Freshwater Region Research Articles

Global biogeography of estuary-associated fishes

AbstractThis study examines global zoogeographic patterns of estuary-associated fishes using meta-assemblages compiled at the marine ecoregion scale. The classification of biogeographic regions based on estuary-associated fish species is assessed in relation to marine and freshwater zoogeographic patterns. Historical (palaeobiogeographic) and contemporary environmental factors that contribute to the establishment and maintenance of these regions are also discussed. Global patterns in estuary-associated fish species richness demonstrated that tropical ecoregions are more diverse and richer in species than temperate ecoregions; the tropical Indo-Pacific and the tropical western Atlantic were two major centres of high global species richness. Multivariate analyses identified several ecoregion groupings that broadly corresponded with both freshwater and marine biogeographic regions. These groupings could also be related to global marine palaeobiogeographic processes such as the closure of the Tethys Sea linkage during the Cenozoic as well as contemporary factors such ocean currents, upwelling areas and climatic factors, particularly rainfall and runoff.

From rice fields to brackish water farms: changing livelihoods in agrarian coastal Bengal, India

The present study attempted to understand the dimensions of changing agrarian livelihoods because of haphazard adaptation of capitalistic shrimp aquaculture. Specifically, using multi-temporal Google-based geodatabase, we quantified the artificial conversion of agrarian landscape in an inland freshwater region of coastal Bengal. Further, we examined the long-term viability of transformed livelihoods by adopting a modified version of the Sustainable Livelihood Approach (SLA). The assessment of changing livelihoods was based on empirical information acquired through field surveys, focus group discussion (FGD) and key informant interviews (KII). Results from the geostatistical analysis depicted that the shrimp culture in the research area was very recent. In 2010, only 0.03 percent of the total area was occupied by shrimp ponds. However, within a decade and an expansion rate of 18 percent/annum, the conversion spread to 1/3 of the total study area. The findings also clarified that the adaptation of shrimp cultivation increased the overall profit by 6400 USD/ha/year over agricultural output, and resulted in a quick rise in the standard of living for the shrimp farmers. However, in the long run, due to decreasing productivity and salinization of the surrounding land, the conversion resulted in massive depeasantization, augmentation of wasteland, and biased wealth accumulation led to a wide rich-poor gap. Therefore, the entire ecosystem will suffer in the near future, if the local government does not strictly impose Standard Operating Procedures (SOPs).

A new species of Cambeva (Siluriformes, Trichomycteridae) from the Rio Iguaçu basin, Paraná State, Brazil and redescription of Cambeva stawiarski (Miranda Ribeiro 1968).

This work aimed to describe Cambeva cauim, sp. nov., endemic to the Rio Iguaçu basin, Brazil and redescribe Cambeva stawiarski using external and internal morphological data through the revision of specimens deposited in fish collections, including the type material. In this process, we have also added comments on the possible type locality of C. stawiarski. C. cauim, sp. nov. and C. stawiarski are mainly diagnosed by the anatomy and number of procurrent caudal-fin rays in addition to colouration and several meristic and morphometric characters. Both species are compared with other possibly related species and their synapomorphic characters are discussed. C. cauim, sp. nov. and C. stawiarski along with eight other congeners are endemic to the Rio Iguaçu basin, a high impacted freshwater region which could be considered as a biodiversity hotspot to the genus.

Ovarian and spawning reference, size at first maturity and fecundity of Glossogobius giuris caught along Vietnamese Mekong Delta

This study investigates the ovarian development, spawning patterns, maturity size and fecundity of the goby Glossogobius giuris–a commercial fish in the Vietnamese Mekong Delta–based on the data analysis of 659 individuals. Specimens were caught using trawl nets from four sites representing freshwater (Cai Rang, Can Tho) to salinized regions in the dry season (Long Phu, Soc Trang), and brackish water regions (Hoa Binh, Bac Lieu and Dam Doi, Ca Mau) over the 12 months of 2020. Histological analysis showed that it was a multi-spawner as different stages of oocytes appeared in mature ovaries. The fish could spawn throughout the year, with a peak in April at the freshwater region and in September at salinized and brackish areas as mature ovaries appeared monthly during the studied period and gonadosomatic index displayed the highest value in April and in September, respectively. This goby’s primary egg releasing time tended to be regulated by salinity changes over the four sampling sites. Likewise, size at first maturity of this species could be related to the salinity variation as this value was the longest in freshwater (6.14 ± 0.17) and the shortest in the salinization region (4.82 ± 0.66). Batch fecundity is measured at 5,118–100,003 eggs/female and related to fish length and weight (r2 > 0.76). Findings can be useful for the development of fish conservation strategies and artificial reproducing studies.

