results indicated that the SOC, total nitrogen(TN),and total sulfur contents of the cores varied between 16.88% and 45.83%, 0.93% and 2.82%, and 1.09% and 3.79%, respectively. The bulk δ^13C and δ^15N varied over a range of 9.85‰, between –26.85‰ and –17.00‰, and between –0.126‰ and 1.002‰, respectively. A total of 134 different pyrolytic products were identified, and they were grouped into alkyl(including n-alkanes(C:0) and n-alkenes(C:1),aliphatics(Al), aromatics(Ar), lignin(Lg), nitrogen-containing compounds(Nc), polycyclic aromatic hydrocarbons(PAHs), phenols(Phs), polysaccharides(Ps), and sulfur-containing compounds(Sc). On average, Phs moieties accounted for roughly 24.11% peak areas of the total pyrolysis products, followed by Lg(19.27%), alkyl(18.96%), other aliphatics(12.39%), Nc compounds(8.08%), Ps(6.49%), aromatics(6.32%), Sc(3.26%), and PAHs(1.12%). Soil organic matter from wetlands had more Phs and Lg and less Nc moieties in pyrolytic products than soil organic matters from forests, lake sediments, pastures, and farmland.δ^13 C distribution patterns implied more C3 plant-derived soil organic matter, but the vegetation was in succession to C4 plant from C3 plant. Significant negative correlations between Lg or Ps proportions and C3 plant proportions were observed. Multiple linear analyses implied that the Ar and Al components had negative effects on SOC. Alkyl and Ar could facilitate ratios between SOC and total nitrogen(C/N), while Al plays the opposite role. Al was positively related to the ratio of dissolved organic carbon(DOC) to SOC. In summary, SOM of wetlands might characterize by more Phs and lignin and less Nc moieties in pyrolytic products. The use of Pyrolysis gas-chromatography/mass-spectrometry(Py-GC/MS) technology provided detailed information on the molecular characteristics of SOM from a typical freshwater wetland.
文摘A series of numerical experiments are carried out to study the tropical upper ocean response to combined momentum and buoyancy forcing, with emphasis on the three-dimensional thermohaline structure in the western Pacific warm pool. In response to climatological winds, heat fluxes and freshwater input, the model is able to simulate the salient dynamic and hydrographic features of the tropical Pacific Ocean and their seasonal variability. In response to idealized episodic westerly wind bursts and rainfall, the simulated upper ocean conditions compare favorably with available observations, thus enabling us to identify important physical processes involved. Local forcing, vertical mixing and meridional advection dominate the salt and heat budgets in the warm pool on short time scales, but it is necessary to include the saline water coming from the east with the South Equatorial Current to close the salt budget on seasonal and longer time scales. Strong westerly wind bursts generate a swift eastward equatorial jet and a pair of meridional circulation cells with convergence at the equator. This results in an equatorward advection of relatively fresh water from the north and a depression of the thermocline at the equator. Heavy rainfall reduces the surface mixed layer depth by creating a shallow halocline, thus trapping the momentum and heat inputs near the surface. The remote influences of the episodic momentum and buoyancy fluxes are very different. Westerly wind bursts can generate large downstream disturbances in both dynamic and thermal fields through the propagation of equatorial waves, while the effect of rainfall is mostly confined to the forcing area.
文摘Model studies point to enhanced warming and to increased freshwater ?uxes to high northern latitudes in response to global warming. In order to address possible feedbacks in the ice-ocean system in response to such changes, the combined e?ect of increased freshwater input to the Arctic Ocean and Arctic warming—the latter manifested as a gradual melting of the Arctic sea ice—is examined using a 3-D isopycnic coordinate ocean general circulation model. A suite of three idealized experiments is carried out: one control integration, one integration with a doubling of the modern Arctic river runo?, and a third more extreme case, where the river runo? is ?ve times the modern value. In the two freshwater cases, the sea ice thickness is reduced by 1.5–2 m in the central Arctic Ocean over a 50-year period. The modelled ocean response is qualitatively the same for both perturbation experiments: freshwater propagates into the Atlantic Ocean and the Nordic Seas, leading to an initial weakening of the North Atlantic Drift. Furthermore, changes in the geostrophic currents in the central Arctic and melting of the Arctic sea ice lead to an intensi?ed Beaufort Gyre, which in turn increases the southward volume transport through the Canadian Archipelago. To compensate for this southward transport of mass, more warm and saline Atlantic water is carried northward with the North Atlantic Drift. It is found that the increased transport of salt into the northern North Atlantic and the Nordic Seas tends to counteract the impact of the increased freshwater originating from the Arctic, leading to a stabilization of the North Atlantic Drift.
