Assessment of Effects on Marine Ecology – Coast and Catchment Ltd

Appendix J Assessment of Effects on Marine Ecology – Coast and Catchment Ltd

Beca // 2 May 2018 4216571 // NZ1-15242655-52 0.52 // page 139

St Marys Bay - Masefield Beach Water Quality Improvement Project

Assessment of effects on marine ecology

St Marys Bay - Masefield Beach Water Quality Improvement Project

Assessment of effects on marine ecology

Shane Kelly Carina Sim-Smith Glen Carbines

March 2018

Client report for Auckland Council Report Number: 2017-13

Disclaimer

This report has been prepared based on the information described to Coast and Catchment Ltd by the client and its extent is limited to the scope of work agreed between these two parties. No responsibility is accepted by Coast and Catchment Ltd or its directors, servants, agents, staff or employees for the accuracy of information provided by third parties, and/or for the use of any part of this report for purposes beyond those described in the scope of work. The information in this report is intended for use by the client and no responsibility is accepted for its use by other parties.

Contents 1 Background ...... 2 2 Methods ...... 4 2.1 Field assessments ...... 4 2.1.1 Preliminary site assessment ...... 4 2.1.2 Detailed site assessment ...... 5 2.2 Data analyses ...... 7 3 Results ...... 8 3.1 Physical characteristics ...... 8 3.1.1 Intertidal areas around Masefield Beach ...... 8 3.1.2 Subtidal areas around proposed outfall ...... 11 3.1.3 Sediment analyses ...... 11 3.2 Ecological characteristics of Masefield Beach ...... 13 3.2.1 Intertidal reefs and sandflats ...... 13 3.2.2 Subtidal habitats ...... 18 3.2.3 Fish ...... 25 3.2.4 Birds ...... 30 4 Potential effects ...... 30 5 Conclusions and recommendations ...... 33 6 Acknowledgements ...... 34 7 References ...... 35 8 Appendices ...... 36

1 Background

The St Mary’s Bay Water Quality Improvement Programme is a joint project involving Auckland Council, Auckland Transport, Panuku Development Auckland and Watercare Services. Key aims of the project include enabling contact recreation to safely occur in St Mary’s Bay, and as far as practicable, to reduce and remove contaminant loads. Those outcomes will be delivered through a package of works that include the reconfiguration of the St Mary’s Bay combined sewer and stormwater network. Among other things that work involves:

▪ Diverting the coastal discharges away from St Mary’s Bay to a more dispersive outfall location adjoining Masefield Beach. This will involve the construction of a new marine outfall pipeline comprising a 1400mm internal diameter, 1600mm outer diameter PE pipe (approximately 450m long) discharging through a diffuser. The marine section of the pipeline will connect to a landward pipe section at the existing seawall, which is feed from a pump station via a screened weir structure in Point Erin Park. There are currently two potential alignments for the proposed pipeline (Figure 1-1), with the final alignment to be selected during detailed design. ▪ Removal of the existing marine outfall pipeline on Masefield Beach, and reinstatement of the coastal marine area. ▪ Diverting low-flow wastewater discharges away from the existing coastal outfall at Masefield Beach and returning the wastewater back to Watercare’s branch five sewer via a new pump station. The system has been designed to store all combined sewer overflows that may occur during rainfall events that are just under the 2 month return period in magnitude. During more extreme rainfall events some overflows will still occur. However, the overall system has been designed to reduce combined sewer overflows at five engineered overflow points from approximately 206 times a year to approximately 20 times per year. The pump station weir is designed to be overtopped when the conveyance and storage pipeline becomes full, and there is no ability to pump the collected combined sewer overflows back into the sewer. The weir will be screened with a 6mm self-cleaning horizontal screen attached to the downstream side, to prevent solids discharging to the outfall. The screen will have capacity up to approximately 900l/s. Overflows exceeding the screen capacity will enter the marine pipeline by passing over an adjacent weir and also overtopping the screen.

