Biological condition of the Stitt River and L Pieman in relation to the TasWater Rosebery WWTP discharge: Survey of aquatic biota, Autumn 2013. Report to TasWater PE Davies and LSJ Cook August 2013 Freshwater Systems Aquatic Environmental Consulting Service fs fs
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Biological condition of the Stitt River and L Pieman in relation to the
TasWater Rosebery WWTP discharge: Survey of aquatic biota, Autumn 2013.
Report to TasWater
PE Davies and LSJ Cook August 2013
Freshwater Systems AAqquuaattiicc EEnnvviirroonnmmeennttaall CCoonnssuullttiinngg SSeerrvviiccee fs
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Table of Contents
1. Introduction and Aims ................................................................................................ 1
2.1 Field sampling – Stitt River .................................................................................. 5 2.2 Field sampling – Lake Pieman .............................................................................. 7
2.3 Data analysis ....................................................................................................... 11
3. Results: Stitt River ................................................................................................. 12 3.1 Macroinvertebrates ............................................................................................. 12
3.2 Stitt River – Habitat conditions ........................................................................... 16 3.3 Stitt River – Vertebrates ...................................................................................... 16
4. Results Lake Pieman ................................................................................................. 19 4.1 Algae ................................................................................................................... 19
NB ‘Distance from source’ is stream length measured on 1:25,000 map from the head of the
stream drainage.
2.2 Field sampling – Lake Pieman
Benthic macroinvertebrates and benthic algae are collected from the shoreline at 15
MMG sites along the eastern side of the upper Lake Pieman reach upstream and
downstream of the Bobadil discharge point. Three new TasWater sites were established
in 2013 downstream of the MMG sites – one upstream, one downstream and one within
the Stitt River junction arm. Site locations are listed in Table 2 and shown in Figure 2.
Sampling was conducted as follows:
2.2.1 Snag algae
A fixed-area benthic pad scourer (Davies and Gee 1993) was used to sample benthic
algae on snag surfaces, with five sample units taken per location within 30 – 50 cm of the
water surface. Individual sample units were analysed for total chlorophyll-a (by a
modified acetone extraction-spectrophotometric method - APHA 1993). We calculated
mean total chlorophyll-a, corrected for phaeophytin, as a surrogate for algal biomass.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 8
2.2.2 Shore-dwelling benthic invertebrates
Sampling was conducted by kick and sweep net sampling with a standard kick net (250
micron mesh) along a 10 m section of shoreline, with one sample collected per site. The
resulting material was preserved in formalin.
All macroinvertebrate sample material was floated in a saturated calcium chloride
solution, with hand-sorting of the residue. The floated material was then sub-sampled to
20% using the Marchant box-sub-sampler (Marchant 1989). The sub-sample was hand-
sorted under magnification. All fauna were counted and identified to family level, with
the exception of Nematodes, Oligochaetes, Copepoda, Turbellaria, and Acarina which
were not resolved to lower taxonomic levels.
Table 2. Sampling site locations in Lake Pieman. See Figure 2 for map.
Sites 1 to 15 = MMG sites; sites 16 – 18 = TasWater sites. Light grey = location of MMG’s Bobadil discharge to L Pieman; Dark grey = location of Stitt R discharge. Water conductivity at the time of sampling also shown (in micro Siemens/cm).
Site Easting
(GDA 1994) Northing
(GDA 1994) Conductivity
1 376914 5377951 36.0
2 376744 5377727 36.0
3 375237 5377539 35.8
4 376229 5376187 43.5
5 376299 5376097 46.0
6 376396 5376081 38.8
7 376457 5376035 367.0
8 376491 5376003 119.6
9 376535 5375973 73.3
10 376593 5375947 59.0
11 376710 5375746 40.2
12 376765 5375672 39.6
13 376862 5375437 38.9
14 377004 5375113 39.2
15 377197 5374778 38.5
16 377183 5374033 38.9
17 377324 5373793 38.8
18 377142 5373406 39.4
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 9
500m
N
S1
S2S3
S4
S5
Main mine site
Bull Lake
Lagoons
Lagoon
Outflow
Mountain
Ck
Stitt
River
To Lake Pieman Stitt
Falls
500m
NN
S1
S2S3
S4
S5
Main mine site
Bull Lake
Lagoons
Lagoon
Outflow
Mountain
Ck
Stitt
River
To Lake Pieman Stitt
Falls
S0
S6
Figure 1. Map of study sites in the Stitt River catchment.