Stock assessment of two populations of Glossogobius sparsipapillus (Osteichthyes, Gobiidae) in the Mekong Delta

Glossogobius sparsipapillus is one of the gobies that inhabits brackish and freshwater regions in the Mekong Delta. However, data on the biological parameters of this species population are limited. Therefore, the present study aims to provide the necessary knowledge on the fishing status of this goby living in freshwater (Cai Rang, Can Tho: CR) and brackish water regions (Long Phu, Soc Trang: LP). Data analysis results of 1379 individuals showed that males outnumbered females in LP (374 males: 288 females); the reverse case was found in CR (351 males: 366 females). There were five-six classes of length frequency, with the highest values between 8 and 12 cm (1122 individuals, 81.36%). The von Bertalanffy curve was L = 15.75(1 − e−0.62(t + 0.30)) in CR and L = 15.85(1 − e−0.83(t + 0.23)) in LP. Its longevity was 4.84 yrs in CR and 3.61 yrs in LP. The growth performance was 2.19 in CR and 2.32 in LP. The total, natural, and fishing mortalities were 2.17 yr−1, 1.49 yr−1, and 0.68 yr−1 in CR; 3.46 yr−1, 1.68 yr−1, and 1.78 yr−1 in LP, respectively. The fish stock has not been overexploited as E (0.31 in CR and 0.51 in LP) were lower than E0.1 (0.465 in CR and 0.652 in LP) 0.3.46 yr−1, 1.68 yr−1, and 1.78 yr−1 in LP, respectively. The fish stock has not been overexploited as E (0.31 in CR and 0.51 in LP) were lower than E0.1 (0.465 in CR and 0.652 in LP).

Enhancing the resolving ability of electrical resistivity tomography for imaging saltwater intrusion through improvements in inversion methods: A laboratory and numerical study

Mapping and monitoring saltwater intrusion are critical for the sustainable management of groundwater in coastal aquifers around the world. Increasingly, geophysical methods, such as electrical resistivity tomography (ERT), have been used to address these needs. We identify methods for the inversion of ERT data that would most accurately map the location and geometry of an intrusion wedge. This is accomplished using laboratory and synthetic experiments, with the classic representation of an intrusion wedge perpendicular to the coast. The laboratory experiments allow us to collect ERT data on a saltwater intrusion wedge in an environment in which we have supporting data that provided (1) the distribution of salinity within the tank with which to verify our inversion results, (2) the resistivity, porosity, and permeability of the porous medium, and (3) the transform between resistivity and salinity. The synthetic experiments allow exploration of issues of specific interest related to the presence of lithologic heterogeneity at a field site: the role of lithologic heterogeneity in introducing complexity into the resistivity-salinity relationship and the geometry of the saltwater intrusion wedge. We find that using a reference model with a good approximation of the wedge to inform the inversion greatly improves the ability of the resulting resistivity profile to map the wedge. Where there is no, or limited, lithologic heterogeneity, a parametric approach, which constrains the range of possible solutions by solving for a sharp interface between the saltwater and freshwater regions, is very effective at capturing the wedge location and geometry. Where there is lithologic heterogeneity, a hybrid between the parametric and informed inversion approaches is most effective, resolving the wedge with a high level of accuracy with little a priori information.

Alborzia kermanshahica gen. nov., sp. nov. (Chroococcales, Cyanobacteria), isolated from paddy fields in Iran.

