scholarly journals Mayfly response to different stress types in small and mid-sized lowland rivers

ZooKeys ◽  
2020 ◽  
Vol 980 ◽  
pp. 57-77
Author(s):  
Marina Vilenica ◽  
Mladen Kerovec ◽  
Ivana Pozojević ◽  
Zlatko Mihaljević
Keyword(s):  
Aquatic Invertebrates ◽  
Aquatic Vegetation ◽  
Freshwater Ecosystems ◽  
Catchment Scale ◽  
Lowland Rivers ◽  
Lowland Streams ◽  
Taxa Richness ◽  
Study Sites ◽  
High Share ◽  
Cloeon Dipterum

Freshwater ecosystems are endangered worldwide by various human pressures, resulting in dramatic habitat and species loss. Many aquatic invertebrates respond to disturbances in their habitat, and mayflies are among the most sensitive ones. Therefore, we investigated mayfly response to anthropogenic disturbances at 46 study sites encompassing slightly to heavily modified small and mid-sized lowland streams and rivers. Mayfly nymphs were sampled between April and September 2016 using a benthos hand net. A total of 21 species was recorded, with Cloeon dipterum (Linnaeus, 1761) being the most frequently recorded one. Nevertheless, the taxa richness was rather low per site, i.e., between zero and nine. Assemblage structure had a high share of lower reaches and lentic (potamic and littoral) elements, and detritivores (gatherers/collectors and active filter feeders). This indicates that hydromorphological alterations lead to assemblage “potamisation” in small and mid-sized rivers. More mayfly species were related to higher oxygen concentration and lower water temperature, abundance of aquatic vegetation and total organic carbon. Additionally, the assemblage diversity and abundance were negatively associated with increasing intensive agriculture area at the catchment scale. This study confirms mayfly bio-indicative properties, i.e., their sensitivity to alterations of their habitat and pollution, but also provides new data related to mayfly response to the impacted environment. Those data can be used for management and protection activities of lowland rivers and their biota according to the requirements of the European Water Framework Directive.

scholarly journals Flow Resistance in Lowland Rivers Impacted with Distributed Aquatic Vegetation

2021 ◽  
Author(s):  
Saeid Okhravi ◽  
Radoslav Schügerl ◽  
Yvetta Velísková
Keyword(s):  
Cross Sections ◽  
Flow Resistance ◽  
Aquatic Vegetation ◽  
Roughness Coefficient ◽  
Sources Of Resistance ◽  
Lowland Rivers ◽  
Lowland Streams ◽  
Resistance Factors ◽  
Seasonal Flow ◽  
Bed Roughness

Abstract The study addresses the research concern that the employment of fixed value for bed roughness coefficient in lowland rivers (mostly ‌sand-bed rivers) is deemed practically questionable in the presence of a mobile bed and time-dependent changes in vegetation patches. To address this issue, we set up 45 cross-sections in four lowland streams to investigate seasonal flow resistance values within a year. The results first revealed that the significant sources of boundary resistance in lowland rivers with lower regime flow are bed forms and aquatic vegetation. Then, the study uses flow discharge as an influential variable reflecting the impacts of the above-mentioned sources of resistance to flow. The studied approach ended up with two new flow resistance predictors which simply connect dimensionless unit discharge with flow resistance factors, Darcy-Weisbach (f) and Manning (n) coefficients. A comparison between the computed and measured flow resistance values indicates that 87-89% of data sets were within the ±20% error bands. The flow resistance predictors are also verified against large independent sets of field and flume data. The obtained predictions using the developed predictors may overestimate flow resistance factors to about 40% for other lowland rivers. From a different view of this research, the findings on seasonal variation of vegetation abundance hint at the augmentation in flow resistance values, both f, and n, in low summer flows when the vegetation covers river bed and side banks. The highest amount of flow resistance was observed during the summer period, July-August.

Advances in Understanding Landscape Influences on Freshwater Habitats and Biological Assemblages

2019 ◽  
Keyword(s):  
Forested Wetlands ◽  
Timber Harvest ◽  
Large Wood ◽  
Catchment Scale ◽  
Southeast Alaska ◽  
Riparian Management ◽  
Freshwater Habitats ◽  
Study Sites ◽  
Landscape Attributes ◽  
Landscape Influences