Note new TasWater monitoring site (S6) added in autumn 2013.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 10
1
2
3
4 5
6
78
910
11 12
13
14
15
16
17
18
Figure 2. Location of sampling sites in Lake Pieman.
Black arrows indicate location of discharges for MMG at Bobadil (northern arrow) and the proposed TasWater WWTP (southern arrow). Sites 1-15 are MMG monitroing sites; sites 16-18 are TasWater sites.
1:25000 map scale, grid squares = 1 km2.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 11
2.3 Data analysis
Macroinvertebrate sample data were analysed to measures of abundance, community
composition and diversity (taxon richness). Taxon richness (number of families) was
derived from each sample. Total abundance data was derived from quantitative samples
only.
AUSRIVAS analysis
All autumn season macroinvertebrate RAP data from the stream sites are entered into the
relevant Tasmanian AUSRIVAS (Australian River Invertebrate Assessment Scheme)
model to derive O/E (observed over expected) scores. O/E scores are derived for data
converted to rank abundance based categories, allowing deviations from reference
condition to be quantified based on changes in ranked relative abundance of taxa within
the sample.
Multivariate analysis
Macroinvertebrate compositional data for all sites was used to derive a similarity matrix
using the Bray-Curtis distance measure, after fourth-root transformation of within-sample
abundances for the autumn season RAP samples (derived by combining riffle and edge
sample data). This measure is used to represent a compositional similarity between
samples, with large values (approaching 100%) representing high similarity (many taxa
in common and with similar relative abundances), and small values (approaching 0%)
representing very low similarity with few taxa in common. This matrix was then
converted into a dimensionless ‘map’ of the similarity of sites surveyed, using the MDS
ordination routine in the Primer-6 software package. This ordination provides a visual
representation of which samples (sites) are most similar and which are dissimilar, with
distances being proportional to the Bray-Curtis similarities, and reveals any disturbance
‘gradients’ in the data or consistent differences in composition between years.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 12
3. Results: Stitt River
The composition of the macroinvertebrate fauna derived from rapid assessment
(AUSRIVAS) sampling in autumn 2013 is shown for riffle and edge habitats in Tables 3
and 4. Data from quantitative (surber) sampling is shown in Table 5.
3.1 Macroinvertebrates
Reference sites:
The fauna of the reference sites in the Sterling (STR1) and upper Stitt River (S0, S1, S2)
sites in autumn 2013 was relatively abundant and diverse, with overall means of 17.5 and
25.5 family–level taxa collected in the AUSRIVAS and quantitative riffle samples
(Tables 3 and 5). A mean of 9.3 families was collected from these sites from edge habitat
AUSRIVAS samples (Table 4).
A mean abundance of 302 individuals per sample was observed in reference site riffle
habitat quantitative samples. This equates to a density of 1697 individuals per square
meter of stream bed – similar to those observed in previous years (e.g. 1611 individuals
per square meter in autumn 2012).
The reference site fauna is dominated by Leptophlebiid mayflies, worms, chironomid
midges, worms, Grypopterygid stoneflies, elmid beetles and hydrobiosid caddis larvae in
riffle habitats (Tables 3 and 5). This ‘clean water’ fauna has remained broadly consistent
in composition since 2004. Several of these groups are sensitive to metals and acid mine
drainage, and are generally absent or severely depressed in abundance when exposed to
pollutants.
Downstream sites:
Plots of the number of taxa for each sampling site are shown in Figure 3 for quantitative
data. Diversity declined downstream from sites S2 to S5 and S6 in quantitative samples
(Figure 3).
Total abundance in quantitative samples was substantially lower at sites S3 to S5 and S6
(Figure 3) relative to reference sites. Abundances of the sensitive taxonomic groups
Leptophlebiidae and Elmidae were moderate to high at Stitt reference sites and declined
markedly in abundance at the most downstream sites (Figure 4, Table 4).
The 2013 autumn O/Erk values for the reference sites S0, S1 and S2 fell within band A
(‘equivalent to reference’), as did sites S3 and S5. O/Erk declined downstream at sites S4
and S6 (Figure 5, Table 6).
O/Erk scores indicate that sites S4 and S6 showed a significant degree of impairment
through changes in relative abundance and loss of macroinvertebrate families (Table 6).
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 13
Table 3. Macroinvertebrate data from RAP (AUSRIVAS) sampling of riffle habitats in the Ring, Stitt and Sterling River catchments, autumn 2013. O/Erk values also shown.
Table 6. Autumn season O/Erk scores for all sites sampled in the Stitt and Sterling River catchments in autumn of 2013. Scores derived using rank abundance data and model, respectively.
