HUNTER WATER
Fish Distribution Study
Burwood Beach WWTW
301020-03413 – 107
August 2013
Infrastructure and Environment
3 Warabrook Boulevard
Newcastle, NSW 2304 Australia
PO Box 814 NEWCASTLE NSW 2300
Telephone: +61 2 4985 0000
Facsimile: +61 2 4985 0099
www.worleyparsons.com
ABN 61 001 279 812
© Copyright 2013 WorleyParsons
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SYNOPSIS
The aim of the Burwood Beach Fish Distribution study was to assess the abundance, richness and
diversity of reef fish assemblages at reefs with increasing distance from the Burwood Beach outfall in
order to establish whether an impact can be detected and, if so, the gradient of impact with distance
from the outfall. The study results can be used to assess any future impact associated with changes
to the volume and quality of effluent from the outfall.
Two fish census techniques were used; underwater visual census (UVC) and baited remote
underwater video stations (BRUVS). UVC was undertaken on four occasions (December 2011, April
2012, October 2012 and April 2013) at sites within three zones at increasing distance from the outfall:
outfall impact zone (< 50 m), mixing zone (~ 200 m) and reference zone (> 2,000 m). Within each
site, larger mobile fish were counted along four replicate 5 m x 25 m belt transects, and smaller,
cryptic fish species and sea urchins were counted along a parallel 1 m x 25 m belt transect. BRUVS
was undertaken by NSW Marine Parks (Port Stephens) on one occasion (December 2011) at five
locations, with three replicate deployments at each.
This study constitutes the first quantitative surveys of reef fish assemblages at the Burwood Beach
outfall, although there have been quantitative surveys elsewhere in the region, including at the
Boulder Bay outfall. While no quantitative studies of fish have been undertaken at Burwood Beach
outfall in the past, anecdotal evidence suggests that a higher abundance of fish occurs at the outfall
than at nearby rocky reefs.
The UVC data shows higher abundance of reef fish at the outfall sites followed by the mixing zone
and then the reference sites. There was greater fish abundance in the two April surveys than in the
October / December surveys, suggesting a seasonal variation. Univariate statistical analysis found
that there were significant differences in mean abundance between the four surveys and between
zones. In addition, there was a significant effect for the interaction of time by zone which shows that
there were inconsistent trends in fish abundance over the four survey events.
The trends in fish species richness in the UVC results were similar to those for mean abundance, with
higher richness values at the outfall sites followed by the mixing zone then reference sites. However,
as for abundance, small variations existed between survey events. Univariate analysis found that
there were significant differences in richness between sampling events and between zones. In
addition there was a significant interaction between time and zone. This demonstrates that the trend
of richness in different survey zones also differed over the surveys.
The Shannon Weiner Index of species diversity was determined for each site on the UVC data.
Higher species diversity indicates higher biodiversity / biological complexity at a given site / location.
Trends in species diversity were not as consistent as those seen for abundance and richness, with no
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zone having consistently higher or lower diversity. Univariate analysis found significant differences in
species diversity between survey events and zones. In addition, there were significant interactions of
time by zone and also time by site (zone), indicating that the trends were again inconsistent over
sampling events.
Overall, the UVC data showed much greater abundance of fish at the outfall sites. Approximately half
the fish observed were yellowtail. Even so, there was higher abundance of other fish species at the
outfall sites compared to the mixing zone or reference sites. The increase in fish abundance can be
attributed to several factors – the discharge may be a source of food, the outfall structures and the
rising plumes act as fish „attractants‟ and there is a larger area of reef at the outfall sites compared to
the mixing zone or reference sites.
Multivariate analysis of UVC data showed strong spatial and temporal trends. There were significant
differences in reef fish assemblages between sites within single surveys. In addition, when data from
all UVC surveys were analysed together, multivariate analysis indicated that there was a gradient of
impact on reef fish assemblages with distance from the outfall (the abundance of fish was highest at
the outfall and abundance decreased with distance from the outfall). Large temporal variation in
assemblages was also evident. When points on the MDS were represented by survey event or
season (i.e. cool or warm water) strong clustering between survey events and seasons was also
evident. In general, data from the two cool water surveys (December 2011 and October 2012) was
more similar to each other than data from the two warm water surveys (April 2012 and April 2013)
and a clear separation of reef fish assemblages between the cool and warm water seasons was also
observed.
In summary, the UVC results showed an impact of the outfall on fish abundance and richness – there
are more fish at the outfall sites than at the reference sites.
For the BRUVS survey, in contrast to the UVC results, fish abundance was higher at the outfall sites
in comparison to the mixing zone and reference reefs, but no significant difference was found.
Species richness measured using BRUVS data appeared to be lower at the outfall and increased with
increasing distance from the outfall (but no significant differences were found). Species diversity was
highest at the mixing zone sites and lowest at the outfall and northern reference sites. As the BRUVS
study only incorporated one sampling event it is difficult to make conclusive interpretations on the
findings.
No previous studies have quantitatively assessed fish abundance, richness or diversity for fish
assemblages at Burwood Beach. Therefore, no comparisons to previous site specific investigations
could be made. However, the high fish abundances recorded at the Burwood Beach outfall impact
zone sites compared to mixing zone and reference sites are in agreement with anecdotal evidence of
higher fish abundances at the outfall by local commercial and recreational fishermen and Hunter
Water divers. In addition, the UVC trends seen here are consistent with the findings of a number of
previous studies which have found greater abundance of fish at outfall sites.
There were significant differences in the results from the UVC and BRUVS techniques in terms of the
species and numbers of fish recorded. This is not surprising given that they employ very different
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methodologies and were undertaken on different days. The BRUVS data did not indicate a significant
effect of the outfall on fish numbers.
One of the objectives of this study was to make a judgment on the likely impact of future discharges
on reef fish assemblages at Burwood Beach. Burwood Beach WWTW is expected to have increased
flows in the future to accommodate an increasing population. While it is difficult to speculate on future
impacts (considering that the response of ecological communities to increased flows is not
necessarily going to be linear) in general, it would be hypothesised that with increasing future flows it
is likely that fish will continue to be more abundant at the outfall due to increased nutrient outputs.
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Disclaimer
This report has been prepared on behalf of and for the exclusive use of Hunter Water, and is
subject to and issued in accordance with the agreement between Hunter Water and
WorleyParsons. WorleyParsons accepts no liability or responsibility whatsoever for it in respect of
any use of or reliance upon this report by any third party.
Copying this report without the permission of Hunter Water or WorleyParsons is not permitted.