<i>Abstract.</i>—Currently, much is known about influences of landscape attributes, including timber harvest practices, on large wood dynamics in streams. Comparatively, much less is known about influences of catchment attributes on Southeast Alaska streams, in part because of a historical lack of consistent catchment-scale data available for the region. As in forested regions elsewhere, large wood is an important resource to stream habitats and fishes in Southeast Alaska. Therefore, the purpose of this study was to characterize catchment-scale influences, including various timber harvest practices, on large wood in Southeast Alaska stream sites. We delineated local catchment boundaries for all stream reaches in the region and summarized landscape influences, including natural and harvest-related attributes in local and network catchments. Relative amounts of variation in four large wood habitat variables explained by natural versus harvest practice-related landscape attributes were evaluated to compare different influences on 28 randomly selected study sites. We used those results to predict variation in large wood variables from our sites through use of both natural and harvest practice-related catchment attributes to identify those that may be most influential to large wood. Natural characteristics, including catchment area, deciduous forests, forested wetlands, and catchment slope, all had significant influences on large wood variables, as did various measures of contemporary and historical timber harvest practices. We found that large wood length was positively related to conventional harvest after 1990, suggesting the potential effectiveness of contemporary logging regulations in protecting large wood characteristics. In our study, both natural and timber harvest practice-related attributes had measureable influences on stream habitat, underscoring the importance of considering catchment-scale attributes, including riparian management schemes, for managing Southeast Alaska streams.

scholarly journals Lake and catchment‐scale determinants of aquatic vegetation across almost 1,000 lakes and the contrasts between lake types

2019 ◽  
Vol 46 (5) ◽  
pp. 1066-1082 ◽  
Author(s):  
Junyao Sun ◽  
Peter D. Hunter ◽  
Andrew N. Tyler ◽  
Nigel J. Willby
Keyword(s):  
Aquatic Vegetation ◽  
Catchment Scale

scholarly journals Assessing the performance of a plastic optical fibre turbidity sensor for measuring post-fire erosion from plot to catchment scale

SOIL ◽  
2015 ◽  
Vol 1 (2) ◽  
pp. 641-650 ◽  
Author(s):  
J. J. Keizer ◽  
M. A. S. Martins ◽  
S. A. Prats ◽  
L. F. Santos ◽  
D. C. S. Vieira ◽  
...  
Keyword(s):  
Optical Fibre ◽  
Overland Flow ◽  
Sediment Concentration ◽  
First Year ◽  
Power Functions ◽  
Forest Residues ◽  
Catchment Scale ◽  
Light Loss ◽  
Erosion Mitigation ◽  
Study Sites

Abstract. This study is the first comprehensive testing of a novel plastic optical fibre turbidity sensor with runoff samples collected in the field and, more specifically, with a total of 158 streamflow samples and 925 overland flow samples from a recently burnt forest area in north-central Portugal, collected mainly during the first year after the wildfire, as well as with 56 overland flow samples from a nearby long-unburnt study site. Sediment concentrations differed less between overland flow and streamflow samples than between study sites and, at one study site, between plots with and without effective erosion mitigation treatments. Maximum concentrations ranged from 0.91 to 8.19 g L−1 for the micro-plot overland flow samples from the six burnt sites, from 1.74 to 8.99 g L−1 for the slope-scale overland flow samples from these same sites, and amounted to 4.55 g L−1 for the streamflow samples. Power functions provided (reasonably) good fits to the – expected – relationships of increasing normalized light loss with increasing sediment concentrations for the different sample types from individual study sites. The corresponding adjusted R2 values ranged from 0.64 to 0.81 in the case of the micro-plot samples from the six burnt sites, from 0.72 to 0.89 in the case of the slope-scale samples from these same sites, and was 0.85 in the case of the streamflow samples. While the overall performance of the sensor was thus rather satisfactory, the results pointed to the need for scale of site-specific calibrations to maximize the reliability of the predictions of sediment concentration by the POF (plastic optical fibre) sensor. This especially applied to the cases in which sediment concentrations were comparatively low, for example following mulching with forest residues.

scholarly journals Littoral mayfly assemblages in South-East European man-made lakes

2019 ◽  
Vol 78 (1) ◽  
Author(s):  
Marina Vilenica ◽  
Natalija Vučković ◽  
Zlatko Mihaljević
Keyword(s):  
Flood Control ◽  
Sampling Site ◽  
Oxygen Demand ◽  
First Record ◽  
Freshwater Ecosystems ◽  
East Europe ◽  
East European ◽  
South East Europe ◽  
Freshwater Habitats ◽  
Cloeon Dipterum

