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  Subjects -> WATER RESOURCES (Total: 160 journals)
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Aquatic Sciences
Journal Prestige (SJR): 1.109
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1015-1621 - ISSN (Online) 1420-9055
Published by Springer-Verlag Homepage  [2467 journals]
  • Biogeographical snapshot of life-history traits of European silver eels:
           insights from otolith microchemistry

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      Abstract: Abstract Life-history traits of eels display a high level of phenotypic plasticity in response to large-scale biogeographical drivers, as well as local conditions encountered during the continental phase. Here, we provided a biogeographical snapshot of the variability of life-history traits of eels (Anguilla anguilla), across a large proportion of their natural distribution range. Silver eels (n = 99) were collected across eleven European catchments to investigate how life-history traits vary along geographical and saline habitats, as it was inferred from the Sr:Ca ratio in otoliths. Among 13 life-history traits tested, 3 of them such as total length, body or liver weight were related to geographical coordinates. Overall, eels grow faster in southern Europe and migrate earlier suggesting that the silvering process is related to the local growth conditions more than fish age. The salinity profiles revealed by the otoliths’ Sr:Ca ratios indicate that eels with a brackish life-history generally grow faster, reach larger size-at-age, and have a better condition than eels living in freshwater. This observation associated with the lower abundance of the sanguivorous swimbladder nematode, Anguillicola crassus, confirms the importance of brackish areas for sustaining the eel production. A large proportion of the observed variation of life-history traits remained unexplained by the biogeographical trends and salinity condition, which suggests that other drivers act at the catchment scale.
      PubDate: 2023-01-30
       
  • Identifying photochemical alterations of dissolved pyrogenic organic
           matter using fluorescence spectroscopy

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      Abstract: Abstract Many streams originate in forested watersheds at risk of wildfires. Wildfires can introduce thermally altered organic compounds to terrestrial and aquatic systems. Understanding the degradation of leachates from these burned organic materials, referred to as dissolved pyrogenic organic material (PyDOM), is critical in determining water quality impacts in forested watersheds. This study used fluorescence spectroscopy to examine photochemical alterations of PyDOM generated by leaching organic matter burned at various temperatures. The PyDOM was exposed to natural sunlight for 25 days and the photochemical formation of hydrogen peroxide was monitored. PyDOM was characterized using ultraviolet–visible absorption, excitation–emission matrix (EEM) fluorescence spectroscopy, and fluorescence indices. Throughout the experiment, the emission intensity of the humic peak for all light-exposed leachates decreased while dark leachates exhibited no significant change in their fluorescence spectra. Additionally, hydrogen peroxide concentrations and UV absorbance decreased progressively over time, providing direct evidence that PyDOM concentrations can be significantly reduced by photodegradation. A characteristically low emission peak was observed in the EEMs of the fresh PyDOM, which could help in detecting fresh PyDOM. These results demonstrate that PyDOM derived from burned leachates is susceptible to photodegradation and that fluorescence measurements could be used as proxies for detecting PyDOM immediately post-wildfire.
      PubDate: 2023-01-27
       
  • Controlling factors of phytoplankton distribution in the river–lake
           transition zone of a large lake

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      Abstract: Abstract River–lake transition zones have been identified as major drivers of phytoplankton growth. With climate change reducing the frequency of complete lake overturns, it is expected that the Rhône River, the main tributary to Lake Geneva (France/Switzerland), will become the major source of nutrients for the lake euphotic zone. The river–lake transition zone was hence examined at the mouth of the Rhône River with the aim of understanding the complexities and controls of phytoplankton distribution in this specific deltaic ecosystem. Two field campaigns were carried out in which water samples were collected from longitudinal and transversal transects across the transition zone. These samples were analyzed for both nutrient and phytoplankton concentrations, while the fraction of Rhône River water in a lake sample was determined by the stable isotope composition of the water. The results indicate contributions in P and Si related to the Rhône intrusion into the lake. Furthermore, this river–lake transition zone appears to be a dynamic area that can locally present optimal conditions for phytoplankton growth. In early spring, a wind event broke the early and weak stratification of the lake, forcing the Rhône River and its turbidity plume to intrude deeper. Thus, this sharp drop of the turbidity within the euphotic zone allowed an increase in the phytoplankton biovolume of 44%. In early fall, outside of the turbid near field of the river mouth, the Rhône interflow, located just below the thermocline, promoted a local deep chlorophyll maximum.
      PubDate: 2023-01-27
       
