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"RUNNING WATER"
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Clonal growth architecture and spatial dynamics of 10 species of the genus Potamogeton across different habitats in Kashmir Valley, India
The plasticity in clonal architecture may enable plants to effectively respond to environmental constraints and to enhance species ecological niche breadth but its role in plant tolerance to water flow is poorly documented. The present study was carried out to determine whether the clonal architecture varies with respect to water flow in 10 species of the genus Potamogeton colonizing habitats differing by flow conditions. For these 10 species, the traits describing clonal architecture were measured on individuals sampled in natural sites and plasticity in clonal architecture was examined in a common garden growth experiment. The clonal growth architecture did not vary significantly in the species which inhabit either standing (P. lucens, P. natans, and P. pusillus) or running water (P. amblyphyllus and P. berchtoldii). However, the species inhabiting both standing as well as running waters (P. crispus, P. nodosus, P. pectinatus, P. perfoliatus, and P. wrightii) showed considerable and significant variation in clonal growth architecture across these habitats. Transplantation experiment revealed that clonal architecture observed between the plants under different conditions is plastic and not due to genetic differentiation. The present study demonstrated that plasticity in the clonal architecture may enable these species to inhabit stressful conditions of flowing water.
Journal Article
Markerless 2D kinematic analysis of underwater running: A deep learning approach
Kinematic analysis is often performed with a camera system combined with reflective markers placed over bony landmarks. This method is restrictive (and often expensive), and limits the ability to perform analyses outside of the lab. In the present study, we used a markerless deep learning-based method to perform 2D kinematic analysis of deep water running, a task that poses several challenges to image processing methods. A single GoPro camera recorded sagittal plane lower limb motion. A deep neural network was trained using data from 17 individuals, and then used to predict the locations of markers that approximated joint centres. We found that 300–400 labelled images were sufficient to train the network to be able to position joint markers with an accuracy similar to that of a human labeler (mean difference < 3 pixels, around 1 cm). This level of accuracy is sufficient for many 2D applications, such as sports biomechanics, coaching/training, and rehabilitation. The method was sensitive enough to differentiate between closely-spaced running cadences (45–85 strides per minute in increments of 5). We also found high test–retest reliability of mean stride data, with between-session correlation coefficients of 0.90–0.97. Our approach represents a low-cost, adaptable solution for kinematic analysis, and could easily be modified for use in other movements and settings. Using additional cameras, this approach could also be used to perform 3D analyses. The method presented here may have broad applications in different fields, for example by enabling markerless motion analysis to be performed during rehabilitation, training or even competition environments.
Journal Article
Impact of agriculture and land use on nitrate contamination in groundwater and running waters in central-west Poland
Protected areas due to their long-term protection are expected to be characterized by good water quality. However, in catchments where arable fields dominate, the impact of agriculture on water pollution is still problematic. In Poland, recently, the fertilization level has decreased, mostly for economic reasons. However, this applies primarily to phosphorus and potassium. In order to evaluate the impact of agriculture on water quality in a protected area with a high proportion of arable fields in the aspect of level and type of fertilization, complex monitoring has been applied. The present study was carried out in Wielkopolska National Park and its buffer zone, which are protected under Natura 2000 as Special Areas of Conservation and Special Protection Areas. The aim of the study were (1) to assess the impact of agriculture, with special attention on fertilization, on groundwater, and running water quality and (2) to designate priority areas for implementing nitrogen reduction measures in special attention on protected areas. In our study, high nitrogen concentrations in groundwater and surface waters were detected in the agricultural catchments. The results demonstrate that in the watersheds dominated by arable fields, high nitrogen concentrations in groundwater were measured in comparison to forestry catchments, where high ammonium concentrations were observed. The highest nitrogen concentrations were noted in spring after winter freezing, with a small cover of vegetation, and in the areas with a high level of nitrogen application. In the studied areas, both in the park and its buffer zone, unfavorable N:P and N:K ratios in supplied nutrients were detected. Severe shortage of phosphorus and potassium in applied fertilizers is one of the major factors causing leaching of nitrogen due to limited possibilities of its consumption by plants.
Journal Article
Browning of Boreal Freshwaters Coupled to Carbon-Iron Interactions along the Aquatic Continuum
The color of freshwaters, often measured as absorbance, influences a number of ecosystem services including biodiversity, fish production, and drinking water quality. Many countries have recently reported on increasing trends of water color in freshwaters, for which drivers are still not fully understood. We show here with more than 58000 water samples from the boreal and hemiboreal region of Sweden and Canada that absorbance of filtered water (a₄₂₀) co-varied with dissolved organic carbon (DOC) concentrations (R² = 0.85, P<0.0001), but that a₄₂₀ relative to DOC is increased by the presence of iron (Fe). We found that concentrations of Fe significantly declined with increasing water retention in the landscape, resulting in significantly lower Fe concentrations in lakes compared to running waters. The Fe loss along the aquatic continuum corresponded to a proportional loss in a₄₂₀, suggesting a tight biogeochemical coupling between colored dissolved organic matter and Fe. Since water is being flushed at increasing rates due to enhanced runoff in the studied regions, diminished loss of Fe along the aquatic continuum may be one reason for observed trends in a₄₂₀, and in particular in a₄₂₀/DOC increases. If trends of increased Fe concentrations in freshwaters continue, water color will further increase with various effects on ecosystem services and biogeochemical cycles.
