Presentation given by Elizabeth Conroy & Mary Kelly-Quinn at the SILTFLUX workshop, UCD, Dublin, February 2016

1. Detection of ecological impact of fine
sediment inputs
Overview of studies & key findings
Elizabeth Conroy & Mary Kelly-Quinn

2. SILTFLUX Biological
Studies
(Focus largely on deposited sediment)Experimental
work
Observational
field
Study 1 Detection and quantification of a
pollutant
Study 3: Linking localised sediment inputs with
ecological conditions
Study 2: Relationship between macroinvertebrate
metrics and sediment metrics
Study 4: Linking land use (catchment scale) with
ecology
Study 5 : Mechanistic study

3. Study 1: Detection and quantification of a
pollutant
A key consideration was how well various methods of measuring deposited
sediment represented the quantities present
Methods evaluated:
 Visual estimation of % sediment surface cover
 Measurement of suspended sediment concentration
 Resuspension of sediment and measurement of turbidity
 Point suction method using Turner-Hills deposited sediment sampler (DSS)
 Added known amounts of sediment

4.  % sediment surface cover gives good estimate of the level of deposited sediment
 Turbidity and re-suspendable sediment methods warranted further investigation
under field conditions
 Further carried these three methods through field studies
 See: International Journal of Sediment Research
An Evaluation of Visual and Measurement-Based Methods for Estimating Deposited
Fine Sediment
Conroy, E.a, Turner, J.N.b, Rymszewicz, A.c, Bruen, M.c, O’Sullivan, J.c, Kelly-Quinn, M.a
a School of Biology and Environmental Science, University College Dublin
b School of Geography, Planning and Environmental Policy, University College Dublin
c UCD Dooge Centre for Water Resources Research, School of Civil, Structural and Environmental Engineering, UCD Earth Institute,
University College Dublin
Study 1: Detection and quantification of a
pollutant - Key Findings

5.  Multiple pressures may be present in river systems including the SILTFLUX
sites
 Need to firstly understand the response to sediment (then consider
combined effects of sediment and other stressors)
 Experimental work - Controlled conditions
 Opportunity to test a range of biological metrics
 Further evaluated in field study
Detecting macroinvertebrate response to
sediment
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6. Study 2: Response to sediment & relationship
between macroinvertebrate metrics and
sediment metrics
Experimental study
 Indoor channels
 Gravel substrate, water and seeded with macroinvertebrates
 Fine sediment added to channels
 Eight treatment levels (0, 5, 10, 30 50, 70, 90, 100% sediment surface cover)
 Four replicates
 Seven days
Measured drift (response) & taxa remaining in
channels
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7. 0
1
2
3
4
5
6
7
8
0 24 48 72 96 120 144
MeanHept.drifting
Control
5%
0
1
2
3
4
5
6
7
8
0 24 48 72 96 120 144
Control
10%
0
1
2
3
4
5
6
7
8
0 24 48 72 96 120 144
MeanHept.drifting
Control
30%
0
1
2
3
4
5
6
7
8
0 24 48 72 96 120 144
Control
50%
0
1
2
3
4
5
6
7
8
0 24 48 72 96 120 144
Time (hours)
Control
90%
0
1
2
3
4
5
6
7
8
0 24 48 72 96 120 144
MeanHept.drifting
Time (hours)
Control
70%
0
1
2
3
4
5
6
7
8
0 24 48 72 96 120 144
Time (hours)
Control
100%
Study 2: Drift response to sediment

8. Study 2: Metrics Tested:
Correlations %EPT and % E abundance with %
sediment surface cover
 Experimental study
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9. Study 2: Relationship between
macroinvertebrate metrics and sediment metrics
 Field study
 % EPT abundance and % EPT richness metrics were most strongly correlated with
sediment surface cover
 % sediment surface cover was better correlated with the biological metrics than
either turbidity or resuspended sediment methods

10. Study 3: Linking localised sediment inputs
with ecological conditions
Cattle access drinking points
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 Eight sites
• four high/good water quality status
• four moderate water quality status
 Two habitats sampled
• mid-channel and
• margins