Autumn 2013
Stream Site O/Erk Band
Sterling R STR1 0.98 A
Stitt R S0 0.87 A
S1 1.05 A
S2 0.98 A
S3 1.02 A
S4 0.50 B
S5 0.82 A
S6 0.66 B
3.2 Stitt River – Habitat conditions
The three variables of interest with regard to biological impacts – conductivity, % silt and
algal cover - are plotted by site in Figure 13 for autumn 2013. Conductivity was slightly
raised at sites S5 and S6 (see Table 5). Low to moderate levels of fine overlying silt-like
material were observed at site S5. Algal cover was low to moderate at all sites, peaking at
sites S2 and S5-S6 (Figure 6).
3.3 Stitt River – Vertebrates
No platypus or crayfish were observed in the Stitt during the autumn surveys, despite
active searching.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 17
0
200
400
600
0
10
20
30
40
STR1 S0 S1 S2 S3 S4 S5 S6
Tota
l ab
un
dan
ce (per 0
.18 m
2)N
Taxa (
per
0.1
8 m
2)
N Taxa Total Abundance
Figure 3. Trends in taxon richness (of all families) and total benthic macroinvertebrate abundance across study sites in the Stitt (S0 to S6) and Sterling (ST R1) Rivers in autumn 2013, derived from quantitative Surber sample data.
0
50
100
150
200
250
300
0
5
10
15
20
25
STR1 S0 S1 S2 S3 S4 S5 S6
N
Lep
top
hle
bii
da
e (p
er 0
.18
m2)
N G
rip
op
tery
gid
ae
& E
lmid
ae
(per
0.1
8 m
2)
Site
Gripopterygidae Elmidae Leptophlebiidae
Figure 4. Trends in abundance of three key habitat- and water-quality sensitive macroinvertebrate families across study sites in the Stitt (S0 to S6) and Sterling (STR1) Rivers, derived from Surber sample data in autumn 2013. Sites STR1, S1 and S2 are reference sites.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 18
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
STR1 S0 S1 S2 S3 S4 S5 S6
O/E
rk
2013 2012 2011 2010 2009 2008 2007 2006 2005 2004
X
A
B-D
Figure 5. Trends in autumn O/Erk scores for riffle macroinvertebrate
assemblages at study sites in the Stitt (S0 to S5) for 2004 - 2013. External reference site value in the Sterling (STR1) is shown for comparison. Horizontal dashed lines indicate bounds for impairment band A (‘equivalent to reference’) for the autumn riffle model. Band labels X, A, B-D) shown.
0
10
20
30
40
50
60
70
STR1 S0 S1 S2 S3 S4 S5 S6
% o
r m
icro
S/c
m
Site
Conductivity % Algal cover % Silt cover
2013
Figure 6. Water column conductivity, % fine silt cover overlying the substrate and % cover of benthic algae in the Stitt River (S0-S6) and Sterling River (STR1) during autumn 2013 sampling.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 19
4. Results Lake Pieman
4.1 Algae
Mean chlorophyll-a values for each site are shown in Table 8, and mean values are
plotted by site in Figure 7.
Visual inspection of the sites revealed, as in previous years, a marked and dense biofilm
just below the water surface to a maximum of ca. 0.5 - 1 m deep, associated with active
gas bubble production.
Chlorophyll-a values peaked just upstream of the Bobadil discharge point (Figure 7), but
similar in magnitude to those at sites 2 and 14.
The upstream reference sites 1-3 had a low overall mean of 6.70 mg chla/m2 (SD = 1.01),
and an upper 95% confidence limit of 8.71 mg chla/m2. Sites 4 to 6 had a mean
chlorophyll-a value of 4.72 and were more variable (SD = 2.11), with the mean falling
below the reference site upper 95% confidence limit.
Sites within the vicinity of the Bobadil outfall (sites 7 and 9) had very low chlorophyll
levels with a mean of 3.16 chla/m2 compared to reference (and to their 2012 mean of 32.2
chla/m2), with values peaking at 8.06 chla/m
2 at site 7.
Sites 11-15 further downstream, had chlorophyll levels similar to reference, with a mean
of 3.51 mg chla/m2, while the TasWater sites 16-18 had a collective mean value of 2.69
mg chla/m2.
These chl-a results indicate that TasWater sites 16 to 18 did not have enhanced benthic
algal biomass, implying a minimal impact of current Stitt River discharge nutrient levels
on local lake algal production.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 20
Table 8. Mean chlorophyll-a values (as mg/m2) for snag surfaces in Lake Pieman (mean of 5
measurements) in autumn 2013. Shading indicates sites adjacent to Bobadil discharge (light grey) and Stitt R discharge to Lake Pieman (dark grey).