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Internal and Client Review Record
PROJECT 301020-03413 – BURWOOD BEACH FISH DISTRIBUTION STUDY
REV DESCRIPTION ORIG REVIEW WORLEY- PARSONS APPROVAL
DATE CLIENT APPROVAL
DATE
A Draft 1 issued for internal review
G Graham / Dr M Priestley
Dr K Newton 11 Jan 2012
B Draft 1 issued for internal review
Dr K Newton Dr K Stewart 18 Jan 2012
C Draft 2 issued for client review
Dr K Newton / Dr M Priestley
Hunter Water / CEE
23 Jan 2012
D Draft 2 issued for internal review
Dr K Newton / Dr M Priestley
Dr Kim Stewart
24 July 2012
E Draft 2 issued for internal review
Dr M Priestley M Holloway / Dr K Newton
7 Aug 2012
F Draft 2 issued for client review
Dr K Newton Hunter Water / CEE
15 Aug 2012
G Draft 3 issued for internal review
Dr M Priestley / Dr K Newton
M Holloway 10 Nov 2012
H Draft 3 issued for client review
Dr K Newton Hunter Water / CEE
14 Nov 2012
I Draft 4 issued for internal review
Dr M Priestley Dr K Newton / H Houridis
29 May 2013
J Draft 4 issued for client review
Dr K Newton Hunter Water / CEE
27 June 2013
K FINAL DRAFT Dr M Priestley/ Dr K Newton
EPA August 2013
L FINAL REPORT Dr K Newton
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CONTENTS
1 INTRODUCTION ................................................................................................................ 1
1.1 Burwood Beach WWTW ..................................................................................................... 1
1.1.1 Treatment Process ................................................................................................. 1
1.1.2 Environmental Protection Licence Conditions ....................................................... 1
1.1.3 Characteristics of Current Effluent and Biosolids Discharges ............................... 4
1.1.4 Effluent and Biosolids Flow Data ......................................................................... 12
1.1.5 Dilution Modelling / Dispersion Characteristics .................................................... 13
1.2 Burwood Beach Marine Environmental Assessment Program ......................................... 14
1.2.1 Initial Consultation ................................................................................................ 15
1.3 Study Area ........................................................................................................................ 15
1.4 Scope of Works / Study Objectives .................................................................................. 15
1.4.1 Null Hypothesis .................................................................................................... 16
1.5 Review of Previous Studies .............................................................................................. 16
1.5.1 Impacts of Sewage Discharges on Fish Assemblages ........................................ 16
1.5.2 Fish Distribution Studies at Burwood Beach ........................................................ 17
2 METHODS ........................................................................................................................ 19
2.1 Underwater Visual Census (UVC) .................................................................................... 19
2.1.1 Spatial and Temporal Replication ........................................................................ 20
2.2 Baited Remote Underwater Video Stations (BRUVS) ...................................................... 23
2.2.1 The BRUVS System ............................................................................................ 23
2.2.2 Spatial and Temporal Replication ........................................................................ 24
2.3 Data Analysis .................................................................................................................... 26
2.3.1 UVC Data – Fish Abundance, Richness and Diversity ........................................ 26
2.3.2 BRUVS Data – Species Richness and MaxN ...................................................... 27
2.3.3 Statistical Analysis ............................................................................................... 27
3 RESULTS: UNDERWATER VISUAL CENSUS ............................................................... 29
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3.1 Univariate Analysis ........................................................................................................... 29
3.1.1 Abundance of Fish and Sea Urchin Species ....................................................... 29
3.1.2 Species Richness................................................................................................. 34
3.1.3 Species Diversity.................................................................................................. 38
3.2 Multivariate Analysis ......................................................................................................... 41
3.2.1 December 2011.................................................................................................... 41
3.2.2 April 2012 ............................................................................................................. 43
3.2.3 October 2012 ....................................................................................................... 46
3.2.4 April 2013 ............................................................................................................. 48
3.2.5 Overall MDS Analysis .......................................................................................... 50
3.3 Power Analysis ................................................................................................................. 53
4 RESULTS: BAITED REMOTE UNDERWATER VIDEO STATIONS ............................... 55
4.1 Univariate Analysis ........................................................................................................... 55
4.1.1 Fish Abundance ................................................................................................... 55
4.1.2 Species Richness................................................................................................. 57
4.1.3 Species Diversity.................................................................................................. 58
4.2 Multivariate Analysis ......................................................................................................... 59
4.3 Power Analysis ................................................................................................................. 60
5 COMPARISON OF UVC AND BRUVS ABUNDANCE DATA .......................................... 61
6 DISCUSSION .................................................................................................................... 63
6.1 Underwater Visual Census ............................................................................................... 63
6.1.1 Trends in Abundance, Richness and Diversity .................................................... 63
6.1.2 Spatial and Temporal Variation ............................................................................ 64
6.1.3 Common / Abundant Fish Species ...................................................................... 66
6.2 Baited Remote Underwater Video Stations ...................................................................... 68
6.2.1 Trends in Abundance, Richness and Diversity .................................................... 68
6.2.2 Spatial Variation ................................................................................................... 69
6.2.3 Comparison to UVC ............................................................................................. 69
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6.2.4 Common / Abundant Fish Species ...................................................................... 70
7 CONCLUSIONS ................................................................................................................ 71
8 ACKNOWLEDGEMENTS ................................................................................................. 73
9 REFERENCES ................................................................................................................. 74
Figures
Figure 1.1 Location of Burwood Beach WWTW.
Figure 1.2 Burwood Beach WWTW and outfall alignment.
Figure 1.3 Effluent and biosolids flow data for the study period (July 2011 - May 2013).
Figure 2.1 Locations of UVC survey sites.
Figure 2.2 BRUVS setup used by the NSW Marine Parks Authority.
Figure 2.3 Locations of BRUVS deployments (sites).
Figure 3.1 Mean fish abundance for all survey events as recorded by UVC.
Figure 3.2 Photographs of some of the most abundant fish species surveyed by UVC.
Figure 3.3 Mean species richness for all survey events as recorded by UVC.
Figure 3.4 Mean species diversity (Shannon Weiner Index) for each UVC survey event.
Figure 3.5 MDS plot of reef fish assemblages for the December 2011 UVC surveys.
Figure 3.6 MDS plot of reef fish assemblages for the April 2012 UVC surveys.
Figure 3.7 MDS plot of reef fish assemblages for the October 2012 UVC surveys.
Figure 3.8 MDS plot of reef fish assemblages for the April 2013 UVC surveys.
Figure 3.9 MDS plot of reef fish assemblages for all events separated by site.
Figure 3.10 MDS plot of reef fish assemblages for all events separated by survey event.
Figure 3.11 MDS plot of reef fish assemblages for all events separated by season.
Figure 4.1 Mean fish abundance for the December 2011 BRUVS surveys or all sites at Burwood
Beach.
Figure 4.2 Abundance of the most abundant fish species surveyed using BRUVS at each site.
Figure 4.3 Mean species richness for the December 2011 BRUVS surveys for all sites at Burwood
Beach.
Figure 4.4 Mean species diversity (Shannon Weiner Index) for the December 2011 BRUVS surveys
for all sites at Burwood Beach.
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Figure 4.5 MDS analysis of reef fish assemblages for the December 2011 BRUVS surveys for all sites
at Burwood Beach.
Tables
Table 1.1 Load limits for effluent and biosolids discharges.
Table 1.2 Summary of physicochemical, metal/metalloid and organics data in effluent collected by
Hunter Water during 2006 - 2013.
Table 1.3 Summary of physicochemical, metal/metalloid and organics data in biosolids collected by
Hunter Water during 2006 - 2013.
Table 1.4 Effluent and biosolids flow data for the study period (July 2011 – May 2013).
Table 1.5 Classification of zones based on prior effluent dilution modelling.
Table 2.1 GPS co-ordinates and approximate depths of UVC survey sites.
Table 2.2 GPS co-ordinates of BRUVS survey sites.
Table 3.1 Mixed model nested ANOVA results for fish abundance measured by UVC.
Table 3.2 Mixed model nested ANOVA for species richness measured by UVC.
Table 3.3 Mixed model nested ANOVA for species diversity measured by UVC.
Table 3.4 Dissimilarity ranking, as determined by SIMPER and corresponding average abundance (in
brackets) of the fish species that contributed the highest dissimilarity to each survey site in December
2011.
Table 3.5 Dissimilarity ranking, as determined by SIMPER and corresponding average abundance (in
brackets) of the fish species that contributed the highest dissimilarity to each survey site in April 2012.
Table 3.6 Dissimilarity ranking, as determined by SIMPER and corresponding average abundance (in
brackets) of the fish species that contributed the highest dissimilarity to each survey site in October
2012.
Table 3.7 Dissimilarity ranking, as determined by SIMPER and corresponding average abundance (in
brackets) of the fish species that contributed the highest dissimilarity to each survey site in April 2013.
Table 3.8 Overall PERMANOVA analysis of fish assemblages across all survey events.
Table 5.1 Comparison of UVC and BRUVS abundance data for December 2011.
Table 6.1 Effluent and biosolids flow data prior to and during UVC survey months.
Appendices
Appendix 1 – Fish Abundance (MaxN) from the UVC Surveys
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Appendix 2 – Fish Abundance (MaxN) from the BRUVS Surveys
Appendix 3 – Statistical Output: ANOVA and ANOSIM
Appendix 4 – Power Analyses
Abbreviations
ANOSIM Analysis of Similarities
ANOVA Analysis of Variance
BRUVS Baited Remote Underwater Video Stations
CEE Consulting Environmental Engineers
EPL Environmental Protection Licence
MDS Multi-dimensional Scaling
MaxN Maximum number of individual for a species
MEAP Marine Environmental Assessment Program
NSW New South Wales
UVC Underwater Visual Census
WWTW Wastewater Treatment Works
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1 INTRODUCTION
1.1 Burwood Beach WWTW
The Burwood Beach Wastewater Treatment Works (WWTW) is located on the Hunter Central Coast
of New South Wales (NSW), approximately 2.5 km south of the city of Newcastle (Figure 1.1). The
plant treats wastewater from Newcastle and the surrounding suburbs, servicing approximately
185,000 people and local industry. There is an average dry weather flow of 44 million litres of
wastewater (44 ML/d). Over the next 30 years these flows are expected to increase to 55 - 60 ML/d,
even with water conservation measures in place.