文摘There are reports on the use of chemicals like sodium tri polyphosphate (STPP) and foreign materials like pearl tapioca (locally called ‘sagu’), jelly (litchi) to adulterate freshwater prawn (Macrobrachium rosenbergii) prior to freeze processing to increase their weight. Studies were, therefore, undertaken to determine the changes in product quality on the use of different concentrations of STPP, sagu and litchi under ice storage condition. Percent weight gain of prawn was 5.46, 18.87 and 23.50 when dipped in 2%, 4% and 6% STPP solution, respectively. In all cases maximum water uptake by prawn muscle was during the first 6 h with fastest weight gain with STPP solutions containing tap water compared to those of ice and tap water. Organoleptic quality of the STPP treated samples became brown and spongy after 8 h of dipping treatment under iced condition. Quality assessment studies conducted after injecting sagu and litchi in prawn muscle showed little or no difference with those of control samples during the first 6 h, which turned whitish and swollen with severe drip loss after 24 h of ice stored condition, indicating characteristics for easy identification of the injected shrimps by organoleptic method.
基金Supported by Faculty of Science,Srinakharinwirot University(Grant No.541/2557)
文摘Objective: To investigate the prevalence of cercarial trematode infection in snails and to examine the reconstruction of the phylogenetic relationship to explain the molecular system of cercarial stage trematodes to estimate the infection rate of in the definite host from the Chao-Phraya Basin.Methods: The snails were collected from 10 provinces of the Chao-Phraya Basin,Thailand by stratified sampling method. The snails were examined for cercarial infection by the crushing method. All DNA specimens were amplified with internal transcribed spacer 3(ITS3) and ITS4 primer based on PCR technique. The sequence data were aligned and used to reconstruct the phylogenetic tree by unweighted pair-group method with arithmetic means with 10 000 bootstraps.Results: The overall rate of cercarial infection was found to be 5.90%(122/2 067). Snails in the family Thiaridae were found to be in the highest prevalence followed by Lymnaeidae, Bithyniidae, Planorbidae, Viviparidae, and Ampullariidae, respectively, while the Buccinidae family(Clea helena) did not reveal any infections. The frequently found species of cercariae were parapleurolophocercous cercariae, cercariae and megarulous cercariae. The monophyletic tree separated the snails into five groups comprised of Heterophyidae, Strigeidae, Lecithodendriidae, Philophthalmidae and Echinostomatidae using the sequence of Angiostrongylus cantonensis as an out-group.Conclusions: This study was the first to report on cercarial infection in the Chao-Phraya Basin, Thailand. This revealed that a high variety of freshwater snails were infected by cercariae stage trematodes with a high prevalence. The sequence data of ITS2 can be used to investigate the phylogenetic relationships of trematodes at the family level and in each clade of different families separated by the definitive hosts.
基金the Sultan Qaboos University for the research grant provided through His Majesty Sultan Qaboos Trust Fund(Project code:#SR/AGR/SWAE/17/01).