Man-made freshwater habitats have been widely used to successfully modify the environment for human benefit, including purposes of irrigation, flood control or electricity generation. Over the past decade, our knowledge about the mayfly fauna and its ecology in South-East Europe has been growing, yet the data related to lentic assemblages remain very scarce. In this study, littoral mayfly assemblages were investigated at artificial and heavily modified lentic habitats in the Dinaric Western Balkan (n=21) and Pannonian Lowland (n=15) ecoregions. Mayfly nymphs were sampled during the summer months of 2016 or 2017. At each sampling site, ten samples were collected using a benthos hand net. A total of 21 mayfly species were recorded, though species richness per site was rather low (i.e., between zero and seven species). Cloeon dipterum (Linnaeus, 1761) was the most frequent species recorded, while Caenis horaria Linnaeus, 1758 was the most abundant. This study showed that the Croatian mayfly fauna is still growing, with the first record of Siphlonurus aestivalis Eaton, 1903 for the country. The assemblage structure was mainly dominated by lower reaches and lentic (potamal and littoral) elements and detritivores (gatherers/collectors and active filter feeders). Orthophosphates and chemical oxygen demand had the highest influence on mayfly assemblages, reflecting a higher level of pollution at sites in the Pannonian Lowland ecoregion, and consequently markedly lower mayfly abundances. As mayflies are widely used as bioindicators of freshwater ecosystems, detailed information about their assemblages in heavily modified and artificial habitats could contribute to future conservation activities of freshwater habitats and their communities. Additionally, these results could be applied in creating a monitoring system for artificial lakes according to the requirements of the European Water Framework Directive.

Effects of aquatic macrophytes on physico-chemical conditions of three contrasting lowland streams: a consequence of diffuse pollution from agriculture?

2001 ◽  
Vol 43 (5) ◽  
pp. 163-168 ◽  
Author(s):  
R. J. Wilcock ◽  
J. W. Nagels
Keyword(s):  
Aquatic Macrophytes ◽  
Aquatic Vegetation ◽  
Submerged Macrophytes ◽  
Third Stream ◽  
Lowland Streams ◽  
Riparian Plants ◽  
Agricultural Catchments ◽  
Physico Chemical ◽  
Photosynthetic Production ◽  
Chemical Conditions

Three lowland streams in developed pasture catchments with different farming intensities exhibited contrasting summer diurnal variations in pH, DO and temperature. These are ascribed to differences in dominant aquatic vegetation and their respective effects on shade, and on photosynthetic production and respiration within each stream. The stream dominated by submerged macrophytes had the greatest amplitude swings in DO and pH, and DO levels of 86–128% saturation. Floating marginal macrophytes reduced photosynthetic inputs while providing additional organic loading for respiration, with consequent flat DO and pH curves and conditions not conducive to healthy stream ecosystems. The third stream was shaded by riparian plants, which inhibited photosynthetic effects on DO and pH so that diurnal variation was intermediate between the other two streams. The interaction between nutrients and increased insolation in agricultural catchments, in stimulating aquatic plants, needs to be better understood for managing the sustainability of stream habitats and ecosystems.

scholarly journals Interactions between aquatic vegetation, hydraulics and fine sediment

2020 ◽  
Author(s):  
Hamish Biggs ◽  
Arman Haddadchi ◽  
Murray Hicks
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Hydraulic Resistance ◽  
Vegetation Cover ◽  
Aquatic Vegetation ◽  
Fine Sediment ◽  
Suspended Sediment Transport ◽  
Sediment Delivery ◽  
Lowland Streams ◽  
Mechanical Removal

Aquatic vegetation, hydraulics and sediment transport have complex interactions that are not yet well understood. These interactions are important for sediment conveyance, sediment sequestration, phasing of sediment delivery from runoff events, and management of ecosystem health in lowland streams. To address this knowledge gap detailed field measurements of sediment transport through natural flexible aquatic vegetation are required to supplement and validate laboratory results. This paper contributes a field study of suspended sediment transport through aquatic vegetation and includes mechanical removal of aquatic vegetation with a weed cutting boat. It also provides methods to quantify vegetation cover through remote sensing with Unmanned Aerial Vehicles (UAVs) and estimate biomass from ground truth sampling. Suspended sediment concentrations were highly dependent on aquatic vegetation abundance, and the distance upstream that had been cleared of aquatic vegetation. When the study reach was fully vegetated (i.e. cover >80%), the maximum recorded SSC was 14.6 g/m (during a fresh with discharge of 2.47 m/s), during weed cutting operations SSC was 76.8 g/m at 0.84 m/s (weedcutting boat 0.5-1 km upstream from study reach), however following weed cutting operations (4.6 km cleared upstream), SSC was 139.0 g/m at a discharge of 1.52 m/s. The data indicates that fine sediment was being sequestered by aquatic vegetation and likely remobilised after vegetation removal. Investigation of suspended sediment spatial dynamics illustrated changes in particle size distribution due to preferential settling of coarse particles within aquatic vegetation. Hydraulic resistance in the study reach (parameterized by Manning’s n) dropped by over 70% following vegetation cutting. Prior to cutting hydraulic resistance was discharge dependent, while post cutting hydraulic resistance was approximately invariant of discharge. Aerial surveying captured interesting changes in aquatic vegetation cover, where some very dense regions of aquatic vegetation were naturally removed leaving behind unvegetated riverbed and fine sediment.