Connecting the landward and seaward sections of the proposed pipeline will involve pipejacking under the seawall. Pipejacking would be undertaken either by a mechanised tunnel boring machine (TBM) or by hand pipejacking. A construction area will be established around the works area using a coffer dam in the coastal marine area. This temporary construction area in the coastal marine area will be approximately 5 m x 9 m wide. The coffer dam is anticipated to be between 3m to 5m deep. It will be required to be in place for five months and then removed.

The method proposed for installing the pipeline in the coastal marine area is open trenching, using an excavator on the back of a barge. The trench will be approximately 2.6 m wide, and up to 6 m deep. As the trench will largely be dug into bedrock, it is anticipated that relatively steep sides can be maintained. However, in weaker materials, the trench will be battered back.

The proposed construction methodology, using an excavator on a barge, would be able to operate in relatively shallow water. In general, the inshore section of the proposed works would be undertaken during high tides to ensure there is sufficient draft for the vessel. The offshore section would be excavated during low tide, to reduce the reach required to dig and increase the ripping power. Material excavated from the trench would be side cast alongside the trench and a proportion reused for back filling.

The pipeline will be initially bedded and surrounded with sand, then backfilled with side cast material excavated during trenching work. It is envisaged that most of the excavated material will be used within the works, however any excess material will be disposed of to the designated marine dump site or bought to the port and unloaded for disposal to an appropriate site on land.

The pipeline will be assembled off-site prior to being towed to site for placement in the trench using weights. Once in place the pipeline would be connected to the pipe within the coffer dam, and the coffer dam removed. No permanent structure at the seawall is required following this connection. Overall, works within the coastal marine area is expected to take approximately 6 months to complete.

An assessment of the marine ecological and fishing values of Masefield Beach, and potential impacts on these values, was required to inform configuration and design options, and to support a resource consent application for the proposed reconfiguration. Coast and Catchment were commissioned to provide advice on these matters. This report includes information on ecological values, habitat quality and fish around the existing Masefield Beach outfall, and in the general area where options for the proposed outfall were considered. It also assesses the potential impacts of constructing the outfall and its ongoing occupation of the coastal area.

Figure 1-1: Proposed options for the outfall pipeline.

2 Methods

The potential ecological effects of the proposed outfall were assessed by:

▪ conducting field and desktop assessments of ecological values and habitat quality around the existing Masefield Beach outfall and the general area where options for the proposed outfall were considered. This identified ecological values that could potentially be affected, and provided information on the potential effects of the existing outfall based on observations and measurements (albeit without the St Mary’s Bay inputs); and, ▪ identifying potential ecological impacts based on information provided on construction methods.

2.1 Field assessments The field assessments were carried out in two stages:

▪ A preliminary, rapid site assessment to identify the key ecological features of the bay, and identify any matters that should be considered during the concept design stage. ▪ A detailed assessment to assess the potential ecological effects of the preferred options.

2.1.1 Preliminary site assessment The rapid assessment was conducted between the 10–17 March 2017 and included:

▪ Intertidal site inspections during low tide to obtain a general description of the intertidal habitats and key species present in Masefield Beach. ▪ Four subtidal video tows to obtain information on species dwelling on the surface of the seafloor. Three tows were run parallel to Masefield Beach and one tow was run along the southern margin of the main Waitemata Channel running under the Harbour Bridge. Time stamped GPS tracks were simultaneously recorded allowing the positions of features identified from the videos to be determined. ▪ Obtaining 16 grab samples that were visually examined on-site to provide a general description of sediment characteristics and the characteristics of the benthic community living in seafloor sediments. ▪ Collation of available information on fish and fishing around Masefield Beach.

Figure 2-1: Map of the area of interest showing run lines for the video tows and the locations where preliminary grab samples were obtained on the 17 March 2017.