文摘Seawater greenhouse(SWGH)is a technology established to overcome issues related to open field cultivation in arid areas,such as the high ambient temperature and the shortage of freshwater.It adopts the humidification-dehumidification concept where evaporated moisture from a saline water source is condensed to produce freshwater within the greenhouse body.Various condenser designs are adopted to increase freshwater production in order to meet the irrigation demand.The aim of this study was to experimentally investigate the practicality of using the packed-type direct contact condenser in the SWGH to produce more freshwater at low costs,simple design and high efficiency,and to explore the impact of the manipulating six operational variables(inlet air temperature of the humidifier,air mass flowrate of the humidifier,inlet water temperature of the humidifier,water mass flowrate of the humidifier,inlet water temperature of the dehumidifier and water mass flowrate of the dehumidifier)on freshwater condensation rate.For this purpose,a direct contact condenser was designed and manufactured.Sixty-four full factorial experiments were conducted to study the effect of the six operational variables.Each variable was operated at two levels(high and low flowrate),and each experiment lasted for 10 min and followed by a 30-min waiting time.Results showed that freshwater production varied between 0.257 and 2.590 L for every 10 min.When using Minitab statistical software to investigate the significant variables that contributed to the maximum freshwater production,it was found that the inlet air temperature of the humidifier had the greatest influence,followed by the inlet water temperature of the humidifier;the former had a negative impact while the latter had a positive impact on freshwater production.The response optimizer tool revealed that the optimal combination of variables contributed to maximize freshwater production when all variables were in the high mode and the inlet air temperature of the humidifier was in the low mode.The comparison between the old plastic condenser and the new proposed direct contact condenser showed that the latter can produce 75.9 times more freshwater at the same condenser volume.
基金supported by the Central Public-Interest Scientific Institution Basal Research Fund,CAFS(2021XT703)Central Public-interest Scientific Institution Basal Research Fund,Freshwater Fisheries Research Center,CAFS(2021JBFM07)。
文摘DEAR EDITOR,Bellamya purificata(Gastropoda:Caenogastropoda;Architaenioglossa;Viviparidae:Bellamyinae;Sinotaia),a homotypic synonym of S.purificata,is widely distributed in freshwater habitats in Asia.It is an economically important edible snail and plays a vital function in freshwater wetland ecology.However,genomic resources for this snail are lacking and no reference genome has been released.In this study,we constructed the first chromosome-level genome of B.purificata using PacBio long-read sequencing and high-throughput chromosome conformation capture(Hi-C)technology.
基金the National Key R&D Program of China(2018YFA0606002)the National Natural Science Foundation of China(41875105)the Startup Foundation for Introducing Talent of NUIST(2018r078)。
文摘Freshwater is recharged mainly by rainfall and stored inland for a period of time,which is directly affected by its storage capability.The storage capability of river basins has different spatiotemporal features that are important for the predictability of freshwater resources.However,the estimation of freshwater storage capability(FSC)remains a challenge due to the lack of observations and quantification indices.Here,we use a metric that characterizes hydrological“inertia”after rainfalls to analyze FSC over the 194 largest global major river basins based on satellite observations from the Gravity Recovery and Climate Experiment(GRACE)and simulations from the Community Land Model version 5(CLM5).During 2003–16,the global land was observed to retain 28%of precipitation after one month based on GRACE observations,and the simulation depicts that the retained proportions decrease from 42%after one day to 26%after one month,with smaller FSC partly attributed to wetter conditions and higher vegetation densities.The root zone contributes about 40%to the global land FSC on daily to monthly time scales.As the time scale increases,the contribution from the surface soil decreases from 26%to 14%,while the contribution from the deep soil increases from 4%to 10%.Snow contributes over 20%of land FSC,especially over high latitudes.With six decades of CLM5 long-term simulations,it is revealed that the change of FSC in most basins is related to internal climate variability.The FSC of river basins which displays the proportion of precipitation retained on land is worthy of further attention regarding the predictability of water resources.
基金financially supported by the National Natural Science Foundation of China(41690141)the National Key Research and Development Program of China(2019YFC1510500)。
文摘As important freshwater resources in alpine basins,glaciers and snow cover tend to decline due to climate warming,thus affecting the amount of water available downstream and even regional economic development.However,impact assessments of the economic losses caused by reductions in freshwater supply are quite limited.This study aims to project changes in glacier meltwater and snowmelt of the Urumqi River in the Tianshan Mountains under future climate change scenarios(RCP2.6(RCP,Representative Concentration Pathway),RCP4.5,and RCP8.5)by applying a hydrological model and estimate the economic losses from future meltwater reduction for industrial,agricultural,service,and domestic water uses combined with the present value method for the 2030 s,2050 s,2070 s,and 2090 s.The results indicate that total annual glacier meltwater and snowmelt will decrease by 65.6%and 74.5%under the RCP4.5 and RCP8.5 scenarios by the 2090 s relative to the baseline period(1980-2010),respectively.Compared to the RCP2.6 scenario,the projected economic loss values of total water use from reduced glacier meltwater and snowmelt under the RCP8.5 scenario will increase by 435.10×10^(6) and 537.20×10^(6) CNY in the 2050 s and 2090 s,respectively,and the cumulative economic loss value for 2099 is approximately 2124.00×10^(6) CNY.We also find that the industrial and agricultural sectors would likely face the largest and smallest economic losses,respectively.The economic loss value of snowmelt in different sectorial sectors is greater than that of glacier meltwater.These findings highlight the need for climate mitigation actions,industrial transformation,and rational water allocation to be considered in decision-making in the Tianshan Mountains in the future.