In Iran, polyphasic studies of unicellular cyanobacteria are still scarce, with more emphasis being placed on filamentous cyanobacteria in paddy fields and fresh water regions. In an effort to increase the knowledge of the diversity of unicellular cyanobacteria from paddy fields in Iran, we have isolated and characterized a new unicellular cyanobacterium strain. The strain was studied using a polyphasic approach based on morphological, ecological and phylogenetic analyses of the 16S-23S ITS rRNA gene region. Complementarily, we have searched for the presence of cyanotoxin genes and analysed the pigment content of the strain. Results showed that the strain was morphologically indistinguishable from the genus Chroococcus, but phylogenetic analyses based on the Bayesian inference and maximum-likelihood methods placed the strain in a separated monophyletic and highly supported (0.99/98, posterior probability/maximum-likelihood) genus-level cluster, distant from Chroococcus sensu stricto and with Chalicogloea cavernicola as sister taxa. The calculated p-distance for the 16S rRNA gene also reinforced the presence of a new genus, by showing 92 % similarity to C. cavernicola. The D1-D1', Box-B and V3 ITS secondary structures showed the uniqueness of this strain, as it shared no similar pattern with closest genera within the Chroococcales. For all these reasons, and in accordance with the International Code of Nomenclature for Algae, Fungi and Plants, we here proposed the description of a new genus with the name Alborzia gen. nov. along with the description of a new species, Alborzia kermanshahica sp. nov. (holotype: CCC1399-a; reference strains CCC1399-b; MCC 4116).

Influence of hydrological factors on bacterial community structure in a tropical monsoonal estuary in India.

In the present study, we analyzed variations in bacterial community structure along a salinity gradient in a tropical monsoonal estuary (Cochin estuary [CE]), on the southwest coast of India, using Illumina next-generation sequencing (NGS). Water samples were collected from eight different locations thrice a year to assess the variability in the bacterial community structure and to determine the physico-chemical factors influencing the bacterial diversity. Proteobacteria was the most dominant phyla in the estuary followed by Bacteroidetes, Cyanobacteria, Actinobacteria, and Firmicutes. Statistical analysis indicated significant variations in bacterial communities between freshwater and mesohaline and euryhaline regions, as well as between the monsoon (wet) and nonmonsoon (dry) periods. The abundance of Betaproteobacteria was higher in the freshwater regions, while Alphaproteobacteria and Epsilonproteobactera were more abundant in mesohaline and euryhaline regions of the estuary. Gammaproteobacteria was more abundant in regions with high nutrient concentrations. Various bacterial genera indicating the presence of fecal contamination and eutrophication were detected. Corrplot based on Pearson correlation analysis demonstrated the important physico-chemical variables (temperature, salinity, dissolved oxygen, and inorganic nutrients) that influence the distribution of dominant phyla, class, and genera. The observed spatio-temporal variations in bacterial community structure in the CE were governed by regional variations in anthropogenic inputs and seasonal variations in monsoonal rainfall and tidal influx.

Site reduction in redundant ecosystem sampling schemes

Data collection for fresh-water regions of The Ecosystem Health Monitoring Program (EHMP), in southeast Queensland, Australia, involves the sampling of over 130 sites among 19 catchments twice per year and has been ongoing for over ten years. The sampling design was derived following an exhaustive process of indicator and site selection to develop a composite indicator that represented aquatic ecosystem health. After 13 years of implementation, there was an interest in identifying redundancies in sampling to reduce sampling costs without making a substantial impact on the integrity of the program and its capacity to report on ecosystem health. This paper focuses on identifying a subset of sites and times that could be removed from sampling with a minimal impact on the subsequent ecosystem health scores. Herein, Mixed models are employed to assess a variance structure from which optimality criteria are utilized to identify the scheme. Integer programs are then used to ensure specific practical constraints are observed.

Diversity of native larvivorous fish fauna during pre- and post-tsunami in Car Nicobar, Andaman & Nicobar Islands, India.

