JUNE 2009
ESTUARINE ECOLOGY PROGRAMME
ENVIRONMENTAL ASSESSMENT OF AHURIRI AND
PORANGAHAU ESTUARIES
Project No
EAM040
Prepared for
HAWKE’S BAY REGIONAL COUNCIL
EMT 09/22
HBRC Plan Number 4145
Prepared by
SHADE SMITH
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Report prepared by: SHADE SMITH MSc (Hons)
Marine Scientist
Reviewed by: JASON STRONG MSc (Hons)
Environmental Scientist
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TABLE OF CONTENTS
Executive summary 1
1.0 Introduction 2
1.1 Site Descriptions 2
1.1.1 Ahuriri Estuary 2
1.1.2 Porangahau Estuary 3
1.2 Statutory Context 3
1.3 Objectives 3
1.4 Recommendations from 2008 4
2.0 Sampling Sites and Methodology 4
2.1 Site and Station Selection 4
2.2 Sediment Composition and Quality 7
2.3 Macroinvertebrate Sampling 8
2.4 Data Analysis 8
2.4.1 Sediment Characteristics 8
2.4.2 Biological Characteristics 9
3.0 Results 9
3.1 Sediment Characteristics 9
3.1.1 Sediment Texture: Present Survey 9
3.1.2 Sediment Texture: Inter-Survey Comparison 10
3.1.3 Sediment Quality: Present Survey 11
3.1.4 Sediment Quality: Inter-Survey Comparison 20
3.1.5 Overview 24
3.2 Biological Characteristics 26
3.2.1 Infaunal Summary Indices: Present Survey 26
3.2.2 Infaunal Summary Indices: Inter-Survey Comparison 28
3.2.3 Infaunal Multivariate Analysis: Present Survey 30
3.2.4 Infaunal Multivariate Analysis: Inter-Survey Comparison 33
3.2.5 Epifaunal Summary Indices: Present Survey 36
3.2.6 Epifaunal Summary Indices: Inter-Survey Comparison 36
3.2.7 Epifaunal Multivariate Analysis: Present Survey 37
3.2.8 Epifaunal Multivariate Analysis: Inter-Survey Comparison 40
3.2.9 Overview 43
4.0 Summary 45
5.0 Conclusion 46
6.0 Recommendations 46
7.0 References 47
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TABLE OF CONTENTS
Apendices
Appendix 1: Sampling Stations 49
Appendix 2: Sediment Data 51
Appendix 3: Infauna Data 56
Appendix 4: Epifauna Data 59
Appenidix 5: Inter-Survey Comparison: PERMANOVA’s, SIMPER’s 61
Appendic 6: Report Limitations 68
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EXECUTIVE SUMMARY
Estuaries represent the downstream receiving environments of the freshwater drainage network and are
sensitive to the same effects of land-use activities as streams and rivers throughout the catchment. In New
Zealand, estuaries are being recognised as the coastal environments most at risk, as they are the
depositional end-point for the accumulative contaminants from the surrounding catchment.
Under the Resource Management Act (1991), Hawke’s Bay Regional Council must establish, implement and
review objectives, policies and methods to promote the sustainable management of the coastal area, and
monitor the effectiveness of plans. The Estuarine Ecology Programme (EEP) was developed as part of the
Coastal Monitoring Strategy to determine and monitor the long-term health and sustainability of Hawke’s
Bay’s estuaries.
As part of the EEP sampling was undertaken at Ahuriri and Porangahau Estuaries in line with the Estuarine
Environmental Assessment and Monitoring: A National Protocol. At each of five sites (four sites within Ahuriri
Estuary, one site within Porangahau Estuary), 12 infaunal cores, 10 surficial sediment samples, 10 sediment
cores were collected, and 10 epifaunal quadrats assessed.
Concentrations of contaminants of concern at all sites are below environmental guidelines designed to
protect ecological values. However, at site AHUD (adjacent to the Tyne Street Drain) concentrations of
trace metals are above relevant regional background levels and zinc is just below guideline values.
There also appears to be an increase in fine sediments, at sites AHUA and AHUB which at site AHUA may be
influencing infaunal communities.
As expected, faunal composition tended to be strongly driven by the sediment composition at each site,
with clear differences evident among the assemblages of infaunal organisms at each of the five sites. .
Groupings were less evident among sites and between years for the epifauna, but differences were
significant.
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1.0 INTRODUCTION
As the interface between land and sea, intertidal, estuarine and fringing coastal habitats are distinctive and
dynamic environments. The animals and plants living in estuaries must contend with harsh physical and
chemical conditions, such as prolonged periods of emersion and immersion, and associated changes in
salinity, temperature and oxygen availability.
In addition to providing valuable habitat for bird roosting, feeding and breeding, and important spawning
and nursery grounds for fish, estuaries also provide the ecological services that help to sustain environmental
quality and integrity. Estuaries not only buffer the effects of land-use extending to the open ocean, but
conversely, also buffer the effects of the ocean on the land. They are productive habitats, have an
important role in water regulation, water quality enhancement, and can assist in the mitigation of erosion
caused by scouring and wave action.
Estuaries represent the downstream receiving environment of the freshwater drainage network, so it is
understandable that they are sensitive to the same effects of land-use activities as streams and rivers
throughout the catchment. In New Zealand, estuaries are being recognised as the coastal environments
most at risk, as they are the depositional end-point for the accumulative contaminants from the surrounding
catchment.
Sedimentation has been identified as having the potential to threaten the health and sustainability of
estuaries, and compromise the ecological values they contain. As land-use has changed, estuaries have
gone from a typical sedimentation regime of approximately 1mm per year, to up to ten times this amount in
some areas (Hume and Swales, 2003). Increased sediment loading can have both sub-lethal and lethal
effects on the animals and plants living in the estuary. An increased level of suspended solids in the water
column increases turbidity, restricting access to light for the plants and thereby restricting photosynthesis
and algal and macrophyte production rates. Increased turbidity can also alter the functional capabilities
of the system from one dominated by visual predators to one dominated by organisms that utilise chemo-
sensory techniques for feeding, and can alter the benthic community from suspension to deposit feeders
(Watling and Norse, 1998). Reproductive condition and feeding rates in filter feeders can be decreased
(e.g. Pecten novaezelandiae – scallop; Boccardia syrtis – polychaete), and increased mortality can occur
in some species (e.g. Macomona liliana – wedge shell) (Nicholls et al, 2002).
In addition to the long-term effects of elevated sediment levels, acute episodic events such as storms can
cause large deposits of sediments in some parts of the estuary. These can bury marine organisms, affecting
access to light, food and oxygen, and result in the accumulation of waste products (Airoldi, 2003). The
biological communities present in marine and estuarine ecosystems are largely driven by the physical
environment, of which the sediment composition plays a significant role. Therefore, changes in the
composition caused by the deposition of fine muds will ultimately cause a change in the ecology of the
area.
Given the importance of estuary ecosystems and the services they provide, and the real risk to the integrity
of the system from the threats they are facing, monitoring of the long-term health and state is required to
ensure that these vital ecosystems are being sustained in a way that will retain these key functions.
1.1 SITE DESCRIPTIONS
1.1.1 Ahuriri Estuary
Formed in the wake of the 1931 earthquake, the Ahuriri Estuary (Te Whanganui-A-Orutu) is located in the
area of the former Ahuriri Lagoon (Figure 2.1). The seismic activity lifted the bed of the lagoon between 1.5
to 3.4 metres, exposing approximately 1300 hectares of land (HDC, HBRC, NCC, and DoC, 1992).
Subsequent drainage and reclamation has reduced the area to its current size of approximately 470 ha of
true estuary, and around 175 hectares of associated wetlands (Cromarty and Scott, 1996).
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The estuary has a tidal exchange of approximately 495 million litres, and seawater to freshwater ratio of
approximately 10:1. Approximately 60% of the estuary drains at low tide (Cromarty and Scott, 1996),
exposing mud, coarse sand and shingle intertidal habitats.
Despite extensive modification, the estuary continues to support a diverse array of flora and fauna,
throughout a range of habitats. It is an important breeding, roosting and feeding area for a number of
water birds, and makes a significant contribution to Hawke’s Bays marine fisheries (Kilner and Ackroyd,
1978). About twenty-nine species of fish use the estuary during some component of their life cycle. Whilst
many (e.g. kahawai, grey mullet, yellow-bellied flounder, stargazer, parore) use the area for feeding,
moving into the estuary on the incoming tide, and retreating back out to sea on the receding tide, around
eleven species of fish also use the estuary as a nursery or spawning ground. These include commercially
important species such as yellow-bellied flounder, grey mullet, sand flounder, common sole, and yellow-
eyed mullet.
Ahuriri Estuary is listed as a Significant Conservation Area under the proposed Regional Coastal Environment
Plan (HBRC, 2006), and a Wildlife Refuge offers protection to areas between the Southern Marsh, Westshore
Lagoon and the estuary from the low level bridge to Pandora Bridge.
1.1.2 PORANGAHAU ESTUARY
At approximately 750 ha in size, Porangahau Estuary is one of the few large estuaries on the north eastern
coast of New Zealand. Situated at the mouth of the Porangahau River, the estuary is the downstream
receiving environment of a catchment dominated by high producing exotic grassland characteristic of
sheep and beef farming. The river-mouth estuary is formed behind a large un-vegetated inshore bar, and
breaks through at one or more locations along the bar to meet the sea.
The estuary and associated dunes and wetlands have been identified as an area recommended for
protection (RAP 22, from RCP, (HBRC, 1999)). The estuary has been recognised for its fisheries values based
on the unique and diverse assemblage of fish species, and constitutes a nationally important fisheries
habitat for whitebait, flounder, mullet and kahawai (Davis, 1987). The adjacent dune provides important
feeding and roosting area for a number of migratory birds (HBRC, 1999), and the estuary provides the only
known breeding site in the region for Caspian terns (Davis, 1987).
Porangahau Estuary is listed as a Significant Conservation Area under the Regional Coastal Plan (HBRC,
1999) and the proposed Regional Coastal Environment Plan (HBRC, 2006).
1.2 STATUTORY CONTEXT
Hawke’s Bay Regional Council has established a long-term Estuarine Ecology Project (Madarasz, 2006) to
provide for a repeated assessment of the estuarine flora and fauna, necessary to determine the state and
health of the estuarine ecosystem, and the effectiveness of Council policy. Under the Resource
Management Act (1991), Hawke’s Bay Regional Council must establish, implement and review objectives,
policies and methods to promote the sustainable management of the coastal area. Council is also
required to monitor the suitability and effectiveness of policy statements and/or plans. The Estuarine
Ecology programme provides the mechanism for this effectiveness monitoring.
1.3 OBJECTIVES
The Estuarine Ecology Project will:
1. Assess the state and health of Hawke’s Bay’s estuarine environments;
2. Assess temporal change in Hawke’s Bay’s estuaries in order to determine optimal monitoring frequency;
and
3. Provide the information necessary for Council to assess the effects of management practises and
policy provisions.
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1.4 RECOMMENDATIONS FROM 2008
Several recommendations were made at the completion of the 2008 monitoring. The following explains
how these recommendations were implemented in 2009.
1. That continued monitoring is undertaken in line with the methodology set out in this report; A C T I O N :
Monitoring was undertaken in March 2009.
2. That heavy metals concentrations in the flesh of shellfish and/or mud snails (sensu Mapua, Nelson) are
assessed at site AHUD; ACTION: This has not as yet been undertaken. However, amphipod toxicity
testing, using sediment from AHUD, conducted in 2008 showed no significant difference in survival
compared to a control.
3. That trace metal concentration on the silt/clay fraction (<63mm), are analysed independently at a
few sites of varying sediment composition to confirm the use of normalised data for relative
differences; ACTION: Three sites at AHUD were also analysed for trace metal concentrations on the
<63mm sediment fraction.
4. That toxicity testing is performed on sediments from site AHUD to identify the actual risk of
contaminants at this site to estuarine fauna; ACTION: Toxicity testing carried out by NIWA.
5. To reduce the sampling frequency for site AHUC from the monitoring programme. This site has been
shown to display similar characteristics to site AHUB and monitoring could be reduced to one in three
years to (or the last year of monitoring if less than a three year period) to track whether this similarity
remains; ACTION: Site AHUC not sampled this year.
6. If budget permits a further depositional site (similar silt/clay content to site AHUD but away from
specific point source discharges) should be added to provide a comparison for site AHUD; ACTION:
Site AHUE identified as having similar mud/silt properties to site AHUD and included in sampling
programme for this year.
7. That the ‘Your Choice’ stormwater programme is continued and the effectiveness monitored.
2.0 SAMPLING SITES AND METHODOLOGY
2.1 SITE AND STATION SELECTION
Sampling was undertaken in line with the Estuarine Environmental Assessment and Monitoring: A National
Protocol (Robertson et al., 2002). Use of the protocol enables the comparison of Hawke’s Bays estuaries
with other estuaries elsewhere in the country, and promotes a robust, scientifically defensible methodology
for estuarine monitoring. Sampling was conducted at low tide at Porangahau on the 10th March and at low
tide at Ahuriri on the 11th and 12th March 2009.
Four sites in the Ahuriri Estuary (sites AHUA, AHUB, AHUD and AHUE) and one in the Porangahau Estuary (site
PORA) were selected to best represent the estuary condition and characteristics within a standardised
benthic habitat, i.e. muddy sand, in the low intertidal zone. Broad scale habitat mapping, conducted by
the Cawthron Institute in June 2005, highlighted areas that meet criteria of the national protocol, and sites
were selected from these areas (Figure 1 and 2). This year the site AHUE was added to the Ahuriri group of
sites, while sampling at the previously surveyed site AHUC was discontinued.
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At each site a 60x30m (where sufficient quantity of habitat allowed) grid was marked out into 12 sections of
equal size. Within each section a randomly selected station was sampled. At each station (12 within each
site), an infaunal and sediment core were taken and an epifaunal/floral quadrat assessed (Figure 3).
Surficial sediment samples and epifaunal quadrats for analysis were only collected at the first 10 sites.
Figures 3 and 4 show the actual location of each sampling station for each site, and GPS coordinates for
each station are included in Appendix 1.
FIGURE 1: AHURIRI ESTUARINE ECOLOGY MONITORING SITES.
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FIGURE 2: PORANGAHAU ESTUARINE ECOLOGY MONITORING SITE.
FIGURE 3: AERIAL PHOTOGRAPHS SHOWING THE LOCATIONS OF SAMPLING STATIONS AT EACH AHURIRI ESTUARY SITE.
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FIGURE 4: AERIAL PHOTOGRAPH SHOWING THE LOCATION OF SAMPLING STATIONS AT THE PORANGAHAU ESTUARY SITE.
2.2 SEDIMENT COMPOSITION AND QUALITY
At each of the 12 stations the sediment profile was examined for qualitative sediment properties and to
determine the depth of the redox discontinuity potential layer (RDPL – the boundary between the
oxygenated and anoxic sediments).