1.1.1 Treatment Process
The secondary treatment process at Burwood Beach consists of physical screening to remove large
and fine particulates, biological filtration and activated sludge processing including aeration and
settling stages. Secondary treated effluent from Burwood Beach WWTW is discharged to the ocean
through a multi-port diffuser which extends 1,500 m offshore, with diffusers at a depth of
approximately 22 m (Figure 1.2). Approximately 2 ML/d of activated sludge (i.e. biosolids), which is
surplus to treatment requirements, is also discharged to the ocean via a separate multi-port diffuser
that extends slightly further offshore than the effluent outfall. Both the effluent and biosolids outfalls
have been operating in their current configuration since January 1994.
1.1.2 Environmental Protection Licence Conditions
The Environment Protection Licence (EPL) for Burwood Beach WWTW specifies limit conditions for
the operation of the plant (latest version of licence is January 2012). These conditions provide an
indication of the characteristics of the effluent and biosolids discharged into the ocean. Condition L1
specifies that the operation of the outfall must not cause or permit waters to be polluted (i.e. the
licencee must comply with section 120 of the Protection of the Environment Operations Act 1997).
Condition L2 specifies limits relating to total loads discharged to the ocean (including both the effluent
and biosolids). These limits are provided in Table 1.1. Condition 3 specifies limits to concentrations
of suspended solids and oil / grease in the effluent discharged to the outfall. The three day geometric
mean concentration limit for suspended solids is 60 mg/L and for oil / grease is 15 mg/L. Condition 4
sets volume and mass limits of effluent and biosolids discharged via the outfalls. The limit for effluent
flow rate is 510 ML/d (to allow for higher flows in wet weather) and for biosolids the flow limit is
5 ML/d. Daily monitoring of flow is required.
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Figure 1.1 Location of Burwood Beach WWTW.
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Figure 1.2 Burwood Beach WWTW and outfall alignment.
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Table 1.1 Load limits for effluent and biosolids discharges.
Parameter Load Limits
kg/year kg/day
Total suspended solids 4,717,189 12,924
Biochemical oxygen demand - -
Total nitrogen 778,257 2,132
Oil and grease 341,290 935
Total phosphorus - -
Zinc 3,943 11
Copper 2,080 5.7
Lead 1,472 4.0
Chromium 224 0.61
Cadmium 124 0.34
Selenium 14 0.038
Mercury 9 0.025
Pesticides and PCBs 7 0.019
1.1.3 Characteristics of Current Effluent and Biosolids Discharges
The final treated effluent and biosolids from Burwood Beach WWTW has been monitored by Hunter
Water for physicochemical parameters and a suite of metals/metalloids and organic chemicals. A
summary of this data during the period 2006 - 2013 is provided in Tables 1.2 (effluent) and 1.3
(biosolids) (data provided by Hunter Water 2013).
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Table 1.2 Summary of physicochemical, metal/metalloid and organics data in effluent collected by Hunter Water during 2006 - 2013.
Group Parameter (units) Period N Median Mean Min Max Std
Error 75%ile 90%ile
Physicochemical Suspended solids (mg/L) 2006-13 449 27 33.6
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Group Parameter (units) Period N Median Mean Min Max Std
Error 75%ile 90%ile
Cadmium Cd-ICP (µg/L) 2006-13 59
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Group Parameter (units) Period N Median Mean Min Max Std
Error 75%ile 90%ile
α Chlordane (ug/L) 2006-13 90
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Group Parameter (units) Period N Median Mean Min Max Std
Error 75%ile 90%ile
Methoxychlor (µg/L) 2006-13 90
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Table 1.3 Summary of physicochemical, metal/metalloid and organics data in biosolids collected by Hunter Water during 2006 - 2013.
Group Parameter (units) Period N Median Mean Min Max Std
Error 75%ile 90%ile
Physicochemical
Total solids (%w/w) 2006-13 458 0.41 0.45 0.00 2.42 0.01 0.50 0.67
Volatile solids (%w/w) 2006-13 440 69.12 66.35 20.61 96.72 0.51 72.68 74.60
Ammonium N_Total (mg/L N) 2006-13 440 24.00 25.03 0.01 85.40 0.55 30.13 39.00
Grease – total low range (mg/L) 2006-13 440 153.5 172.0 1.0 841.0 5.5 230.0 328.2
Fluoride (mg/L) 2006-13 3 0.77 0.67 0.42 0.82 0.13 0.80 0.81
Metals / Metalloids
Silver-Ag-AASurnace (µg/L) 2006-13 152 22 23 4 63 1 29 40
Silver Ag-ICP (µg/L) 2006-13 279 11 12 0.5 38 0 15 18
Arsenic As-vga (µg/L) 2006-13 431 14.7 18.33 2.6 130 0.70 19.75 30.5
Cadmium Cd-furnace (µg/L) 2006-13 152 4 5.93 0.5 128 1.04 6 8
Cadmium Cd-ICP (mg/L) 2006-13 279 0.005 0.01 0.005 0.06 0.00 0.01 0.01
Chromium Cr VI-furnace (µg/L 2006-13 152 1 1.00 1 1 0.00 1 1
Chromium Cr_VIi-furnace (µg/L ) 2006-13 279 5 10 5 25 0.00 5 25
Chromium Cr-furnace (µg/L) 2006-13 152 46.5 68.16 1 750 7.41 68.5 105
Chromium cr- ICP (µgLl) 2006-13 279 30 50 5 3200 10 40 70
Copper Cu-furnace (µg/L) 2006-13 152 839 954 125 3930 42.8 1134 1426
Copper Cu-ICP (µg/L) 2006-13 279 830 880 5 3300 20 1000 1300
Mercury Hg- VGA ug/L) 2006-13 431 3.7 3.93 0.005 10.2 0.08 4.8 6.3
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Manganese Mn-furnace (µg/L) 2006-13 152 339 360 33 1270 13.73 446.25 512.5
Manganese -ICP (mg/L) 2006-13 279 0.39 0.41 0.06 1 0.01 0.47 0.57
Nickel Ni-furnace (µg/L) 2006-13 152 40 47.21 13 180 2.49 55 77.7
Nickel Ni-ICP (mg/L) 2006-13 279 0.03 0.04 0.005 0.33 0.00 0.05 0.07
Lead Pb-furnace (µg/L) 2006-13 152 187 224 13 900 11.37 269.25 375
Lead Pb ICP µg/L) 2006-13 279 120 130 10 450 0.01 150 212
Selenium Se-VGA (µg/L)) 2006-13 431 0.1 0.91 0.05 5.9 0.06 1.7 2.7
Zinc Zn (mg/L) 2006-13 152 2.4 3.03 0.78 15.6 0.16 3.515 5.39
Zinc Zn-ICP (mg/L) 2006-13 279 2.2 2.46 0.13 6.9 0.06 2.8 3.7
Organics
Aldrin (µg/L) 2006-13 96 0 0 0 0 0 0 0
α-BHC Bhc-a (µg/L) 2006-13 96 0 0 0 0 0 0 0
β-BHC-b (µg/L) 2006-13 96 0 0 0 0 0 0 0
α Chlordane (ug/L) 2006-13 96 0 0 0 0 0 0 0
Chlordane (ug/L) 2006-13 96 0 0 0 0 0 0 0
λ Chlordane- (µg/L) 2006-13 13 0 0 0 0 0 0 0
Chlorpyrifos (µg/L) 2006-13 96 0 0.003 0 0.239 0.003 0 0
DDT (uµ/L) 2006-13 96 0 0 0 0 0 0 0
DDD (µg/L) 2006-13 96 0 0 0 0 0 0 0
DDE (µg/L) 2006-13 96 0 0 0 0 0 0 0
Diazinon (ug/L) 2006-13 96 0 0 0 0 0 0 0
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Dieldrin (µg/L) 2006-13 96 0 0.006 0 0.315 0.004 0 0
Endosulfan-s (µg/L) 2006-13 96 0 0 0 0 0 0 0
Endrin (µg/L) 2006-13 96 0 0 0 0 0 0 0
HCB (µg/L) 2006-13 96 0 0 0 0 0 0 0
Heptachlor-epoxide (µg/L) 2006-13 96 0 0.0001 0 0.013 0.0001 0 2.8
Heptachlor (µg/L) 2006-13 96 0 0 0 0 0 0 0
Lindane (µg/L) 2006-13 96 0 0 0 0 0 0 0
Malathion (µg/L) 2006-13 96 0 0 0 0 0 0 0
Methoxychlor (µg/L) 2006-13 96 0 0 0 0 0 0 0
Parathion (ug/L) 2006-13 96 0 0 0 0 0 0 0
Total PCBs (µg/L) 2006-13 96 0 0 0 0 0 0 0
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1.1.4 Effluent and Biosolids Flow Data
Effluent and biosolids flow data for the study period was obtained from the Burwood WWTW. A
summary of flow data for the period July 2011 to May 2013 is provided in Table 1.4 and Figure 1.3.