2.1.2 Detailed site assessment The detailed site assessment was conducted on the 25 May 2017 and included:

▪ Obtaining additional, qualitative information on intertidal habitats and species. ▪ Obtaining grab samples collected from 10 subtidal sites around the location of the proposed new outfall (Figure 2-2). Grab samples were collected using a 2 L van Veen grab deployed from a boat. Samples were sieved to 0.5 mm in the field and preserved in 100% isopropyl

alcohol. The samples were sent to an experienced benthic taxonomist for identification and enumeration of the infauna present. ▪ At five of the subtidal stations around the proposed outfall (Figure 2-2), an additional grab was taken for analysis of: o total organic carbon (TOC); o trace concentrations of total recoverable copper, lead and zinc; o sediment grain size. Samples were sent to Hill Laboratories for analysis using standard analytical methods.

▪ Sediment cores taken from five intertidal sites near the existing outfall, with the northern- most site located at the end of the pipe (Figure 2-2). For each site, the top 2 cm of the surface was sampled in three areas within 2 m of one another and combined for the analysis of TOC, copper, lead, zinc and grain size. ▪ 10 baited1 underwater video drops (BUV), each of 20 mins in duration (Figure 2-3). The type and number of fish seen were recorded.

Figure 2-2. Sediment sample locations. Sites near the proposed outfall were sampled for infauna (circles) or infauna and chemistry (triangles), while sites near the existing outfall were just sampled for chemistry (squares). Inset map shows the location of Masefield Beach within the Waitemata Harbour.

1 5 pilchards were used for each video drop.

Figure 2-3. Location of the baited underwater video drops.

2.2 Data analyses Data were plotted and summarised using a combination of univariate and multivariate statistics, and diversity indices. Diversity indices included number of individuals (N), number of taxa (S), Pielou’s Evenness and Shannon Diversity Index.

T-tests were conducted to investigate whether there were any differences in the concentration of metals and TOC between the proposed and existing sites. A standard t-test was conducted on lead data after the assumptions of normality and equal variance were confirmed. Variance in copper, zinc and TOC was unequal, and therefore, non-parametric Mann-Whitney t-tests were conducted for these parameters.

Multivariate analyses were conducted using the Primer statistical software package. Benthic infaunal abundances were square root transformed and analysed using multivariate cluster analysis and multi- dimensional scaling (MDS) using Bray-Curtis similarities. Differences among groups were investigated using similarity percentages (SIMPER) analysis.

3 Results

3.1 Physical characteristics

3.1.1 Intertidal areas around Masefield Beach Masefield Beach is situated on the western side of Auckland Harbour Bridge’s southern terminus. Its eastern shore consists of a seawall revetment, which provides a barrier between the coast and reclaimed land. Curran St runs along the top of the revetment, with the Curran St motorway onramp and a mix of open space and commercial land slightly further back (Figure 3-2a & b).

The natural seabed immediately along the shore contains a mix of exposed sandstone reef and boulders, and sediment-covered reef flats (Figure 3-1). A pronounced section of intertidal reef (‘East reef’), covering an area of around 2000 m2, is located half way along the seawall (Figure 3-1 & Figure 3-2c). A lower lying platform reef, with scattered boulders extends south of this feature. Together these reefs appear to be remnants of a larger intertidal reef system that has been buried beneath reclaimed land. North of the intertidal reefs, the subtidal zone extends right up to the seawall, while the southern end of the seawall ends in a small “pocket” beach of around 35 m in length (Figure 3-1 & Figure 3-2e & f). Pohutukawa-lined sandstone cliffs run along the western edge of Masefield Beach. Various boat houses, launching ramps and other structures are situated along this section of coast. The intertidal zone gradually broadens towards the south, and on the days of the site visits the low tide mark was around 50–60 m from the base of the seawall2.

Figure 3-1: Physical characteristics of Masefield beach and the surrounding area. The reef names have been created for ease of reference.