  • Allocation of phosphorus (P) into biomass and calcite encrustation in
           Chara at high and low P availability

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      Abstract: Abstract Chara is usually found in hard and alkaline waters with low level of phosphorus (P) concentration. Calcite encrustation with P co-precipitation is very important for the growth of Chara and the maintenance of a low nutrient state in aquatic ecosystems. However, the effects and mechanisms of elevated P content in water on the growth, uptake and allocation of P in Chara are not well understood. This study performed an experiment to clarify how Chara vulgaris Linn, a common and widely distributed macroalga, allocated the P it uptake at different P availability. The results indicated that the growth rate of C. vulgaris in low P treatments (LP, less than 6 μg P /L) was 0.8 times higher than that in high P treatments (HP, more than 100 μg P /L), and the growth rate was significantly increased when C. vulgaris were transferred from the water with high P content to water with low P content, indicating that high P contents in water inhibited the growth of C. vulgaris. The increase of P content in water resulted in a fourfold increase in inorganic P (IP) content, while only 0.2-fold increase in organic P (OP) content, making the stoichiometric homeostasis index (1/H) of IP 7.9 times that of OP. More than 70% of the total P (TP) accumulated in Chara in LP was used for biomass growth, while more than 60% of the TP in C. vulgaris in HP was precipitated into calcite encrustation. This study highlighted that C. vulgaris had high growth rate under low P environment, and the inhibiting effect of high P to C. vulgaris was reversible, which may be a special P competition mechanism for this species in low P water. However, in high P condition, the Ca-P co-precipitation may limit the apparent P availability and be expressed as an inhibition of growth.
      PubDate: 2023-01-25
       
  • Nitrogen-15 NMR study on the incorporation of nitrogen into aquatic NOM
           upon chloramination

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      Abstract: Abstract Chloramination is being used increasingly in water treatment to lower the formation of regulated disinfection byproducts (DBPs). How monochloramine nitrogen becomes incorporated into aquatic natural organic matter (NOM) and potentially affects the formation of nitrogenous DBPs is an unresolved question in the chemistry of humic substances. To address the problem, Suwannee River NOM and Suwannee River fulvic acid were reacted with preformed 15NH2Cl and analyzed by solid and liquid state 15N NMR spectrometry. Both samples were also reacted with 15NH4Cl as a control. A majority of the monochloramine nitrogen incorporated into the samples matched the structural forms resulting from the control reaction with ammonia, indicating that condensation reactions of ammonia with the carbonyl functionality can partly explain the transformation of the 15NH2Cl nitrogen into the NOM. These structural forms include aminohydroquinone, 1° amide, indole, and pyridine-like nitrogens. Spectra of the samples reacted with 15NH2Cl also showed possible evidence for nitrosophenol nitrogens, which would arise from the reaction of hydroxylamine or nitrite, intermediates in the chemical oxidation of the inorganic nitrogen to nitrate.
      PubDate: 2023-01-23
       
  • Investigation of environmental factors on Enterococcus survival in
           Oklahoma streams