Location 2013
1 6.32
2 7.84
3 5.93
4 2.29
5 5.93
6 5.93
7 8.06
8 2.99
9 1.20
10 0.98
11 2.07
12 4.46
13 2.34
14 7.02
15 1.63
16 2.01
17 3.48
18 2.56
0
2
4
6
8
10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Mea
n B
enth
ic c
hlo
rop
hy
ll-a
Site
Autumn 2013
Figure 7. Distribution of mean chlorophyll-a on snag surfaces in Lake Pieman in autumn (April) 2012, as means of 5 measurements, for each shore site. Arrows indicate locations of Bobadil discharge (grey) and Stitt discharge (black). Values for the three upstream reference sites are shown separately at left.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 21
4.2 Macroinvertebrates
Samples of macroinvertebrates collected from the lake shoreline again contained
substantial numbers of benthic animals and were dominated by Leptocerid caddis larvae,
nematodes and midges (Chironomids) (Table 9).
The total diversity of truly benthic aquatic taxa from all 18 MMG and TasWater shore
sites was moderate at 26 taxa, and fell within the range observed in previous MMG
surveys.
The three TasWater sites contained a total of 24 of these 26 taxa, and were similar only to
the reference sites 2 and 3 in having the most diverse and abundant macroinvertebrate
fauna.
Spatial patterns in macroinvertebrate diversity (number of taxa) and abundance are shown
in Figure 8, for benthic taxa only (taxa living in the water column or on the surface are
ignored in this analysis, as they are highly mobile and not necessarily associated with the
sites sampled).
The upstream reference site samples (sites 1 to 3) had low diversity (mean of 9.0 taxa per
site) and were dominated by worms, and the larvae of midges and Leptocerid caddis
(Table 9).
Samples from TasWater sites (16 – 18) had a mean taxon richness of 13 taxa per site, and
were dominated by the same taxa. Taxon richness peaked at site 17 (the Stitt River
discharge site), and total abundance also showed a local peak at the same site (Figure 8).
The bulk of the peak in abundance in the vicinity of the Stitt River discharge was due to
peaks in abundance of midges (Chironomids) and freshwater worms (Oligochaetae), (see
Figure 9), indicating that these sites were most likely responding to organic nutrient
enrichment.
A similarity in community composition between TasWater sites 16 to 18 and the
reference sites is also shown in the ordination plot (Figure 10), where these sites are
loosely grouped and distinct from the remaining MMG monitoring sites. It is noteable
that sites 17 (Stitt River discharge) and 8 (Bobadil discharge) lie at either end of the site
distribution in this ordination plot, characterised by a shift from high to low abundance
and diversity.
Overall, it appears that sites 17 to 18 have the highest macroinvertebrate diversity and
abundance overall, are most closely related to the reference sites in composition, while
also showing a small response to organic enrichment in the form of greater diversity
combined with enhanced midge and worm abundances.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 22
Table 9. Macroinvertebrate data from eastern shore zone sampling sites in upper Lake Pieman in autumn (April) 2011. Abundances are n
per 20% of 10 m kick sample (approx. n per 0.6 m2 shoreline habitat).
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 23
0
5
10
15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
N B
enth
ic T
ax
a
Site
Autumn 2013
0
50
100
150
200
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
To
tal
Ben
thic
ab
un
da
nce
Site
Autumn 2013
Figure 8. Number and total abundance of benthic taxa per sample of lake edge habitat in Lake Pieman in autumn (April) 2013. Arrows indicate locations of Bobadil discharge (grey arrow) and Stitt River discharge (black arrow). Upstream reference site values are shown at left.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 24
0
20
40
60
80
100
120
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
N C
hir
on
om
idae
Site
Autumn 2013
0
10
20
30
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
N O
ligoch
aet
ae
Site
Autumn 2013
Figure 9. Total abundance of midges (Chironomids) and freshwater worms (Oligochaetae) per sample of lake edge habitat in Lake Pieman in autumn (April) 2013. Arrows indicate locations of Bobadil discharge (grey arrow) and Stitt River discharge (black arrow). Upstream reference site values are shown at left.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 25
Figure 10. MDS ordination of 2013 samples from 18 sites along Eastern shore of Lake Pieman. Sites 1 – 15 = MMG Bobadil outfall impact monitoring sites; sites 16 – 18 = TasWater Stitt River outfall monitoring sites. Light grey hashed ellipse = reference and TasWater site grouping; black dashed ellipse = grouping of remaining MMG sites. Bobadil and Stitt discharge sites indicated in red.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 26
5. Overall Biological Condition
5.1 Stitt River
The lower Stitt is in poor to moderate ecological condition. A moderate degree of impact
on the biota was observed at site S3, downstream of the Bull Lagoon discharge point.