基金Srinakharinwirot University,Thailand for providing funding(Project Nos.071/2562,184/2563)
文摘Objective:To investigate the prevalence of cercarial infections in freshwater snails from several water sources in Nakhon Nayok,Nonthaburi,and Pathum Thani provinces of Central Thailand,and to reconstruct a phylogenetic tree for improved understanding of the relationships in the cercarial stage.Methods:The snail specimens were collected from 34 total sampling sites and investigated for cercarial infections using the crushing method.The cercarial specimens were classified and used for the phylogenetic tree analysis using the Internal Transcribed Spacer 2(ITS2).Results:A total of 1921 snail specimens were classified into five families and seven species.The results showed that four snail species were identified as intermediate hosts of the larval stages of trematodes,with an overall prevalence of infection of 2.45%(47/1921).The infected snail specimens included five groups of the cercarial type:cercariaeum cercariae,echinostome cercaria,megalurous cercaria,parapleurolophocercous cercaria,and xiphidiocercariae.This is particularly true of xiphidiocercariae,which was found to be the dominant type among cercarial infections in bithyniid snails by approximately 38.00%.With regard to molecular identification,the phylogenetic tree was reconstructed using the neighbor-joining method with 10000 bootstraps and separated the trematodes into three clades:Echinostomatoidea,Microphalloidea and Opisthorchioidea.Conclusions:The study reveals a high prevalence of cercarial infection for each cercarial type and maturation into a definite trematode genus and delineates morphological characteristics and evolutionary trends among each larval trematode in Nakhon Nayok,Nonthaburi and Pathum Thani provinces.In addition,the ITS2 sequence data of cercariae could be used to examine classification of these species at the family level.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40805031 and 40875047) the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Nos. KZCX2-YW-218 and KZCX2- YW-BR-14)
文摘It has been reported recently that the simulated Atlantic meridional overturning circulation(AMOC) using the coupled Bergen climate model(BCM) showed initial intensity declines followed by gradual recoveries over a 150-year enhanced freshwater input experiment.Stratification-dependent oceanic diapycnal mixing has been hypothesized as a reason for the simulated recovery of the AMOC.This study investigated the role of diapycnal mixing in transient responses of simulated AMOCs.Our results showed that stratification-dependent diapycnal mixing can cause stronger upwelling of deep water in the tropical Atlantic than that produced under conditions of fixed diapycnal mixing.Moreover,simulated AMOCs were more sensitive to active stratification-dependent diapycnal mixing than fixed mixing.However,stratification-dependent diapycnal mixing cannot be conclusively singled out as the critical cause of the recoveries of simulated AMOCs under enhanced-freshwater inputs.
文摘Due to the rapid economic growth and the continuous increase of human, ecosystem disturbances and habitat destructions, the biodiversity of freshwater ecosystems in China is rapidly declining. This issue is gradually gaining the government’s attention as its environmental policy becomes more and more equally-weighed on both “pollution prevention and control” and “ecological conservation” issues while only the former was emphasized in the past. However, some unsolved issues still exist with regard to aquatic biodiversity monitoring and management in China. For example, there are functional overlaps among governmental departments; regional ecological function divisions are not clarified; biodiversity is usually neglected or not emphasized in environmental impact assessment for construction projects; and so on. In our opinion, the following areas should be emphasied: (a) enhancing the cooperation among governmental departments; (b) setting up mechanisms to allow ecological watershed management; (c) establishing the biodiversity conservation and ecological restoration planning for local freshwater ecosystem; (d) clarifying the ecological function divisions; (e) enhancing the biodiversity monitoring and management for freshwater ecosystem in environmental impact assessment studies for industrial construction and rural development projects; (f) establishing a technical regulatory framework for related monitoring and management activities which includes an index system for monitoring and assessment; (g) studying and establishing the related biological criteria for formulating assessment standards; and (h) paying attention to aquatic vegetation, fishes, benthic macro-invertebrates and other key aquatic assemblages.
