Insufficient oxygen delivery to tissues is hypothesised to limit thermal tolerance, but evidence in ectotherms is mixed. We assessed heat tolerance under hypoxia, normoxia and hyperoxia to test ...whether the extent in which oxygen can lower or increase heat tolerance differed with mode of respiration, comparing gill-breathing caenogastropods and lung-breathing pulmonates with or without an accessory gill. Hypoxia lowered heat tolerance in three of the four pulmonates (Physa fontinalis, Physa acuta and Planorbis carinatus) by 1.2–2.1°C. Hyperoxia, however, did not increase the heat tolerance in any of the pulmonate species. Thus, heat tolerance limits of these pulmonates does not appear to be oxygen limited under normoxia, possibly because of their high capacity to regulate oxygen consumption associated with aerial gas exchange. Instead, other processes may become limiting at thermal extremes such as loss of protein function, loss of membrane stability or neuronal dysfunction. The caenogastropod species tested (Potamopyrgus antipodarum, Bithynia tentaculata) closed their operculum during the warming experiments. This behavioural response prevented us from obtaining clear results. Nevertheless, our results suggested hyperoxia may increase heat tolerance in B. tentaculata. This could be related to its lower capacity to regulate oxygen, owing to its fully aquatic gas exchange mechanism.
Riverine macroplastic pollution (>0.5 cm) negatively impacts ecosystems and human livelihoods. Monitoring data are crucial for understanding this issue and for the design of effective interventions ...strategies. Macroplastic pollution floating on the river surface and plastic deposited on riverbanks are studied relatively often. Data on riverine plastics in the water column remain scarce. In this study, we utilized trawl nets at different depths to sample plastic pollution in the water column at the entry point of the river Rhine to the Netherlands. We show that plastic concentrations in the water column increased during higher discharge. Moreover, the results indicate that the vertical distribution of macroplastic pollution changes during different flow conditions. Significantly higher concentrations of macroplastic can be seen near the riverbed during low discharge conditions, while no significant differences in concentration are observed between the bottom, middle, and surface samples during high discharge conditions. Taking into account the recurrence time of low discharge conditions the transport of plastic during low discharge conditions is substantial. These findings provide first insights into the key role of hydrology in explaining macroplastic transport in the water column. These insights can be used to improve future monitoring and intervention strategies.
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•Macroplastic (>0.5 cm) pollution in the water column was sampled with a novel method at the entry point of the river Rhine to the Netherlands•Macroplastic concentrations increased with higher discharge levels•Vertical macroplastic distributions changed with higher discharge, likely due to increased vertical mixing
Although studies on plastic concentrations mainly focus on the marine environment, recently, an increasing number of studies point out environmental consequences in freshwater environments around the ...world. However, there still is a paucity of field data on the abundance of riverine plastic items, in particular in the water column. In this study, we provide an overview of macro- and mesoplastic concentrations, categories, ages, and origin over several years in the water column of the river Waal, in the Netherlands. The river water column was passively sampled at two selected locations using a stow net at very low and low discharges (range 537 - 1345 m3.s−1). The most dominant macro- and mesoplastic categories were ‘Miscellaneous plastic waste’, including “Plastic film 2.5 - 50 cm (soft)” and “Plastic film 0 - 2.5 cm (soft)” as main categories. Macro- and mesoplastic categories were found to show limited variability during several years of monitoring. The mean macroplastic concentration (± SD) ranged between 2.2 × 10−3 ± 0.001 and 7.4 × 10−3 ± 0.003 particles.m−3 for October 2020 and November 2018, respectively. In 2020, the plastic concentrations showed a sharp decrease compared to the previous years, most likely as a consequence of the COVID-19 crisis. The origin of the plastics (e.g., countries) also showed little variability during monitoring. The consistency of several characteristics of the collected plastic suggests that the same sources were responsible for the macro- and mesoplastic input into the river Waal during low discharges and over multiple years. We present the first temporal assessment of macro- and mesoplastic concentrations and composition in the water column of the river Waal. The outcome of the current study can be used to support the development of management measures by decision makers.
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•12,832 plastic items were collected during monitoring campaigns.•“Plastic film (soft)” was the most dominant macroplastic and mesoplastic category recorded.•Inland shipping is a relevant source of plastic pollution in the freshwater environment.•Under low flow conditions concentrations and composition showed a limited temporal variability.
Summary
Laboratory data on desiccation tolerance of native and non‐native mollusc species were used to derive species sensitivity distributions (SSDs), to predict effects of desiccation on mollusc ...assemblages in rivers during low discharge events and to prioritise various environmental stressors (i.e. desiccation, temperature and salinity).
The predicted absence and observed absence of mollusc species by desiccation at a specific site were expressed as potentially not occurring fraction (PNOF) and not occurring fraction (NOF) of their regional species pool in the River Rhine.