2 Low tidal height predictions during the two site visits carried out in March 2017 were 0.8 m and 0.7 m. Auckland’s predicted low tide heights for standard barometric pressure range from 0.1 to 1.1 m in 2017.

Figure 3-2: a & b) Seawall revetment running along Curran St; c & d) exposed sandstone reef; e & f) “pocket” beach at the southern end of Masefield Beach.

Multiple combined sewer and stormwater outfalls discharge to the beach, and power cables and a deteriorating outfall pipe run across the south-eastern section of the shoreline (Figure 3-3). Discharges from the two larger outfalls have created shallow drainage channels, which traverse the intertidal area. During the site visit, gross solids were observed in the vicinity of outfalls, an odour was apparent, and sediments had a shallow redox discontinuity layer.

Figure 3-3: a–c) Large, combined sewer discharge outfalls; and, d) cables on Masefield Beach. Note the deteriorating outfall pipe shown in photo b).

3.1.2 Subtidal areas around proposed outfall Video transects, grab samples and marine charts indicate that the subtidal habitats in Masefield Beach consist of a nearshore area of gently sloping sand flats that adjoin the main channel of Waitemata Harbour. The transition between the sand flats and channel is marked by an abrupt change in depths from around 2–4 m on the flats to 24 m in the central part of the channel. The channel is also expected to be subject to relatively strong currents.

3.1.3 Sediment analyses The sediment around the existing outfall was sandy with moderate amounts of gravel and low levels of mud. Sediments around the proposed outfall site also contained a high proportion of sand, but mud and gravel fractions were quite variable (one sample contained around 38% gravel, Figure 3-4 & Figure 3-5 – stations are shown in Figure 3-7).

Copper, lead and zinc concentrations in the sampled sediment were all below the threshold effects level (TEL) concentrations (< 19 mg/kg for copper, < 30 mg/kg for lead, <124 mg/kg for zinc (Figure 3-6a–c)) (MacDonald et al. 1996, CCME 1999). There is some indication that zinc concentrations in the proposed outfall sites 4 and 5, which were located closest to the Harbour Bridge were slightly higher than the other sites, but there was no significant difference between the existing and proposed sites for any of the metals (p > 0.05).

Total organic carbon concentrations at all sites were very low. Sites around the proposed outfall appeared to be slightly higher than sites around the existing outfall, but these differences were not significant (Figure 3-6d).

Figure 3-4: Grainsize composition of the sites around the existing outfall (E1–5) and the proposed outfall (P1–5).

Figure 3-5: Examples of unsieved (left) and sieved (right) grab samples obtained from around the proposed outfall area.

Figure 3-6: a) Copper, b) lead; c) zinc; and d) total organic carbon concentration of the sampled sediment around the existing (E) outfall and proposed (P) outfall. The red lines indicate the threshold effects level (TEL) concentrations.

Figure 3-7: Sediment sampling stations referenced in previous plots.

3.2 Ecological characteristics of Masefield Beach

3.2.1 Intertidal reefs and sandflats Masefield Beach and the surrounding coastal area contains a mix of hard shore and sandflat habitat (Figure 3-1). The hard shore habitat was divided into a seawall revetment and three separate areas of reef:

▪ low-lying reef platforms on the eastern (East reef) and western (West reef) sides of the bay; ▪ an elevated platform east of the bay, halfway along the seawall (Big reef platform) The species assemblage on the intertidal reefs were generally consistent with assemblages on other sheltered north-eastern New Zealand reefs. Key features of each area are provided below.