Following visual assessments surficial sediments (top 2cm) were sampled at 10 of the 12 stations using a small plastic scoop and placed in pre-labelled, plastic, re-sealable bags. Samples were refrigerated overnight
and the following day, one chilled sub-sample, of approximately 250g, was sent to the Cawthron Institute,
Nelson for sediment textural, chlorophyll a and Ash Free Dry Weight (AFDW) analysis. Another 250g sub-
sample was sent to Hill Laboratories, Hamilton for trace metal and nutrient concentration analysis.
Sediments were analysed for basic sediment textural composition with particles grouped into 3 size classes; granules (>2mm), sand (63µm – 2mm) and fines/mud (<63µm). The data were standardised to obtain a
distribution of granules, sand and fines/mud totalling 100%. Sediments were also analysed for trace metal
concentrations, with the following tested for; Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu),
Nickel (Ni), Lead (Pb) and Zinc (Zn). Nutrients tested for included Total Nitrogen and Total Recoverable
Phosphorus. Analytical methods used are detailed in Table 1.
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TABLE 1: SUMMARY OF ANALYTICAL METHODS USED FOR SEDIMENT ANALYSES
2.3 MACROINVERTEBRATE SAMPLING
At each station an infaunal core was collected using a circular PVC 130mm (internal diam.) core (total area
0.013m2). Samples were collected by pushing the core into the sediment to a depth of 150mm (Robertson
et al., 2002) and digging down the outside of the core, placing a hand over the bottom and extracting the
core and intact sample. Samples were ejected from the core into a 0.5mm mesh sieve and sediment
gently washed through, leaving infauna on the screen. Samples were then washed into sample jars with
95% Ethanol and fixed in same. After transporting samples back to the lab a few drops of Rose Bengal
solution was added to each sample, and left for several hours to allow samples to uptake the stain.
Samples were then poured into shallow trays and all biological material carefully picked out. The material
was then examined under a dissecting microscope, and all biology enumerated and identified to the
lowest possible taxonomic grouping.
0.25m2 quadrats were also placed on the substratum at the each of the first ten stations at each site and epifauna contained within identified and enumerated.
2.4 DATA ANALYSIS 2.4.1 Sediment characteristics
Spatial differences in sediment characteristics (texture, trace metals, nutrients, organic matter – expressed
as AFDW, and chlorophyll a) between sites in the present survey were explored using one-way ANOVA
(StatSoft, 2004). Differences between sites and years (2006 – present) were explored using a two factor
ANOVA, with the factors being site and year. The assumption of homogeneity of variance for ANOVA was
checked using Levene’s test.
Trace metal results were compared against national sediment quality guidelines (ANZECC, 2000) These guidelines or Interim Sediment Quality Guidelines (ISQG) consist of upper (ISQG-high) and lower (ISQG-low)
thresholds above which biological effects can be expected. Where trace metal concentrations are below
ISQG-low values then adverse biological effects are expected only on rare occasions. Trace metal
concentrations falling between ISQG-low and ISQG-high are expected to cause adverse biological effects
occasionally, while a result above the ISQG-high would be expected to cause adverse biological effects
frequently.
Currently there are no guidelines for assessing the effects of sediment-bound nutrients such as nitrogen or phosphorus, on the environment. If there are no obvious signs of nutrient enrichment at a site it may be
difficult to assess a particular site for the effects of nutrient enrichment. Therefore concentrations of these
nutrients were compared against New Zealand estuarine reference sites (Robertson et al., 2002).
Parameter Method Description
Texture Sieving, gravimetric, Air drying 35°
C overnight
Granules > 2mm
Sand 63µm – 2mm
Fines/mud < 63µm
Metals As,Cd,Cr,Cu,Hg,Ni,Pb,Zn Dry/sieve sample, Digestion
US EPA 200.2
Air dry 35°C/2mm sieve
Nitric/HCl acid digestion, ICP-MS
Total N thermal conductivity detector
(Elementar Analyser)
Catalytic combustion (900°C, O2), separa-
tion
Total Recoverable P USEPA 200.2 Nitric/Hydrochloric acid digestion, ICP-MS
Chlorophyll a NIWA periphyton monitoring
manual
acetone extraction, fluorometric
Organic content (AFDW) APHA 21st Ed. 2540 D+ E (Mod.) Air Dry 60°C/Ignition in muffle furnace 550°
C, 1hr, gravimetric
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2.4.2 Biological characteristics
Benthic infaunal and epifaunal data were compared between sites, and between years. Differences in
abundance, diversity indices, richness and evenness (collectively known as biological summary indicies)
were explored by single or two factor ANOVA (StatSoft, 2004) with post hoc analysis of individual terms by
Tukeys HSD test.
Data were also contrasted using non-metric multidimensional scaling (Kruskal and Wish, 1978) ordination
based on the Bray-Curtis distance matrix in PRIMER v5 (Clarke and Gorley, 2001).
The model was based on permutation of raw data for the fixed factor ‘site’ and or ‘year’. Data were
ln(x+1) transformed before analysis, as this type of transformation scales down the effect of highly abundant
species thus increasing the equitability of the dataset (variance standardisation). The major taxa
contributing to the similarities of each site were identified using analysis of similarities (Clarke and Gorley,
2001; Clarke and Warwick, 1994).
3.0 RESULTS
3.1 SEDIMENT CHARACTERISTICS
3.1.1 Sediment texture: present survey
Visual assessment of Ahuriri cores revealed a high variability in RDPL depths between and within sites (Table
2). This variability was a general reflection of the differing proportions of the mud to sand fractions of the
observed cores from each site. Conversely cores from Porangahau were fairly consistent in both RDPL
depth and constitution with cores deemed to be uniformly mud. In addition, none of the sites at either
estuary showed signs of significant organic enrichment, or noticeable odours associated with the sediment.
TABLE 2: MEAN DEPTH OF THE REDOX POTENTIAL DISCONTINUITY LAYER (RDPL)FOR SITES IN THE AHURIRI (AHU) AND PORANGAHAU (POR)
ESTUARIES (± 1 SE)
Sediment grain size analyses showed significant differences in sediment composition occurred between
sites. Ahuriri Estuary was predominantly characterised by fine sands, whilst Porangahau had a far greater
silt/clay fraction (Figure 5). Inter-site differences were evident among Ahuriri sites, with sites AHUE and AHUD
muddier than sites AHUA and AHUB. At site AHUE it was evident that fine sediment had been depositing on
a historical gravel/shell bank, while at site AHUD a large number of plastic fragments, glass and pieces of foil
were found incorporated throughout sediments. As well as general differences between sites there was
also intra-site differences, with patches of gravel (e.g. at site AHUA) and mud (e.g. at sites AHUB and AHUD)
evident at Ahuriri while sediments at Porangahau were consistent throughout stations sampled.
Site RPDL depth (mm) Observation of sediment matrix
AHUA 38 ± 9 Sand some mud/gravel
AHUB 67 ± 9 Sand some mud
AHUD 25 ± 7 Mud some sand
AHUE 43 ± 13 Mud/sand/shell/gravel
PORA 3 ± 1 mud
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3.1.2 Sediment texture: inter-survey comparison
Statistically significant differences in sediment texture between the 2006 and 2007 surveys and the present
survey were evident in sand and the silt/clay (“fine”) fractions at both site AHUA (F(3, 40)=6.01, p = 0.002 –
sand, F(3, 40)=8.25, p < 0.001 – fines) and site AHUB (F(3, 40)=6.26, p = 0.001 – sand, F(3, 40)=5.94, p = 0.002 –
fines), while at site AHUD there was no difference between years (Figure 6b, 6c). The increasing fines
fraction and corresponding decrease in sand between the initial 2006 survey and the present represents an
average increase of 8.6%w/w and 9.4%w/w in the fine sediments at sites AHUA and AHUB respectively and
an average decrease of 11.6%w/w and 10.0%w/w of sandy sediments at sites AHUA and AHUB respectively.
Because of the relatively small amount of fines at the sites compared to sand, essentially the increase in the
fines fraction represents a doubling of the amount of fine sediments while sand decreased relatively a lot
less, between 11-13%. At site PORA there was a significant difference, being an increase, between the 2007
and present survey in gravels (F(2, 29)=4.26, p = 0.024), while the sand and fines fraction differed significantly
between the 2008 survey and the present, being a decrease (F(2, 29)=3.50, p = 0.043) and increase (F(2,
29)=3.81, p = 0.034) respectively (Figure 6b, 6c).
FIGURE 5: COMPARISON OF SEDIMENT TEXTURE AT STATIONS WITHIN AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARIES (TOP) AND MEAN
PROPORTIONS OF GRAVEL, SAND AND CLAY/SILT (BOTTOM) DURING THE PRESENT SURVEY. ERROR BARS ± 1SE.
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
P1
P2
P3
P4
P5
P6
P7
P8
P9
P10
% w
et weight
0
20
40
60
80
100
Gravel (>2mm)
Sands (<2mm - 63um)
Silt and Clay (<63um)
AHUA AHUB AHUE AHUD PORA
% w
et weight
0
20
40
60
80
100
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FIGURE 6: COMPARISON OF MEAN SEDIMENT TEXTURAL FRACTIONS; A) GRAVEL, B) CLAY/SILT AND C) SAND AT SITES WITHIN AHURIRI (AHU)
AND PORANGAHAU (POR) ESTUARIES FROM ANNUAL MONITORING SURVEYS (2006 – PRESENT). ERROR BARS ± 1S.E.
3.1.3 Sediment quality: present survey
Trace metals
Trace metals were present in the sediments at levels not exceeding ANZECC sediment quality guidelines
(Figure 7). At these levels the contaminant load at each site would rarely be expected to induce adverse
biological effects. It is worthwhile noting however that site AHUD is approaching the ISQG – Low limit for
Zinc.
2006 2007 2008 2009
% C
lay/s
ilt (<63µm
) ±
1SE
0
10
20
30
40
50
2006 2007 2008 2009
% G
ravel (>
2m
m) ± 1
SE
0
5
10
15
20
Site AHUA
Site AHUB
Site AHUC
Site AHUD
Site AHUE
Site PORA
2006 2007 2008 2009
% S
ands (63µm
-2m
m) ± 1
SE
40
50
60
70
80
90
100
A. B.
C.
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FIGURE 7: MEAN TRACE METAL CONCENTRATIONS AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES DURING THE PRESENT
SURVEY (2009). ERROR BARS ± 1 SE, RESULTS EXPRESSED ON A DRY WEIGHT BASIS.
AHUA AHUB AHUE AHUD PORA
Arsenic (mg/kg) +/- se
0
2
4
6
8
10
AHUA AHUB AHUE AHUD PORA
Lead (mg/kg) +/- se
0
5
10
15
20
25
30
35
AHUA AHUB AHUE AHUD PORA
Zinc (mg/kg) +/- se
0
50
100
150
200
250
AHUA AHUB AHUE AHUD PORA
Cadmium (mg/kg) +/- se
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
AHUA AHUB AHUE AHUD PORA
Chro
mium (mg/kg) +/- se
0
10
20
30
40
50
AHUA AHUB AHUE AHUD PORA
Copper (m
g/kg) +/- se
0
5
10
15
20
25
AHUA AHUB AHUE AHUD PORA
Nickel (m
g/kg) +/- se
0
2
4
6
8
10
12
14
ISQG-Low: 1.5mg/kg ISQG- Low: 80mg/kg
ISQG-Low: 65mg/kg ISQG-Low: 21mg/kg
ISQG-Low: 50mg/kg ISQG-Low: 200mg/kg
ISQG-Low: 20mg/kg
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Nutrients
Across all sites within the Ahuriri Estuary sediment phosphorus levels varied between 280–1400mg/kg, with a
mean of 447 ± 31 mg/kg (1SE). At Porangahau, levels varied between 350–450 mg/kg, with a mean of 396 ±
35mg/kg (1SE). Comparing between sites, site AHUD was significantly higher (F(4, 45)=8.87, p < 0.001) in
phosphorus than any other site (Figure 8).
Within the Ahuriri Estuary sediment nitrogen levels were highest at site AHUE, and although not significantly
different to site AHUD they were significantly higher than sites AHUA (p = 0.01) and AHUB (p = 0.04). Across
the estuary nitrogen levels were in general quite low varying between levels below the detection limit
(0.005g/100g) to 0.12g/100g and averaging 0.052 ± 0.004g/100g (1SE). Porangahau recorded the highest
average levels of nitrogen, however as there were no obvious signs of nuisance algal growth at any of the
sites, it is unlikely that sediments were nutrient enriched.
Organic matter and Chlorophyll a
In terms of sediment associated organic matter, as measured by the AFDW of samples, levels in Ahuriri
Estuary ranged between 0.6–3.5%w/w with a mean of 1.96 ± 0.1%w/w (1SE). Levels at Porangahau ranged
between 0.27–3.7%w/w with a mean of 1.63 ± 0.39%w/w (1SE). There was no significant difference between
any of the monitoring sites at either estuary and the levels found were within average levels reported for
coastal Hawke’s Bay sediments (Smith, 2007).
Assessment of sediment associated chlorophyll a provides a measure of the live biomass of the
microphytobenthic community and thus trophic status of a site. It can also be a preliminary indicator of
nutrient enrichment if levels are unusually high. In the current survey levels across sites within the Ahuriri
Estuary varied between 2300–14000mg/m3, averaging 5003 ± 328mg/m3 (1SE) while Porangahau levels
varied between 1800–4500mg/m3, averaging 2910 ± 260mg/m3 (1SE). There was no significant difference
between the Ahuriri sites. However including the Porangahau site in the comparison, it was evident that
Chlorophyll a at PORA was significantly lower than two of the Ahuriri sites AHUA (p = 0.008) and AHUE (p =
0.002).
CLIENT REF: EAM040
ESTUARINE ECOLOGY PROGRAMME
FIGURE 8: MEAN NUTRIENT (N AND P), ORGANIC MATTER (AFDW) AND CHLOROPHYLL A CONCENTRATIONS AT AHURIRI (AHU) AND
PORANGAHAU (POR) ESTUARINE SITES DURING THE PRESENT SURVEY (2009). ERROR BARS ± 1 SE.
Comparison between sites: present survey
To account for differences in sediment composition among sites, sediment data (AFDW, nutrients and
metals) were normalised to 100% of the mud/fines component. Normalisation1 of data allows an accurate
assessment of between site data, and also allows comparison against other Hawke’s Bay and New Zealand
reference estuary sites.
Metals
When normalised for mud/fines content, site AHUD had significantly elevated levels of chromium, copper,
lead and zinc compared to all other Ahuriri sites (all p < 0.001). Moreover, site AHUD was also significantly
higher in arsenic compared to site AHUA (p = 0.036) and significantly higher in cadmium compared to site
AHUB (p = 0.049) Figure 9).