Table 1.4 Effluent and biosolids flow data for the study period (July 2011 - May 2013).
Date
Rainfall (mm)
Secondary Flow (ML)
1
By-Pass Flow (ML)
2
Total Flow (ML)
WAS (ML)
3
July 2011 238.2 2068.14 777.24 2845.38 71.66
Aug 2011 47.8 1775.64 0 1775.64 87.73
Sep 2011 136.0 1731.62 205.9 1937.52 82.86
Oct 2011 161.4 1966.85 301.27 2268.12 94.93
Nov 2011 184.5 2004.51 465.58 2470.09 86.71
Dec 2011 110.8 1825.98 6.37 1832.35 92.83
Jan 2012 53.6 1481.64 22.32 1503.96 93.38
Feb 2012 336.7 2296.60 485.42 2782.02 89.47
Mar 2012 188.0 2083.66 403.74 2487.40 96.36
Apr 2012 174.0 1889.04 306.14 2195.18 88.98
May 2012 26.2 1470.51 0 1470.51 94.01
Jun 2012 188.0 2255.16 373.09 2628.25 95.01
Jul 2012 83.5 1839.45 24.17 1863.62 86.77
Aug 2012 71.0 1704.78 62.22 1767.00 93.44
Sep 2012 16.7 1305.15 0 1305.15 87.82
Oct 2012 13.5 1257.72 0 1257.72 76.17
Nov 2012 44.6 1201.80 0 1201.80 86.92
Dec 2012 114.2 1375.59 52.98 1428.57 98.06
Jan 2013 229.0 1488.58 322.25 1810.83 99.86
Feb 2013 175.0 1855.55 397.11 2252.66 87.39
Mar 2013 241.0 1954.00 629.58 2583.58 112.08
Apr 2013 94.5 1702.77 116.92 1819.69 102.98
May 2013 60.0 1538.14 55.7 1593.84 95.64
Note 1. Secondary Flow is total secondary treated flow through the plant (i.e. Total volume of screened and degritted sewage
into secondary plant over a 24 hour period from 12 midnight and discharged to ocean).
Note 2. By-Pass Flow is total volume of screened and degritted sewage which bypasses the secondary plant over a 24 hour
period from 12 midnight and is discharged to ocean.
Note 3. WAS is the volume of Waste Activated Sludge (i.e. biosolids) pumped from the clarifier underflow over a 24 hour period
from 12 midnight and is discharged to ocean.
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Figure 1.3 Effluent and biosolids flow data for the study period (July 2011 - May 2013).
1.1.5 Dilution Modelling / Dispersion Characteristics
Consulting Environmental Engineers (CEE 2007) calculated a predicted initial dilution for the Burwood
effluent outfall, assuming a discharge rate of 43 ML/d and all duckbill valves in operation. The model
predicted a typical dilution of 219:1 for the effluent field. Allowing for the reduction in dilution due to
the orientation of the diffuser ports parallel to the currents, initial dilution is expected to be in the range
of 180:1 to 220:1. The Water Research Lab (WRL 2007) also carried out field tests of effluent dilution
using rhodamine dye. The dilution of the surface field showed a typical dilution of 185:1. WRL (2007)
reported that the average near-field dilution was 207:1 and the 95th percentile minimum dilution was
78:1. CEE (2010) therefore considers it reasonable to base the environmental risk assessment of the
effects of effluent discharge on an effluent plume near the ocean surface with an initial dilution in the
range of 100:1 to 200:1.
The dilution of a combined biosolids and effluent discharge through the biosolids diffuser was also
calculated (CEE 2007). The CEE model predicted a typical dilution of 475:1 for discharged biosolids if
they rose to the ocean surface, or about 250:1 if trapped by stratification at mid-depth (CEE 2007).
The WRL hydrodynamic computer model showed a median dilution of 300:1, with a minimum dilution
of 100:1 when strong stratification decreases the rise and dilution of the small biosolids plumes, and a
maximum dilution at times of strong currents exceeding 1,000:1 (WRL 2007). The WRL model also
showed the biosolids plume is often trapped well below the surface by the natural stratification of the
ocean water column. WRL field tests of the biosolids plume, with dilution measured using rhodamine
dye, showed a typical dilution of 841:1. WRL reported that the average near-field dilution of the
biosolids plume was 268:1 and the 95th percentile minimum dilution was 205:1, for a submerged
plume (WRL 2007). Based on these results, it is considered reasonable to base the assessment of
the effects of biosolids discharge on two conditions; surface plume with an initial dilution of 300:1 and
submerged plume with an initial dilution of 200:1 (CEE 2010). WRL (1999) modelled the biosolids
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plume at 10 m depth and showed that at the centre of the plume, at about 10 m depth, the dilution
achieved is between 200:1 and 1,000:1. At a distance of 200 m from the diffuser, the dilution
exceeds 1,000:1 and increases further with distance travelled. The diluted biosolids extends to the
south of the diffuser, but would be indistinguishable except by the sensitive techniques used in the
field studies. Based on the field tests and dilution modelling undertaken by WRL (1999, 2007) and
CEE (2007), the following putative mixing zones (Table 1.5) were determined for reporting purposes
only.
Table 1.5 Classification of zones based on prior effluent dilution modelling.
Distance from Diffuser Zones
< 50 m outfall impact zone outfall impact
> 50 - 100 m
putative mixing zone
nearfield mixing zone
> 100 - 200 m midfield mixing zone
> 200 - 2,000 m farfield mixing zone
> 2,000 m reference zone reference
1.2 Burwood Beach Marine Environmental Assessment Program
A number of monitoring programs and studies have previously been undertaken to assess the impact
of treated effluent and biosolids discharge on the marine environment at Burwood Beach (e.g. NSW
Environment Protection Authority (EPA) 1994, 1996; The Ecology Lab 1996, 1998; Australian Water
Technologies (AWT) 1996, 1998, 200, 2003; Sinclair Knight Merz (SKM) 1999, 2000; Ecotox Services
Australasia (ESA) 2001, 2005; BioAnalysis 2006; Andrew-Priestley 2011; Andrew-Priestley et al.
2012). While providing a wealth of data on the marine environment here, it is considered that these
previous studies have not effectively assessed the spatial extent and ecological significance of the
outfalls impact (CEE 2010). The aim of the Burwood Beach Marine Environmental Assessment
Program (MEAP) was to establish the impact footprint of the existing outfall, establish the gradient of
impact with distance to the edge of the outfall and predict the potential footprint of future impacts.
The Burwood Beach Fish Distribution Study aimed to address one of the perceived knowledge gaps
by assessing the spatial and temporal distribution of reef fish assemblages along the effluent
dispersion pathway, as a function of distance from the outfall. Multiple survey sites located at a range
of distances north and south of the outfall were surveyed using a combination of Underwater Visual
Census (UVC) and Baited Remote Underwater Video Stations (BRUVS) techniques, over a two year
period.
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1.2.1 Initial Consultation
Prior to commencement of the Burwood Beach MEAP, details of the proposed sampling program and
survey methodology were discussed with Hunter Water, CEE and the NSW EPA (then the Office of
Environment and Heritage (OEH) on 10 October 2011. This initial consultation was undertaken to
ensure that the proposed MEAP was adequate in addressing the requirements of both the Client
(Hunter Water) and the Regulator (NSW EPA). During this meeting, concerns with the proposed
survey / sampling program were raised and where required the methodology was subsequently
altered accordingly. Consultation was also undertaken with the NSW Marine Parks Authority (Port
Stephens) regarding the MEAP, in particular the Burwood Beach Fish Distribution Study. It was at
this time that the NSW Marine Parks Authority suggested that the BRUVS survey method should be
incorporated into the study to contribute to the data set.
1.3 Study Area
Burwood Beach is located in Newcastle, on the Hunter Central Coast of NSW. It lies to the south of
Merewether Beach and to the north of Dudley Beach (refer to Figure 1.1). The seabed in the vicinity
of the outfall consists of small areas of low profile patchy rocky reef, which is subject to strong wave
action and periodic sand movement, interspersed between large areas of soft sediment (sandy)
habitat. These low profile reefs are emergent approximately 1 m above the sand. Water depth is
approximately 22 m at the outfall diffuser (refer to Figure 1.2). Fine mobile sandy sediments occur in
the gutters and low-lying seabed between reef patches. Extensive sandy beaches with intertidal
rocky reef habitats occur along the shoreline adjacent to the outfall.