3.2.1.1 East reef East of Masefield beach is a low-lying reef platform. High on the shore there is a band of native oysters (Saccostrea glomerata) (particularly along the seawall (Figure 3-2b)), which gives way to Pacific oysters (Cassostrea gigas) lower down on the seawall. Pacific oysters were also present on the reef flat and boulders (Figure 3-2c & d). Black nerita (Nerita melanotragus) were common within the upper band of oysters. Little black mussels (Xenostrobus pulex) were common on the pronounced section of intertidal reef, half way along the seawall, along with low numbers of blue mussels (Mytilus galloprovincialis) and barnacles (Austrominius modestus). An 11-armed starfish (Coscinasterias muricata) was also seen along the intertidal margin in that area. The diversity of other intertidal reef

13 invertebrates appeared to be low, but the species present included cat’s eye (Lunella smaragdus), the spotted top shell (Diloma aethiops), and the snake skin chiton (Sypharochiton pelliserpentis).

The algae community is dominated by Neptune’s necklace (Hormosira banksii), which occurred in dense beds on the reef flats, in patchy clumps, or as individual plants in the surrounding area (Figure 3-2d and Figure 3-10b). Other algae species included clumps of the green algae Codium fragile (Figure 3-10b), patches of coralline turf (Coralline sp., Figure 3-10c), and the red algae Chondracanthus chapmanii, which was mainly growing amongst oysters (Figure 3-10d). A band of Carpophyllum sp. was also apparent along the sublittoral margin of the intertidal reef, half way along the seawall.

3.2.1.2 West reef Immediately west of Masefield Beach there is a sandstone reef platform that has a similar intertidal community to ‘East reef’. The reef is covered with Neptune’s necklace, Coralline turf, C. fragile and Pacific oysters (Figure 3-8a & b). Cat’s eyes, black nerita, snakeskin chitons and little black mussels are scattered over the high intertidal zone, while blue mussels, spotted top shells, cushion stars (Patiriella regularis), horn shells (Zeacumantus lutulentus) and speckled whelks (Cominella adspersa) are scattered over the mid to low intertidal zone. Further west, an extensive bed of intertidal seagrass (Zostera sp.) exists on the sandflats of the adjacent bay (Figure 3-1 & Figure 3-8c).

3.2.1.3 Big reef platform Northeast of the outfall, midway along the causeway, there is a large sandstone platform reef (‘Big reef platform’ (Figure 3-1). The upper half of the platform has large exposed bare areas, but water accumulates in the shallow depressions where horn shells and cat’s eyes are found. The sides and lower margin of the platform are densely covered with Pacific oysters (Figure 3-9a). Near the low tide margin the rocks are covered with a variety of seaweeds (Coralline turf, Neptune’s necklace, Codium convolutum and Colpomenia sp.) (Figure 3-9b & c). Scattered amongst the seaweeds are cat’s eyes and a 11-armed starfish. In the shallow subtidal region there is a dense bed of Carpophyllum sp., and the occasional Ecklonia radiata and Mediterranean fanworm (Figure 3-9d).

3.2.1.4 Sandflats Few species were visible on the sandflats within Masefield Beach. The most significant were cockles (Austrovenus stutchburyi), with live specimens being exposed along the margins of outfall channels during a discharge event (Figure 3-10e). Low numbers of burrows were also observed on the sandflats and upper beach margin. These are likely to have been created by crabs on the sandflats and sand hoppers (isopods) on the beach.

The area directly below the existing outfall has a thin layer of muddy sand over a firmer base. Similar species occur in the pools and on the rocks below the outfall to that found in the mid to low intertidal zone of ‘west reef’. One orange butterfly chiton (Cryptoconchus porosus) was found amidst the rocks (Figure 3-8f). Numerous worm tubes protrude through the surface of the sediment near the water’s edge (Figure 3-8e), and patches of seagrass occur in the shallow subtidal area around the outfall (Figure 3-8d).

Figure 3-8: a) ‘West reef’ platform covered in Neptune’s necklace and Coralline turf in the foreground and Pacific oysters in the background; b) close up of Neptune’s necklace and C. fragile; c) extensive intertidal seagrass beds west of Masefield beach; d) the end of the outfall with subtidal seagrass in the foreground; e) worm tubes protruding through the sediment; f) an orange butterfly chiton.