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      Abstract: Abstract In this study, we assessed six Oklahoma streams for Enterococcus sediment and water concentrations along with water quality, sediment, hydrologic and geographical factors. We also conducted a microcosm experiment from two stream sediments to evaluate Enterococcus survivability under stable laboratory conditions. Stream sites exhibited common relationships between Enterococcus and other environmental factors, including significant correlations to antecedent dry period, Escherichia coli, impervious area, dissolved oxygen, and turbidity. These correlations were found for Enterococcus in both water and sediment. Specifically for Enterococcus in sediment, concentrations were also significantly correlated to turbidity and sediment percent organic matter, but not to hydrological conditions. Conversely, concentrations of Enterococcus in water exhibited significant moderate correlations to precipitation, antecedent dry period, drainage area, impervious area, and discharge, as well as streambed particle size. High variability between geographical attributes and stream conditions increased uncertainties and relationships between Enterococcus concentrations in the stream among most factors. However, when grouping sites by similar watershed and sediment characteristics, strong significant relationships for water-quality parameters and Enterococcus concentrations in water and sediment were observed. The microcosm study indicated that sediment Enterococcus concentrations for two streams with contrasting sediment properties were stable, except for a considerable increase between day 0 and day 1, with no decay shown for a 31 day period. Collectively, our field and laboratory results revealed that Enterococcus can survive for extended periods under both dynamic and stable sediment and water conditions, and that environmental factors can be used to characterize freshwater streams and rivers for Enterococcus concentrations in freshwater streams and rivers.
      PubDate: 2023-01-20
       
  • The impact of permanganate pre-oxidation on subsequent drinking water
           treatment operations

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      Abstract: Abstract The efficient removal of dissolved organic matter (DOM) from drinking water is important to protect public health. However, the changes to DOM during drinking water treatments are poorly understood on a molecular level. Here, we investigated the changes induced by permanganate oxidation, alum coagulation, and activated carbon sorption for three DOM isolates, one derived from terrestrial materials, Suwanee River fulvic acid (SRFA), and two derived from microbial inputs, Grand Lake St. Mary’s (GLSM) DOM, and Jackson Pike wastewater effluent DOM (EfOM). These treatments were investigated individually, and in realistic treatment sequences, using conventional bulk characterization techniques and ultrahigh-resolution mass spectrometry. We found that permanganate pre-oxidation improved DOM removal by subsequent alum coagulation through the oxidation of aromatic components and the formation of tannin-like components. This effect was most prominent for SRFA and was less pronounced for the microbial DOM isolates. The impact of permanganate pre-oxidation had little to no effect on subsequent activated carbon treatment following coagulation. Removal of SRFA was impacted by the application order of alum coagulation and activated carbon sorption with coagulation followed by activated carbon sorption leading to the greatest organic matter removal efficiency. The favorable efficacy of this treatment series is likely caused by the removal of high molecular weight organic matter components by coagulation that would otherwise block sorption to activated carbon sites. Treatment application order impacted the removal of GLSM DOM and EfOM to a lesser extent, resulting in similar overall organic matter removal efficiencies that could be treated as additive for coagulation and activated carbon sorption. These observations, overall, suggest that permanganate pre-oxidation is most effective for improving DOM removal when aromatic terrestrial inputs are present, and pretreatments, including permanganate oxidation and activated carbon sorption, may be most effective when microbial inputs are present due to the absence of aromatic chemical species.
      PubDate: 2023-01-10
       
  • Identification of next-generation International Humic Substances Society
           reference materials for advancing the understanding of the role of natural
           organic matter in the Anthropocene

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      Abstract: Abstract Many challenges remain before we can fully understand the multifaceted role that natural organic matter (NOM) plays in soil and aquatic systems. These challenges remain despite the considerable progress that has been made in understanding NOM’s properties and reactivity using the latest analytical techniques. For nearly 4 decades, the International Humic Substances Society (IHSS, which is a non-profit scientific society) has distributed standard substances that adhere to strict isolation protocols and reference materials that are collected in bulk and originate from clearly defined sites. These NOM standard and reference samples offer relatively uniform materials for designing experiments and developing new analytical methods. The protocols for isolating NOM, and humic and fulvic acid fractions of NOM utilize well-established preparative scale column chromatography and reverse osmosis methods. These standard and reference NOM samples are used by the international scientific community to study NOM across a range of disciplines from engineered to natural systems, thereby seeding the transfer of knowledge across research fields. Recently, powerful new analytical techniques used to characterize NOM have revealed complexities in its composition that transcend the “microbial” vs. “terrestrial” precursor paradigm. To continue to advance NOM research in the Anthropocene epoch, a workshop was convened to identify potential new sites for NOM samples that would encompass a range of sources and precursor materials and would be relevant for studying NOM’s role in mediating environmental and biogeochemical processes. We anticipate that expanding the portfolio of IHSS reference and standard NOM samples available to the research community will enable this diverse group of scientists and engineers to better understand the role that NOM plays globally under the influence of anthropogenic mediated changes.
      PubDate: 2023-01-09
       