1.4 Scope of Works / Study Objectives
Prior to commissioning this study, no quantitative assessment of fish assemblages around the
Burwood Beach outfall had been undertaken, so further studies were undertaken to assess the
relationship between fish abundance, richness and diversity and distance from the outfall diffuser.
Quantitative surveys would also check the anecdotal reports of higher fish abundance around the
outfall.
The objectives of the Burwood Beach Fish Distribution Study were to:
Assess the abundance, species richness and diversity of mobile and cryptic reef fish species
and sea urchins at rocky reef sites around the Burwood Beach outfall, and equivalent reef
sites with increasing distance from the outfall, using UVC and BRUVS methods.
Establish whether the characteristics of reef fish assemblages, including abundance, species
richness and diversity, differ between reefs around the Burwood Beach outfall in comparison
to equivalent reef habitats with increasing distance from the outfall.
Establish the zone in which the outfall discharge has a significant effect on fish populations.
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Extrapolate findings to make a judgment on the likely impact of future discharges on reef fish
assemblages at Burwood Beach.
1.4.1 Null Hypothesis
The null hypothesis of this study was:
There is no significant difference between the abundance, species richness or diversity of reef
fish and sea urchin species at the Burwood Beach outfall when compared to equivalent rocky
reef habitats with increasing distance from the outfall.
1.5 Review of Previous Studies
1.5.1 Impacts of Sewage Discharges on Fish Assemblages
Variables used in the monitoring of fish assemblages, such as species richness and diversity, can be
useful in the detection of impacts, both spatially and temporally (Guidetta et al. 2002). While coastal
fish species have also been described as a suitable indicator of the impacts of sewage effluent on the
receiving environment, the majority of scientific literature in environmental impact assessment
focuses on changes to soft bottom macrobenthic fauna (Warwick 1993). This may be attributed to the
difficulties associated with quantitative sampling of fish which include the ability to capture a dataset
that is representative of both conspicuous mobile and cryptic species (Warwick 1993).
Using fish to monitor environmental impacts can have advantages over assessments that rely on
other fauna assemblages. Fish have a comparatively easy taxonomy (Warwick 1993) and underwater visual methods (e.g. UVC) can be undertaken in-situ. Underwater visual methods are
considered to be a quick and efficient standard method for collecting quantitative fish data (Harmelin-
Vivien et al. 1985. In: Guidetta et al. 2002). However, fish mobility and visible distance may also
present bias in the assessment of anthropogenic impacts at the spatial scales at which many studies
are undertaken (Clarke and Warwick 1994). Therefore, using precise sampling methods and
determining appropriate communities and assemblages as a basis for monitoring are integral for
environmental assessment.
Several authors have detected a negative relationship between fish assemblage attributes (e.g.
abundance, richness and diversity) and / or populations and sewage outfalls. Sewage effluent
discharge has been shown to affect the diversity, abundance, mortality and fecundity of fish, causing
increased susceptibility to infection and parasitic invasion (e.g. Wharfe et al. 1984; Claridge et al.
1986; Gray 1989; Smith and Suthers 1999). Guidetta et al. (2002) assessed the impact of sewage
discharge on fish assemblages in the Mediterranean Sea, Italy. Multivariate Analysis of Similarities
(ANOSIM) demonstrated a significant difference between impact (outfall) and reference locations,
with fish abundance found to be higher at the sewage outfall in comparison to reference locations.
More locally, Smith et al. (1999) investigated spatial and temporal variations in fish assemblages
exposed to sewage in NSW, at the Boulder Bay WWTW. They detected differences between fish
assemblages at outfall and reference sites at the community and individual species levels during a
single sampling event. They observed significant effects of the outfall on the decline of the
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abundance of several common resident species of reef fish, and estimated a decrease of 33% of
species richness at the outfall location.
In comparison, other studies have detected impacts and found that fish abundance and diversity may
be higher at sewage outfalls in comparison to reference locations (e.g. Bell et al. 1982; Grigg 1994;
Hall et al. 1997; Guidetta et al. 2002, 2003). These patterns have been attributed to localised nutrient
enrichment caused by sewage effluent discharge, resulting in a higher density of plankton and
suspended organic matter (i.e. fish food) in the receiving environment of WWTW‟s. For example, Hall
et al. (1997) reported that at the Tyne Estuary in England, total fish abundance rose by 300% at the
WWTW outfall site and this variation was entirely due to small pelagic species. Bell et al. (1982) also
found that there was a higher abundance of planktivorous fish at a sewage outfall in Marseille,
France, in comparison to reference locations. In Hawaii, Grigg (1994) reported that while
planktivorous fishes and particulate organic matter feeders increased around the outfalls, species
richness was low. Similarly, Guidetta et al. (2002) and Guidetta et al. (2003) found (in separate
studies) that fish species richness was approximately 27% lower at a sewage outfall compared to the
reference location, but total fish abundance was 5 to 7 fold higher. Overall, these studies indicate that
while fish abundance may be higher at outfall locations, possibly due to the increased presence of
planktivorous species, species richness may be affected by the discharge of treated effluent.
Effects of sewage outfalls on fish assemblages may vary temporally and spatially. In Sydney, fish
assemblages were assessed before and after the commissioning of three deep-water sewage outfalls
(Otway 1995). While sustained impacts were detected at all three outfalls, they were not consistent
among outfalls and varied in their magnitude and direction, despite similar effluent quality and
treatment processes. The mean number of fish captured by long line increased for a short period
after the Malabar outfall was commissioned, whereas the mean abundance of longspined flathead
(Platycephalus longispinus) trawled near the Bondi outfall exhibited a sustained increase following
commissioning. Episodic impacts were only detected at the Malabar outfall and resulted in short-term
increases in abundance (Otway 1995). The majority of sustained impacts on commercially and
recreationally important fish at the North Head and Malabar outfalls included decreases in
abundance, whereas those at Bondi were mostly increases in abundance. The lack of consistency
and high variability in fish abundance between outfalls resulted in low statistical power to detect
impacts (Otway 1995) and raises doubt over the actual impacts of effluent discharge. This study
indicates the importance of power analysis in quantitative experimental designs to ensure that
adequate replication is employed for the detection of significant differences, should they be present.
1.5.2 Fish Distribution Studies at Burwood Beach
General qualitative descriptions of fish in the vicinity of the biosolids diffuser at Burwood Beach were
provided in an Environmental Monitoring and Performance Review (Hunter Water 2007). Following
the commissioning of the biosolids diffuser in 1994, monthly dive inspections were undertaken.
Divers reported that, “generally fish life in the vicinity of the diffuser has been…plentiful and abundant
throughout the period of inspections” (Hunter Water 2007 pg. 17). Species reported around the
diffuser included kingfish, yellow-tailed pike, blue groper, jewfish, blue morwong, red morwong,
bream, flathead, yellow tail trevally, small squire and wobbegong.
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However, there have been no quantitative assessments of fish assemblages undertaken at Burwood
Beach to date. A quantitative assessment of fish abundance, richness and diversity was therefore
commissioned to address this issue. An experimental design which assesses assemblage measures
at a number of zones with increasing distances from the outfall would check anecdotal reports of
higher fish abundance around the outfall and determine if species richness and diversity are affected.
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2 METHODS
Reef fish assemblages at Burwood Beach were assessed using a combination of two survey
methods; UVC and BRUVS. UVC is conducted in-situ and involves the use of divers to identify and
count fish species along underwater transects of a defined length. This survey method allows larger
mobile and smaller cryptic fish species, as well as larger marine invertebrate species such as sea
urchins, to be targeted in the field. The UVC surveys were undertaken using a gradient sampling
design, with the position of survey sites dependent on bottom type (i.e. the presence of rocky reef
habitat) and the dilution / dispersion modelling (refer to Section 1.1.5).
In comparison, BRUVS uses a remotely deployed (i.e. from a vessel) baited video system to attract
fish present in a given area, which are then captured on underwater video. This method may
therefore be biased towards fish species that are attracted to bait (Willis et al. 2000). The BRUVS
method has been shown to have the potential to attract rare larger predatory fishes and smaller
cryptic species, resulting in reduced sampling effort in comparison to UVC or un-baited video stations
(Watson et al. 2005; Malcolm et al. 2007). BRUVS techniques have been used successfully to
monitor fish recovery and assemblages in marine protected areas (Westera et al. 2003; Willis et al.
2003) and to assess spatial differences in fish assemblages (Stobart et al. 2007). The BRUVS
method is a non-destructive option for describing fish assemblages and is increasingly considered an
essential method for studies located within marine protected areas where conserving sensitive habitat
is a priority (Cappo et al. 2004).