Calculations of PNOFs for desiccation explained 57% (LT99) and 65% (LT50) of the NOFs of the mollusc species. Sensitivity to desiccation did not differ between native and non‐native mollusc species pools.
Due to differences in frequency of low river discharge events and water level fluctuations, mollusc species in an impounded reach of the River Meuse were less affected by desiccation than in a free‐flowing distributary of the River Rhine.
Earlier calculations of the PNOFs for combined effects of temperature and salinity in the River Rhine explained 22 and 3% of the NOFs of native and non‐native species, respectively, for the period 1988–2003. Accounting for the effects of desiccation, 62 and 80% of the NOFs of the native and non‐native species pool, respectively, were explained, indicating that desiccation during low discharge events was an important stressor in comparison with water temperature or salinity.
Since a relatively high percentage of the NOFs of native species in the River Rhine still remain unexplained, an effort to assess potential effects of other stressors is recommended (e.g. toxic substances or water turbulence caused by commercial shipping).
River plastic transport and storage budget Schreyers, Louise J.; van Emmerik, Tim H.M.; Huthoff, Fredrik ...
Water research (Oxford),
08/2024, Letnik:
259
Journal Article
Recenzirano
Odprti dostop
Rivers are one of the main conduits that deliver plastic from land into the sea, and also act as reservoirs for plastic retention. Yet, our understanding of the extent of river exposure to plastic ...pollution remains limited. In particular, there has been no comprehensive quantification of the contributions from different river compartments, such as the water surface, water column, riverbank and floodplain to the overall river plastic transport and storage. This study aims to provide an initial quantification of these contributions. We first identified the main relevant transport processes for each river compartment considered. We then estimated the transport and storage terms, by harmonizing available observations on surface, suspended and floodplain plastic. We applied our approach to two river sections in The Netherlands, with a focus on macroplastics (≥2.5 cm). Our analysis revealed that for the studied river sections, suspended plastics account for over 96% of item transport within the river channel, while their relative contribution to mass transport is only 30%–37% (depending on the river section considered). Surface plastics predominantly consisted of heavier items (mean mass: 7.1 g/#), whereas suspended plastics were dominated by lighter fragments (mean mass: 0.1 g/#). Additionally, the majority (98%) of plastic mass was stored within the floodplains, with the river channel accounting for only 2% of the total storage. Our study developed a harmonized approach for quantifying plastic transport and storage across different river compartments, providing a replicable methodology applicable to different regions. Our findings emphasize the importance of systematic monitoring programs across river compartments for comprehensive insights into riverine plastic pollution.
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•We developed a river plastic budget method including key transport processes.•We estimated plastic flux and storage at river surface, subsurface and floodplains.•98% of plastic mass was stored within floodplains for the studied Rhine sections.•Floating plastic accounted for 4% (item) to 70% (mass) of total plastic transport.•Lateral transport between channel and floodplain remains unresolved.
As filter-feeders, freshwater mussels provide the ecosystem service (ES) of biofiltration. Chemical pollution may impinge on the provisioning of mussels' filtration services. However, few attempts ...have been made to estimate the impacts of chemical mixtures on mussels' filtration capacities in the field, nor to assess the economic benefits of mussel-provided filtration services for humans. The aim of the study was to derive and to apply a methodology for quantifying the economic benefits of mussel filtration services in relation to chemical mixture exposure. To this end, we first applied the bootstrapping approach to quantify the filtration capacity of dreissenid mussels when exposed to metal mixtures in the Rhine and Meuse Rivers in the Netherlands. Subsequently, we applied the value transfer method to quantify the economic benefits of mussel filtration services to surface water-dependent drinking water companies. The average mixture filtration inhibition (filtration rate reduction due to exposure to metal mixtures) to dreissenids was estimated to be <1% in the Rhine and Meuse Rivers based on the measured metal concentrations from 1999 to 2017. On average, dreissenids on groynes were estimated to filter the highest percentage of river discharge in the Nederrijn-Lek River (9.1%) and the lowest in the Waal River (0.1%). We estimated that dreissenid filtration services would save 110–12,000 euros/million m3 for drinking water production when abstracting raw water at the end of respective rivers. Economic benefits increased over time due to metal emission reduction. This study presents a novel methodology for quantifying the economic benefits of mussel filtration services associated with chemical pollution, which is understandable to policymakers. The derived approach could potentially serve as a blueprint for developing methods in examining the economic value of other filter-feeders exposed to other chemicals and environmental stressors. We explicitly discuss the uncertainties for further development and application of the method.
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•We derive the economic value of mussel filtration services under chemical exposure.•Dreissenids on groynes on average filter 0.1–9.1% of Dutch river discharge.•Dreissenid filtration may save 110–12,000 €/million m3 in producing drinking water.•The method can be applied in valuing other filter-feeders exposed to stressors.
