Assessing suspended sediment dynamics in relation to ecological thresholds and sampling strategies in two Irish headwater catchments

Thompson, Joshua; Cassidy, Rachel; Doody, Donnacha G.; Flynn, Raymond

doi:10.1016/j.scitotenv.2013.08.069

Cited by 31 publications

(25 citation statements)

References 61 publications

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“…The best fit linear regressions at site A and, in particular, site B have a slight offset from the zero intercept, indicating instrumental error in the optical turbidity probe. Despite this, the calibrations for sites A and E remain robust and the R 2 values are consistent with those reported in other studies (Harrington and Harrington 2013;Thompson et al 2014). …”

Section: Turbidity-suspended Particulate Matter (Spm) Calibrationsupporting

confidence: 88%

Diel turbidity cycles in a headwater stream: evidence of nocturnal bioturbation?

2016

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Purpose A small number of recent studies have linked daily cycles in stream turbidity to nocturnal bioturbation by aquatic fauna, principally crayfish, and demonstrated this process can significantly impact upon water quality under baseflow conditions. Adding to this limited body of research, we use highresolution water quality monitoring data to investigate evidence of diel turbidity cycles in a lowland, headwater stream with a known signal crayfish (Pacifastacus leniusculus) population and explore a range of potential causal mechanisms. Materials and methods Automatic bankside monitoring stations measured turbidity and other water quality parameters at 30-min resolution at three locations on the River Blackwater, Norfolk, UK, during 2013. Specifically, we focused on two 20-day periods of baseflow conditions during January and April 2013 which displayed turbidity trends typical of winter and spring seasons, respectively. The turbidity time-series, which were smoothed with 6.5-h Savitzky-Golay filters to highlight diel trends, were correlated against temperature, stage, dissolved oxygen and pH to assess the importance of abiotic influences on turbidity. Turbidity was also calibrated against suspended particulate matter (SPM) over a wide range of values via linear regression.Results and discussion Pronounced diel turbidity cycles were found at two of the three sites under baseflow conditions during April. Spring night-time turbidity values consistently peaked between 21:00 and 04:00 with values increasing bỹ 10 nephelometric turbidity units (NTU) compared with the lowest recorded daytime values which occurred between 10:00 and 14:00. This translated into statistically significant increases in median midnight SPM concentration of up to 76 % compared with midday, with night-time (18:00-05:30) SPM loads also up to 30 % higher than that recorded during the daytime (06:00-17:30). Relating turbidity to other water quality parameters exhibiting diel cycles revealed there to be neither any correlation that might indicate a causal link nor any obvious mechanistic connections to explain the temporal turbidity trends. Diel turbidity cycles were less prominent at all sites during the winter. Conclusions Considering the seasonality and timing of elevated turbidity, visual observations of crayfish activity and an absence of mechanistic connections with other water quality parameters, the results presented here are consistent with the hypothesis that nocturnal bioturbation is responsible for generating diel turbidity cycles under baseflow conditions in headwater streams. However, further research in a variety of fluvial environments is required to better assess the spatial extent, importance and causal mechanisms of this phenomenon.

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Section: Turbidity-suspended Particulate Matter (Spm) Calibrationsupporting

confidence: 88%

Diel turbidity cycles in a headwater stream: evidence of nocturnal bioturbation?

2016

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“…The temporal variability in SS transport at a particular point in the river, otherwise called the sediment regime, is determined by the interaction of various catchment-scale drivers (Grove et al, 2015;Thompson et al, 2013), which can be classified into four main, but often strongly interlinked, categories: (i) hydro-meteorological factors (ii) sediment source variations; (iii) natural landscape disturbances; and (iv) human interventions (Figure 1). …”

Section: Temporal Variability In Suspended Sediment Transportmentioning

confidence: 99%

Suspended sediment transport dynamics in rivers: Multi-scale drivers of temporal variation

Vercruysse

Grabowski

Rickson

2017

Earth-Science Reviews

333

219

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Suspended sediment is a natural part of river systems and plays an essential role in structuring the landscape, creating ecological habitats and transporting nutrients. It is also a common management problem, where alterations to sediment quantity and quality negatively impact ecological communities, increase flood hazard and shorten the lifespan of infrastructure. To address these challenges and develop appropriate sustainable management strategies, we need a thorough understanding of sediment sources, pathways and transport dynamics and the drivers that underlie spatial and temporal variability in suspended sediment transport in rivers. However, research to date has not sufficiently addressed the temporal complexity of sediment transport processes, which is limiting our ability to disentangle the hydro-meteorological, catchment, channel and anthropogenic drivers of suspended sediment transport in rivers. This review critically evaluates previously published work on suspended sediment dynamics to demonstrate how the interpretation of sediment sources and pathways is influenced by the temporal scale and methodology of the study. To do this, the review (i) summarizes the main drivers of temporal variation in suspended sediment transport in rivers; (ii) critically reviews the common empirical approaches used to analyze and quantify sediment sources and loads, and their capacity to account for temporal variations; (iii) applies these findings to recent case studies to illustrate how method and timescale affect the interpretation of suspended sediment transport dynamics; and finally (iv) synthesizes the findings of the review into a set of guidelines for a multi-timescale approach to sediment regime characterization. By recognizing a priori that study design and temporal scale have an impact on the interpretation of SS dynamics and employing methods that address these issues, future research will be better able to identify the drivers of suspended sediment transport in rivers, improve sediment transport modelling, and propose effective, sustainable solutions to sediment management problems.

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“…Horowitz et al, 2015;Johnes, 2007;Thompson et al, 2014). Alternative approaches for characterising the temporal and spatial variability of sediment fluxes are required (Littlewood and Marsh, 2005).…”

Section: Impact Of Sampling Frequency On Apparent Fine Sediment Exposurementioning

confidence: 99%

Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management

Perks

Warburton

Bracken

et al. 2017

Journal of Environmental Management

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Assessing suspended sediment dynamics in relation to ecological thresholds and sampling strategies in two Irish headwater catchments

Cited by 31 publications

References 61 publications

Diel turbidity cycles in a headwater stream: evidence of nocturnal bioturbation?

Diel turbidity cycles in a headwater stream: evidence of nocturnal bioturbation?

Suspended sediment transport dynamics in rivers: Multi-scale drivers of temporal variation

Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management

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