1.Reactive surface properties of fine sediments such as in the silt/clay fraction have been shown to promote preferential adhesion of trace
metals. Therefore, differences in trace metal concentrations between sites may simply reflect differences in the proportion of sediments in
this fraction. Normalising sediment contaminant data allows standardisation of sediment contaminants to sediment composition.
AHUA AHUB AHUE AHUD PORA
Tota
l N
itro
gen (g/1
00g) +/- s
e
0.00
0.02
0.04
0.06
0.08
0.10
AHUA AHUB AHUE AHUD PORA Tota
l R
ecovera
ble
Phosphoru
s (m
g/k
g) +/- s
e
0
200
400
600
800
AHUA AHUB AHUE AHUD PORA
Ash F
ree D
ry W
eig
ht (%
w/w
)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
AHUA AHUB AHUE AHUD PORA
Chlo
rophyll
a (µg/k
g)
0
2000
4000
6000
8000
CLIENT REF: EAM040
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In general the lowest concentrations of trace metals were found at Porangahau, with significant differences
evident in normalised levels of nickel (F(4, 45)=9.04, p<0.001) lower than any of the Ahuriri sites. Furthermore
normalised levels of lead were significantly lower at Porangahau than sites AHUB (p=0.008), AHUD (p<0.001)
and AHUE (p=0.003) while levels of chromium and zinc were significantly lower than sites AHUA, AHUB and
AHUD (all p<0.002) (Figure 9).
In general, with the exception of nickel, all contaminants displayed similar patterns between sites.
Contaminant levels were consistently highest at site AHUD and lowest at site PORA.
In general, many of the normalised trace metal contaminant levels at Ahuriri and Porangahau occur within
the mid-range observed in New Zealand reference estuaries (Table 3), except for site AHUD which was
grouped among the more polluted reference estuaries. Comparing normalised trace metal levels in the
present survey to normalised background levels of Hawke’s Bay estuaries and lagoons site AHUD showed
elevated levels for all trace metals analysed except nickel (Table 3). Furthermore site PORA showed
elevated levels of copper, site AHUE had elevated levels of lead and zinc and all sites reported levels
above derived background levels for arsenic (Table 3).
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FIGURE 9: MEAN TRACE METAL CONCENTRATIONS AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES DURING THE PRESENT
SURVEY (2009) NORMALISED TO 100% MUD/FINES CONTENT. ERROR BARS ± 1 SE, RESULTS EXPRESSED ON A DRY WEIGHT BASIS.
AHUA AHUB AHUE AHUD PORA
Cadmium ± 1SE
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
AHUA AHUB AHUE AHUD PORA
Chro
mium ± 1SE
0
50
100
150
200
AHUA AHUB AHUE AHUD PORA
Copper ± 1SE
0
20
40
60
80
100
AHUA AHUB AHUE AHUD PORA
Nickel ± 1SE
0
10
20
30
40
50
60
AHUA AHUB AHUE AHUD PORA
Lead ± 1SE
0
20
40
60
80
100
120
140
160
AHUA AHUB AHUE AHUD PORA
Zinc ± 1SE
0
200
400
600
800
AHUA AHUB AHUE AHUD PORA
Arsenic ± 1SE
0
10
20
30
40
50
CLIENT REF: EAM040
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To assess the efficacy of normalising whole sediment trace metal levels to 100% fines content (i.e. particles
sized <63mm), an additional analysis of trace metal levels of the fines component was also undertaken at
three stations at site AHUD.
The results indicate that although the normalisation process typically overestimates the true trace metal
levels attached to the <63mm sediment fraction (Figure 10), the ratio concentration of the <63mm trace
metal levels to the normalised trace metal levels, is reasonably consistent across all trace metals (Figure 10),
making it a good estimate of relative concentrations between sites.
FIGURE 10: PLOT SHOWING THE VARIOUS RATIOS OF THE NORMALISED TRACE METAL DATA (ALL SEDIMENT FRACTIONS) TO TRACE METAL
LEVELS ON THE <63MM SEDIMENT FRACTION FOR 3 RANDOMLY SELECTED STATIONS WITHIN SITE AHUD.
Arsenic
Cadmium
ChromiumCopper
LeadNick
elZinc
Ratio N
orm
alis
ed tra
ce m
eta
l le
vels
:63µm
tra
ce m
eta
l le
vels
0.0
0.5
1.0
1.5
2.0
AHUD1
AHUD2
AHUD5
CLIENT REF: EAM040
ESTUARINE ECOLOGY PROGRAMME
SITE
Tota
l
Recovera
ble
Cadm
ium
Tota
l
Recovera
ble
Chro
mium
Tota
l
Recovera
ble
Copper
Tota
l
Recovera
ble
Nic
kel
Tota
l
Recovera
ble
Lead
Tota
l
Recovera
ble
Zinc
Tota
l
Recovera
ble
Arsenic
B
GL
BG
L1
B
GL1
BG
L1
BG
L1
B
GL1
BG
L1
Ah
uriri
AH
UA
20
09
0.23
0
.42
75.88
1
03
.56
31.84
5
4.3
6
46.04
7
3.6
3
48.78
5
4.3
6
303.55
3
04
.70
19.63
1
9.3
4
Ah
uriri
AH
UB
20
09
0.19
0
.47
86.31
1
15
.74
37.49
6
0.7
5
49.12
8
2.2
9
58.68
6
0.7
5
334.94
3
40
.54
24.53
2
1.6
1
Ah
uriri
AH
UD
20
09
1.10
0
.30
171.87
7
3.2
9
80.95
3
8.4
7
35.54
5
2.1
1
121.75
3
8.4
7
616.01
2
15
.64
36.38
1
3.6
8
Ah
uriri
AH
UE 2
00
9
0.20
0
.29
56.42
7
2.6
6
34.58
3
8.1
4
34.54
5
1.6
6
62.86
3
8.1
4
235.04
2
13
.79
21.96
1
3.5
7
Po
ran
-
ga
ha
u
PO
RA
20
09
0.09
0
.15
21.60
3
7.6
2
23.86
1
9.7
4
19.94
2
6.7
4
11.82
1
9.7
4
79.27
1
10
.67
12.84
7
.02
Ah
uriri
Ge
org
es2
0
.67
80
.43
58
.18
46
.92
77
.08
60
1.8
8
3
3.5
1
Ah
uriri
Pu
rim
u2
1.0
2
9
5.5
1
4
0.2
65
.31
55
.92
36
9.3
9
5
1.0
2
Ah
uriri
Ra
il B
rid
ge
2
1.4
1
1
57
.63
55
.08
10
4.5
2
1
09
.04
64
9.7
2
9
8.8
7
Oth
er
NZ
Ota
ma
tea
3
0.7
1
3
6.4
8
2
4.5
6
1
6.7
3
2
0.2
8
6
9.9
8
N
S
Oth
er
NZ
Oh
iwa
3
0.4
9
3
6.8
2
2
0.0
2
1
9.4
16
.92
13
7.8
1
N
S
Oth
er
NZ
Ru
ata
niw
ha
3
1.0
9
2
60
.87
77
.17
14
8.9
1
5
1.0
9
4
07
.61
NS
Oth
er
NZ
Wa
ime
a3
1.2
2
2
75
.97
39
.18
29
5.9
2
3
0.2
17
0.6
1
N
S
Oth
er
NZ
Ha
ve
loc
k3
1.5
7
2
55
.49
56
.02
13
8.7
4
2
9.3
2
2
25
.13
NS
Oth
er
NZ
Av
on
-
He
ath
co
te3
1.8
5
2
88
.89
59
.26
12
2.2
2
1
16
.67
70
9.2
6
N
S
Oth
er
NZ
Ka
iko
rai3
0
.37
17
7.9
4
6
1.7
6
5
7.3
5
1
66
.54
67
7.2
1
N
S
Oth
er
NZ
Ne
w R
ive
r3
5.8
8
6
52
.94
22
3.5
3
2
94
.12
41
.18
10
05
.9
N
S
TABLE 3: COMPARISON O
F M
EAN TRACE M
ETAL LEVELS NORMALISED TO 100% M
UD/FINES CONTENT FOR AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES FROM THE PRESENT
STUDY (2009) TO M
EAN HAWKE’S BAY BACKGROUND LEVELS FROM LAGOON AND ESTUARINE SITES (BGL) NORMALISED TO THE M
UD/FINES CONTENT O
F EACH RESPECTIVE STATION IN
THE PRESENT STUDY. FURTHER C
OMPARISONS INCLUDE N
ORMALISED D
ATA FROM A
PREVIOUS SEDIM
ENT STUDY W
ITHIN THE A
HURIRI ESTUARY A
ND A
RANGE O
F A
VERAGE VALUES
FROM NEW ZEALAND ESTUARINE REFERENCE SITES.
1. (S
tro
ng
, 2
00
5).
2
. (B
en
ne
tt,
20
06
).
3. (
Ro
be
rtso
n e
t a
l.,
20
02
). Sh
ad
ed
c
ells
in
dic
ate
e
lev
ate
d le
ve
ls c
om
pa
red
to
b
ac
kg
rou
nd
le
ve
ls fo
r
Ha
wke
’s B
ay e
stu
arie
s a
nd
la
go
on
s.
CLIENT REF: EAM040
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Nutrients
When normalised to 100% mud content, sediment nitrogen levels across all sites and for both estuaries did
not differ significantly (Figure 11). Comparing sediment phosphorus levels between sites; only a single
significant result was evident, being elevated levels at site AHUD compared to PORA (p = 0.003)(Figure 11).
When compared against New Zealand reference estuaries, levels within Ahuriri lay in the mid range of
values while Porangahau recorded the lowest values among all sites and reference estuaries (Table 4).
Organic matter
Normalised levels of organic matter (AFDW) were not significantly different among Ahuriri sites but between
estuaries PORA was significantly lower than any of the Ahuriri sites (F(4, 45)=8.59, p < 0.001) (Figure 11).
Compared to New Zealand reference estuaries levels of organic matter recorded during the present survey
were ranked in the lower half of the range of results (Table 4).
TABLE 4: COMPARISON OF THE MEAN TOTAL RECOVERABLE PHOSPHORUS (TRP), MEAN TOTAL NITROGEN (TN) AND MEAN ORGANIC MATTER
(AFDW) NORMALISED TO 100% MUD/FINES CONTENT FOR AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES FROM THE PRESENT
STUDY (2009), AND NEW ZEALAND ESTUARY REFERENCE SITES.
1.(Robertson et al., 2002).
SITE TRP (mg/kg) (± 1SD)
TN (mg/kg) (± 1SD)
AFDW (%w/w) (± 1SD)
Ahuriri AHUA 2009 1965 ± 376 2070 ± 918 8.96 ± 2.11
Ahuriri AHUB 2009 2254 ± 858 2507 ± 1438 11.36 ± 4.62
Ahuriri AHUD 2009 2881 ± 2331 2255 ± 832 8.49 ± 3.03
Ahuriri AHUE 2009 1939 ± 647 2672 ± 454 9.38 ± 2.86
Porangahau PORA 2009 857 ± 104 1663 ± 203 2.56 ± 0.81
Other NZ Otamatea1 1117 ± 637 3084 ± 584 10.94 ± 0.26
Other NZ Ohiwa1 1815 ± 1045 3919 ± 1370 13 ± 8.4
Other NZ Ruataniwha1 5193 ± 365 3094 ± 549 13.8 ± 3
Other NZ Waimea1 2241 ± 949 2000 ± 1000 6.2 ± 1.6
Other NZ Havelock1 1754 ± 317 2217 ± 876 8.4 ± 0.8
Other NZ Avon-Heathcote1 6736 ± 1529 6230 ± 2321 20.1 ± 4.7
Other NZ New River1 17397 ± 3036 17104 ± 5576 39.5 ± 9.4
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FIGURE 11: MEAN NUTRIENT (N AND P) AND ORGANIC MATTER (AFDW) CONCENTRATIONS AT AHURIRI (AHU) AND PORANGAHAU (POR)
ESTUARINE SITES, NORMALISED TO 100% MUD/FINES CONTENT. ERROR BARS ± 1 SE.
3.1.4 Sediment quality: inter-survey comparison
Metals
At site AHUA normalised levels of cadmium, copper, and zinc in the present survey are significantly lower
than all other survey results (all p ≤ 0.002) (Figure 12). Similarly at site AHUD normalised levels of chromium
and zinc in the present survey are significantly reduced compared to each survey since the initial 2007
survey (all p ≤ 0.005) (Figure 12).
Site AHUA also exhibited significantly lower levels of chromium, nickel and lead in the present survey compared to the surveys of 2006 (all p ≤ 0.004), 2007 (all p ≤ 0.001), while at site AHUD levels of copper and
lead were significantly lower in the present survey compared to the initial 2007 survey (p = 0.003, p = 0.001)
(Figure 12). At site AHUB normalised levels of all trace metals tested for were in general lower in the present
survey than those reported in the 2006 and 2007 surveys, yet the comparison between the two latest surveys
of 2008/2009 yielded no significant differences (Figure 12).
AHUA AHUB AHUE AHUD PORA
Tota
l N
itro
gen (+/- s
e)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
AHUA AHUB AHUE AHUD PORA
Tota
l R
ecovera
ble
Phosphoru
s (+/- s
e)
0
1000
2000
3000
4000
AHUA AHUB AHUE AHUD PORA
AFD
W (+/- s
e)
0
2
4
6
8
10
12
14
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At PORA normalised levels of copper and chromium are significantly higher in the present survey compared
to the previous two surveys of 2007 (p = 0.04, p = 0.006) and 2008 (both p < 0.001), while cadmium is
significantly higher in the present survey compared to last year (p = 0.04) but not the initial 2007 survey
(Figure 12). Among the other trace metals analysed, there were no significant differences.
Nutrients
Examining the normalised data from all surveys to date sediment nitrogen levels at AHUA and AHUD were
significantly lower in the present survey compared to the previous year (p < 0.001, p = 0.024) but were no
different to the results from the 2006/2007 surveys (Figure 13). Site AHUB showed no significant difference in
nitrogen levels between the 2006/2008 and present surveys but these years were significantly lower than
normalised results from the 2007 survey (all p ≤ 0.02) (Figure 13). Nitrogen levels at site PORA did not differ
significantly between years.
Normalised phosphorus levels at site AHUA and site AHUB have decreased for the second successive year
and although there is no difference between this year and last levels are significantly lower than the initial
2006 survey (p < 0.001, p = 0.017) (Figure 13). At sites AHUD there was no significant difference between
years, while at PORA normalised phosphorus levels were significantly lower in the present survey compared
to last year (p = 0.003).
Organic matter and Chlorophyll a
This was the second year normalised levels of organic matter (AFDW) were lower among sites AHUA and
AHUB. For all Ahuriri sites organic matter was significantly lower in the present survey compared to the 2007
survey (all p < 0.01). At site PORA there has been no change in normalised organic matter levels over time.
