Ecohydrology & Hydrobiology最新文献

Non-native plants can significantly affect biodiversity and ecological functions of local ecosystems. The effects of Kandelia obovata introduction and Spartina alterniflora invasion on benthic bacterial communities, predicted ecological functions and interactions between macrobenthos and microorganisms were studied. High-throughput sequencing of the 16S rRNA gene was used to investigate the bacterial communities in sediments covered by S. alterniflora and K. obovata at different stand ages. Bacterial communities showed obvious spatial variation. With increasing in planting age, K. obovate sediments were occupied by higher proportions of bacteria involved in degradation of organic carbon compounds, including various sulfate reduction bacteria, Bacteroidetes, Alphaproteobacteria, and pathogenic bacteria Vibrio, while the relative abundances of Actinomatinales and Sulfurovum were more abundant in younger K. obovate sites. Compared to adjacent mudflat, higher abundances of sulfate reduction bacteria were observed in S. alterniflora. This study indicated that K. obovata introduction had greater effects on bacterial communities, and sediment pH, grain size, soil organic carbon, total nitrogen and total phosphorus contents were main environmental factors affecting variation in bacterial communities. Tax4fun analysis further suggested that higher potentials of nitrogen fixation and dissimilatory sulfate reduction were observed after K. obovata restoration and S. alterniflora invasion. There were significant correlations between macrobenthos and bacterial communities, especially variations in relative abundance of infaunas and herbivores after K. obovata introduction and S. alterniflora invasion, which significantly affected bacterial communities and potentials involved in nitrogen cycling. The present study provided valuable information in scientific assessing the impacts of non-native plant disturbance on local ecosystems.

Unionid populations are declining worldwide as they are threatened by anthropogenic habitat alterations, the introduction of invasive alien species and the effects of climate change. Several studies have focused on the habitat preferences of adult mussels but none to date have reported on the importance of the habitat preferences of host fish species. The aim of this study was to determine the habitat preferences of unionid host fish species in the Netherlands, to examine potential differences between native and alien host fish species, and to evaluate the effect of alien host fish species on unionid dispersal. Species sensitivity distributions (SSDs) were constructed for the range of occurrences and laboratory tolerance of host fish species in the Netherlands for water temperature, substrate type, flow velocity, and water depth. A case study was selected to assess the suitability to substrate type, flow velocity and water depth of a novel river habitat along longitudinal training dams in the river Waal. Unionid host fish species in the Netherlands preferred shallow littoral zones (0.1 m) with low flow velocity (0.05 m/s), an average water temperature of the Rhine delta (15°C), and most substrate types (ranging from silt to cobbles). Boulder substrate was the most limiting factor of the abiotic factors assessed for both native and alien host fish species. Management options for unionid populations should include host fish species in their assessments while focusing on creating and maintaining areas with limited boulders and implementing alien host fish species removal measures.

Woody vegetation cover in South Africa has increased over the past 100-150 years owing to the establishment of commercial forestry plantations, the spread of alien invasive plants (AIPs) and indigenous woody encroachment (WE). Extensive research conducted over the past 50 years has shown that AIPs can lead to dramatic declines in catchment water yields as a result of their high evapotranspiration (ET) rates. This has raised concern that WE may also be responsible for increasing ET losses and adversely impacting the country's limited water resources. In this paper, we used a combined systematic review and meta-analysis approach to explore trends in the water use of different vegetation types located in various climates across South Africa, to ultimately evaluate the likelihood of WE increasing ET losses in South Africa's savannas. This study revealed mixed support for whether WE in South Africa's savannas is increasing ET losses. On one hand, the fact that WE species replace grasses and form dense thickets indicates that there is high potential for WE to increase ET losses. On the other hand, rainfall, appears to be a primary factor limiting ET in semi-arid climates, indicating little potential for WE to have any effect on ET, unless there is an above-average rainfall year, or the vegetation has access to an additional water source. This study justifies the need for additional ET monitoring in South Africa's savannas in order to determine whether large-scale WE control should be implemented to conserve water resources in one of the country's driest regions.