Figure 3-9: a) ‘Big reef platform’; b) golden-brown Colpomenia sp. scattered between Coralline turf; c) the dark green Codium convolutum; d) Carpophyllum sp. and Ecklonia radiata in the shallow subtidal region.

Figure 3-10: Examples of key intertidal biota along Masefield Beach. a) Little black mussels; b) Neptune’s necklace; c) Neptune’s necklace and coralline turf; d) Pacific oysters; e) cockles.

3.2.2 Subtidal habitats

3.2.2.1 Subtidal epifauna Visibility was limited, but larger taxa could be distinguished in video footage, including:

▪ horse mussels (Atrina zelandica); ▪ various sponges; ▪ various seaweeds; ▪ Mediterranean fanworm (Sabella spallanzanii); ▪ clubbed tunicate (Styela clava). The latter two species (S. spallanzanii and S. clava) are classified unwanted organisms under the Biosecurity Act (1993).

Horse mussels and sponges (which commonly grow on horse mussels) were widespread within the survey area, with greatest numbers recorded in the two innermost transects (Figure 3-12 & Figure 3-13). Horse mussels are a bivalve species that forms distinct biogenic habitats, providing complex three-dimensional structure in otherwise “featureless” areas. These habitats are colonised or utilised by a range of other species that grow on, or live among, the mussels (e.g. juvenile snapper, sponges, crayfish). The high ecological value of “beds of large bivalves” (including horse mussels) and “sponge gardens” are recognised in the inclusion of these habitats in the Ministry for the Environment’s list of sensitive marine environments (MacDiarmid et al. 2013) (Figure 3-11). However, it is unlikely that populations of horse mussels and sponges around Masefield Beach would meet the interim definitions of these habitats, which are based on thresholds for the percent cover and volume of biota. MacDiarmid et al. (2013) define beds of large bivalves and sponge gardens as:

▪ Beds of large bivalves—where living and dead specimens of bivalve species cover 30% or more of the seabed in imaging surveys covering 100 m2 or more, contribute 30% or more by weight or volume to the catch in a single grab sample or dredge tow. ▪ Sponge gardens—characteristic indicators of sponge gardens include an average 25% or greater percentage cover of one or more sponge species in uniform or clumped distribution over an area of 100 m2 or more. The occurrence of 25% or greater volume of mixed sponges or single sponge species in successive samples obtained using point sampling gear, or 20% or greater volume in a sample obtained using mobile sampling gear, is sufficient to indicate the presence of a sponge garden.

Seaweeds were more limited in extent, being restricted to the area around the Harbour Bridge and the eastern end of the middle longshore transect (Figure 3-14). Mediterranean fanworm were prevalent in the main channel, around the Harbour Bridge and at the eastern end of the inner-most transect (Figure 3-15). Only two clubbed tunicates were observed, both along the innermost transect (Figure 3-16).

Figure 3-11: Examples showing the variety of epibiota that can grow on horse mussels (photos from Kawau Bay).

Figure 3-12: Distribution of horse mussels observed in video footage obtained along four tracks in Masefield Beach.

Figure 3-13: Distribution of sponges observed in video footage obtained along four tracks in Masefield Beach.

Figure 3-14: Distribution of attached seaweed observed in video footage obtained along four tracks in Masefield Beach.

Figure 3-15: Distribution of Mediterranean fanworm observed in video footage obtained along four tracks in Masefield Beach.

Figure 3-16: Distribution of clubbed tunicate observed in video footage obtained along four tracks in Masefield Beach.

3.2.2.2 Subtidal infauna The benthic infaunal community in the general area of the proposed outfall site was relatively diverse, with a total of 79 taxa and 690 individuals collected. The number of taxa per grab ranged from 18–33, with an average of 24.7 ± 1.7 S.E., while the number of individuals per grab ranged from 26–153, with an average of 69 ± 11 S.E. (Figure 3-17 & Figure 3-20). The benthic community mainly comprised polychaetes (30 taxa and 227 individuals), amphipods (5 taxa, 91 individuals), and molluscs (12 taxa, 44 individuals). Five species dominated the community, accounting for nearly half of the total number of individuals. These were brittle stars, the polychaete Heteromastus filiformis, a phoxocephalid amphipod, an unidentified amphipod, and hermit crabs (Pagrus sp.) (Figure 3-18).