Chlorophyll a levels rose for a third successive year at sites AHUA and AHUB (all p < 0.02), while levels at site
AHUD although significantly higher than in 2007 (p = 0.02) were no different to 2008. No significant temporal
difference was detected at site PORA (Figure 13).
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FIGURE 12: COMPARISON OF MEAN ANNUAL (2006 – PRESENT) SEDIMENT TRACE METAL LEVELS NORMALISED TO 100% MUD/FINES CONTENT
AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE MONITORING SITES. ERROR BARS ± 1 SE.
2006 2007 2008 2009
Cadmium ± 1SE
0.0
0.5
1.0
1.5
2.0
2.52006 2007 2008 2009
Chro
mium ± 1SE
0
50
100
150
200
250
300
350
2006 2007 2008 2009
Copper ± 1SE
0
20
40
60
80
100
120
1402006 2007 2008 2009
Nickel ± 1SE
0
20
40
60
80
100
120
140
2006 2007 2008 2009
Lead ± 1SE
0
50
100
150
200
250
2006 2007 2008 2009
Zinc ± 1SE
0
200
400
600
800
1000
1200
1400
1600
2008 2009
Arsenic ± 1SE
10
15
20
25
30
35
40
45
50
Site AHUA
Site AHUB
Site AHUD
Site AHUC
Site AHUE
Site PORA
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FIGURE 13: COMPARISON OF MEAN ANNUAL (2006 – PRESENT) SEDIMENT NUTRIENT AND ORGANIC MATTER LEVELS NORMALISED TO 100%
MUD/FINES CONTENT AND NON-NORMALISED CHLOROPHYLL A LEVELS AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE MONITORING
SITES. ERROR BARS ± 1 SE.
2006 2007 2008 2009
AFD
W ±
1SE
0
5
10
15
20
25
302006 2007 2008 2009
nitro
gen ±
1SE
0.0
0.2
0.4
0.6
0.8
1.0
2006 2007 2008 2009
Chl. a ±
1S
E
0
2000
4000
6000
8000
Site AHUA
Site AHUB
Site AHUD
Site AHUE
Site PORA
2006 2007 2008 2009
phosphoru
s ±
1SE
0
1000
2000
3000
4000
5000
6000
7000
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3.1.5 Overview
Site AHUA
• Second shallowest RPD layer (oxygenated layer) among Ahuriri sites
• Predominantly sandy sediment but increasing fines fraction over time (doubling of fines fraction since
2006)
• Low levels of trace metals, with lower and lower levels recorded over successive years.
• No apparent nutrient enrichment, and lower in phosphorus than in initial 2006/2007 surveys and lies in
the mid range for nutrients (total N, total P) compared to other New Zealand estuaries.
• Organic matter low and further decreasing over time while Chlorophyll a levels increasing over time.
Site AHUB
• Deepest RPD layer among Ahuriri sites
• Highest sand content, but increasing in fines (doubling of fines fraction since 2006).
• Present levels of trace metals significantly lower compared to initial 2006, 2007 survey results.
• No apparent nutrient enrichment, phosphorus levels also decreasing over time, while nitrogen is more
variable.
• Overall nutrient levels lie in the mid range of values compared to other New Zealand estuaries.
• Organic matter low and further decreasing over time while Chlorophyll a levels increasing over time.
Site AHUD
• Shallowest RPD layer among Ahuriri sites
• Highest mud content among Ahuriri sites, no significant change in composition over time. Numerous
fragments of plastic incorporated with sediments.
• Moderate to high levels of trace metals, especially zinc, but all below ANZECC ISQG-low guidelines,
and levels decreasing with each successive survey.
• Highest trace metal levels among all Ahuriri sites with levels lying in the upper (i.e. more polluted) range
compared to other New Zealand estuaries and exceeding background levels for Hawke’s Bay
estuarine and lagoon sites.
• No apparent nutrient enrichment and no significant difference in nutrient levels compared to initial
2006, 2007 surveys.
• Presently, organic matter significantly lower than 2007, 2008 surveyed levels, while chlorophyll a
generally increasing over time, but significantly different to 2007 levels only.
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Site AHUE
• First year of monitoring at this site.
• Second shallowest RPD layer among Ahuriri sites.
• Sediment mostly muddy sand with patches of a gravely shell pan beneath the surface sediments
across the site.
• Low levels of trace metals, but normalised levels of lead and zinc are elevated compared to
normalised background levels for Hawke’s Bay estuaries and lagoons.
• Highest nitrogen and organic matter levels among Ahuriri sites.
• Overall nutrient levels lie in the mid range of values compared to other New Zealand estuaries.
Site PORA
• Shallowest RDP layer in either estuary
• Sediments comprised of a high proportion of fines with a significantly higher level of fines in the present
survey compared to last year.
• Lowest normalised levels of trace metals among all sites, but normalised levels of copper elevated
compared to normalised background levels of Hawke’s Bay estuaries and lagoons.
• Lowest normalised nutrient (N and P) and organic matter levels among all sites, including other New
Zealand estuaries.
• Low levels of chlorophyll a and generally very little variation between years.
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3.2 BIOLOGICAL CHARACTERISTICS
3.2.1 Infaunal summary indices: present survey
A complete list of benthic infaunal data from the present survey is included in Appendix 3.
Total number of individuals (N) at Ahuriri sites ranged between 3 and 134 core-1, averaging 29.6, while at
Porangahau N ranged between 5 and 26 core-1, averaging 13.6. For a list of the highest contributing spe-
cies to the N of each site see Table 6.
The most abundant species among Ahuriri sites was the cockle, Austrovenus stutchburyi, accounting for ap-
proximately 36% of all individuals counted. On average site AHUE recorded the highest cockle abundance
(23.7 ± 5.3 (1SE) core-1), followed by site AHUA (12.1 ± 3.5 core-1), site AHUB (5.5 ± 2.1 core-1) and site AHUD
(3.7 ± 0.9 core-1. Of those individuals found at sites AHUA, AHUB and AHUE a large proportion (43 – 45%)
were new recruits, while at site AHUD the proportion of new recruits was less than 1%. For the purposes of
this study new recruits are defined as identifiable individuals that have entered the population, and are rep-
resented here as individuals ≤5mm shell length. Examining the size frequency distribution of cockles at the
various Ahuriri sites it is evident that a continuum of recruitment success occurs between sites, with the pat-
tern of recruitment mirroring that of abundance, i.e. site AHUE recording the highest number of recruits, fol-
lowed by site AHUA, site AHUB and finally site AHUD, which had virtually no recruitment (Figure 14). There is
also evidence of a number of size cohorts emerging across all sites, and particularly at sites AHUE and AHUA
(Figure 14).
Overall the six most numerous taxa among Ahuriri sites, in decreasing order, were, cockles, the spionid poly-
chaete worm, Aonides trifida, the estuarine limpet, Notoacmea helmsi, wedge shell, Macomona liliana,
mud crab; Helice crassa, and the polychaete worm Nicon aestuariensis (Appendix 3). Collectively, these six
taxa accounted for approximately 83% of all the individuals counted.
At site PORA the most abundant species was the anthozoan anemone Edwardsia sp. followed by the spi-
onid polychaete, Scolecolepides sp., crane-fly (Erioptera) larvae, and nereid polychaete Nicon aestuarien-
sis. Collectively these species accounted for approximately 76% of all individuals counted.
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FIGURE 14: SIZE – FREQUENCY PLOTS OF AUSTROVENUS STUTCHBURYI (COCKLES) FROM AHURIRI (AHU) ESTUARINE MONITORING SITES.
0 5 10 15 20 25 30
frequency
0
10
20
30
40
50
AHUA
0 5 10 15 20 25 30
frequency
0
10
20
30
40
50
AHUB
0 5 10 15 20 25 30
frequency
0
10
20
30
40
50
AHUD
shell length (mm)
0 5 10 15 20 25 30
frequency
0
10
20
30
40
50
AHUE
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Number of taxa (S), or species diversity in each core from the present survey ranged from 3 – 9 with an
average of 5.9 (site AHUA), 2 – 10 with an average of 6.7 (site AHUB), 3 – 6 with an average of 4.1 (site
AHUD), 3 – 12 with an average of 6.8 (site AHUE) and 2 – 6 with an average of 4.7 (site PORA) (Figure 15b)
The Shannon-Weiner diversity index (H’) is a measure of the likelihood that the next individual will be the
same species as the previous individual, the higher the number the more diverse the sample. In the present
survey site AHUB had the highest average H’ followed by site AHUA, PORA, AHUD and finally AHUE (Figure
15c).
Pielou’s evenness (J’) is a measure of the similarity of the abundances of different species in a group or
community, and the nearer values are to 1 the more even abundances are among species. In the present
survey the highest average value for evenness occurred at site AHUB (0.83), followed by site PORA (0.77),
site AHUA (0.71), and site AHUE (0.64) (Figure 15d).
Margalef’s Richness (d) is a measure of biodiversity based on the number of species, adjusted for the
number of individuals sampled, with values increasing with the number of species and decreasing with
relative increases in number of individuals. In the present survey site AHUB had the highest average d,
followed by AHUE, AHUA, PORA and lastly AHUD (Figure 15e).
3.2.2 Infaunal summary indices: inter-survey comparison
Analysing all previous survey data on abundance, or number of individuals (N), at site AHUA it is evident that
following a significant decrease in numbers between the 2006/2007 surveys numbers have remained
relatively constant (Figure 15a). At site AHUB N has increased significantly in the present survey compared
to results from both the 2007/2008 surveys but not compared to 2006 (Figure 15a). Site AHUD has seen no
significant change in N between last year and the present but remains significantly higher than the initial
2007 result (Figure 15a). At PORA N has not differed significantly between any of the annual surveys (Figure
15a).
Between years significant differences in the number of taxa (S) occurred at sites AHUB and PORA only
(Figure 15b). The difference in S at site AHUB was between the present survey and the 2007 survey, with this
year being the second annual increase in S. At site PORA the difference stemmed from the low number of
taxa recorded there in the initial 2006 survey. Since 2007 however there has been no change in S at site
PORA.
Similar to the differences observed for S, the temporal comparison for H’ shows the only significant
differences occurred at sites AHUB and PORA, with the present survey result for S higher than the 2007 result
(site AHUB) and the 2006 result lower than all successive results (site PORA) (Figure 15c).
In terms of J’ there has been a significant decrease at sites AHUA and AHUD, with J’ lower in the present
survey at site AHUA compared to the previous year and site AHUD lower in the present survey compared to
the initial 2007 (Figure 15d). At site PORA the present survey result for J’ was no different to any of the
previous three annual surveys however the 2007/2008 results were significantly elevated compared to the
initial 2006 survey result (Figure 15d).
The only significant difference between years and within sites for d was at site PORA where results in the
2007/2008 and present surveys were elevated compared to the initial 2006 survey (Figure 15e).
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FIGURE 15: PLOTS COMPARING MEANS OF A) INDIVIDUAL ABUNDANCE, B) NUMBER OF TAXA, C) SHANNON-WEINER DIVERSITY INDEX, D)
PIELOU’S EVENNESS AND E) MARGALEF’S RICHNESS OF BENTHIC MACROINFAUNA FROM ANNUAL MONITORING SURVEYS (2006 – PRESENT) AT
ESTUARINE MONITORING SITES WITHIN THE AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARIES. ERROR BARS ± 1SE
2006 2007 2008 2009
Mean #
of ta
xa (S)
0
2
4
6
8
10
2006 2007 2008 2009
Mean #
of in
divid
uals (N)
0
10
20
30
40
50
60
2006 2007 2008 2009
Mean S
hannon-W
ein
er Divers
ity Index (H')
0.0
0.4
0.8
1.2
1.6
2.0
A. B.
C.
Site AHUA
Site AHUB
Site AHUC
Site AHUD
Site AHUE
Site PORA
2006 2007 2008 2009
Mean M
arg
ale
f's R
ichness (d)
0.0
0.5
1.0
1.5
2.0
2006 2007 2008 2009
Mean P
ielo
u's E
venness (J')
0.0
0.2
0.4
0.6
0.8
1.0
D.
E.
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3.2.3 Infaunal multivariate analyses: present survey
Multivariate analysis of infaunal data allows a comparison between sites, and years in multidimensional
space. Similarities in species abundance between sites and years are expressed on a two dimensional
plane called a multi-dimensional scaling (MDS) plot. The plot comparing infaunal communities between
Ahuriri sites and the Porangahau site in the present survey shows that they can indeed be separated out
(Figure 16 and Appendix 3). A permutational multivariate analysis of variance confirmed the spatial
variation (Table 5) observed in the MDS plot while pair-wise a posteriori comparisons revealed that each site
was significantly different from every other site (p = 0.04). A species correlation plot and SIMPER analysis
identify the species associations that account for these observed differences in community structure
between sites and are shown in Figure 17 and Table 6. These analyses show a number of key species
primarily driving the community variability; Edwardsia sp. (site PORA), Macomona liliana (sites AHUA and
AHUB), and Helice crassa (sites AHUD and AHUE) (Figure 17 and Table 6).
Examining the community structure at each site, it is evident that generally site PORA is distinct from Ahuriri
sites, the exceptions being stations P1 and P8 from which Edwardsia sp. was absent (Figure 16). Species
contributing most to the observed assemblage included; Erioptera larvae, Scolecolepides sp., and
Edwardsia sp. (Table 6). This association is illustrated on the left of the species correlation plot (Figure 17).
At sites AHUD and AHUE, the infaunal community was characterised primarily by Austrovenus stutchburyi,
Nicon aestuariensis, and Helice crassa (Table 6). Despite the similarities in community composition a clear
difference between the sites is evident with the common occurrence of Notoacmea helmsi at site AHUE
accounting for a large part of the differentiation (Figure 16). This limpet was found attached to the many
old cockle and wedge shells within the sediment matrix at sites AHUE and AHUB. The other important
difference between AHUD and AHUE was the relative abundance of Austrovenus stutchburyi at site AHUE
compared to site AHUD.
Infaunal community structure at sites AHUA and AHUB were more similar to one another than to sites AHUD
and AHUE but were nonetheless distinct and also more variable than sites AHUD and AHUE (Figure 16).
However in general the community assemblage at sites AHUA and AHUB could be characterised by the
Austrovenus stutchburyi, Aonides trifida, and Macomona liliana association (Table 6).
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FIGURE 16: METRIC MDS PLOT OF BENTHIC MACROINFAUNA DATA FROM THE PRESENT (2009) SURVEY AT AHURIRI (AHU) AND PORANGAHAU
(POR) ESTUARINE MONITORING SITES. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON BRAY-
CURTIS DISSIMILARITIES.
TABLE 5: PERMANOVA RESULTS EXAMINING THE EFFECT OF SITE (AHUA – PORA) ON ESTUARY INFAUNA. ALL DATA WERE TRANSFORMED
(LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC)
INDICATES THE MONTE CARLO P-VALUE.