Journal Article
Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions
Carbon dioxide (CO
2
) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO
2
concentrations. Using a global compilation of high-frequency CO
2
measurements, we demonstrate that nocturnal CO
2
emissions are on average 27% (0.9 gC m
−2
d
−1
) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO
2
by photosynthesis. Because current global estimates of CO
2
emissions to the atmosphere from running waters (0.65–1.8 PgC yr
−1
) rely primarily on discrete measurements of dissolved CO
2
obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO
2
emissions may elevate global estimates from running waters to the atmosphere by 0.20–0.55 PgC yr
−1
.
Failing to account for emission differences between day and night will lead to an underestimate of global CO
2
emissions from rivers by up to 0.55 PgC yr
–1
, according to analyses of high-frequency CO
2
measurements.
Journal Article
Global methane emissions from rivers and streams
Methane (CH
4
) is a potent greenhouse gas and its concentrations have tripled in the atmosphere since the industrial revolution. There is evidence that global warming has increased CH
4
emissions from freshwater ecosystems
1
,
2
, providing positive feedback to the global climate. Yet for rivers and streams, the controls and the magnitude of CH
4
emissions remain highly uncertain
3
,
4
. Here we report a spatially explicit global estimate of CH
4
emissions from running waters, accounting for 27.9 (16.7–39.7) Tg CH
4
per year and roughly equal in magnitude to those of other freshwater systems
5
,
6
. Riverine CH
4
emissions are not strongly temperature dependent, with low average activation energy (
E
M
= 0.14 eV) compared with that of lakes and wetlands (
E
M
= 0.96 eV)
1
. By contrast, global patterns of emissions are characterized by large fluxes in high- and low-latitude settings as well as in human-dominated environments. These patterns are explained by edaphic and climate features that are linked to anoxia in and near fluvial habitats, including a high supply of organic matter and water saturation in hydrologically connected soils. Our results highlight the importance of land–water connections in regulating CH
4
supply to running waters, which is vulnerable not only to direct human modifications but also to several climate change responses on land.
A spatially explicit global estimate reveals that land–water connections are important for regulating methane supply to running waters, and that these connections are vulnerable to both climate change and direct human modifications of the land.
Journal Article
Towards Methodological Problems of Trophic State Assessment of Running Waters
Deep analysis of trophic state assessment methods has led to conclusion, that currently there is no universal methodology and existing methods are characterized by significant shortcomings. The approach proposed by the authors is different from generally used. Authors start from the assumption, that trophic state can be reflected by the state of biotic balance, which can be described by the values of Index of Trophic State. Researches were carried out in order to assess the trophic state of running waters and to estimate the limiting role of biogenic substances for eutrophication process development on the base of author's concept founded on above mentioned index.
Journal Article
Drought alters the biogeochemistry of boreal stream networks
Drought is a global phenomenon, with widespread implications for freshwater ecosystems. While droughts receive much attention at lower latitudes, their effects on northern river networks remain unstudied. We combine a reach-scale manipulation experiment, observations during the extreme 2018 drought, and historical monitoring data to examine the impact of drought in northern boreal streams. Increased water residence time during drought promoted reductions in aerobic metabolism and increased concentrations of reduced solutes in both stream and hyporheic water. Likewise, data during the 2018 drought revealed widespread hypoxic conditions and shifts towards anaerobic metabolism, especially in headwaters. Finally, long-term data confirmed that past summer droughts have led to similar metabolic alterations. Our results highlight the potential for drought to promote biogeochemical shifts that trigger poor water quality conditions in boreal streams. Given projected increases in hydrological extremes at northern latitudes, the consequences of drought for the health of running waters warrant attention.
High latitude droughts are increasing, but their effects on freshwater systems are poorly understood. Here the authors investigate Sweden’s most severe drought in the last century and show that these dry conditions induce hypoxia and elevated methane production from streams.
Journal Article
Sources of and processes controlling CO2 emissions change with the size of streams and rivers
Rivers and streams are key sources of CO
2
. Estimated emissions and aquatic productivity from across the US show that small streams predominantly emit CO
2
produced in soils, but the contribution from aquatic metabolism increases with river size.
Carbon dioxide (CO
2
) evasion from streams and rivers to the atmosphere represents a substantial flux in the global carbon cycle
1
,
2
,
3
. The proportions of CO
2
emitted from streams and rivers that come from terrestrially derived CO
2
or from CO
2
produced within freshwater ecosystems through aquatic metabolism are not well quantified. Here we estimated CO
2
emissions from running waters in the contiguous United States, based on freshwater chemical and physical characteristics and modelled gas transfer velocities at 1463 United States Geological Survey monitoring sites. We then assessed CO
2
production from aquatic metabolism, compiled from previously published measurements of net ecosystem production from 187 streams and rivers across the contiguous United States. We find that CO
2
produced by aquatic metabolism contributes about 28% of CO
2
evasion from streams and rivers with flows between 0.0001 and 19,000 m
3
s
−1
. We mathematically modelled CO
2
flux from groundwater into running waters along a stream–river continuum to evaluate the relationship between stream size and CO
2
source. Terrestrially derived CO
2
dominates emissions from small streams, and the percentage of CO
2
emissions from aquatic metabolism increases with stream size. We suggest that the relative role of rivers as conduits for terrestrial CO
2
efflux and as reactors mineralizing terrestrial organic carbon is a function of their size and connectivity with landscapes.
Journal Article