Malaria is a serious public health problem in Car Nicobar Island, Andaman & Nicobar Islands, India. Using larvivorous fishes has proved to be the cheapest method for vector management approach, with long suppression of mosquito population. This study aims to scale-up the diversity of larvivorous fishes and their potential larvivoracity to evolve an appropriate biological intervention strategy against the immature stages of malaria vectors. During 2003 (pre-tsunami) and 2014-2016 (post-tsunami), an ecological descriptive survey was carried out in the water bodies around Car Nicobar Island. Fishes were captured using fishing nets and cast nets; and placed in plastic jars and preserved in formalin solution. Fishes were identified and classified according to the available keys. Their abundance and data on the current conservation status was recorded and analyzed. Their potential larvivoracity was graded according to their feeding intensity. Pre-tsunami, a total of 27 larvivorous fish species belonging to 11 orders, 23 families and 23 genera were identified. Order Perciformes and the family Cyprinidae were the most ascendant group constituting 51.9 and 11.1%, respectively. While, 80.8% of species were preferred to inhabit the freshwater region, only 37% of species were surface feeders (SF). According to the conservation, assessment and management plan (CAMP, 1998), 44.4% species were at lower risk least concern (LRlc), while 55.6% species were at least concerned (LC) as per the IUCN, 2017 categorization. However, after the tsunami, 17 fish species had gone extinct and 10 fish species were found to remain alive in the local water bodies. Post-tsunami, the larvivoracity analysis indicated that Ophiocara aporos, Ophiocara procephala, Valamugil seheli, Channa punctata, Kuhlia rupestris, Khulia mugil, and Terapon jarbua possess high-level larvivorous potentiality in nature and are recommended for vector control in the study area. These fish species were facing several anthropogenic threats, such as human interference, loss of habitat, trade, overexploitation, and fishing. Therefore, it is important to protect the water bodies from external impact and implement the conservation strategies. Further, periodic fish fauna surveys, identification of breeding sites, scale-up of the larvivorous potentiality at the field level, creating public awareness through health education on establishment of larvivorous fish ponds and planning for mass rearing of the native fish species should be adopted as part of vector management approach in the endemic malarious region of Car Nicobar Island.

Drowning in the elderly in Paraíba-Brazil

Drowning is a global problem, and is among the main causes of death in the world, and the elderly are part of this new reality as a special group who also suffer submersion accidents. The aim of this study was to analyze deaths due to drowning in the elderly in the state of Paraíba from 2005 to 2015. This is a retrospective, descriptive study associated with spatial analysis of regions with a higher incidence of drowning in people aged 60 years or older in the state of Paraíba. Data were collected from the IML (Gemol and Numol) records from 2005 to 2015, totaling 80 cases of drowning. Sociodemographic characteristics such as age group, gender, spatiality and local description of the occurrence (rivers, dams, sea, waterfall, cacimbas, dams and domestic environments), care provider, file of the Legal Medical Institute of the Scientific Police, international code of diseases – ICD 10 (code W74), shift of occurrence. As results we located the region of Mari sector of the wild region of Paraíba – Açude Olho D’agua (Latitude 7.11º S and Longitude 35.2º ), was the place with the highest number of drownings, where dams/lakes (55%), male (91%), married (46%), aged between 60 and 69 years (60%), the local population made the first care (41%), 14h was of higher occurrence (11%), and on Sundays (29%). We can conclude that drowning occurs in several aquatic scenarios, and in this study occurred in fresh water, several factors were associated with drowning in the elderly, such as cognition deficits, polypharmaceuticals and physical limitations, such outcomes can help encourage protection policies for this group as well as family members guide in freshwater regions and accentuate care.

Carbon storage and sediment trapping by Egeria densa Planch., a globally invasive, freshwater macrophyte