This study aimed to evaluate the structure, taxonomic, and trophic composition of an assemblage of chironomid larvae associated with leaf litter in a tropical stream (Brazilian Cerrado biome) during different seasonal periods. Additionally, the study aimed to examine the relationship between the activity of decomposing microorganisms and the abundance and total richness of chironomids. To conduct the study, leaves were collected in buckets from the Boiadeiro stream at five sampling points over 30 consecutive days, resulting in a total collection of 12 months. Then, they were placed in litter bags (n =  3 per point) and incubated in the stream for 30 days to evaluate chironomid colonization and microbial activity. A total of 3,892 chironomid larvae were identified. Among the functional feeding groups (FFGs) of chironomid larvae, the food collector-gatherer group displayed higher diversity than other FFGs. The richness of chironomids was positively associated with the number of conidia produced by aquatic hyphomycetes' during leaf decomposition. We found that during the dry season (April–August), the highest values of abundance and total richness of chironomids were recorded, accompanied by the lowest taxonomic variability of chironomid larvae. Conversely, environmental variations in the rainy season contributed to greater taxonomic variability but lower abundance and total richness of chironomids associated with leaf detritus.

This study simplifies the recession process, includes the hourly evapotranspiration, and modifies the surface layer of the green-roof hydrological model based on the Green-Ampt (G-A) method and Curve Number (CN) method. The existing G-A and CN methods are usually applied for event-total runoff. The results show that the proposed model improves the predicting accuracy of the outflow, and the model performs well for rainfall events with different intensities, duration, and hyetograph. the CN method performs as prominent as the G-A method but is more efficient. Based on observation, the retained volume and peak reduction are close to 50 % on average with a 1-to-2-hour peak delay. The results of the three-year simulation show that the retained volume and peak reduction reach 50 % for 75 % of the events when the antecedent water content is 30 %. Almost all rainfall is retained for events with rainfall amounts smaller than 20 mm when the antecedent water content is smaller than 30 %. On the other hand, 50 % (60 %) rainfall (peak) is retained (reduced) for events larger than 20 mm when the antecedent water content is smaller than 20 %. With the model verified using various rainfall events, the study generalizes an equation to estimate the rainwater retained by green roofs. Moreover, the stormwater-detention performance of a green roof in general is concluded quantitatively under different antecedent water content to assist the decision-making of irrigation concerning the goal of stormwater detention.

Fish entrainment from reservoirs to downstream rivers by various water release structures may result in serious consequences for reservoir ecosystems. This study proposed an integrated modeling approach for determining fish entrainment risk zones and suitable reservoir regulations. The modeling approach combines hydrodynamic and fish risk assessment modeling with using fuzzy rules set defined by expert knowledge in fish ecology. We applied this modeling approach in the Maling Reservoir in China, where fish entrainment in the reservoir has been observed in the turbine, spillway, and irrigation system. Percocypris pingi (Tchang, 1930) and Onychostoma simum (Sauvage & Dabry de Thiersant, 1874), representing the main and protected fish species, were selected as target fish species. Five reservoir operation schemes were investigated under normal and designed water levels. The modeling results suggest that the fish entrainment risk for protected fish species (Onychostoma simum) is higher than that for the main fish species (Percocypris pingi). The results indicate a ranking of the fish entrainment risk from high to low in the following scenarios: with all spillways in operations, with one spillway in operation, with intakes in operation, with an irrigation system in operation, and with intakes and the irrigation system in combined operations. In addition, under normal and designed water levels, dead fish entrainment zone areas and percentages were extremely low compared to the entire forebay of the reservoir. These results indicate that the operation of the Maling Reservoir does not affect the ecological status of fish. These findings are generally applicable to any fish species in reservoirs that balance reservoir operations and ecological protection of fish, and could assist reservoir managers in making informed decisions on how to mitigate and compensate for fish entrainment.