Longitudinal training dams (LTDs) are novel hydraulic engineering structures in the river Waal intended to facilitate intensive navigation and safe discharges in the main channel while providing ...sheltered habitats for aquatic biota in shore channels. Monitoring data collected using light detection and ranging, multibeam echosounder and aerial photography for the years during and after the construction of the LTDs were analysed in order to determine patterns of erosion and deposition, the retreat rate of steep eroding banks and shoreline length change through time. The LTD shore channels and two traditional groyne fields (references) were divided into nine mesohabitats based on physical attributes. Net erosion was estimated for eight out of the nine mesohabitats for the 2015–2020 period. Generally, there was a pattern of riverbed aggradation towards the LTDs and degradation or bank erosion towards the littoral zones of the LTD shore channels. This kind of continuous behaviour could be indicative of current or eminent channel and thus habitat stability. The bankline erosion in shore channels had mean retreat rates of 1.4–1.6 m/year. The shorelines were longer in sand‐dominated mesohabitats, which could be key for habitat heterogeneity. The LTD shore channels offered more complex relatively natural continuous littoral zones than the traditional groyne fields while maintaining the multifunctionality of the river. Thus, the development of sandy shorelines in the LTD shore channels should be encouraged through management in order to enhance biodiversity. Geomorphological monitoring of the shore channels should continue in the future in order to detect any long‐term changes in the sedimentary processes and ecological functions.
Longitudinal training dams (LTDs) are novel hydraulic engineering structures in the river Waal intended to facilitate intensive navigation and safe discharges in the main channel while providing sheltered habitats for aquatic biota in shore channels. Net erosion was estimated for eight out of the nine mesohabitats for the 2015‐2020 period. The LTD shore channels offered more complex, relatively natural continuous littoral zones than the traditional groyne fields while maintaining the multifunctionality of the river.
Rising surface water temperatures in fluvial systems increasingly affect biodiversity negatively in riverine ecosystems, and a more frequent exceedance of thermal tolerance levels of species is ...expected to impoverish local species assemblages. Reliable prediction of the effect of increasing water temperature on habitat suitability requires detailed temperature measurements over time. We assessed (1) the accuracy of high-resolution images of water temperature of a side channel in a river floodplain acquired using a consumer-grade thermal camera mounted on an unmanned airborne vehicle (UAV), and (2) the associated habitat suitability for native and alien fish assemblages. Water surface temperatures were mapped four times throughout a hot summer day and calibrated with 24 in-situ temperature loggers in the water at 0.1 m below the surface using linear regression. The calibrated thermal imagery was used to calculate the potentially occurring fraction (POF) of freshwater fish using species sensitivity distributions. We found high temperatures (25–30 °C) in the side channel during mid-day resulting in reduced habitat suitability. The accuracy of water temperature estimates based on the RMSE was 0.53 °C over all flights (R2 = 0.94). Average daily POF was 0.51 and 0.64 for native and alien fish species in the side channel. The error of the POF estimates is 76% lower when water temperature is estimated with thermal UAV imagery compared to temperatures measured at an upstream gauging station. Accurately quantifying water temperature and the heterogeneity thereof is a critical step in adaptation of riverine ecosystems to climate change. Our results show that measurements of surface water temperature can be made accurately and easily using thermal imagery from UAVs allowing for an improved habitat management, but coincident collection of long wave radiation is needed for a more physically-based prediction of water temperature. Because of climate change, management of riverine ecosystems should consider thermal pollution control and facilitate cold water refugia and connectivity between waterbodies in floodplains and the cooler main channel for fish migration during extremely hot summer periods.
Plastic pollution in the ocean occurs mainly
via
riverine transport. In rivers, plastic is pervasive in sediments and in the water column. Monitoring of floating plastics in rivers is time consuming ...as it is usually collected using nets and classified by hand, or counted and classified visually. To make plastic detection in the water column more time- and cost-efficient, there is a need to explore remote sensing options. Here we present the results of two semi-controlled pilot tests in standing water using two imaging sonar technologies: an Adaptive Resolution Imaging Sonar (ARIS) sonar and a low-cost side-scan sonar (SSS). Additionally, the ARIS sonar was tested in flowing water at a sheltered shore channel behind a longitudinal training dam in the river Waal, Netherlands. Both technologies were able to detect 100% of the macroplastics tested in standing water. The ARIS sonar provided higher resolution images of the targets tested due to its high operation frequency detecting macroplastics down to a size of 1 cm
2
. The ARIS sonar detected macroplastics in the field, however, the detection decreased to 67% in flowing water. This sonar was limited to the 2D horizontal position of targets. The SSS is a low-cost option for monitoring of plastics and is integrated with CHIRP sonar technology that combines side and down imaging providing the 3D position of targets. For future monitoring, an ARIS sonar in motion or two ARIS sonars used simultaneously may provide the necessary 3D spatial information of plastic targets.
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