Ecohydrology & Hydrobiology最新文献

Food quality (e.g. the presence of cyanobacteria) may affect the behavior, morphology and life history of cladocerans. However, little is known about how diet quality may affect the effectiveness of Daphnia's behavioral defenses against predators. Here we test the hypothesis that the presence of non-toxic cyanobacteria in Daphnia's diet reduces its ability to escape fish attack. The animals cultured under two different food quality regimes (green alga vs. cyanobacteria) were subjected to two types of predation experiments. In the first, we tested Daphnia's ability to avoid a predator whose feeding was simulated using a pipette, while in the second we tested Daphnia's ability to escape when confronted with a foraging fish (Poecilia reticulata). In both types of experiments, the ability to avoid predator attack was greater in Daphnia fed high quality green algae than in Daphnia fed low quality cyanobacteria.. We conclude that low food quality can affect the fitness of Daphnia not only by slowing their growth and reproduction rates, but also by increasing their susceptibility to predation.

Assessing the profitability of river restoration requires knowledge of the importance of individual ecosystem elements for the value of specific ecosystem services. The aim of this study was to experimentally estimate the effect of the presence of bed load on the processes of water self-purification from suspended solids, organic matter and microplastic fibres. The experiment was carried out in channels with and without bed load, simulating conditions in a lowland river. The system was supplemented with artificial sewage containing FPOM and polypropylene fibres. Changes in the amount of suspended solids in the water, as well as organic matter and microplastics in the water and sediment, were recorded over the course of a week. The presence of a bed load increased the rate of suspension removal from the river water many times over. The decomposition rate of organic matter in the sediment was much higher than in the water, reaching 1 g of organic carbon per week. Bed load favoured the immobilisation of large microplastic fibres, facilitating their incorporation into bottom biofilms. The fibres formed a 'skeleton' that led to the formation of larger bed load biofilms. The study suggests that, even without restoring the connection between river water and groundwater, the supply of bed load to the river significantly increases the efficiency of natural processes in the river ecosystem, including self-purification.

Benthic macroinvertebrates were sampled at 28 sites situated on ten urban streams (Łódź, Poland) representative of a wide range of anthropogenic modifications of water chemistry and bed structure. A total of 5,043 individuals, comprising 121 species belonging to 37 families and 15 orders, were collected. Diptera (35.8 %) and Ephemeroptera (31.8 %) were dominant.

The studied sites were grouped into clusters based on separately-analyzed environmental parameters, various levels of taxonomic diversity, and bioassessment variables. All analyses demonstrated similar trends of anthropogenic modification, intensifying concentrically from the suburbs towards the city centre. The first cluster included the upper section of streams; less polluted, richer in ecotone zones and natural stream bed substrate. The second cluster comprised streams demonstrating the influence of moderate human pressure. The third cluster included streams flowing through the city center in concreted beds and which were connected to a combined sewage system in which sewage and rain water are transported through a single canal system and enters the nearest stream. Modification of stream beds was significantly negatively correlated with the number of species, families and orders, but not with total abundance.

The number of species, the number of families and the number of orders were highly mutually correlated. Moreover, they were similarly correlated with biodiversity and biotic indices, which are used to assess the ecological status of the aquatic environment. Hence, different levels of taxonomic identification demonstrate similar effectiveness in assessment, i.e. higher taxa of aquatic macroinvertebrates may be suitable for simplified ecological monitoring of urban watercourses.

The study compares the structure of invertebrate communities inhabiting two types of bottom sediments in Krzynia Reservoir, known also as Lake Krzynia (on the Słupia River, northern Poland). The lake is prone to intensive sedimentation because it is limnic. This limnicity is due to the impact of the river, rather than to surface runoff from the catchment area, where the heavy predominance of natural habitats over transformed ones slows the transport of mineral suspensions from adjacent terrain. In the organic-poor sediments dominated by sand and gravel, the mean density of benthic invertebrates was ten-fold higher than in silty, organic-rich sediments, while invertebrate biomass was only slightly and non-significantly higher in organic-poor sediments than in organic-rich sediments. Simultaneously, the mean invertebrate body weight was markedly lower in organic-poor sediments (0.03 g) than in organic-rich sediments (0.18 g). No significant differences in taxonomic diversity (number and Shannon index of taxa) were found between the studied sediment types in the analysed communities. Among the major invertebrate groups, the Oligochaeta and Mollusca significantly differed in density between sediment types, while the Oligochaeta and Chironomidae differed in biomass. An increased percentage of silt fraction in bottom sediments resulted in a drastic decrease in abundance of benthic fauna, but their biomass declined only slightly. Thus, plans to construct new reservoirs should aim to reduce the rate of silt accumulation in them, in order to preserve their primary function and support biodiversity in transformed river valleys.