Invasive plants have long been recognized for altering ecosystem properties, but their long-term impacts on ecosystem processes remain largely unknown. In this study, we determined the impact of Egeria densa Planch, a globally invasive freshwater macrophyte, on sedimentation processes in a large tidal freshwater region. We measured carbon accumulation (CARs) and inorganic sedimentation rates in submerged aquatic vegetation SAV dominated by E. densa and compared these rates to those of adjacent tidal freshwater marshes. Study sites were chosen along a range of hydrodynamic conditions in the Sacramento-San Joaquin Delta of California, USA, where E. densa has been widespread since 1990. Cores were analyzed for bulk density, % inorganic matter, % organic carbon, 210Pb, and 137Cs. Our results show that E. densa patches constitute sinks for both “blue carbon” and inorganic sediment. Compared to marshes, E. densa patches have greater inorganic sedimentation rates (E. densa: 1103–5989 g m−2 yr−1, marsh: 393–1001 g m−2 yr−1, p < 0.01) and vertical accretion rates (E. densa: 0.4–1.3 cm yr−1, marsh: 0.3–0.5 cm yr−1, p < 0.05), but similar CARs (E. densa: 59–242 g C m−2 yr−1, marsh: 109–169 g C m−2 yr−1, p > 0.05). Sediment stored by E. densa likely reduces the resilience of adjacent marshes by depleting the sediment available for marsh-building. Because of its harmful traits, E. densa is not a suitable candidate for mitigating carbon pollution; however, currently invaded habitats may already contain a meaningful component of regional carbon budgets. Our results strongly suggest that E. densa patches are sinks for carbon and inorganic sediment throughout its global range, raising questions about how invasive SAV is altering biogeochemical cycling and sediment dynamics across freshwater ecosystems.

Notes on the occurrence of a rare pufferfish, Chelonodontops leopardus (Day, 1878) (Tetraodontiformes: Tetraodontidae), in the freshwaters of Payaswini River, Karnataka, India

The Banded LeopardblowFish, Chelonodontops leopardus (Day 1878) has been recorded in the freshwater region of Payaswini River, near Sullia Town, Dakshin Kannada District, Karnataka about 65km away from coastline of the Arabian Sea. The paper provides the taxonomic account of the fish and its distribution is discussed.

Numerical study of sediment transport time scales in an ebb-dominated waterway

Understanding the transport time scales for sediment in an estuary is important to study the retention of pollutants, such as heavy metals, that adsorb to sediment. In this study, a three-dimensional hydrodynamic and sediment transport model was developed to investigate the transport time scales of sediment in the Modaomen Waterway (MW), China. The results show that approximately 100 and 240 days are required for fine-grained (settling velocity, ωs = 0.2 mm/s) and coarse-grained sediment (ωs = 0.5 mm/s) to transport from the headwater to the estuary mouth, respectively. Unlike dissolved materials, sediment undergoes intermittent settling and resuspension, which are key processes that determine the sediment age. The sediment stays longer at the seabed than suspended in the water column. The sediment has more potential to be eroded from the seabed in the freshwater region because of the strong bottom shear stress. These eroded sediments can be rapidly diffused to the upper water column and advected seaward. In contrast, sediment tends to deposit within the turbidity maximum zone due to low bottom shear stress and weak turbulent mixing. Downstream of the turbidity maximum, turbulent mixing is further suppressed by density stratification and the eroded sediment is rarely diffused to the upper water column. As a result, sediment travels more rapidly in the freshwater region than in the brackish zone. The sediment in the upper water column is mostly advected from upstream, and the difference in the sediment ages near the surface and at the bottom can reach 40 days for the coarse-grained sediment. The sediment age has an effect on water quality because a long sediment retention time facilitates the accumulation of pollutants in the MW.

Trapping of Suspended Sediment by Submerged Aquatic Vegetation in a Tidal Freshwater Region: Field Observations and Long-Term Trends

Widespread invasion by non-native, submerged aquatic vegetation (SAV) may modify the sediment budget of an estuary, reducing the availability of inorganic sediment required by marshes to maintain their position in the tidal frame. The instantaneous trapping rate of suspended sediment in SAV patches in an estuary has not previously been quantified via field observations. In this study, flows of water and suspended sediment through patches of invasive SAV were measured at three tidally forced, freshwater sites, all located within the Sacramento-San Joaquin Delta in California. An acoustic Doppler current profiler deployed from a roving vessel provided velocity and backscatter data used to quantify fluxes of both water and suspended sediment. Sediment trapping efficiency, defined as instantaneous net trapped flux divided by incident flux, was positive in 24 of 29 cases, averaging + 5%. Coupled with 3 years of measured sediment flux data at one site, this suggests that trapping averages 3.7 kg m−2 year−1. This estimate compares favorably with the mean mass accumulation rate of 3.8 kg m−2 year−1 estimated from dated sediment cores collected at the study sites. Long-term measurements made upstream reveal a strong negative trend (− 1.8% year−1) in suspended sediment concentration, and intra-annual changes in both suspended sediment concentration and percent fines. The large footprint and high spatial density of invasive SAV coupled with declining sediment supply are diminishing downstream suspended sediment concentrations, potentially reducing the resiliency of marshes in the Delta and lower estuary to future sea-level rise.