For the current study it was considered that a combination of both survey methods would be ideal to
comprehensively assess fish assemblages at the Burwood Beach outfall and reference reefs.
However, due to the different sampling techniques and site locations required, the results from UVC
and BRUVS are analysed in this report as separate data sets / studies.
2.1 Underwater Visual Census (UVC)
Assessments of fish assemblages using UVC incorporated the following:
In-situ identification of all mobile and cryptic fish and sea urchin species present at the study
sites.
In-situ estimates of the abundance of all fish and sea urchin species present at the study
sites (i.e. fish counts).
An assessment of fish and sea urchin abundance, richness and diversity to determine any
differences in assemblages between reefs with increasing distances from the outfall.
For consistency, all UVC surveys were undertaken by a single observer and reef fish expert, Dr Tony
Ayling (Sea Research, Queensland). All surveys took place between 0900 and 1600 hours in
underwater visibility of > 5 m. A standardised transect length (25 m) and width (5 m) was used. The
observer swam at a height of 1 m to 2 m above the seabed, depending on underwater visibility at the
time of survey (i.e. the observer swam closer to the seabed in poor visibility conditions).
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2.1.1 Spatial and Temporal Replication
TEMPORAL REPLICATION
Underwater Visual Census (UVC) for the Burwood Beach Fish Distribution Study was undertaken four
times over a two year period, during cool and warm water periods, including December 2011 (cool),
April 2012 (warm), October 2012 (cool) and April 2013 (warm). Water temperature data can be found
in the Burwood Beach Water Quality Report (WorleyParsons 2013).
It must be noted that the underwater visibility encountered during the surveys differed quite
substantially between survey sites and events as listed below:
December 2011: 5 m
April 2012: 10 - 15 m
October 2012: 5 m
April 2013: 5 - 15 m
The underwater visibility encountered during all surveys was not prohibitive to the study except for at
one site (reference south) in October 2012 which could not be surveyed. However visibility was
noticeably higher during both the April surveys than in the October / December surveys.
SURVEY ZONES AND S ITES
Three survey zones (outfall impact, mixing and reference zones), located at various distances from
the outfall, were chosen for the UVC fish surveys for reporting purposes (refer to Section 1.1.5 for
further classification of zones). Within each of these zones, two sites were surveyed (one site located
to the north and one site located to the south of the outfall) (refer to Figure 2.1). GPS co-ordinates
and the approximate depths of each of the survey sites are provided in Table 2.1.
All fish surveys were undertaken over similar low profile rocky reef habitat, as is present around the
Burwood Beach outfall. Selection of fish survey sites was based upon the following:
Similarity to the reef type present at the Burwood Beach outfall (i.e. low profile rocky reef
with a lack of urchin barren habitat).
Similarity in depths to those encountered at the outfall (i.e. between 20 to 24 m).
Distance from the outfall (< 50 m, ~ 200 m and > 2,000 m north and south).
The three survey zones and six survey sites for UVC included the following:
1. Outfall impact zone (two sites were surveyed within 50 m of the outfall; north and south).
2. Mixing zone (two sites were surveyed ~ 200 m from the outfall; north and south).
3. Reference zone (two sites were surveyed > 2,000 m north (Merewether) and south
(Redhead) of the outfall).
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Table 2.1 GPS co-ordinates and approximate depths of UVC survey sites.
Zone Survey Site Latitude (S) / Longitude (E) Depth (m)
Outfall impact zone Outfall north 32°58.208' / 151°45.156' 22
Outfall south 32°58.272' / 151°45.119' 22
Putative mixing zone Mixing zone north 32°58.097' / 151°45.259' 21
Mixing zone south 32°58.323' / 151°45.080' 21
Reference Reference north (Merewether) 32°56.849' / 151°46.290' 23
Reference south (Redhead) 33°01.605' / 151°42.980' 23
W ITHIN S ITE REPLICATION
Within each survey site larger mobile fish were counted along four replicate 5 m x 25 m belt transects
while smaller, cryptic fish species and sea urchins were counted along a parallel 1 m x 25 m belt
transect (as per Smith 1989).
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Figure 2.1 Locations of UVC survey sites.
Outfall N
Outfall S Mixing zone S
Reference N
Mixing zone N
Reference S
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2.2 Baited Remote Underwater Video Stations (BRUVS)
Assessments of fish assemblages using BRUVS incorporated the following:
Identification of mobile fish species present at the outfall and reference locations using
remotely analysed video data.
Estimates of the abundance of all fish species present at outfall and reference locations (i.e.
fish counts) using remotely analysed video data.
An assessment of fish abundance, richness and diversity to determine any differences in fish
assemblages between outfall and reference reefs.
BRUVS surveys and video analysis were undertaken by NSW Marine Parks Authority (Port Stephens)
personnel to complement the UVC survey method.
2.2.1 The BRUVS System
Each BRUVS unit consisted of a high definition Canon HG21 (hard drive) video camera (with a wide
angle lens), contained in an underwater housing with an attachment frame, and a bait-pole with a
mesh flat-pack holder containing approximately 800 g of bait (Figure 2.2). The bait used to attract
fish was the Australian sardine or pilchard (Sardinops neopilchardus) which was contained within a
plastic mesh bait bag attached to the end of the bait-pole at a distance of approximately 1.5 m from
each camera. Each unit was attached to a rope and float system linking each BRUVS unit to the
surface. Housings consisted of a high-density polyethylene pipe with flat acrylic end-ports, bolted to
stainless steel frames so that fish could be viewed in a horizontal orientation to the benthos (Malcolm
et al. 2007). The field of view on the video was standardised to approximately 2 m behind the bait.
Figure 2.2 BRUVS setup used by the NSW Marine Parks Authority.
Source: NSW Marine Parks Authority, http://www.mpa.nsw.gov.au (2012).
Video camera
Bait on bait pole
http://www.mpa.nsw.gov.au/
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2.2.2 Spatial and Temporal Replication
TEMPORAL REPLICATION
One BRUVS survey was undertaken at 5 sites at Burwood Beach, with three replicates at each site,
during December 2011. After the initial sampling event, it was decided that no further BRUVS
surveys would be undertaken at this location. This decision was made by Hunter Water considering
advice from the NSW Marine Parks Authority indicating that the regularly poor visibility and the lack of
suitable reef offshore were problematic for this type of survey here.
SURVEY LOCATIONS AND S ITES
BRUVS was used to survey fish in three main zones including the Burwood Beach outfall impact zone
(< 50 m from outfall), mixing zone (> 200 m from the outfall to the north and south) and reference
zone (> 2,000 m from the outfall to the north and south). Five locations were sampled (outfall, north
1, south 1, north 2, south 2). BRUVS survey locations were selected by the NSW Marine Parks
Authority based on standard requirements for this survey method.
Three replicate deployments (i.e. survey sites) were undertaken at each location and these sites were
spaced at least 200 m from each other (a minimum distance of 200 m is required between sites to
avoid attracting and counting the same fish twice). The location of BRUVS deployments at Burwood
Beach are indicated in Figure 2.3 and the GPS co-ordinates of the sites are provided in Table 2.2.
The optimal soak time (i.e. time in which bait and video were deployed) was 30 minutes.
Table 2.2 GPS co-ordinates of BRUVS survey sites.
Zone Location BRUVS sites GPS co-ordinates
Outfall impact zone
Outfall
NC01 32°58.2290 / 151°45.1408
NC02 32°58.2433 / 151°45.0859
NC03 32°58.2894 / 151°45.1424
Mixing zone
North 1
NC04 32°57.4139 / 151°45.5752
NC05 32°57.5420 / 151°45.4998
NC06 32°57.3303 / 151°45.7637
South 1
NC12 32°59.4263 / 151°44.2212
NC13 32°59.5199 / 151°44.1556
NC14 32°59.5812 / 151°44.0597
Reference zone
North 2
NC07 32°57.4895 / 151°46.7046
NC08 32°57.3907 / 151°46.6874
NC09 32°57.1610 / 151°46.5399
South 2
NC15 33°00.4881 / 151°44.7859
NC17 33°00.5838 / 151°44.8236
NC18 33°00.5069 / 151°44.8580
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Figure 2.3 Locations of BRUVS deployments (sites).
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2.3 Data Analysis
Fish abundance, richness and diversity were calculated for both the UVC and BRUVS datasets
separately. A brief definition of each of these parameters is provided below:
Fish abundance: Relates to how common or rare a species is relative to other species in a
defined location or community. Abundance may be calculated for the total number of
individuals of a single species or the total number of individuals of all species present.
Species richness: A measure related to the total number of different species present within
a sample.