-2 -1 0 1 2
-2
-1
0
1
2
A1
A2A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
B1B2
B3
B4
B5B6
B7
B8
B9
B10
B11B12
E1
E2
E3
E4E5
E6
E7
E8
E9E10E11
E12
D1
D2
D3D4
D5
D6
D7D8
D9
D10
D11
D12
P1
P2
P3P4
P5P6
P7
P8
P9
P10
P11
P12
Site AHUAA1
Site AHUBB1
Site AHUEE1
Site AHUDD1
Site PORAP1
Stress 0.19
Source df SS Mean Square F-Value P (perm) P (MC)
Site 4 58796.6 14699.2 8.95 0.0017 0. 0.0017
Residual 55 90297.1 1641.8
Total 59 149093.7
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FIGURE 17: PLOT SHOWING CORRELATIONS BETWEEN INFAUNAL SPECIES ABUNDANCES AND MDS AXES FROM PREVIOUS PLOT AT AHURIRI
AND PORANGAHAU ESTUARINE MONITORING SITES DURING THE PRESENT SURVEY (2009).
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Edwardsia sp.
Nemertea
Cominella
Diloma subro
Notoacmea
Zeacumantus sub
Arthritica
Austrovenus
Macomona
Aonides trifida
Prionospio sp.
Scolecolepides
Heteromastus
Erioptera larva
Armandia
Nicon aestua.
Mysidacea
Amphipoda
Halicarcinus v.
Helice crassa
Elminius modes.
Paraonid
Scolelepis sp.
Onuphis Auck.
Lumbrinereis sp
Nematode
Halicarcinus w.Crab megalopae
Isopoda
Harpact copepodPeronaea g.
Nucula spp.
Amphibolidae
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TABLE 6: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES WITHIN AHURIRI (AHU) AND PORANGAHAU
(POR) ESTUARIES (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 90% OF CONTRIBUTING SPECIES.
3.2.4 Infaunal multivariate analyses: inter-survey comparison
Sites AHUA and PORA show distinct grouping indicating apparent temporal variation in community
composition while at sites AHUB and AHUD temporal variability is less evident (Figure 18a, 18b, and Figure
19a, 19b). Although 2D stress values for all MDS plots range between 0.17 and 0.22 indicating reasonably
high levels of distortion in the data as represented in the MDS plot, PERMANOVA results confirm differences
between years for all sites (all p < 0.01 – Appendix 5). Pair-wise a posteriori comparisons between years
(within sites) identified significant differences in community structure between each annual survey at sites
AHUA and PORA (all p < 0.01), while at sites AHUB and AHUD although most years differed significantly to
one another (all p < 0.05) there were some years where community structure did not differ significantly (e.g.
between 2006/2007 for site AHUB, and between 2007/2008 for both sites AHUB and AHUD).
Site Species Av. abund Av. Sim Sim/SD Contrib % Cum%
AHUA
(av. sim.
42%)
Austrovenus stutchburyi 9.08 14.89 1.32 35.65 35.65
Macomona liliana 4.67 10.4 1.05 24.89 60.54
Helice crassa 1.58 3.77 0.59 9.02 69.57
Aonides trifida 6.58 3.7 0.4 8.86 78.43
Edwardsia sp. 1.08 3.63 0.81 8.69 87.12
Nemertea 2.25 2.38 0.49 5.7 92.82
AHUB
(av. sim.
42%)
Macomona liliana 5.42 8.84 1.11 21.18 21.18
Notoacmea helmsi 9.75 8.17 1.02 19.57 40.75
Austrovenus stutchburyi 4.75 7.28 1.14 17.42 58.17
Aonides trifida 10.08 6.23 0.97 14.92 73.1
Nicon aestuariensis 1.67 3.47 0.7 8.32 81.41
Prionospio sp. 3 2.62 0.65 6.27 87.68
Heteromastus filiformis 3 2.37 0.53 5.67 93.35
AHUD
(av. sim.
51%)
Helice crassa 2.92 19.29 1.38 38.16 38.16
Austrovenus stutchburyi 3.67 15.67 1.23 31 69.16
Nicon aestuariensis 1.5 6.2 0.81 12.26 81.42
Scolecolepides sp. 1.08 5.95 0.8 11.76 93.18
AHUE
(av. sim.
56%)
Austrovenus stutchburyi 23.83 24.96 2.88 44.37 44.37
Helice crassa 4.33 13.49 2.36 23.98 68.36
Notoacmea helmsi 3.33 8.82 1.16 15.69 84.04
Nicon aestuariensis 1 2.5 0.66 4.44 88.48
Prionospio sp. 0.67 2.02 0.67 3.59 92.07
PORA
(av. sim.
38%)
Edwardsia sp. 4.17 16.21 1.04 42.85 42.85
Scolecolepides sp. 3.33 8.48 0.91 22.42 65.27
Erioptera larvae 1.25 7.27 1.03 19.22 84.49
Nicon aestuariensis 1.33 2.12 0.41 5.59 90.9
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Examining the underlying infaunal species dynamics that account for these differences in community
structure, at site AHUA it is evident that over time the community is becoming comprised of more species
likely to be associated with fine sediments, such as Helice crassa, Scolecolepides sp. and Edwardsia sp.
(Figure18c). Moreover, the temporal SIMPER analysis for site AHUA also confirms a general pattern of a
decrease over time of species sensitive to fine sediments such as Aonides trifida, and Macomona liliana.
At site AHUB there is less obvious grouping evident however the SIMPER analysis shows the estuarine limpet
Notoacmea helmsi accounting for the largest proportion of community temporal variation, with an
abundance of limpets found in the present survey compared to virtually none in any of the previous surveys.
Additionally, increased numbers of Macomona liliana and Aonides trifida in the present survey compared
to previous surveys also contribute significantly to the observed temporal differences in community
structure. The species correlation plot shows the effect of these species on community structure through
time with the location of these species on the right skewing the plot to the right also (Figure 18d).
FIGURE 18: METRIC MDS PLOTS OF BENTHIC MACROINFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2006 – 2009) AT ESTUARINE
MONITORING SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUA, B) SITE AHUB, C) SITE AHUA SPECIES CORRELATION
PLOT, D) SITE AHUB SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON
BRAY-CURTIS DISSIMILARITIES.
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Edwardsia sp.
Edwardsia tri
Nemertea
Cominella glan
Diloma sub
Notoacmea
Zeacumantus l
Zeacumantus s
Macomona
Oligochaeta
Aonides trifida
Microspio spp.
Prionospio sp.
Scolecolepides
Heteromastus
Erioptera Nicon aestGlycera ovigera
Goniada sp.
Halicarcinus v
Helice crassa
Macrophthalmus Elminius mod
Scolelepis sp.
NematodeAmphibolidae
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3AHUA 2006
AHUA 2007
AHUA 2008
AHUA 2009
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Edwardsia sp.
Edwardsia tri
Nemertea
Cominella glan
Diloma subNotoacmea
Zeacumantus l
Arthritica bi
Austrovenus
Macomona Paphies aust
Aonides trifida
Microspio spp.
Prionospio sp.
Scolecolepides
Erioptera
Armandia mac
Nicon aest
Goniada sp.
Pectinaria austHelice crassa
Macrophthalmus
Elminius mod
Scolelepis sp.
Onuphis Auck
Halicarcinus w
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3AHUB 2006
AHUB 2007
AHUB 2008
AHUB 2009
A.
C. D.
B.
2D stress 0.18 2D stress 0.19
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At site AHUD community structure appears to have changed very little over time, with no obvious grouping
in the MDS plot. The SIMPER analysis however, shows a group of four species, including Austrovenus
stutchburyi, Scolecolepides spp., Helice crassa, and Nicon aestuariensis, accounting for the vast majority of
community temporal variation (Appendix 5). Generally speaking, the relative abundance of these species
has changed over time e.g. Austrovenus stutchburyi and Helice crassa predominate in the present surveys
whereas in the previous surveys Scolecolepides spp., and Nicon aestuariensis were more common. This
difference however is not considered ecologically significant as all these species, except Austrovenus
stutchburyi, are more commonly associated with sites having a high fines component.
At site PORA the relatively high stress value (0.22) somewhat distorts groupings, however it appears the 2008
and present survey group out to the right of the plot, indicating a shift in composition over the last two years
compared to the initial two surveys. The SIMPER analysis shows this difference is principally driven by lower
numbers of the bivalve Arthritica bifurca in the latter surveys compared to the initial 2006/2007 surveys, and
conversely higher numbers of Edwardsia spp., and crane fly larvae (Erioptera) in 2008/2009 compared to
2006/2007 (Appendix 5).
FIGURE 19: METRIC MDS PLOTS OF BENTHIC MACROINFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2007 – 2009 SITE AHUD, 2006 – 2009
SITE PORA) ESTUARINE MONITORING SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUD, B) SITE PORA, C) SITE AHUD
SPECIES CORRELATION PLOT, D) SITE PORA SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND
GROUPINGS ARE BASED ON BRAY-CURTIS DISSIMILARITIES.
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Edwardsia sp.
Nemertea
Cominella glan
Arthritica bi
Austrovenus Macomona
Oligochaeta
Orbinia pap
Aonides tri
Prionospio sp.
Scolecolepides
Pseudonerine
Erioptera
Nicon aestPerinereis nun
Platynereis
Mysidacea
Amphipoda
Halicarcinus v
Helice crassa
Halicarcinus w
Crab mega
Isopoda
Upogenia
Nucula spp.
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3PORA 2006
PORA 2007
PORA 2008
PORA 2009
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Edwardsia sp.Nemertea
Cominella glan
Arthritica
Austrovenus
Macomona Aonides tri
Microspio spp.Prionospio sp.
Scolecolepides
Erioptera
Armandia mac
Nicon aest
Perinereis nun
Platynereis
Mysidacea
Halicarcinus v
Helice crassa
LumbrinereisIsopoda
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3AHUD 2007
AHUD 2008
AHUD 2009
2D stress 0.17 2D stress 0.22
A B
C D
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3.2.5 Epifaunal summary indices: present survey
A complete list of benthic epifaunal data from the present survey is included in Appendix 4.
For a list of the highest contributing species to the N of each site see Table 8. Total number of individuals per
quadrat (N) at Ahuriri sites ranged between 0 and 81, averaging 11.6 quadrat-1, while at Porangahau the
sole epifaunal species found was the mud snail, Amphibola crenata which ranged between 4 and 13,
averaging 11 individuals quadrat-1. Given only one epifaunal species was found at site PORA the diversity
indices for H’, J’ and d were not calculated.
The most abundant species among Ahuriri sites was the turret shell, Zeacumantus lutulentus, accounting for
approximately 26% of all individuals counted. Together with its congener, Zeacumantus subcarinatus, turret
shells accounted for around 48% of all epifauna. Site AHUA recorded the highest turret shell abundance
(129), followed by site AHUD (56), site AHUE (50) and site AHUB (16).
Overall the four most numerous epifaunal taxa among Ahuriri sites, in decreasing order, were the two turret
shell species, the mudflat topshell, Diloma subrostrata, and the estuarine barnacle, Eliminius modestus.
(Appendix 4). Collectively, these four taxa accounted for approximately 76% of all the individuals counted.
Examining diversity, number of taxa (S) at each site in each quadrat from the present survey ranged from 1
– 5 with an average of 2.6 at site AHUA, 1 – 4 with an average of 2.3 at site AHUB, 1 – 4 with an average of
2.6 at site AHUD, and 2 – 4 with an average of 2.9 at site AHUE (Figure 20b)
Site averaged Shannon-Weiner diversity index (H’) scores showed that site AHUE, had the highest score
followed by sites AHUA, AHUD and then AHUB (Figure 20c).
Margalef’s Richness (d) scores showed a similar pattern with site AHUE again having the highest average
score followed by sites AHUD, and AHUA, and lastly AHUB (Figure 20e).
Despite the relatively low diversity among sites Pielou’s evenness (J’) scores indicated that abundances of
species were fairly even among stations within sites with site AHUD (0.84) having the highest average score
followed by site AHUA (0.83), site AHUE (0.80), then site AHUB (0.76) (Figure 20d).
3.2.6 Epifaunal summary indices: inter-survey comparison
At sites AHUA and AHUD the number of individuals (N) has remained relatively constant through time with
no significant differences observed between years (Figure 20a). At site AHUB last years’ result for N was the
highest to date and was significantly higher than the initial 2006 survey. This year, N was no different to
results from any other year. Similarly at site PORA last years result for N was significantly higher than the initial
2007 result but this years result was not significantly different to either the 2008, or 2007 results.
Between years significant differences in the number of taxa (S) occurred at site AHUB only (Figure 20b). The
difference in S at site AHUB was between the 2008/2006 surveys. At all other sites no significant differences
in S were evident.
The temporal comparison for H’ reveals relatively little changes at sites, with the only significant differences
occurring at site AHUB (between 2006/2008) and site AHUA (between 2006/2007) (Figure 20c).
Margalef’s richness (d) scores also differed very little between years, with no significant differences evident
at sites AHUB, AHUD or PORA and none in the last three years at site AHUA, with the sole difference between
the 2006/2007 results (Figure 20e).
Examining J’, at site AHUA there has been an incremental increase over time resulting in a significant
difference this year compared to the initial 2006 survey. Conversely J’ has decreased at site PORA
(2007/2008), while at sites AHUB and AHUD J’ no differences have been observed through time at all (Figure
20d).
3.2.7 Epifaunal multivariate analyses: present survey
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A species correlation plot and SIMPER analysis identify and quantify the similarities in community structure
between sites and are shown in Figure 22 and Table 8. The key species driving epifaunal community
structure at Ahuriri are the turret shells and mudflat topshell, Diloma subrostrata, and Amphibola crenata at
Porangahau.
FIGURE 20: PLOTS COMPARING MEANS OF A) INDIVIDUAL ABUNDANCE, B) NUMBER OF TAXA, C) SHANNON-WEINER DIVERSITY INDEX, D)
PIELOU’S EVENNESS AND E) MARGALEF’S RICHNESS OF EPIFAUNA FROM ANNUAL MONITORING SURVEYS (2006 – PRESENT) AT ESTUARINE
MONITORING SITES WITHIN THE AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARIES. ERROR BARS ± 1SE
2006 2007 2008 2009
Mean # o
f taxa (S)
0
1
2
3
4
5
2006 2007 2008 2009
Mean # o
f individuals (N)
0
10
20
30
40
50
2006 2007 2008 2009
Mean S
hannon-W
einer Divers
ity Index (H')
0.0
0.2
0.4
0.6
0.8
1.0
1.2
A. B.
C.
Site AHUA
Site AHUB
Site AHUC
Site AHUD
Site AHUE
Site PORA
2006 2007 2008 2009
Mean M
arg
alef's
Richness (d)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
2006 2007 2008 2009
Mean P
ielou's E
venness (J')
0.0
0.2
0.4
0.6
0.8
1.0
1.2
D.
E.