Fish Assemblage Structure Comparison between Freshwater and Estuarine Habitats in the Lower Nakdong River, South Korea

Variabilities of biological communities in lower reaches of urban river systems are highly influenced by artificial constructions, alterations of flow regimes and episodic weather events. Impacts of estuary weirs on fish assemblages are particularly distinct because the weirs are disturbed in linking between freshwater and estuarine fish communities, and migration successes for regional fish fauna. This study conducted fish sampling at the lower reaches of the Nakdong River to assess spatio-temporal variations in fish assemblages, and effects of estuary weir on structuring fish assemblage between freshwater and estuary habitats. In total, 20,386 specimens comprising 78 species and 41 families were collected. The numerical dominant fish species were Tachysurus nitidus (48.8% in total abundance), Hemibarbus labeo (10.7%) and Chanodichthys erythropterus (3.6%) in the freshwater region, and Engraulis japonicus (10.0%), Nuchequula nuchalis (7.7%) and Clupea pallasii (5.2%) in the estuarine site. The fish sampled were primarily small species or the juveniles of larger species at the estuary region, while all life stages of fishes were observed at the freshwater habitats. The diversity patterns of fish assemblages varied greatly according to study site and season, with higher trends at estuarine sites during the warm-rainy season. No significant difference in diversity between freshwater and estuarine sites during the cold-dry season were found. Multivariate analyses of fish assemblage showed spatial and seasonal differences of assemblage structures. Higher effects of between-site variability but not within seasonal variability at each site were observed. Variations in assemblage structures were due to different contributions of dominant species in each habitat. Common freshwater species characterized the fish assemblage in the freshwater region, while marine juveniles were significantly associated with the estuarine habitat. The results from the ecological guild analyses showed distinct ecological roles for freshwater and marine species, and overlapping roles for fish sampled at the fishways. The lower reaches of the Nakdong River are an important ecosystem for both freshwater and marine juveniles. Nakdong River estuarine residents and migrant fishes, however, have been negatively affected by the construction of the weir (gravity dam), due to the obstruction to migration from and to freshwater habitats. Conservation and management policies aimed at minimizing anthropogenic influences on estuary ecosystems should focus on evaluating ecological functions of estuary weirs.

Water supply network model for sustainable industrial resource use a case study of Zeeuws-Vlaanderen in the Netherlands

Matching regional water supply and demand can be improved by allocating local renewable water resources through decentralized water supply networks (WSNs). The feasibility of decentralized WSNs depends on the costs for the required pipeline infrastructure. The lowest costs for pipeline infrastructure depend on the local landscape characteristics. We present a model that designs decentralized WSNs to supply water with regional supply sources. The objective of the model is to include the effects of landscape characteristics on infrastructure costs and to minimize overall WSN costs. We tested the model on a case study in the fresh-water scarce region of Zeeuws-Vlaanderen in the southwestern part of The Netherlands with known (hydro)geological, geographical and climate data. The model was tested to supply a large industrial water user with groundwater resources operated within sustainable yields. The generated WSNs cover a demand between 0.5 and 5.5 million m3 year−1. Between 1 and 12 supply locations are needed to cover the demand. The pipeline infrastructure needed ranges from 25.1 to 114.5 km. The model determines the optimal pipeline route, the amount of water flowing over each pipeline segment, and reveals if a small increase in demand causes a relatively large increase in costs. The results can be used to determine if water transport is preferred over other water supply options, such as wastewater re-use or desalination of saline water resources.