  • Dissolved organic matter from surface and pore waters of a discontinuous
           permafrost watershed in central Alaska reveals both compositional and
           seasonal heterogeneity

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      Abstract: Abstract In areas of active permafrost thaw, changes in organic carbon pools may significantly impact water quality and ecosystem services across the landscape. Surface and pore waters were collected from streams and lakes in the Goldstream Valley near Fairbanks Alaska over a period of three years, 2016–2018, to compare and contrast different thermokarst regimes, their water quality, and dissolved organic matter (DOM). Waters were characterized by elemental analysis, major ions, and optical characterization of DOM. We found DOM composition to be spatiotemporally heterogeneous, and influenced by complex hydrology. This result is evidenced by analyzing DOM character between differing water bodies and depths, seasonality, as well extent of metal association with DOM. Pore water DOM overall varied from the surface waters, with respect to both optical metrics and seasonality. Optical parameters typically associated with terrestrial signals were observed to become more prevalent in pore waters as summer progressed toward winter in an active thermokarst lake, potentially corroborating a hypothesis of downward flow into the talik or rapid turnover of authochthonous-sourced DOM. In addition, winter sampling, where surface inputs were assumed to be frozen, is essential to observe annual patterns of DOM composition. A principal components analysis separated water bodies based on their thermokarst activity and by season. Dissolved organic matter in these permafrost-impacted systems was found to be more complex than simply terrestrial or microbial, and extracted isolates from these waters were not necessarily bounded by existing end-member references.
      PubDate: 2023-01-09
       
  • Signal crayfish as a threat for European ectosymbionts: overlooked
           biodiversity losses

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      Abstract: Abstract The decline of native crayfish biodiversity caused by introductions of invasive crayfish has been well documented; however, the fate of their associated biota remains overlooked. Native European branchiobdellids (Annelida: Clitellata)—crayfish ectosymbionts—were monitored in Czech Republic in three localities with past or present sympatric occurrence of the native noble crayfish Astacus astacus (AA) and invasive signal crayfish Pacifastacus leniusculus (PL). No branchiobdellids were detected in two localities with abundant populations of PL but with absences of AA, although they were recently recorded there. Two species of branchiobdellids (Branchiobdella parasita and B. pentadonta) were detected on both crayfish species in the locality where AA still coexists with PL. However, PL harboured a significantly lower abundance of both branchiobdellids than AA (80.7% and 90.8% decrease, respectively) and a significantly lower number of their attached cocoons (95.7% and 95.0% decrease, respectively). Nevertheless, the abundance of branchiobdellids was positively correlated with the carapace length in both crayfish species. Other potential predictors related to crayfish biological parameters (e.g. sex or missing appendages) were not significantly related to the abundances of both branchiobdellids and their cocoons. We also performed laboratory experiments with both branchiobdellids distributed on size-matched individuals of AA and PL to verify the results of field observations. The probability for branchiobdellid survival was significantly higher on AA in both branchiodellids for all the time of the experiments. The absence or decreased abundances of the native branchiobdellids in the invasive crayfish suggest their limited capability to deal with the replacement of host species.
      PubDate: 2023-01-07
       
  • Predicting the density of zooplankton subsidy to a stream with multiple
           impoundments using water quality parameters