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ESTUARINE ECOLOGY PROGRAMME
Figure 21: Metric MDS plot of epifaunal data from the present (2009) survey at Ahuriri (AHU) and
Porangahau (POR) estuarine monitoring sites. Data were transformed ln(x+1) prior to analysis and groupings
are based on Bray-Curtis dissimilarities. Depauperate stations were removed from analysis.
TABLE 7: PERMANOVA RESULTS EXAMINING THE EFFECT OF SITE (AHUA – PORA) ON ESTUARY EPIFAUNA. ALL DATA WERE TRANSFORMED
(LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC)
INDICATES THE MONTE CARLO P-VALUE.
-2 -1 0 1 2
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
A1
A2
A3
A5
A6
A7
A8
A9
A10B1B2
B3B4B5
B6
B7
B8B9
B10
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
E1
E2
E3
E4
E5
E6
E7
E8
E9P1
P2P3P4P5
P6P7
P8
P9P10
site AHUAA1
site AHUBB1
site AHUDD1
site AHUEE1
site PORAP1
2D Stress 0.08
Source df SS Mean Square F-Value P (perm) P (MC)
Site 4 90400.46 22600.12 14.57 0.0010 0.0010
Residual 45 69809.76 1551.36
Total 49 160210.22
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FIGURE 22: PLOT SHOWING CORRELATIONS BETWEEN EPIFAUNAL SPECIES ABUNDANCES AND MDS AXES FROM PREVIOUS PLOT AT AHURIRI
AND PORANGAHAU ESTUARINE MONITORING SITES DURING THE PRESENT SURVEY (2009).
TABLE 8: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES WITHIN AHURIRI (AHU) AND PORANGAHAU
(POR) ESTUARIES (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 90% OF CONTRIBUTING SPECIES.
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Cominella gland
Diloma subrostr
Zeacumantus lut
Zeacumantus sub
AmphibolaAustrovenus
Helice crassa
Eliminus mod
Diloma zelandic
Microlenchus
Notoacmea
Paphies aust
Cominella mac
Site Species Av. abund Av. Sim Sim/SD Contrib % Cum%
AHUA
(av. sim.
38%)
Diloma subrostrata 3.30 14.01 1.08 36.56 36.56
Zeacumantus lutulentus 4.70 13.60 0.86 35.48 72.04
Zeacumantus subcarinatus 8.80 7.05 0.50 18.39 90.43
AHUB
(av. sim.
50%)
Diloma subrostrata 6.09 43.51 3.06 86.70 86.70
Eliminius modestus 4.18 5.02 0.41 10.00 96.71
AHUD
(av. sim.
52%)
Zeacumantus lutulentus 4.80 44.68 4.04 85.48 85.48
Cominella glandiformis 0.70 4.09 0.50 7.83 93.32
AHUE
(av. sim.
45%)
Zeacumantus lutulentus 5.22 26.52 2.10 58.44 58.44
Diloma subrostrata 2.11 14.14 1.05 31.15 89.59
Paphies australis 3.00 2.46 0.30 5.42 95.01
PORA
(av. sim.
91%) Amphibola crenata 9.17 91.00 12.51 100.00 100.00
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3.2.8 Epifaunal multivariate analyses: inter-survey comparison
Some temporal variability in epifaunal community structure at sites is evident, with a degree of data
grouping visible at all sites (Figures 23a, 23b and Figure 24a, 24b). PERMANOVA results confirm differences
between years for all sites (all p < 0.02 – Appendix 5). Pair-wise a posteriori comparisons between years
(within sites) identified the community structure at site AHUB to be highly variable, with all years significantly
different to one another (all p < 0.04). Whereas at sites AHUA, AHUD and PORA there were some years
where there was no evidence to suggest community structure was different. These years were 2006/2008,
and 2007/2008 at site AHUA (p = 0.14, 0.11 respectively), 2007/2009 at site AHUD (p = 0.07) and 2008/2009 at
site PORA (p = 0.16).
The MDS plot representing the community through time at site AHUA shows a strong grouping of the 2009
data towards the top of the plot (Figure 23a). This grouping is driven by Notoacmea helmsi and Z.
subcarinatus (Figure 23c). The corresponding SIMPER analysis confirms the role of these key species in
differentiating the 2009 community from that of the 2007/2008 surveys. The main differences between these
surveys and the present were that these species were not sampled in the 2007/2008 surveys and fewer D.
subrostrata were sampled in 2009 compared to 2007/2008 (Appendix 5).
Site AHUB exhibited high between years variation in community structure yet showed low within site
variability during some surveys. The MDS plot shows strong grouping of the 2007 and 2008 communities
indicative of low within site variability while the 2006 and 2009 communities were more diverse and less even
(Figure 23b). SIMPER analysis identified three species accounting for the majority of the observed temporal
variability; the estuarine barnacle Eliminius modestus, mudflat topshell, D. subrostrata, and cockles.
The community at site AHUD has remained reasonable stable through time but maintains a high diversity of
fine sediment tolerant species, as evidenced by the broad groupings in the MDS plot (Figure 24a). The MDS
plot and species correlation plots turret shell, Z. lutulentus, mud snail, Amphibola crenata, and cockles
accounting for the majority of variation in community structure between years.
The MDS plot and species correlation plots clearly show the dynamics of the epifaunal community at play
at site PORA (Figures 24b, 24d). During the initial 2007 survey of site PORA the epifaunal community
comprised two species, A. crenata and cockles. Last year 5 cockles were sampled and this year none were
observed.
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FIGURE 23: METRIC MDS PLOTS OF BENTHIC EPIFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2006 – 2009) AT ESTUARINE MONITORING
SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUA, B) SITE AHUB, C) SITE AHUA SPECIES CORRELATION PLOT, D) SITE
AHUB SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON BRAY-CURTIS
DISSIMILARITIES.
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3AHUB 2006
AHUB 2007
AHUB 2008
AHUB 2009
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3AHUA 2006
AHUA 2007
AHUA 2008
AHUA 2009
2D Stress 0.16 2D Stress 0.13
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Cominella gland
Diloma subrostr
Zeacumantus lut
Zeacumantus sub
AmphibolaAustrovenus
Helice crassa
Eliminus mod
Diloma zelandic
Microlenchus
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Cominella gland
Diloma subrostr
Zeacumantus lut
Zeacumantus sub
Macomona lilAustrovenus
Eliminus mod
Microlenchus
Notoacmea
A. B.
C. D.
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FIGURE 24: METRIC MDS PLOTS OF BENTHIC EPIFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2007 – 2009) AT ESTUARINE MONITORING
SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUD, B) SITE PORA, C) SITE AHUD SPECIES CORRELATION PLOT, D) SITE
PORA SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON BRAY-CURTIS
DISSIMILARITIES.
-2 -1 0 1 2
-2
-1
0
1
2PORA 2007
PORA 2008
PORA 2009
2D Stress 0.04
-3 -2 -1 0 1 2 3
-3
-2
-1
0
1
2
3AHUD 2007
AHUD 2008
AHUD 2009
2D Stress 0.15
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Zeacumantus lut
Amphibola
Austrovenus
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Cominella gland
Diloma subrostr
Zeacumantus lut
Zeacumantus sub
Amphibola
Austrovenus
Helice crassa Cominella mac
C. D.
B.A.
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3.2.9 Overview
Site AHUA
• Moderate numbers of cockles, including large proportion of new recruits
• Highest number of turret shells, Zeacumantus sp. of all Ahuriri sites
• Average of 5.9 infaunal species core-1, moderate infaunal species diversity,
• Average of 2.3 epifaunal species quadrat-1, low epifaunal diversity
• Relatively stable in terms of both infaunal and epifaunal diversity, richness and evenness indices over
time.
• Infaunal assemblage during present survey characterised by the Austrovenus stutchburyi, Aonides
trifida, and Macomona liliana association.
• Epifaunal community structure dominated by the turret shell, Zeacumantus lutulentus and the mudflat
topshell, Diloma subrostrata
• High interannual variability in infaunal community structure, but community tending toward one
dominated by fine sediment tolerant species.
• Limited variability in epifaunal community structure over time
Site AHUB
• Low numbers of cockles, high proportion of these were juvenile recruits. (<5mm shell length)
• Lowest number of turret shells, Zeacumantus sp. of all Ahuriri sites
• Average of 6.7 infaunal species core-1, highest infaunal species diversity, richness and evenness among
Ahuriri sites
• Average of 2.3 epifaunal species quadrat-1, low epifaunal diversity
• Increased numbers of infaunal individuals and taxa over time
• Little change in epifaunal diversity, richness, or evenness indices over time
• Infaunal assemblage during present survey characterised by the Austrovenus stutchburyi, Aonides
trifida, and Macomona liliana association.
• Epifaunal community structure dominated by the turret shell, Zeacumantus lutulentus and the mudflat
topshell, Diloma subrostrata
• Some variability in infaunal community structure over time, with the present survey having increased
numbers of Aonides trifida, and Macomona liliana compared to previous surveys
• Limited variability in epifaunal community structure over time
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Site AHUD
• Lowest numbers of cockles among Ahuriri sites
• Second highest number of turret shells, Zeacumantus sp. among Ahuriri sites
• Average of 4.1 infaunal species core-1, low infaunal S-W diversity, richness and evenness indices
• Average of 2.6 epifaunal species quadrat-1, low epifaunal diversity, but high evenness indices
• Relatively stable diversity and evenness indices but number of individuals higher than initial 2007 survey.
• Little change in epifaunal species diversity, richness, or evenness indices over time
• Infaunal assemblage during present survey characterised by Austrovenus stutchburyi, Nicon
aestuariensis, and Helice crassa.
• Epifaunal community structure characterised by the turret shell fine sediment tolerant species,
Zeacumantus lutulentus, mudflat topshell, Diloma subrostrata, mud whelk, Cominella glandiformis, mud
snail, and Amphibola crenata.
• Little change in infaunal community structure over time
• Low variability in epifaunal community structure over time
Site AHUE
• First year of monitoring
• Highly productive recruitment site for cockles, highest numbers among Ahuriri sites
• Second highest number of turret shells, Zeacumantus sp. among Ahuriri sites
• Average of 6.8 infaunal species core-1, low infaunal S-W diversity, but high evenness
• Average of 2.9 epifaunal species quadrat-1, highest epifaunal S-W diversity, but still relatively low and
highest richness among Ahuriri sites.
• Infaunal assemblage during present survey characterised by Austrovenus stutchburyi, Nicon
aestuariensis, and Helice crassa.
• Similar epifaunal community structure to site AHUA with community structure characterised by
Zeacumantus lutulentus and the mudflat topshell, Diloma subrostrata.
Site PORA
• Average of 4.7 infaunal species core-1, moderate infaunal S-W diversity, richness indices and evenness
• Epifaunal community now solely comprised of mud snail, Amphibola crenata, with fewer cockles
sampled then previous years.
• Relatively stable numbers of infaunal individuals, species diversity, evenness and richness over time.
• Infaunal assemblage during present survey characterised by Edwardsia sp., the spionid polychaete,
Scolecolepides sp., crane-fly (Erioptera) larvae, and nereid polychaete Nicon aestuariensis.
• High variability in infaunal community structure over time with increased numbers of Edwardsia sp
occurring over last two years and fewer of the bivalve, Arthritica bifurca.
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4.0 SUMMARY
Sediment characteristics
Overall, sediments at site AHUA were the most similar to site AHUB in terms of composition and contaminant
status, and also in the relative changes of these parameters over time. Site AHUE was more similar to AHUD,
in terms of composition but resembled sites AHUA and AHUB more in terms of contaminant status. Site
AHUD was the most polluted of all sites. PORA represents a meaningful rural comparison to the urbanised
Ahuriri sites and in general yielded the lowest levels of contaminants among all sites.
The increase in fines at sites AHUA and AHUB over time and concomitant decrease in, particularly, trace
metal contamination is suggested to be a result of increased input and subsequent deposition of fine
sediments into the estuary. Although there was no significant change to composition at site AHUD this is the
second year where the fines fraction has increased and sand has decreased. Given the much higher level
of fines at site AHUD compared to sites AHUA and AHUB, and that monitoring at site AHUD only began in
2007 it is not surprising the changes to composition at site AHUD are not yet significant. Thus, the decreases
in trace metals at site AHUD are also suggested to be a result of the deposition of fine sediments. Although
the ‘Your Choice’ stormwater programme has been in operation a number of years, it is unknown what the
contribution of this programme is to the observed decrease in trace metal levels. It is suggested that the
data collected from monitoring of the Ahuriri stormwater discharges be analysed alongside the state of the
environment data to quantify in real terms the efficacy of the ‘Your Choice’ stormwater programme.
Furthermore, there is also a clear need to assess sediment dynamics along the length of the estuary, and
particularly to identify the main source areas of sediments.
Biological characteristics
Infaunal patterns at Ahuriri were generally typical of northern east coast estuaries in New Zealand, with
spatial variation between sites indicative of differences in sediment composition. This was particularly
evident between sites AHUD, AHUE and the other Ahuriri sites. Community variability between sites
appeared to be largely driven by key species that are either sensitive or tolerant to increased silt/clay
content. These analyses suggest that at site PORA the fine sediment tolerant anemone Edwardsia sp. is the
key driver, while at Ahuriri sites AHUA and AHUB Macomona liliana, generally sensitive to increased fines, is
important, while at sites AHUD and AHUE the fines tolerant Helice crassa is key.
Interesting inter-survey differences in infaunal populations were identified at sites AHUA and PORA which
showed communities tending towards species more tolerant of fine sediments. Given the apparent
increase in fines at site AHUA in the present survey it is suggested that the infaunal community may be
responding to these changes. It appears that increasing sediment fines content has a positive effect on the
occurrence of Helice crassa, Edwardsia sp., Scolecolepides sp., and Nicon aestuariensis, and a negative
effect on Macomona liliana and Aonides trifida. These generalisations are applicable across both estuaries.
However, there were also examples where some species did not respond consistently to the higher fines
content. For example Austrovenus stutchburyi, showed a wide tolerance to fines content, although it is
known to generally prefer sediments with low fines content (Thrush et al., 2003).
Epifaunal communities were not as variable either spatially or temporally as their infaunal counterparts. The
predominance of turret shells and the mudflat topshell throughout Ahuriri sites and generally low species
diversity suggests that epifaunal communities are generally more robust to environmental perturbations
than their infaunal counterparts.
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5.0 CONCLUSION
These surveys were the fourth consecutive annual monitoring of the Ahuriri and Porangahau Estuary systems.
Estuaries are dynamic systems at the end-point of freshwater systems. Ensuring the integrity of these systems
over time requires long-term monitoring to identify where trends in state may be indicating a reduction in
environmental quality.
The surveys provided a good snapshot of the estuarine ecology, with important structural points being; a
healthy supply of cockle recruits at Ahuriri, key drivers of infaunal community structure are Edwardsia sp.
(site PORA), Macomona liliana (sites AHUA and AHUB), Helice crassa (sites AHUD and AHUE), and epifaunal
community drivers are Zeacumantus sp. and Diloma subrostrata (Ahuriri) and Amphibola crenata
(Porangahau).