基金the comprehensive ecological baseline survey programme of the Department of Agriculture ,Fisheries and Conservation
文摘We surveyed the distribution, composition and diversity of freshwater fish in Hong Kong, China from 2002 to 2004. Sites surveyed were mainly streams, marshes and estuaries. There are ponds for aquaculture and reservoirs in Hong Kong but no large natural water bodies. From the 220 sites surveyed, 114 species of 37 families were found. Gobiidae (with 24 species) and Cyprinidae (21 species) were the dominant families. This survey has increased the number of freshwater fish species recorded in Hong Kong to 167. Among these, 71 (42.5%) are primary freshwater fish, 44 are brackish and 46 are vagrants. The remaining 6 species are diadromous. In Hong Kong, freshwater fish are conserved by a combination of measures. About 38% of Hong Kong’s land area is designated as country parks and/or special areas, and is managed for nature conservation and educational purposes. In addition, another 5% of land area is zoned for conservation in the statutory land use zoning system to protect them from development and incompatible land uses. Major development projects have to go through the statutory environmental impact assessment process to ensure that they will not have adverse impact as far as practicable. There are conservation action plans for important species. For example, captive-bred individuals of the endemic Hong Kong Paradise Fish Macropodus hongkongensis have been released to suitable and secure sites inside country parks and their populations are regularly monitored. Other measures such as wetland creation, restoration and enhancement programmes are also implemented for freshwater fish conservation.
基金supported by the Natural Science Foundation of China(Grant no.41806229)the Ministry of Natural Resources of the People’s Republic of China(Impact and Response of Antarctic Seas to Climate Change,Grant no.IRASCC 02-04-01).
文摘Antarctica’s marginal seas are of great importance to atmosphere-ocean-ice interactions and are sensitive to global climate change.Multiple factors account for the freshwater budget in these regions,including glacier melting,seasonal formation/decay of sea ice,and precipitation.Hydrogen(H)and oxygen(O)isotopes represent useful proxies for determining the distribution and migration of water masses.We analyzed the H and O isotopic compositions of 190 seawater samples collected from the Amundsen Sea during the 34th Chinese Antarctic Research Expedition in 2017/2018.The upper-oceanic structure(<400 m)and freshwater(meteoric water and sea ice melt)distribution in the Amundsen Sea were identified based on conductivity-temperature-depth data and the H and O isotopic composition.Antarctic Surface Water,characterized as cold and fresh with low H and O isotopic ratios,was found distributed mainly in the upper~150 m between the Antarctic Slope Front and Polar Front,where it had been affected considerably by upwelled Upper Circumpolar Deep Water(UCDW)between 68°S and 71°S.A three-endmember(meteoric water,sea ice melt,and Circumpolar Deep Water)mixing model indicated that waters with relatively high proportions(>3%)of freshwater generally lie in the upper~50 m and extend from Antarctica to~65°S in the meridional direction(anomalously low freshwater proportion occurred between 68°S and 71°S).Winter Water mainly occupied the layer between 50 and 150 m south of 71°S in the western Amundsen Sea.The water structure and spatial distribution of freshwater in the upper Amundsen Sea were found influenced mainly by the rates of basal and surficial melting of ice shelves,seasonal alternation of sea ice melt/formation,wind forcing,and regional bathymetry.Owing to the distance between heavy sea ice boundary(HSIB)and ice shelves is much shorter in the western HSIB than the east HSIB,the western part of the heavy sea ice boundary includes a higher proportion of freshwater than the eastern region.This study,which highlighted the distribution and extent of freshwater derived from ice(ice shelves and sea ice)melt,provides important evidence that the offshore drift pathway of cold and fresh Antarctic continental shelf water is likely interrupted by upwelled UCDW in the Amundsen Sea.