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      Abstract: Abstract Damming a stream inserts a lentic system (an impoundment or reservoir) into a lotic system, changing downstream hydrological, biogeochemical, and ecological processes. One such ecological effect of damming is to create a resource subsidy of easily captured and consumed zooplankton, which are preyed upon by filter-feeders and visual predators. In this study, we sought to predict the density of lentic zooplankton subsidizing downstream habitats using water quality parameters as an alternative to microscopy. We monitored zooplankton subsidy from 4 polymictic reservoirs over 3 summers and assessed 22 water quality variables for their ability to predict subsidies, ultimately finding that about half (48.3%) of the variation in zooplankton subsidy can be predicted using the water quality variables we assessed. While this level of variation explained is not sufficient to replace traditional microscopy for quantifying zooplankton density, conductivity stood out as an important and potentially useful predictor of zooplankton subsidy, and so might be very useful as a screening tool for identifying lentic–lotic transitions with higher subsidies. We also detected three different water quality regimes (high conductivity, high-colored dissolved organic matter (CDOM), and a remaining category) during the study, with differences in the density of zooplankton among these water quality regimes, suggesting that the reservoir’s water quality does impact downstream zooplankton subsidy.
      PubDate: 2023-01-06
       
  • Effects of predation risk on invertebrate leaf-litter shredders in
           headwater streams in three Brazilian biomes

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      Abstract: Abstract We evaluated the effect of predation risk for larvae of Phylloicus (Trichoptera: Calamoceratidae) on leaf-litter consumption and case-building in experimental microcosms performing three Brazilian biomes: Amazon Forest, Atlantic Rainforest, and Brazilian Savanna (Cerrado). We hypothesized the following: (1) predation risk by fish would decrease the feeding rate but increase the sheltering activities of Phylloicus larvae, mainly in a high-stimulus treatment (visual and chemical cues from predators’ presence); and (2) when offered a resource with the same palatability, leaf consumption by Phylloicus larvae from Amazon Forest and Atlantic Rainforest will be higher than in those from the Savanna, independent of the predation risk. We found that larvae of Phylloicus species from the three biomes use the leaf disks in different proportions for case-building and consumption: Amazon Forest (case-building = 44% and consumption = 50%), Atlantic Rain Forest (60% and 36%), and Brazilian Savanna (32% and 26%). The larvae case-building and leaf consumption by Phylloicus were higher under predation than in the control treatment using data uncorrected by the biomass of the individual. On the other hand, case-building was not different among all treatments, and leaf consumption was lower under predation than in the control treatment when corrected by biomass. Our results indicate that predation risk can affect the behavior of Phylloicus due to a stress response to predator presence. Therefore, it might mean top-down effects on shredders during leaf-litter processing in Neotropical headwater streams. Besides, insectivorous fish could be the key group for functioning in these ecosystems.
      PubDate: 2023-01-04
       
  • New insight into and characterization of DOC and DON for inland
           waterbodies in the Songnen Plain, Northeast China

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      Abstract: Abstract Dissolved organic matter (DOM), usually measured as concentrations of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in inland waterbodies, plays a vital role in the global carbon and nitrogen cycles. The spatial patterns of DOC and DON concentrations, DOC:DON weight ratios and their correlations with water physicochemical variables for 19 waterbodies in the Songnen Plain of Northeast China were first examined with data collected in May 2021. These 19 waterbodies can be further divided into two groups: fresh and brackish waterbodies according to electrical conductivity (EC) (EC threshold = 1200 μS cm−1) and mesotrophic and eutrophic waterbodies according to trophic state index (TSI) (TSI threshold = 50). Results showed that significant differences in average DOC and DON concentrations were observed between fresh and brackish waterbodies as well as between different trophic states (t-test, p < 0.01), respectively. A significant positive linear relationship between DOC and DON concentrations was found (R2 = 0.791, p < 0.01). DOC was moderately related to both EC (R2 = 0.617, p < 0.01) and TSI (R2 = 0.629, p < 0.01). DON showed a strong significant positive linear correlation with both EC (R2 = 0.734, p < 0.01) and TSI (R2 = 0.757, p < 0.01). These results suggested that DOC and DON were impacted by various parameters associated with TSI and most importantly EC could be used to estimate dissolved salts in DOC and DON through in-situ or remote sensing methods on large regional scales for these brackish waterbodies in the semiarid Songnen Plain of Northeast China.
      PubDate: 2022-12-28
       