scholarly journals Response of the mollusc communities to environmental factors along an anthropogenic salinity gradient

2019 ◽  
Vol 106 (11-12) ◽  
Author(s):  
Agnieszka Sowa ◽  
Mariola Krodkiewska ◽  
Dariusz Halabowski ◽  
Iga Lewin
Keyword(s):  
Alien Species ◽  
Nitrate Nitrogen ◽  
Salinity Gradient ◽  
Ammonium Nitrogen ◽  
Freshwater Ecosystems ◽  
Underground Coal Mining ◽  
Taxa Richness ◽  
Elevated Salinity ◽  
Large Gradient ◽  
Sand And Gravel

AbstractAnthropogenic salinisation of freshwater ecosystems is frequent across the world. The scale of this phenomenon remains unrecognised, and therefore, monitoring and management of such ecosystems is very important. We conducted a study on the mollusc communities in inland anthropogenic ponds covering a large gradient of salinity located in an area of underground coal mining activity. A total of 14 gastropod and 6 bivalve species were noted. No molluscs were found in waters with total dissolved solids (TDS) higher than 17.1 g L−1. The share of alien species in the communities was very high in waters with elevated salinity and significantly lower in the freshwaters. Canonical correspondence analysis (CCA) showed that TDS, pH, alkalinity, nitrate nitrogen, ammonium nitrogen, iron, the content of organic matter in sediments, the type of substrate and the content of sand and gravel in sediments were the variables that were significantly associated with the distribution of molluscs. The regression analysis revealed that total mollusc density was positively related to alkalinity and negatively related to nitrate nitrogen. The taxa richness was negatively related to TDS, which is consistent with previous studies which indicated that a high salinity level is a significant threat to freshwater malacofauna, causing a loss of biodiversity and contributing to the colonisation and establishment of alien species in aquatic ecosystems.

The «Empty Forest Syndrome» and the Herpetofaunal Communities in Laos (South-Eastern Asia)

2021 ◽  
Vol 28 (6) ◽  
pp. 333-347
Author(s):  
Tomas Zuklin ◽  
Nathanael Maury ◽  
Saly Sitthivong ◽  
Thong Van Pham ◽  
Olivier Le Duc ◽  
...  
Keyword(s):  
Conservation Status ◽  
Habitat Type ◽  
Great Majority ◽  
Terrestrial Ecosystems ◽  
Freshwater Ecosystems ◽  
Amphibian Species ◽  
Turtle Species ◽  
Main River ◽  
In The Wild ◽  
Study Sites

Nowadays, Laos remains one of the scientifically least known countries of Asia in terms of herpetological knowledge. Here, we evaluate composition of species in freshwater ecosystems (main river courses) and terrestrial ecosystems (forests) in two distinct regions using Visual Encounter Surveys along designed transects, examination of fishers’ catches and standardized interviews. In Northern Laos, we recorded only 18 reptile individuals (2 turtle and 1 snake species). Interview surveys demonstrated that in Nam Xam River, fishers are more likely to hunt turtles and we identified one potential site where the world’s rarest turtle, Rafetus swinhoei, could be still present in the wild. In Nam Et Phou Louey National Park, we found 19 reptile species (8 lizard, 10 snake, 1 turtle species) in the different study sites, demonstrating a low species density in all different surveyed habitats. In Central/Southern Laos, we observed 30 species of reptiles (14 snake, 16 lizard, 35 amphibian species). Our study offers preliminary insights into the composition of amphibians and reptiles in Laos. The great majority of the species were non-threatened or not evaluated, and a few were threatened, suggesting that more research is needed to proper understand the conservation status of Laos’ herpetofauna. We highlighted, indirectly by interviews with local fishers, the possible presence of the turtle Rafetus swinhoei, thus providing a new hope for avoiding the extinction of this species. Finally, we observed a relatively low number of species in each habitat type, which is remarkably lower than in tropical forests of other continents or of nearby south-east Asian countries, indicating that the herpetofauna communities in Laos are depleted, reflecting an ‘empty forest syndrome’.

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