Turbidity is a precursor of several biotic phenomena in aquatic ecosystems, including differentiation of the zooplankton ensemble. We tested the hypothesis that the turbidity gradient in shallow artificial reservoirs can control the biomass of the most evenly distributed, i.e. the best adapted, population of a zooplankton species. This species can be sequentially linked to other zooplankton taxa to indicate a particular turbidity gradient. We assumed that each of the three water turbidity classes: high turbidity (HT), moderate turbidity (MT) and low turbidity (LT) can be represented by the best adapted species that establishes relationships with other species. These networks can indicate adaptation to the higher and lower levels of turbidity in the class. Random forest classification and regression models were used. The classification of zooplankton adaptation showed that variation in copepod nauplii biomass best reflected the turbidity classifications. Patterns of species occurrence by Daphnia cucullata Sars, 1862, Difflugia spp. and Cephalodella spp. (LT), Keratella cochlearis (Gosse, 1851) (MT), and K. cochlearis and Filinia longiseta (Ehrenberg, 1834) (HT) were formed at successive levels of the network. The adaptation patterns in each of the three turbidity classes were based on an optimal set and sequence of zooplankton functional traits, the ability to satisfy food needs, and interspecific relationships. Random forest modelling supported a comprehensive interpretation of the results, innovatively expanding existing knowledge on the functioning of turbid water ecosystems.

In order to effectively cope with the destruction of natural hydrological cycle mechanism, frequent urban flood, serious water pollution and other problems, which are caused by the rapid urbanization process, the ‘sponge city’ concept has been widely used in China. This paper mainly focuses on how to rationally arrange the sponge grey and green facilities in built-up urban areas. With background analysis as the premise, model construction as the platform and swarm intelligence optimization as the method, the optimal proportion of sponge green facilities is determined. Furthermore, gray facilities are strengthened for the problem area, and the optimal allocation scenario of sponge facilities with the combination of gray and green is obtained through continuous circulation. The final results show that the optimal layout proportion of rain garden, sunken green space, permeable pavement and green roof are 3.88%, 7.95%, 2.01% and 0.99% respectively, which can meet the 80% runoff control rate and 40% pollution load control rate in the standard. Based on the simulation results of 50a rainfall, regulation and storage facilities are arranged near the severely overloaded node and the diameter of the overloaded pipes are increased. It can be proved that runoff and pollution can be effectively controlled and urban flood can be alleviated with grey facilities by model. The research results of this paper are expected to provide the overall idea and method of layout optimization of grey-green facilities for sponge city construction in built-up urban areas.

Among freshwater benthic fauna, one of the most frequently observed groups of insects is midges of the family Chironomidae (Diptera). Their identification to the species level by morphology alone is difficult or even impossible (e.g., at larval and pupal stages). This basically results from their high phenotypic plasticity, the existence of cryptic species, and the need for access to complete, identified individuals for comparison. Consequently, DNA barcoding is becoming more popular. This technique uses the sequence of base pairs in a specific DNA fragment section as barcodes for individual species. This method not only allows the identification of sister species but also facilitates the discovery of new, previously unknown ones. Despite these benefits, molecular techniques have some limitations, including the lack of a complete barcode library and the need for access to properly purified genetic material. What is needed is to combine new taxonomic methods with elementary knowledge about the ecology of individual chironomid species. In this study, we have attempted to compare and synthesize the advantages and disadvantages of conventional vs. molecular methods of identification and to show the benefits of their integration into a hybrid approach. The suggested integration seems to be an optimal methodological solution that includes elements of Artificial Intelligence to accurately assess chironomid communities in terms of qualitative structure, which usually indicates the biodiversity of freshwater ecosystems. Thus, it is a fundamental tool for assessing the natural potential of water bodies according to the principles of the EU Biodiversity Strategy for 2030.

The transformation of blue and green water is an important hydrological process at the watershed, which is an important supplement to the study of hydrological processes. The Soil and Water Assessment Tool (SWAT) was used to investigate the evolution characteristics of hydrological processes and the transformation mechanism at the watershed and ecosystem scales in the Dongjiang River. The results show that: (1) the annual average total water flows in the Dongjiang River Basin are 37.80 and 22.287 billion m³, respectively. The blue and green water flows during the wet season account for more than 75% of the total year. The blue and green flows of the grassland ecosystem increased significantly, with the most significant change in the downstream ecosystem. (2) From 1980 to 1990 and from 2010 to 2020, the Dongjiang River Basin experienced a transition from blue to green water flow. Blue water flow accounts for the majority of total water flow in the paddy field and dry cropland ecosystems, and green water flow changed to blue water flow from 1980 to 2010. (3) The correlation between blue and green flow and land use was weak throughout the year and during the wet season, but it was significant during the dry season. This study can serve as a model for the integrated management of water resources and ecosystems in the Dongjiang River Basin.