  • Small hydropower plants lead to higher litter breakdown rates in by-passed
           sections than in impounded reaches

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      Abstract: Abstract Reservoirs and by-passed sections may alter downstream ecological processes of rivers, so understanding their effects is essential for watersheds impacted by small hydropower power plants (SHPs). We investigated the ecological impacts of river sections (upstream vs. reservoir vs. by-passed vs. downstream) of four run-of-river SHPs distributed in two Neotropical watersheds on leaf litter breakdown (Eucalyptus grandis and Inga uruguensis by k in d−1 and dd−1) and its associated invertebrate community. Hydropower schemes promoted breakdown rates, although mechanisms differed: increased shredder abundance in by-passed sections, and increased scrapper abundance in impounded sections, both for coarse mesh litterbags. Variation among river sections of SHPs was a more important driver of invertebrate colonization than was leaf litter species. Mass loss was higher for E. grandis (high-quality detritus) compared to I. uruguensis. The influence of litter quality was lower for invertebrates than for microorganisms, mainly due to fast litter breakdown. Clearly, changes in hydrology can cause severe damage and may impact river litter breakdown. The process of leaf litter breakdown proved to be a sensitive tool for assessing the impacts of SHPs.
      PubDate: 2022-12-15
       
  • Differential abundance, composition and mesohabitat use by aquatic
           macroinvertebrate taxa in ponds with and without fish

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      Abstract: Abstract Fish are known to pose strong effects on invertebrate abundance, species richness and assemblage structure. Littoral vegetation may play a crucial role as a refuge for invertebrates vulnerable to fish predation. We studied relative densities and taxonomic composition of water mites, aquatic beetles and bugs in large lake-like ponds with different fish status (fish-free and containing fish) and mesohabitats (emergent littoral vegetation and open water zone). The macroinvertebrate taxa differed in their responses to the fish presence and in mesohabitat preferences. The density and species richness of water mites were greater in fish-containing ponds, while no differences were found between littoral and open-water habitats. In contrast, beetles were far more numerous and species-rich in fish-free ponds and in littoral vegetation. Total densities of aquatic bugs were non-significantly higher in fish-containing ponds, and they preferred littoral areas, but species richness was independent of fish presence and mesohabitat. No statistical interactions between fish presence and the densities of individual macroinvertebrate groups in the littoral habitat were detected, indicating that their use of emergent littoral vegetation was not an antipredator response to fish. The assemblages of the three macroinvertebrate taxa exhibited nested structures of a different order, consistent with their species richness patterns. Our research stresses the importance of littoral vegetation for the distribution and abundance of aquatic insects; however, high fish presence may not affect or may even benefit ecologically important macroinvertebrate groups, such as water mites or bugs.
      PubDate: 2022-12-14
       
  • Effects of dissolved inorganic level and sediment types on the plant
           traits of Myriophyllum spicatum L. and its exudates input to sediment