Biological condition is poor further downstream however, with sites S4, S5 and S6 being
in a severely degraded state with low to very low macroinvertebrate densities and
reduced diversity.
Site S6, downstream of the proposed TasWater WWTP, is in an overall poorer state than
sites S5 and S4 upstream, with reduced taxon richness and total abundance, a
substantially reduced number of water quality sensitive macroinvertebrate taxa (caddis,
Leptophlebiid mayflies, beetle larvae) and greater densities of organic-tolerant worms.
It is apparent that site S6 is also suffering from the effects of mine-water related pollution.
The impact of sewage discharge from Bull Lagoon, observable at site S3, is not a major
contributor to biological decline in the lower reaches of the Stitt where biological
condition appears to be largely dictated by historical mining-related declines in water
quality.
Despite these effects, there is a still just a sufficient fauna at both sites S5 and S6 to act as
a basis for future monitoring and detection of any potential impact from the proposed
WWTP discharge.
5.2 Lake Pieman
Overall, it appears that the shoreline of Lake Pieman showed no substantive algal
response to the existing inflow of the Stitt River discharge in autumn 2013, with algal
levels falling well below the upper limit derived from reference site values.
By contrast, the benthic macroinvertebrate response was marked, with substantially
higher total abundance and taxon richness at all three TasWater sites (peaking at site 17).
This response, combined with the relatively high abundances of Chironomids and
freshwater worms, suggests a minor positive supplementation effect of the Stitt river
inflow on the Lake Pieman shoreline fauna. This suggests a stimulatory effect of
enhanced organic/nutrient levels on the near-shore fauna of the lake within the vicinity of
the Stitt inflow.
The observed biological patterns around the Stitt discharge area in Lake Pieman are
currently not of major ecological significance.
We have identified that there is both sufficient benthic fauna and algal biomass to allow
future detection of any effect from the proposed WWTP discharge to the Stitt River on
the lake shore ecosystem.
TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 27
6. References
APHA 1993. Standard Methods for Water and Wastewater Analysis. APHA-AWWA, Vol. 19.,
Princetown USA.
Bowling LC, Steane MS and Tyler PA 1986. The spectral distribution and attenuation of
underwater irradiance in Tasmanian inland waters. Freshwat. Biol. 16:313-335.
Davies AL and Gee JHR 1993. A simple periphyton sampler for algal biomass estimates in
streams. Freshwat. Biol. 30, 47-51.
Davies PE and Cook LSJ 2002. Aquatic bioassessment of the Savage River catchment. 2001
Survey report. SRRP Project 038. Final Report to DPIWE, January 2002. 55 pp.
Davies PE and Cook LSJ 2013. Biological Condition of the Ring and Stitt Rivers: Survey of
aquatic biota, Spring 2012 and Autumn 2013. Final Report to MMG, Rosebery, 33 pp.
Davies PE, Cook LSJ and Sloane T 2004. Biological Condition of the Ring and Stitt Rivers:
Survey of fish and macroinvertebrates, 2003/04. Final Report to Pasminco, 37 pp.
Davies PE, Cook LSJ and Sloane T 2005. Definition of Bobadil discharge mixing zone in Lake
Pieman by in-lake biological sampling. Report to Zinifex Pty Ltd, Rosebery Mine. March
2005. 22 pp.
Davies PE, Cook LSJ and Sloane T 2005a. Biological Condition of the Ring and Stitt Rivers:
Survey of macroinvertebrates, autumn 2005. Final Report to Pasminco, 24 pp.
Davies PE, Cook LSJ and Sloane T 2005b. Biological Condition of the Ring and Stitt Rivers:
Survey of macroinvertebrates, spring 2005. Final Report to Pasminco, 16 pp.
Davies PE, Mitchell N and Barmuta LE 1996. The impact of historical mining operations at
Mount Lyell on the water quality and biological health of the King and Queen River
catchments, western Tasmania, Mount Lyell Remediation R&D Program, Supervising
Scientist Report 118, Office of the Supervising Scientist, Barton ACT.
Marchant R 1989. A subsampler for samples of benthic invertebrates. Aust. Soc. Limnol. Bull. 12,