11. Study 3: Cattle Access – Key findings
 Some evidence of site specific impacts downstream of cattle access points
 Impacts were generally more evident in autumn samples, particularly in
high/good status rivers – due to higher use of access points during summer
 Community structure was altered downstream of cattle access points in 3 out of
the 4 good status rivers and downstream changes in univariate metrics were
observed for all four high/good status rivers
 Two of the four moderate status streams showed downstream changes in
community structure, abundance and richness metrics
 These two moderate status rivers had high or prolonged livestock activity
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12. Study 4: Linking land use with ecological
conditions
Instrumented and intermediate sites
 Quantitative and semi-quantitative macroinvertebrate sampling
 Hydrochemistry and environmental data
 Pasture: Clodiagh and Slaney catchments
• low % pasture < 30% and high % pasture > 30%
 Tillage: Urrin and Glyde catchments
• Low % tillage < 15% and high % tillage > 15%
U/S Control
Site:
Reference
conditions
Q-value ≥ 4
D/S Site:
Defined by
land-use
gradient
Intermediate
sites
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13. Study 4: Land use effects –Key findings
Pasture land use (Clodiagh and Slaney catchments)
 Spring reach-scale samples indicated no significant differences in community
structure between sites with low percentage pasture and those with a high
percentage of pasture in either catchment
 Autumn patch and reach-scale differences in community structure were
reported in both catchments mainly due to increases in tolerant taxa
 Low % pasture sites had very lower abundances of tolerant taxa
 The high % pasture sites pasture had greater abundances of tolerant taxa e.g.
Chironomidae

14. Study 4: Land use effects –Key findings
Tillage land use (Glyde and Urrin catchments)
 Only River Urrin showed significant changes in macroinvertebrate communities
between high and low percentage tillage sites
 Autumn patch and reach-scale indicated increases in tolerant taxa e.g. Glossosoma
spp., Chironomidae and Oligochaeta in the high % tillage sites in the Urrin
 Spring reach-scale samples indicated downstream increase in a number of EPT
taxa together with substantial reductions in abundances of Chironomidae
 This spring increase in EPT was partially due to higher abundances of Seretella
ignita, which is considered to be a pollution-tolerant taxon in the Irish Q-value
metric (Mc Garrigle, 2002)
 The limited or complete lack of differences between sites in the Glyde may be
related to hydromorphological conditions
 Glyde channelised and has low slope

15. Mechanisms involved
Schematic showing the direct and indirect effects of suspended, saltating, and deposited fine sediment on stream
properties (green boxes), their in-stream physical effects (purple boxes) and aquatic biota impacted (orange boxes)

16. Study 5: Macroinvertebrate responses to burial
by sediment
• Three Ephemeroptera
 Baetis rhodani,
 Ecdyonurus insignis
 Rhithrogena semicolorata
• Two Trichoptera
 Hydropsyche siltalai,
 Rhyacophila dorsalis
• Amphipoda
 Gammarus duebeni
• Five different sediment particle sizes
• Two burial depths
• Upland and lowland species
• Body size
 MEASURED EMERGENCE TIMES FOR HEAD & WHOLE BODY
 Video clips

19. Study 5: Macroinvertebrate responses to burial
by sediment burial
 Responses were variable across the species tested
 burial depth > sediment particle class > taxa source
 No detectable effect linked to body size
 Variable responses of taxa from upland and lowland locations. Some upland taxa
taking longer or failing to emerge from burial e.g. Ecdyonurus insignis
 Upland taxa may be more sensitive to sediment effects than lowland taxa (Matthaei
et al., 2006; Connolly and Pearson, 2007; Larsen et al., 2009)
 This may have implications for the development and applicability of proposed
sediment-sensitive biological metrics across large geographical areas

20.  Further analysis of the SILTFLUX data will test the relationship between
the macroinvertebrate metrics and sediment fluxes
 Further mechanistic studies, based on EPT taxa at family and species level,
are required to enhance our understanding of how, and at what level,
pressures such as sediment impact taxa – essential for identification of
indicators and metrics of sediment impact
 Sediment impact remain to be disentangled from other stressor impacts
 At present, EPT metrics fulfil a useful role as general indicators of
ecological degradation in agricultural catchments
 It would also be useful to test the new metric developed by Murphy et al.
(2015) in an Irish context. This will require the collection of data on the
amount of organic sediment in erosional zones (oFSIsp) and the total fines
in depositional zones (ToFSIsp)
Conclusions
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21. 21
Thank you