The study objective was to assess microbiological activity of sediments during the application of an EM preparation on the in Lake Skiertąg. Samples were taken before and after microbial bioremediation in the period 2020–2021 from five sediment layers. The abundance, biomass, and efficiency of the respiratory chain of sediment bacteria were determined by the direct methods in a fluorescence microscope. The rate of organic carbon oxidation was measured by the respiratory method. The abundance of benthic bacteria showed significant variability in the profile of each core, and decreased with an increase in sediment depth. The significant decrease in the number and biomass of bacteria in the sediment after the application of the EM technology, was observed during the second year of application of the preparation, and not immediately after its application. In the tested sediments, an significant increase in the percentage of cell with active dehydrogenases ETS+ in the total number of bacteria after application of the preparation was found, but at the same time significantly higher values of this parameter were demonstrated in 2021 compared to the first year of using microbial bioremediation. A significant positive correlation between the potential rate of organic carbon oxidation in the surface layer of sediments and the temperature in the water above the sediment indicates that the temperature conditions stimulated the respiration activity of the sediment microflora.

This study investigated potential relationships between land-use structure in the catchments of six southern Baltic coastal lakes that differ in the level of hydrological connection with the sea and the lakes’ trophic states. Our results indicate that three types of catchments can be distinguished, each of which has a high contribution of agricultural areas, plus: (i) considerable contributions of wetlands and water bodies (C1); (ii) a large contribution of wooded and seminatural habitats (C2); or (iii) a considerable contribution of artificial surfaces (C3). Correlations were analysed between land-use types and single-parameter Carlson's trophic state indices of lakes (TSI_Chl, TSI_TP, TSI_SD, TSI_TOC). Type C2 clearly differed from the others and was linked with the lowest trophic state index values. The other two catchment types were similarly related to the fertility of the coastal lakes. The results show that the analysed lakes’ levels of connection with the sea do not affect the trophic state of their waters. Catchment structure, analysed using CORINE Land Cover data, is significantly linked with TP and TOC values, but it does not relate to Secchi depth or chlorophyll content of water in the lakes. Wetlands (especially peat bogs) in the catchment area most strongly reduced the phosphorus and organic carbon content of lake water. Furthermore, comparable contributions of natural vs. anthropogenic components (∼1:1) are associated with a lower trophic state of water. The presented results may be important for shaping the proper management of various catchment types in the future, especially when implementing climate change mitigation strategies.

The Supraśl River is a stable water ecosystem in North-Eastern Poland. This is indicated by the flow rate over many years, as well as the water quality monitored for years. Despite this, there are periods of oxygen deficiency in the water, causing massive fish kills. Our research shows that climate change resulting in an increase in the frequency of hydro-meteorological extremes may contribute to negative processes taking place in aquatic ecosystems. On the example of Supraśl Water System (SWS), we present an analysis of the phenomenon of suspension caused by the underground inflow, supplying the surface waters with a significant load of organic matter. The accelerated decomposition of peat formations in the Supraśl River catchment after heavy rains makes it easier for organic matter to penetrate into the aquatic ecosystem. Intensive flushing of valley and river bed sediments during summer floods has a particularly negative impact on the ecosystem of inland waters. If there are organic sediments on the bottom, their re-suspension is very dangerous. Then there is the immediate demand for oxygen, which can lead to deoxygenation of the water. Although this is a natural process, alarm and monitoring procedures should be established and countermeasures sought to respond in time and prevent mass fish kills.

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.

Understanding plant water consumption is crucial for artificial afforestation under drought environments and water stress in desert regions. However, the water consumption characteristics of desert species responding to the irrigation regimes are often neglected. By conducting a field test in the Taklimakan Desert Highway shelterbelt, this study examines the sap flow traits of two typical woody halophyte species (Calligonum mongolicum and Haloxylon ammodendron) and how they react to weather conditions and watering practices. Under the same irrigation treatment, the stem flux of C. mongolicum on sunny days was 1.5–5.3 times that on dusty days, while the stem flux of H. ammodendron on sunny days was 3.5–5.5 times that on dusty days. Both species demonstrated some sap flow during the night, representing 14.3%–24.9% and 7.3%–10.4% of the total sap flow for C. mongolicum and H. ammodendron, respectively. H. ammodendron maintained a higher stem flow during daytime and was more drought resistant than C. mongolicum. The daily sap flow patterns of these two species varied, showing both ‘single’ and ‘double peak’ curves depending on the watering conditions. A delay was also observed between the sap flow of these two species and the environmental factors. The factors influencing plant sap flow were found to be in the order of solar radiation, temperature, relative humidity, and saturated water vapor pressure difference. A BP-neural network proved highly effective for accurately simulating the sap flow of these two species. This research provides insights into how two common desert tree species adapt their water use in response to drought conditions, which is vital for artificial forest creation in desert areas.