There is also evidence that fine sediments have been accumulating at some sites around Ahuriri estuary
(e.g. sites AHUA and AHUB) and that at some sites the infaunal community is responding to this change (e.g.
site AHUA).
It is also clear that sediment contamination at the most polluted site (site AHUD) is above relevant regional
background levels. However, these levels appear to be decreasing over time, but the underlying reasons
as to why the contaminant levels are reducing is less clear. Possible reasons include; reduction in
contaminant loads of stormwater going into the estuary or increases in fine sediments that have been
buffering the contaminant load.
The results of the surveys suggest that site specific differences in sediment characteristics are an important
determinant to the spatial patterns of the resident biota. Further investigation of the underlying processes
influencing sediment characteristics is thus warranted.
6.0 RECOMMENDATIONS
• That continued monitoring is undertaken at the same sites as the present survey, and in line with the
methodology set out in this report.
• That heavy metals concentration in the flesh of shellfish and/or mud snails are assessed at site AHUD.
• Investigate the feasibility of explicit monitoring of sedimentation at various points along the estuaries
using sediment traps.
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7.0 REFERENCES
Airoldi, L., 2003. The effects of sedimentation on rocky coast assemblages. Oceanogr. Mar. Biol. Annu. Rev.,
41: 161-236.
ANZECC, 2000. Australian and New Zealand guidelines for fresh and marine water quality 2000, Volume 1.,
National Water Quality Management Strategy Paper No. 4. Australian and New Zealand Environment and
Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand,
Canberra.
Bennett, C., 2006. Ahuriri Stormwater Discharge Compliance Monitoring. . Cawthron Report No. 1146,
Cawthron, Napier.
Clarke, K.R. and Gorley, R.N., 2001. PRIMER v5: User manual. PRIMER-E Ltd, Plymouth Marine Laboratory,
United Kingdom.
Clarke, K.R. and Warwick, R.M., 1994. Changes in marine communities; an approach to statistical analysis
and interpretation. Natural Environment Research Council, United Kingdom, 144 pp.
Cromarty, P. and Scott, D.A., 1996. A directory of wetlands in New Zealand. In: D.o. Conservation (Editor),
Wellington, New Zealand, pp. 395.
Davis, S.F., 1987. Wetlands of national importance to fisheries. New Zealand Freshwater Fisheries Report
Number 90, Freshwater Fisheries Centre, MAFFish, Christchurch.
HBRC, 1999. Regional Coastal Plan. ISBN 1-877174-16-5, Hawke's Bay Regional Council, Napier.
HBRC, 2006. Regional Coastal Environment Plan: Proposed - August 2006 (As amended by Council Decisions
Issued 19 July 2008). ISBN 1-877405-23-X. HBRC Plan Number 4071, Hawke's Bay Regional Council, Napier.
HDC, HBRC, NCC and DoC, 1992. Ahuriri Management Plan. , Hastings District Council, Hawke’s Bay
Regional Council, City of Napier, and Department of Conservation.
Hume, T. and Swales, A., 2003. How estuaries grow old. , NIWA Water and Atmosphere.
Kilner, A.R. and Ackroyd, J.M., 1978. Fish and invertebrate macrofauna of the Ahuriri Estuary, Napier. Fisheries
Technical Report No. 153, New Zealand Ministry of Agriculture and Fisheries, Wellington, New Zealand.
Kruskal, J.B. and Wish, M., 1978. Multidimensional scaling. Sage University, Beverely Hills, California.
Madarasz, A.L., 2006. Coastal Monitoring Strategy for Hawke's Bay: 2006-2011. EMI 06/07
HBRC plan number 3850.
Nicholls, P., 2002. Determining impacts on marine ecosystems: the concept of key species. Water and
Atmosphere, 10(2).
Robertson, B.M. et al., 2002. Estuarine environmental assessment and monitoring: a national protocol
Sustainable Management Fund Contract No. 5096, Prepared for supporting Councils and the Ministry for the
Environment
Smith, S., 2007. Coastal Sediment Characteristics of the Hawke Bay. . Report prepared for the Hawke's Bay
Regional Council. EMI 07/24. HBRC Plan no. 3975, EAM Ltd., Napier.
StatSoft, 2004. STATISTICA version 7, data analysis software system. www.statsoft.com.
CLIENT REF: EAM040
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7.0 REFERENCES
Strong, J.M., 2005. Background sediment trace metal concentrations of major estuarine, and lagoon
systems in the Hawke's Bay region, New Zealand. MSc Thesis, University of Auckland.
Thrush, S.F., Hewitt, J. E. , Norkko, A., Nicholls, P.E., Funnell, G.A. and Ellis, J.I., 2003. Habitat change in
estuaries: predicting broad-scale responses of intertidal macrofauna to sediment mud content. Marine
Ecology Progress Series, Vol. 263: 101-112.
Watling, L. and Norse, E.A., 1998. Disturbance of the seabed by mobile fishing gear: A comparison to forest
clearcutting. Conservation Biology, 12: 1180-1197.
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APPENDIX 1 SAMPLING STATION
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TABLE A1-1: LOCATIONS OF STATIONS SAMPLED AT SITES AHUA, AHUB, AHUD, AHUE AND PORA FOR THE PRESENT SURVEY.
AHUA NZ Map Grid Coordinates AHUB NZ Map Grid Coordinates
Station Northing Easting Station Northing Easting
A1 6184000 2843550 B1 6183595 2843587
A2 6183992 2843580 B2 6183626 2843559
A3 6183999 2843541 B3 6183623 2843572
A4 6183966 2843544 B4 6183570 2843566
A5 6184018 2843516 B5 6183600 2843586
A6 6183985 2843539 B6 6183601 2843561
A7 6183993 2843522 B7 6183621 2843553
A8 6183978 2843541 B8 6183580 2843572
A9 6183999 2843499 B9 6183590 2843564
A10 6184000 2843507 B10 6183613 2843548
A11 6184028 2843511 B11 6183612 2843575
A12 6184019 2843532 B12 6183578 2843586
AHUD NZ Map Grid Coordinates AHUE NZ Map Grid Coordinates
Station Northing Easting Station Northing Easting
D1 6183609 2844230 E1 6184108 2844049
D2 6183596 2844234 E2 6184112 2844036
D3 6183624 2844245 E3 6184122 2844064
D4 6183600 2844251 E4 6184085 2844022
D5 6183582 2844259 E5 6184118 2844035
D6 6183576 2844274 E6 6184138 2844061
D7 6183579 2844263 E7 6184131 2844054
D8 6183611 2844263 E8 6184117 2844042
D9 6183588 2844284 E9 6184128 2844045
D10 6183611 2844253 E10 6184108 2844063
D11 6183590 2844273 E11 6184095 2844039
D12 6183603 2844273 E12 6184103 2844028
PORA NZ Map Grid Coordinates
Station Northing Easting
P1 6098702 2823685
P2 6098707 2823663
P3 6098725 2823646
P4 6098692 2823647
P5 6098713 2823637
P6 6098691 2823633
P7 6098697 2823620
P8 6098706 2823646
P9 6098698 2823640
P10 6098714 2823652
P11 6098708 2823634
P12 6098686 2823640
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APPENDIX 2 SEDIMENT DATA
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SEDIMENT TEXTURE
TABLES A2-1: SEDIMENT TEXTURE, AFDW AND CHLOROPHYLL A LEVELS OF STATIONS SAMPLED DURING THE PRESENT SURVEY FOR SITES
AHUA, AHUB, AHUD, AHUE AND PORA.
Site Station Gravel (>2mm)
(%w/w)
Sand
(63µm – 2mm)
(%w/w)
Clay/Silt
(<63µm)
(%w/w)
AFDW
(%w/w)
Chl a
(mg/m3)
AHUA A1 24.7 52.3 23 2.4 4700
A2 0.9 85.6 13.5 1.4 5400
A3 11.5 77.2 11.4 1.2 6200
A4 <0.1 78.9 21.1 1.1 14000
A5 1.4 84.3 14.3 1.7 5300
A6 2.6 82.5 14.9 1.5 4200
A7 0.3 83.4 16.3 1.3 4000
A8 0.1 82.8 17.1 1.6 3600
A9 0.1 77.4 22.4 1.6 5500
A10 2.1 75.3 22.5 1.5 6700
Site Station Gravel (>2mm)
(%w/w)
Sand
(63µm – 2mm)
(%w/w)
Clay/Silt
(<63µm)
(%w/w)
AFDW
(%w/w)
Chl a
(mg/m3)
AHUB B1 1 88.5 10.5 1.7 6200
B2 3.3 76.2 20.5 1.8 6400
B3 0.2 81.8 18 1.6 7000
B4 1.2 79.6 19.2 1.8 4300
B5 0.5 84.7 14.8 1.7 3800
B6 0.5 87.4 12.1 1.3 4900
B7 0.2 91.6 8.1 1.8 5400
B8 <0.1 68.5 31.4 1.9 3800
B9 0.3 78.2 21.5 2.3 4000
B10 0.3 84.4 15.3 1.4 7600
Site Station Gravel (>2mm)
(%w/w)
Sand
(63µm – 2mm)
(%w/w)
Clay/Silt
(<63µm)
(%w/w)
AFDW
(%w/w)
Chl a
(mg/m3)
AHUD D1 <0.1 42.3 57.7 2.5 2800
D2 0.1 52.6 47.4 2.2 6100
D3 6.5 78 15.5 2.2 4500
D4 0.6 77.1 22.2 1.7 7900
D5 0.6 56.3 43 2.8 4300
D6 0.3 80.7 19 2 9500
D7 1.6 82 16.3 1.8 5900
D8 0.9 71.1 28 2.1 8300
D9 2.5 81.3 16.2 1.6 8100
D10 0.8 74.9 24.4 2.1 6900
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Site Station Gravel (>2mm)
(%w/w)
Sand
(63µm – 2mm)
(%w/w)
Clay/Silt
(<63µm)
(%w/w)
AFDW
(%w/w)
Chl a
(mg/m3)
AHUE E1 25.8 55.9 18.3 1.9 4500
E2 17.4 55 27.5 0.64 4500
E3 14.6 57.4 28 2.4 6100
E4 10.4 77.5 12.1 1.5 2300
E5 16.9 55.1 28 3 5800
E6 17 50.7 32.3 2.6 5100
E7 22.3 46.1 31.6 3.4 5200
E8 18.6 51.6 29.8 3.5 5000
E9 21.2 46.8 32.1 2.7 6500
E10 10.2 68.8 21 2.2 8300
Site Station Gravel (>2mm)
(%w/w)
Sand
(63µm – 2mm)
(%w/w)
Clay/Silt
(<63µm)
(%w/w)
AFDW
(%w/w)
Chl a
(mg/m3)
PORA P1 2 48.5 49.5 0.27 4500
P2 0.5 42.6 56.9 0.59 3200
P3 0.5 53.3 46.2 1.3 2800
P4 3.1 47.4 49.5 1.2 3900
P5 2.9 55.2 41.9 1.5 1800
P6 3.9 54.4 41.7 1.2 1900
P7 3.2 58.9 37.8 0.32 2800
P8 0.6 44 55.4 3.7 3000
P9 0.5 59.1 40.4 3 2500
P10 14 37.7 48.3 3.2 2700
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SEDIMENT QUALITY
TABLES A2-2: SEDIMENT NUTRIENT AND TRACE METAL LEVELS OF STATIONS SAMPLED DURING THE PRESENT SURVEY FOR SITES AHUA,
AHUB, AHUD, AHUE AND PORA.
Site Station TRP
(mg/kg)
TN
(g/100g)
As
(mg/kg)
Cd
(mg/kg)
Cr
(mg/kg)
Cu
(mg/kg)
Pb
(mg/kg)
Ni
(mg/kg)
Zn
( m g /
kg)
AHUA A1 470 0.085 4.6 0.074 18 11 12 9.3 70
A2 280 <0.051 3.7 0.051 12 5.1 7.9 6.8 50
A3 310 <0.051 3.3 0.056 13 5.4 7.7 7 54
A4 330 0.051 2.6 0.022 13 4.6 7.5 7.6 42
A5 320 0.051 2.6 0.042 13 5 7.5 7 54
A6 320 <0.051 2.7 0.026 12 4.6 7.7 7.4 48
A7 320 <0.051 3 0.025 11 4.2 6.9 7.7 44
A8 320 <0.051 3.1 0.027 12 5 7.8 8.8 52
A9 340 <0.051 4.2 0.021 12 4.9 10 8.5 47
A10 340 <0.051 3.6 0.023 12 4.7 8.4 8.3 46
Site Station TRP
(mg/kg)
TN
(g/100g)
As
(mg/kg)
Cd
(mg/kg)
Cr
(mg/kg)
Cu
(mg/kg)
Pb
(mg/kg)
Ni
(mg/kg)
Zn
( m g /
kg)
AHUB B1 330 <0.051 2.6 0.029 12 5.5 7.8 7.2 52
B2 410 0.12 4.3 0.024 13 6.9 10 7.3 52
B3 350 0.062 4.1 0.03 14 7 9.6 7.9 52
B4 330 0.052 3.3 0.037 14 6.6 8.9 7.2 56
B5 320 <0.051 2.9 0.026 12 5.1 7.6 7.1 48
B6 310 <0.051 3.9 0.022 13 5.2 9 7.2 49
B7 330 <0.051 3.5 0.028 12 4.5 7.6 7.1 42
B8 330 <0.051 3.1 0.04 13 5.6 8.2 7.4 56
B9 330 <0.051 4.3 0.038 14 6.2 10 8 56
B10 360 <0.051 5.3 0.017 14 5.5 11 7.6 51
Site Station TRP
(mg/kg)
TN
(g/100g)
As
(mg/kg)
Cd
(mg/kg)
Cr
(mg/kg)
Cu
(mg/kg)
Pb
(mg/kg)
Ni
(mg/kg)
Zn
( m g /
kg)
AHUD D1 530 0.076 6 0.25 53 21 35 9.3 210
D2 540 0.08 6.4 0.13 52 22 36 9.3 160
D3 1400 0.061 13 0.86 38 20 41 8.3 180
D4 690 0.059 6.2 0.13 36 15 28 8.6 140
D5 500 0.071 10 0.17 51 23 28 8.9 170
D6 430 0.052 11 0.065 38 20 21 7.7 98
D7 380 <0.051 9.9 0.095 30 17 19 8.5 100
D8 680 0.075 5.4 0.23 51 19 35 8.4 180
D9 490 <0.051 6.4 0.16 35 17 21 7.7 130
D10 830 0.068 6.7 0.24 51 23 35 8.9 170
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Site Station TRP
(mg/kg)
TN
(g/100g)
As
(mg/kg)
Cd
(mg/kg)
Cr
(mg/kg)
Cu
(mg/kg)
Pb
(mg/kg)
Ni
(mg/kg)
Zn
( m g /
kg)
AHUE E1 490 0.067 6.5 0.043 13 7.6 19 7.9 54
E2 430 0.068 4.6 0.052 14 9.4 15 8.7 59
E3 480 0.08 5.5 0.054 14 9.1 14 8.2 59
E4 410 <0.051 5 0.027 11 5.8 13 7.7 46
E5 480 0.08 5 0.054 14 8.9 15 8.3 57
E6 450 0.071 4.6 0.055 14 9.3 15 8.7 60
E7 480 0.076 4.9 0.055 16 9.9 14 8.6 64
E8 450 0.074 4.5 0.06 15 9.7 15 8.7 62
E9 520 0.092 4.4 0.07 16 11 15 9.3 68
E10 480 0.06 6.3 0.04 12 6.5 15 7.5 50
Site Station TRP
(mg/kg)
TN
(g/100g
)
As
(mg/kg)
Cd
(mg/kg)
Cr
(mg/kg)
Cu
(mg/kg)
Pb
(mg/kg)
Ni
(mg/kg)
Zn
( m g /
kg)
PORA P1 450 0.1 6.3 0.05 11 12 6.4 10 41
P2 390 0.097 4.9 0.059 9.8 13 6.2 10 39
P3 440 0.082 7 0.042 11 12 6 10 40
P4 350 0.07 5.5 0.046 9.4 11 5.2 8.8 34
P5 360 0.073 5.8 0.048 9.7 11 5.3 9.4 36
P6 380 0.068 6.1 0.04 9.6 11 4.9 8.7 35
P7 360 0.058 6 0.02 8.5 9 4.5 7.9 31
P8 420 0.076 5.5 0.052 10 10 5.3 8.6 37
P9 390 0.063 6.1 0.036 9.8 9.7 5.1 8.8 35
P10 420 0.091 5.5 0.051 11 12 6 10 39
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APPENDIX 5 INTER-SURVEY COMPARISON: PERMANOVA’S
SIMPER’S
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TABLES A5-1: PERMANOVA RESULTS EXAMINING THE EFFECT OF YEAR ON INFAUNA AT ESTUARINE MONITORING SITES WITHIN THE AHURIRI
(AHU) AND PORANGAHAU (POR) ESTUARIES. ALL DATA WERE TRANSFORMED (LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS
DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC) INDICATES THE MONTE CARLO P-VALUE.