Diversity, pattern and ecological drivers of freshwater fish in China and adjacent areas

China is one of the megadiverse freshwater regions in the world, but the detailed diversity inventory, distribution pattern and ecological drivers are incompletely known, which hinders large-scale freshwater diversity conservation and pattern analysis at the global scale. Aiming to fill this knowledge gap, we compiled a comprehensive richness and distribution database of freshwater fishes in China and adject areas based on our long-term survey and exhaustive data collection from 165 hydrologic units at tributary and sub-basin grain. Then, we elucidated a biogeographical pattern using a β dissimilarity matrix with species presence/absence data and taxonomic relationships. Finally, we evaluated the explanatory power of three hypotheses, i.e., ‘area’, ‘energy’, and ‘history’, in explaining the diversity patterns. A total of 2,063 species utilizing freshwater habitats were identified in the study area. Among them, 1,651 freshwater species were recorded in China, of which 1034 species are endemic to China. Four major freshwater zoogeographic regions, the Palearctic, High Central Asia, East Asia, and South Asia, were identified from a dendrogram, and each region was characterized by different taxonomic categories (i.e., from species to order). ‘Historical’ factors play the most important role (43.64–62.96% of the total variation), or at least a comparable role to that of contemporary climate, in explaining the freshwater fish diversity patterns (species richness and species endemicity). In conclusion, the uplift of the Qinghai-Tibetan Plateau, nearby orogeny, and the following formation of the East Asian monsoon climate had profound impacts on the diversification and distribution of ichthyofauna in China and adjacent areas.

De novo transcriptome assembly and analysis of Phragmites karka, an invasive halophyte, to study the mechanism of salinity stress tolerance

With the rapidly deteriorating environmental conditions, the development of stress tolerant plants has become a priority for sustaining agricultural productivity. Therefore, studying the process of stress tolerance in naturally tolerant species hold significant promise. Phragmites karka is an invasive plant species found abundantly in tropical and sub tropical regions, fresh water regions and brackish marshy areas, such as river banks and lake shores. The plant possesses the ability to adapt and survive under conditions of high salinity. We subjected P. karka seedlings to salt stress and carried out whole transcriptome profiling of leaf and root tissues. Assessing the global transcriptome changes under salt stress resulted in the identification of several genes that are differentially regulated under stress conditions in root and leaf tissue. A total of 161,403 unigenes were assembled and used as a reference for digital gene expression analysis. A number of key metabolic pathways were found to be over-represented. Digital gene expression analysis was validated using qRT-PCR. In addition, a number of different transcription factor families including WRKY, MYB, CCCH, NAC etc. were differentially expressed under salinity stress. Our data will facilitate further characterisation of genes involved in salinity stress tolerance in P. karka. The DEGs from our results are potential candidates for understanding and engineering abiotic stress tolerance in plants.

Occurrence of Nematophagous Fungi in Freshwater Samples of Toba Lake, North Sumatra, Indonesia

Root-knot nematodes are important agricultural pests causing serious economical loss to harvestable crops. Biological control using nematophagous fungi is one option to mitigate these infection through mechanism of physical or chemical killing methods. The present study tried to explore a possibility of finding native nematophagous fungal strains in the hope on discovery of novel and potential isolates originating from freshwater region of Toba Lake, North Sumatra, Indonesia. Isolation of nematophagous fungi was based on sprinkle and pour combination method on Chloramphenicol-Water Agar (CWA) incubated for 30 days. Freshwater samples of soil and sediments were collected from 28 sampling sites characterized by different anthropogenic activities as natural, fishery, residential, plantation and tourism area. Daily examination is conducted to obtain a single culture of nematophagous fungi sub-cultured on Potato Dextrose Agar (PDA) medium. Eleven isolates were observed to initiate predatory activities against tested Caenorhabditis elegans based on qualitative screening. The isolates showed either mechanical killing or chemical killing of nematodes during co-inoculation with nematodes. Micromorphological and molecular analysis are currently being conducted to obtain species identity from each isolate.