Species diversity: Species diversity accounts for the number of species and the evenness
of species giving a measure of the biodiversity and complexity of a population. Species
diversity consists of two components, species richness and species evenness. Species
richness is a simple count of species, whereas species evenness quantifies how equal the
abundances of the species are.
2.3.1 UVC Data – Fish Abundance, Richness and Diversity
Fish abundance, richness and diversity were calculated for the UVC data.
Total abundance (i.e. the total number of all fish species) was calculated for each site. Abundance of
each individual fish species was also determined.
Species richness was calculated for a) the total number of species at a site, and b) the mean number
of different species at a site.
Species diversity was calculated using the Shannon Weiner diversity index. This is calculated using
the equation:
S
H = Σ - (Pi * ln Pi)
i = 1
Where:
H = the Shannon diversity index
Pi = fraction of the entire population made up of species i
S = numbers of species encountered
Σ = sum from species 1 to species S
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2.3.2 BRUVS Data – Species Richness and MaxN
BRUVS video data was analysed remotely (i.e. analysed in the lab following field surveys). The field
of view on the video was standardised to approximately 2 m behind the bait. This was to reduce the
effects of underwater visibility on species richness and relative abundance measures (i.e. maximum
number (MaxN) of individual species).
BRUVS analysis was used to establish the zone in which outfall discharge has a significant effect (if
any) on fish populations. This was achieved through measurements of species richness (number of
different species in a given area) and MaxN (maximum number of individual fish of each species in
the frame at any one time during the 30 minutes, reducing the possibility of counting the same fish
twice). Fishes observed on the BRUVS video footage were counted by NSW Marine Parks Authority
personnel and all fish data was recorded using Event Measure Software (SeaGis).
2.3.3 Statistical Analysis
UNIVARIATE ANALYSIS
Univariate statistical analyses were performed using Statistica Version 7. Species richness (for large
fishes, smaller cryptic fishes and urchin species) and total abundance (MaxN) were examined for
normality, using a normal probability plot and homogeneity of variance, using a means versus
standard deviation test and the data transformed where applicable.
For analysis of UVC results, nested ANOVA was used to test for significant differences (p < 0.05) in
fish abundance, richness and diversity at the zone and site levels. There were eight replicates (i.e.
transects) per zone.
For the BRUVS results, a nested ANOVA could not be used as there was only one site available for
the outfall location (due to site distance requirements). Therefore all sites were compared using a
one-way ANOVA to test for significant differences (p < 0.05).
MULTIVARIATE ANALYSIS
Multi-dimensional scaling (MDS) plots were generated in PRIMER 6 to identify whether differences in
the abundance of fish assemblages were evident among zones. Ordination of parameters was
performed using MDS scaling in PRIMER 6, based on ranked matrices of dissimilarities between
samples, employing the square root transformation and Bray-Curtis distance, as a measure of
dissimilarity. Goodness of fit (stress) was assessed using Kruskal‟s stress formula and compared to
maximum values recommended by Sturrock and Rocha (2000).
POWER ANALYSIS
Power analysis can be used to identify a) the sample size required to detect a given effect size at a
given power and type 1 error rate or, b) the effect size that can be detected with a given sample size,
power and type 1 error rate. Sample size determination is usually most valuable as a design tool
prior to the commencement of an experiment using baseline or past studies to estimate the proportion
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of natural variability. This ensures that experiments are designed to have adequate replication to
detect significant differences between treatments, should differences be present.
However, for the current study no previous quantitative fish survey data were available to undertake
power analysis prior to the survey design so it was decided (during initial consultation with Hunter
Water and the NSW EPA) that power analysis would be undertaken after the first survey round and
changes to the survey methods made at that stage if required.
After a sampling program or survey has commenced the most powerful evidence of adequate sample
replication is the detection of significant differences. In the case that significant differences have
been detected, power analysis will only confirm that sample replication was sufficient to detect the
maximum significant difference between treatments.
Power analysis was undertaken on the first round of fish survey data in order to confirm that adequate
replication was being applied or to help design and modify, where applicable, future fish distribution
studies. A Type I error rate of 5% (0.05) was adopted, a Type II error rate of 20% (0.2, power 80%) is
considered acceptable and an effect size of 50% was adopted. Results of power analysis are
addressed in Section 3.
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3 RESULTS: UNDERWATER VISUAL CENSUS
In the following sections UVC fish data is analysed individually for each survey event, followed by an
overall analysis combining all surveys.
3.1 Univariate Analysis
3.1.1 Abundance of Fish and Sea Urchin Species
The abundance of various fish species and total fish abundance for each UVC survey and site are
detailed in the sections below. Figure 3.1 provides a graphical representation of fish abundance at
each site for each survey event. Images of some of the most common fish species recorded during
the four UVC surveys at Burwood Beach are provided in Figure 3.2.
3.1.1.1 DECEMBER 2011
The outfall impact zone sites had the highest total abundance of fish surveyed (388 fish) when
compared to the mixing zone sites (174 fish) and reference sites (37 fish). In addition, the northern
outfall impact zone site outfall N had considerably higher fish abundance than the southern site,
outfall S (Figure 3.1). Species that were most abundant included yellowtail (Trachurus
novaehollandiae), small scale bullseye (Pempheris compressa), bream (Acanthopagrus australis) and
Australian mado (Atypichthys strigatus) (see Appendix 1 for raw data).
The total combined abundance of fish at the putative mixing zone sites was second highest of the
three zones with 174 individuals. The majority of these fish were recorded from the site mixing zone
N (Figure 3.1). Similar to at the outfall impact zone, yellowtail (T. novaehollandiae) was highest in
abundance, followed by small scale bullseye (P. compressa) and flathead (Platycephalus bassensis).
The total abundance of fish at the reference zone sites was the lowest of all survey zones with just 37
individuals. Reference S had higher total fish abundance than reference N, as can be seen in Figure
3.1. It must be noted here that sand cover over the reef at reference N was considerable during this
December 2011 survey, potentially affecting the fish counts. Yellowtail (T. novaehollandiae) were the
most abundant species, however counts were low for all other species (i.e. < three individuals per
transect).
APRIL 2012
The data for this period showed similar trends to the December 2011 surveys with total fish
abundance being highest in the outfall impact zone (a combined site total of 2347 fish, with 1550
being yellowtail), followed by the mixing zone (combined total of 476 fish) and then the reference
zone (combined total of 189 fish). However, the number of species recorded and total fish
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abundance in each zone was higher during this warm water survey than the first cool water survey
(Figure 3.1).
At the outfall impact zone sites (i.e. outfall N and outfall S), species which were highest in abundance
were similar to in December 2011 and included yellowtail (T. novaehollandiae), spiny sea urchin
(Centrostephanus rodgersii), small scale bullseye (P. compressa) and bream (A. australis) (see
Appendix 1 for raw data). And similar to December 2011, total fish abundance was much higher at
outfall N than outfall S (Figure 3.1).
At the mixing zone sites (i.e. mixing zone N and mixing zone S), small scale bullseye (P. compressa)
was high in abundance, followed by yellowtail (T. novaehollandiae), silver sweep (Scorpis lineolatus)
and bream (A. australis). The northern site, mixing zone N, had higher fish abundance than the
southern site, mixing zone S, as was seen in December 2011 (Figure 3.1).
At the reference zone sites (i.e. reference N and reference S) yellowtail (T. novaehollandiae) had the
highest abundance followed by bream (A. australis), while all other species had an average
abundance of less than three. Total fish abundance was also similar, but slightly higher, at reference
N than reference S (Figure 3.1). Unlike during the December 2011 surveys, sand cover at the
northern reference site was minimal.
Overall, fish abundance was higher during the April 2012 warm water surveys than the previous
December 2011 cool water surveys, however, the trends observed between zones and sites for fish
abundance were quite similar. It should be noted that underwater visibility during the April 2012
survey was considerably higher (~ 10 m to 15 m) than in December 2011 (~ 5 m), which may be a
factor in the UVC results.
OCTOBER 2012
The second cool water UVC surveys (and third survey overall) was undertaken in October 2012.
Data exhibited similar trends to both previous surveys, especially to the first cool water survey of
December 2011. Again, fish abundance was highest in the outfall impact zone (a combined total of
811 individuals), followed by the mixing zone (combined total of 133) then the reference zone
(combined total of 16; but the southern reference site could not be surveyed during this round due to
very poor visibility). Overall, the number of different species and total fish abundance was lower than
in April 2012 but higher than in December 2011 (Figure 3.1).
At the outfall impact zone sites (i.e. outfall N and outfall S) species which were high in abundance
included yellowtail (T. novaehollandiae), small scale bullseye (P. compressa), bream (A. australis),
spiny sea urchin (C. rodgersii) and white ear (Parma microlepis) (see Appendix 1 for raw data).