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      Abstract: Abstract Rising atmospheric carbon dioxide (CO2) increases the dissolved inorganic carbon (DIC) level in overlying water, photosynthesis of macrophytes and further exudates input to sediment. Such effects of rising CO2 are closely coupled to sediment types with various levels of available nutrients. However, how sediment types influence the effect of rising CO2 on aquatic plant traits, root-derived carbon (C) and nitrogen (N) inputs to the sediment are poorly understood. We explored the effects of DIC levels (normal or high) and sediment types (sand or clay) on the submerged macrophyte Myriophyllum spicatum with a pot experiment. Plant traits (such as tissue C or N contents, branch number, specific root length, and height) and biomass accumulation were assessed. The C and N availabilities of the aquatic environment (sediment, overlying water and porewater) and microbial enzymes activities and biomass were measured during the beginning, middle and end of the experiment. The high DIC level increased the specific root length and leaf N content of M. spicatum but decreased the root/shoot ratio, leaf C content and root C content. However, sediment types and its interaction with the DIC level had almost little effect on plant traits (except the leaf N content and root C content). The environmental C and N availabilities were significantly affected by the DIC level, sediment type and sampling time. Sediment microbial properties (microbial biomass and enzymes) were affected by the sediment type and sampling time. We observed that rising CO2 exerted small changes in sediment dissolved organic carbon (DOC), and DOC in the porewater and overlying water increased over time, which implied diffusion fluxes from the pore space to the overlying water. The path model indicated that plant traits directly contributed to an increase in plant biomass or indirectly through microbial properties. In summary, rising atmospheric CO2 strongly affects plant traits, biomass and exudates input to sediment. The canopy traits respond more sensitively under rising CO2, which possibly leads to a higher biomass allocation to the aboveground and further a dominance of M. spicatum in natural communities of submerged macrophytes. The diffusion of organic C from sediment to overlying water possibly weaken the role of root exudates in the priming effect and further affect the decomposition of organic matter, which should be considered in the future study of C cycling.
      PubDate: 2022-12-12
       
  • Combined effect of stream drying and nutrient enrichment on
           macroinvertebrate community: experimental study from artificial stream
           mesocosms

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      Abstract: Abstract Ongoing climate change and rising water demands are resulting in the increasingly frequent occurrence of stream drying, particularly in smaller streams in humid temperate climates. These streams are often situated in outlying regions with insufficient wastewater treatment management leading to inconsistent inputs of nutrients into receiving water systems. Both stream drying and nutrient enrichment negatively affect local aquatic macroinvertebrate communities, but their combined effect is still unclear. This study aimed to investigate the combined effect of stream drying and nutrient enrichment on taxonomic and functional composition of aquatic macroinvertebrate communities. Towards this aim, an artificial stream system was used consisting of 36 mesocosms with aquatic macroinvertebrates. The mesocosms were exposed to four independent treatments based on different flow (perennial-drying) and nutrient (pristine-nutrient enriched) status. After 28 days of experiment, samples from different treatments were compared to evaluate combined effect of stream drying and nutrient enrichment. Despite expectations, no effect of drying on taxonomic and functional alpha diversity was observed, but beta diversity has significantly increased. Nutrient enrichment though caused to decrease in the alpha diversity indices, which resulted in high pre- and post-experiment samples dissimilarity within all treatments. Moreover, the combined effect of both stressors was antagonistic as stream drying moderated harsher impact of nutrient enrichment. Results emphasize an unexplored role of intermittent streams in nutrient cycling in temperate climates and highlight the need for further investigation of recently novel intermittent streams since they provide different environmental conditions for macroinvertebrates than perennial streams.
      PubDate: 2022-12-10
       
  • Temperature, nutrients and planktivorous fish predation interact to drive
           crustacean zooplankton in a large plateau lake, southwest China