AHUA
Source df SS Mean Square F-Value P (perm) P (MC)
Site 3 26612.1 8870.7 7.60 0.0012 0.0012
Residual 44 51304.1 1166.1
Total 47 77916.2
AHUB
Source df SS Mean Square F-Value P (perm) P (MC)
Site 3 16355.7 5451.9 3.38 0.0012 0.0012
Residual 44 70868.9 1610.6
Total 47 87224.6
AHUD
Source df SS Mean Square F-Value P (perm) P (MC)
Site 2 8803.8592 4401.9296 3.0680 0.0062 0.0050
Residual 33 47347.6884 1434.7784
Total 35 56151.5475
PORA
Source df SS Mean Square F-Value P (perm) P (MC)
Site 3 40391.8758 13463.9586 7.4012 0.0012 0.0012
Residual 44 80042.6823 1819.1519
Total 47 120434.5581
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TABLE A5-2: PERMANOVA RESULTS EXAMINING THE EFFECT OF YEAR ON EPIFAUNA AT ESTUARINE MONITORING SITES WITHIN THE AHURIRI
(AHU) AND PORANGAHAU (POR) ESTUARIES. ALL DATA WERE TRANSFORMED (LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS
DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC) INDICATES THE MONTE CARLO P-VALUE.
AHUA
Source df SS Mean Square F-Value P (perm) P (MC)
Site 3 13509.1596 4503.0532 4.1328 0.0010 0.0010
Residual 36 39225.1193 1089.5866
Total 39 52734.2789
AHUB
Source df SS Mean Square F-Value P (perm) P (MC)
Site 3 17480.5458 5826.8486 4.7654 0.0010 0.0010
Residual 36 44018.2675 1222.7297
Total 39 61498.8133
AHUD
Source df SS Mean Square F-Value P (perm) P (MC)
Site 2 13153.9043 6576.9522 2.8397 0.0020 0.0060
Residual 27 62534.0562 2316.0762
Total 29 75687.9605
PORA
Source df SS Mean Square F-Value P (perm) P (MC)
Site 2 36686.9163 18343.4581 33.5510 0.0010 0.0010
Residual 27 14761.7882 546.7329
Total 29 51448.7045
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TABLE A5-3: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE A (AHUA)
(SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
TABLE A5-4: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE B (AHUB)
(SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
AHUA
2006
(av. sim.
72%)
Macomona liliana 10.5 19.71 5.21 27.44 27.44
Aonides trifida 19.25 19.18 3.39 26.7 54.14
Heteromastus filiformis 4.83 11.92 3.07 16.59 70.73
Austrovenus stutchburyi 2.83 7.26 1.28 10.11 80.84
AHUA
2007
(av. sim.
59%)
Aonides trifida 11.33 18.84 1.88 31.76 31.76
Macomona liliana 7.17 18.55 3.15 31.28 63.04
Nicon aestuariensis 1.67 7.28 1.29 12.27 75.3
Austrovenus stutchburyi 1.33 4.35 0.8 7.33 82.64
AHUA
2008
(av. sim.
50%)
Macomona liliana 5.5 22.63 3.15 45.66 45.66
Nicon aestuariensis 2.17 8.33 0.99 16.8 62.46
Scolecolepides sp. 1.42 6.44 0.93 13 75.46
Prionospio sp. 1.42 4.08 0.61 8.23 83.69
AHUA
2009
(av. sim.
42%)
Austrovenus stutchburyi 9.08 14.89 1.32 35.65 35.65
Macomona liliana 4.67 10.4 1.05 24.89 60.54
Helice crassa 1.58 3.77 0.59 9.02 69.57
Aonides trifida 6.58 3.7 0.4 8.86 78.43
Edwardsia sp. 1.08 3.63 0.81 8.69 87.12
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
AHUB 2006
(av. sim.
55%)
Austrovenus stutchburyi 9.83 23.8 4.13 43.15 43.15
Macomona liliana 5.42 16.58 1.98 30.05 73.21
Aonides trifida 2.5 7.06 0.98 12.8 86
AHUB 2007
(av. sim.
47%)
Macomona liliana 4.5 11.32 0.76 24.06 84.92
Macomona liliana 4.67 17.7 1.22 43.04 43.04
AHUB 2009
(av. sim.
42%)
Macomona liliana 5.42 8.84 1.11 21.18 21.18
Notoacmea helmsi 9.75 8.17 1.02 19.57 40.75
Austrovenus stutchburyi 4.75 7.28 1.14 17.42 58.17
AHUB
Macomona liliana 5.42 8.84 1.11 21.18 21.18
Notoacmea helmsi 9.75 8.17 1.02 19.57 40.75
Austrovenus stutchburyi 4.75 7.28 1.14 17.42 58.17
Aonides trifida 10.08 6.23 0.97 14.92 73.1
Nicon aestuariensis 1.67 3.47 0.7 8.32 81.41
2009
(av. sim.
42%)
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TABLE A5-5: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE D (AHUD)
(SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
TABLE A5-6: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT PORANGAHAU SITE A
(PORA) (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
AHUD
2007
(av. sim.
54)
Nicon aestuariensis 2 23.1 1.84 42.71 42.71
Scolecolepides sp. 1.75 20.13 1.82 37.2 79.92
Austrovenus stutchburyi 0.83 5.21 0.52 9.62 89.54
AHUD
2008
(av. sim.
46%)
Scolecolepides sp. 3.75 14.65 1.17 31.75 31.75
Nicon aestuariensis 1.92 14.49 1.86 31.41 63.16
Austrovenus stutchburyi 2.08 9.48 0.8 20.55 83.72
AHUD
2009
(av. sim.
41%)
Helice crassa 2.92 19.29 1.38 38.16 38.16
Austrovenus stutchburyi 3.67 15.67 1.23 31 69.16
Nicon aestuariensis 1.5 6.2 0.81 12.26 81.42
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
PORA 2006
(av. sim.
55%)
Austrovenus stutchburyi 9.83 23.8 4.13 43.15 43.15
Macomona liliana 5.42 16.58 1.98 30.05 73.21
Aonides trifida 2.5 7.06 0.98 12.8 86
PORA 2007
(av. sim.
47%)
Macomona liliana 4.5 11.32 0.76 24.06 84.92
Macomona liliana 4.67 17.7 1.22 43.04 43.04
PORA 2009
(av. sim.
42%)
Macomona liliana 5.42 8.84 1.11 21.18 21.18
Notoacmea helmsi 9.75 8.17 1.02 19.57 40.75
Austrovenus stutchburyi 4.75 7.28 1.14 17.42 58.17
PORA
Macomona liliana 5.42 8.84 1.11 21.18 21.18
Notoacmea helmsi 9.75 8.17 1.02 19.57 40.75
Austrovenus stutchburyi 4.75 7.28 1.14 17.42 58.17
Aonides trifida 10.08 6.23 0.97 14.92 73.1
Nicon aestuariensis 1.67 3.47 0.7 8.32 81.41
2009
(av. sim.
42%)
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TABLE A5-7: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE A (AHUA)
(SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
TABLE A5-8: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE B (AHUB)
(SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
AHUA 2006
(av. sim.
69%)
Zeacumantus lutulentus 14.73 49.15 4.78 70.87 70.87
Diloma subrostrata 5.18 18.95 1.3 27.32 98.18
AHUA 2007
(av. sim.
65%)
Diloma subrostrata 13.42 36.76 3.9 56.92 56.92
Zeacumantus lutulentus 5.17 20.31 1.42 31.46 88.38
Austrovenus stutchburyi 0.92 5.81 0.82 9 97.38
AHUA 2009
(av. sim.
73%)
Zeacumantus lutulentus 9.25 35.72 5.29 48.62 48.62
Diloma subrostrata 11.83 33.5 3.93 45.6 94.22
AHUA
2009
(av. sim.
38%)
Diloma subrostrata 5.42 8.84 1.11 21.18 21.18
Zeacumantus lutulentus 10.08 6.23 0.97 14.92 73.1
Zeacumantus lutulentus 1.67 3.47 0.7 8.32 81.41
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
AHUB 2006
(av. sim.
37%)
Diloma subrostrata 3.42 29.99 1.21 82.13 82.13
Austrovenus stutchburyi 0.58 3.03 0.3 8.29 90.41
AHUB 2007
(av. sim.
66%)
Diloma subrostrata 6.67 49.11 3.65 74.19 74.19
Austrovenus stutchburyi 5.58 13.2 0.93 19.95 94.13
AHUB 2009
(av. sim.
66%)
Diloma subrostrata 11.75 42.21 4.46 64.35 64.35
Eliminus modestus 15.67 16.62 1.04 25.34 89.69
Zeacumantus lutulentus 0.92 3.33 0.52 5.07 94.76
AHUB
2009
(av. sim.
50%)
Diloma subrostrata 6.09 43.51 3.06 86.7 86.7
Zeacumantus lutulentus 4.18 5.02 0.41 10 96.71
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TABLE A5-9: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE D (AHUD)
(SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
TABLE A5-10: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT PORANGAHAU SITE A
(PORA) (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
AHUD
2007
(av. sim.
32)
Zeacumantus lutulentus 1.64 21.16 0.94 65.15 65.15
Helice crassa 0.64 4.16 0.32 12.79 77.94
Amphibola crenata 1.73 3.3 0.24 10.17 88.11
AHUD
2008
(av. sim.
27%)
Diloma subrostrata 1.25 8.23 0.51 30.37 30.37
Zeacumantus lutulentus 1.67 6.41 0.52 23.64 54.01
Austrovenus stutchburyi 0.42 5.39 0.39 19.88 73.88
AHUD
2009
(av. sim.
52%)
Zeacumantus lutulentus 4.8 44.68 4.04 85.48 85.48
Cominella glandiformis 0.7 4.09 0.5 7.83 93.32
Site Year Species Av.
abund
Av. Sim Sim/
SD
Contrib % Cum%
PORA 2007
(av. sim.
62%) Austrovenus stutchburyi 5.5 59.03 1.97 95.32 95.32
PORA 2008
(av. sim.
84%) Amphibola crenata 10.17 82.28 9.3 98.25 98.25
PORA 2009
(av. sim.
91%) Amphibola crenata 9.17 91 12.51 100 100
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APPENDIX 6 REPORT LIMITATIONS
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REPORT LIMITATIONS
This Document has been provided by Environmental Assessments & Monitoring Ltd (EAM) subject to the
following limitations:
I. This Document has been prepared for the particular purpose outlined in EAM’s proposal and no
responsibility is accepted for the use of this Document, in whole or in part, in other contexts or for any
other purpose.
II. The scope and the period of EAM’s Services are as described in EAM’s proposal, and are subject to
restrictions and limitations. EAM did not perform a complete assessment of all possible conditions or
circumstances that may exist at the site referenced in the Document. If a service is not expressly
indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any
determination has been made by EAM in regards to it.
III. Conditions may exist which were undetectable given the limited nature of the enquiry EAM was
retained to undertake with respect to the site. Variations in conditions may occur between
investigatory locations, and there may be special conditions pertaining to the site which have not
been revealed by the investigation and which have not therefore been taken into account in the
Document. Accordingly, additional studies and actions may be required.
IV. In addition, it is recognized that the passage of time affects the information and assessment provided
in this Document. EAM’s opinions are based upon information that existed at the time of the
production of the Document. It is understood that the services provided allowed EAM to form no
more than an opinion of the actual conditions of the site at the time the site was visited and cannot
be used to assess the effect of any subsequent changes in the quality of the site, or its surroundings,
or any laws or regulations.
V. Any assessments made in this Document are based on the conditions indicated from published
sources and the investigation described. No warranty is included, either express or implied, that the
actual conditions will conform exactly to the assessments contained in this Document.
VI. Where data supplied by the Client or other external sources, including previous site investigation
data, have been used, it has been assumed that the information is correct unless otherwise stated.
No responsibility is accepted by EAM for incomplete or inaccurate data supplied by others.
VII. The Client acknowledges that EAM may have retained sub-consultants affiliated with EAM to provide
Services for the benefit o EAM. EAM will be fully responsible to the Client for the Services and work
done by all of its sub-consultants and subcontractors. The Client agrees that it will only assert claims
against and seek to recover losses, damages or other liabilities from EAM and not EAM’s affiliated
companies, and their employees, officers and directors.
VIII. This Document is provided for sole use by the Client and is confidential to it and its professional
advisers. No responsibility whatsoever for the contents of this Document will be accepted to any
person other than the Client. Any use which a third party makes of this Document, or any reliance on
or decisions to be made based on it, is the responsibility of such third parties. EAM accepts no
responsibility for damages, if any, suffered by any third party as a result of decisions made or actions
based on this Document.