However, in contrast to the two previous surveys, fish abundance was considerably higher at the
southern outfall impact zone site, outfall S, than at the northern site, outfall N (Figure 3.1).
At the mixing zone sites (i.e. mixing zone N and mixing zone S) bream (A. australis) was highest in
abundance, followed by big scale bullseye (Pempheris multiradiata) and yellowtail
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(T. novaehollandiae). In contrast to the previous two surveys, fish abundance was higher at mixing
zone S than mixing zone N (Figure 3.1).
At the reference zone sites (i.e. reference N and reference S) no individuals were detected at
reference S. This was because underwater visibility during the October 2012 survey at reference S
was too poor for the UVC survey to be undertaken. At reference N, flathead (P. bassensis) had the
highest abundance followed by white ear (P. microlepis). The northern reference site was again
found to have high sand cover during the October 2012 survey as it did in December 2011.
APRIL 2013
Fish abundance during the second warm water survey (and final UVC survey) undertaken in April
2013 showed similar trends to the past sampling events, particularly to the first warm water survey.
Combined fish abundance was highest at the outfall impact zone sites (combined total of 1684
individuals), followed by the mixing zone sites (318 individuals), then the reference zone sites (207
individuals) (Figure 3.1).
At the outfall impact zone sites (i.e. outfall N and outfall S), species that were highest in abundance
included yellowtail (T. novaehollandiae), bream (A. australis), big scale bullseye (P. multiradiata) and
Australian mado (A. strigatus) (see Appendix 1 for raw data). Similar to the findings of the December
2011 and April 2012 surveys, fish abundance was considerably higher at outfall N when compared to
outfall S (Figure 3.1).
At the mixing zone sites (i.e. mixing zone N and mixing zone S) bream (A. australis) was high in
abundance, followed by white ear (P. microlepis), Australian mado (A. strigatus) then big scale
bullseye (P. multiradiata). Fish abundance was similar at mixing zone S and mixing zone N (Figure
3.1).
At the reference zone sites (i.e. reference N and reference S), similar to the mixing zone, bream
(A. australis) was highest in abundance, followed by white ear (P. microlepis), Australian mado
(A. strigatus) and big scale bullseye (P. multiradiata). Fish abundance at the reference zone sites in
April 2013 was similar to that recorded during the first warm water survey in April 2012.
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Figure 3.1 Mean ±SE fish abundance for all survey events as recorded by UVC (Note: the site
reference S was not surveyed in October 2012 due to extremely low visibility). Different
colours indicate different distances (zones) from the WWTW outfall.
December 2011
April 2012
October 2012
April 2013
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Trachurus novaehollandiae (yellowtail)
Acanthopagrus australis (bream)
Pempheris compressa (small scale bullseye)
Atypichthys strigatus (Australian mado)
Platycephalus bassensis (flathead)
Figure 3.2 Photographs of some of the most abundant fish species surveyed by UVC.
Source: The Underwater Photo Gallery, www.daveharasti.com/, David Harasti (2012).
http://www.daveharasti.com/
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ALL SURVEYS
A mixed model nested ANOVA was used to assess whether there were significant differences in
mean fish abundance between the factors of time (December 2011 vs. April 2012 vs. October 2012
vs. April 2013), zone (outfall impact zone vs. mixing zone vs. reference zone) and site (nested within
zone), and to determine if there were any interactions between time by zone or interactions between
time by site (zone) (refer to Table 3.1 for ANOVA results).
Results of the analysis found that there were significant differences between time (i.e. between the
four survey events) and zones and there was also a significant effect for the interaction of time by
zone. This significant interaction was due to inconsistent trends in fish abundance over the four
survey events. The outfall impact zone had significantly higher fish abundance (in comparison to the
mixing zone and / or the reference zone) during the warm water surveys in April 2012 and April 2013,
but this was not consistent for the cool water surveys December 2011 and October 2012. In April
2012, there was significantly higher fish abundance at the outfall impact zone in comparison to the
putative mixing zone and reference zone. During April 2013, there was significantly higher fish
abundance at the outfall impact zone in comparison to the reference zone (Table 3.1).
Table 3.1 Mixed model nested ANOVA results for fish abundance measured by UVC.
Factor Effect (F/R) DF MS F p
Time Fixed 3 14.35 26.67 0.00**
Zone Fixed 2 54.32 82.92 0.00**
Site(Zone) Random 9 0.66 1.22 0.33
Zone*Time Fixed 6 1.53 2.84 0.03*
Site(Zone)*Time Random 27 0.54 0.33 1.00
Error
48 1.63
* p < 0.05, ** p < 0.01. Note: data was log transformed prior to analysis (ln(x+1).
3.1.2 Species Richness
Species richness refers to the number of different species recorded at a given site / location. Total
species richness (i.e. of all four transects per site) and mean species richness (i.e. average of four
transects per site) were measured using data from each UVC survey at the Burwood Beach outfall
impact zone, mixing zone and reference zone sites. Mean species richness data is presented in
Figure 3.3. Species richness for each survey event is discussed in the sections below.
DECEMBER 2011
During the cool water December 2011 UVC surveys species richness (total and mean) was higher at
the outfall impact zone sites than the mixing zone or reference sites. At the outfall impact zone sites
(i.e. outfall N and outfall S) total richness of 20 and 27 fish species was recorded. A total of nine and
20 fish species were present at the mixing zone sites, and at the reference zone sites (i.e. reference
N and reference S) nine and three different fish species were identified. Outfall impact S had higher
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average species richness than outfall impact N, while the mixing zone site, mixing zone S had similar
average species richness to outfall N. Mean species richness was found to be lowest overall at the
reference zone sites (Figure 3.3).
APRIL 2012
The April 2012 data showed a similar trend to December 2011, with overall higher mean species
richness at the outfall impact zone sites, however, mean species richness during this survey was also
high at the northern mixing zone site. Again, mean species richness was found to be lowest at the
reference zone sites (Figure 3.3). At the outfall impact zone sites (i.e. outfall N and outfall S), total
richness of 37 and 26 was recorded, at the mixing zone sites (i.e. mixing zone N and mixing zone S),
37 and seven different fish species were recorded and the total number of species present at the
reference zone sites (i.e. reference N and reference S) was very similar with 16 and 15 species
identified respectively. Overall, total and mean levels of species richness were higher in April 2012
than in December 2011 (Figure 3.3).
OCTOBER 2012
The second cool water UVC survey in October 2012 survey found similar trends to those seen in the
first cool water surveys of December 2011 (Figure 3.3). As for December 2011, outfall impact S had
the highest mean species richness, being higher than outfall impact N, and the mixing zone site
mixing zone S had similar mean species richness to outfall N. Mean species richness was low at
mixing zone N and reference N, while no data could be analysed for reference S due to the extremely
poor visibility during the survey (Figure 3.3). Total species richness at the outfall impact zone sites
(i.e. outfall N and outfall S) was 31 and 54 respectively. At the mixing zone sites, (i.e. mixing zone N
and mixing zone S) seven and 30 different species were recorded and at the reference zone sites (i.e.
reference N and reference S) there were seven different species recorded at reference N but no
individuals were detected at reference S.
APRIL 2013
The final warm water UVC survey in April 2013 found that while mean species richness was higher at
the outfall impact zone, the difference (in comparison to the mixing zone and reference zone) was
much less pronounced than for previous surveys. Mean species richness was similar at the reference
N site and the outfall impact sites (Figure 3.3). Total richness values at the outfall impact zone sites
(i.e. outfall N and outfall S) were 51 and 53 different species respectively. At the mixing zone sites
(i.e. mixing zone N and mixing zone S), 36 and 21 different species were recorded and at the
reference zone sites (i.e. reference N and reference S), 45 and 26 different species were recorded
respectively.
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ALL SURVEYS
A mixed model nested ANOVA was used to assess whether there were significant differences in
species richness between the factors of time (December 2011 vs. April 2012 vs. October 2012 vs.
April 2013), zone (outfall impact zone vs. putative mixing zone vs. reference zone) and site (nested
within zone) and to determine if there were any interactions between time by zone or between time by
site (zone) (refer to Table 3.2 for ANOVA results).
Results of the analysis found that there were significant differences in richness between sampling
events (time) and between zones, in addition there was a significant interaction between time by
zone. This demonstrates that the trend of richness in different survey zones differed over the
surveys. This was due to a significant difference between richness at the outfall impact zone in
comparison to the reference zone during October 2012, but not during the other sampling events.
Table 3.