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      Abstract: Abstract Introduction of planktivorous fish or eutrophication can alter lake food webs, especially the zooplankton communities are susceptible to changes in top–down and bottom-up controls, and eventually lead to the dominance of harmful cyanobacteria. Hence, for the recovery of large-size zooplankton abundance that graze on cyanobacteria, there is an urgency to understand the relative roles of top–down and bottom-up effects. Although much is known about these two effects in temperate lakes, little knowledge about their relative importance in subtropical highland lakes exists, where eutrophication and stocked planktivorous fish are of particular concern. Thus, we conducted research in Lake Erhai in Yunnan plateau, China, to examine the drivers affecting the dynamics of crustacean zooplankton. Redundancy analysis (RDA) was used to analyze the effects of environmental variables, phytoplankton biomass, and planktivorous fish on the biomass and body weight of zooplankton taxa in the lake, and variance decomposition analysis was applied to examine the relative roles of the bottom–up and top–down controlling factors on zooplankton biomass. The results of RDA and Pearson correction analysis showed that total nitrogen (TN) in the water column affected phytoplankton and altered the biomass of cladocerans, while water temperature directly affects the biomass of cladocerans. These findings indicate a pronounced bottom–up control link exists from nutrients to phytoplankton, and then to zooplankton. The abundance of Japanese smelt was negatively correlated both with the biomass and body weight of cladocerans. This finding suggests the pronounced top–down control link exists from fish to zooplankton. The results of variance decomposition analysis showed that TN and zooplanktivorous predation were more important in driving total zooplankton biomass, while TN, water temperature and fish predation were more essential in the variation of zooplankton biomass. Our study provides a reference for the recovery of large-size zooplankton populations in eutrophicated lakes.
      PubDate: 2022-12-08
       
  • Littoral periphyton dynamics in newly established post-mining lakes

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      Abstract: Abstract Hydric recultivation—flooding of abandoned mining pits—creates a completely new, underexplored habitat for a wide range of aquatic organisms. Periphyton, dominated by algae and cyanobacteria, is frequently a key component of newly established aquatic ecosystems. Periphyton and its response to abiotic factors were studied in the littoral zone of three post-mining lakes with different ages of foundation situated in the Czech Republic. The microbial diversity of phototrophs as a major component of periphyton is largely unknown in such localities. The studied habitat proved to harbour a huge periphytic diversity—25% of diatom species found in the respective watershed (~ 5500 km2) inhabited exlusively the studied lakes. Species composition of phototrophic microorganisms varied significantly (Permutational Multivariate Analysis of Variance) among the studied lakes, seasons, and sampling years. However, the sampling depths and sampling site of the studied lake have not shown a significant impact on the diversity, indicating the homogeneous composition of the littoral periphyton within a particular lake and growing season. The seasonal dynamics of periphyton were unique for each lake, documenting three distinct successional patterns. The proportion of diatoms in the periphytic community decreases with the higher trophic state and flooding age of the post-mining lakes. Cyanobacteria and mobile diatom forms prevailed later in the growing season, suggesting that they could utilise nutrients released from the accumulated periphyton biomass. Calcium ions were one of the best correlates of species data among other abiotic variables tested, offering the intriguing question of the role of calcium in the formation of periphytic mats for future research.
      PubDate: 2022-12-05
       
  • Spatial ecology of non-native common carp (Cyprinus carpio) in Lake
           Ontario with implications for management

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      Abstract: Abstract Common carp, Cyprinus carpio, are a non-native species that established within the Laurentian Great Lakes more than a century ago and are abundant in some locations. Common carp have negatively impacted freshwater ecosystems, including in the Great Lakes, by increasing turbidity and uprooting vegetation through foraging and/or spawning activities. Knowledge of spatial ecology is necessary to effectively manage non-native species and aid in the development of remediation strategies. The aim of this study was to examine the spatial ecology of common carp across multiple spatial scales within Lake Ontario using passive acoustic telemetry. First, Residency Index (RI), as a metric for habitat preference, was calculated for common carp in Toronto Harbour (TH) and Hamilton Harbour (HH). Linear mixed modelling revealed that season, as well as the interaction between season and physical habitat conditions significantly affected RI. Specifically, during spring and summer common carp had significantly higher RI at sites with increased submerged aquatic vegetation, which could be associated with spawning activities. All common carp tagged in HH were resident, compared to half of individuals tagged in TH. Larger individuals tagged in TH were more likely to be absent from the array during summer. Non-resident common carp tagged at TH made extensive movements in spring and summer along the nearshore of Lake Ontario and were detected throughout the entire basin. Knowledge of spawning habitat could inform efforts to exclude common carp from these specific locations. Based on our findings, common carp should be managed at a regional level, as opposed to single sites, owing to their extensive movements.
      PubDate: 2022-12-02
       
 
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