The Shannon Diversity Index is an indicator of how many taxa are present in the community and how evenly represented the taxa are. The higher the number of taxa present, and the more evenly distributed they are, the higher the Shannon Diversity Index. The index typically varies from 0 (low) to 5 (high) (Keeley et al. 2012). Shannon Diversity scores in the proposed outfall area were moderate for most sites, with a mean of 2.7 ± 0.1 S.E. and a range of 1.8–3.1 (Figure 3-17c).

Pielou’s Evenness is an indicator of how evenly represented all taxa are in a community. Uneven communities that are dominated by a few species have an evenness score near zero, whereas evenly represented communities have an evenness score near one (Keeley et al. 2012). Pielou’s Evenness scores in the proposed outfall area were generally very high for most sites, with a mean of 0.84 ± 0.04 S.E. and a range of 0.55–0.97 (Figure 3-17d).

Site 8, located west of the Harbour Bridge had an unusually high number of brittle stars that resulted in a higher abundance, a lower diversity and a lower evenness score.

A MDS with a similarity profile analysis of the infauna found two distinct groups (Figure 3-19), but the results of a SIMPER analysis didn’t show any large differences in the average abundances or dissimilarities of individual taxa between the two groups, which suggests that the differences may be of little ecological significance.

Figure 3-17: a) Number of individuals per grab; b) number of taxa per grab; c) Shannon diversity index; and d) Pielou’s evenness score for the sampled sites near the proposed outfall.

Figure 3-18: The ten most abundant taxa found in the sites around the proposed outfall.

Transform: Square root Resemblance: S17 Bray Curtis similarity 2D Stress: 0.11 Similarity Grab 2 38

Grab 4 Grab 3

Grab 6 Grab 5 Grab 7

Grab 9 Grab 8 Grab 10

Grab 1

Figure 3-19: MDS of the infauna showing two groups that have an average dissimilarity of 65%.

Figure 3-20: a) Bubble plot showing the number of individuals per grab; and, b) the number of taxa per grab. Site numbers are labelled in a).

3.2.3 Fish

3.2.3.1 Baited underwater video survey In total, 14 finfish and one crab was observed in the BUV. The most common species were juvenile snapper, though two eels and a school of unidentified pelagic fish were also observed (Table 1). Visibility in the BUV was limited, preventing the identification of some of the species observed.

Table 1: Fish species observed in the baited underwater video drops.

Drop number Depth (m) Fish 1 6.9 No fish 2 8.0 1 crab 3 6.7 No fish 4 6.6 1 snapper (< 10 cm) 5 8.3 1 snapper (10–20 cm) 6 4.1 2 snapper (< 10 cm) 7 10.2 1 snapper (10–20 cm), 5 pelagic fish (unidentified) 8 8.2 1 eel 9 6.5 1 eel, 1 unidentified fish 10 4.5 1 snapper (< 10 cm)

3.2.3.2 Desktop review Waitemata Harbour is a popular site for recreational fishing. Both land-based and boat fishing occurs in and around Masefield Beach. Aerial surveys of recreational fishing from boats were carried out in 2011–12 (Hartill et al. 2013). The results of those surveys indicate that Waitemata Harbour is intensively fished. Boat-based fishing effort tends to be concentrated in and around the main harbour channel, with greater use of the adjoining sand flats on the western side of the central Waitemata (Figure 3-21). Sites in and around Masefield Beach are among those targeted by boat-based fishers, while the Curran St seawall is a focal area for land-based fishing.

Detailed information on the make-up of the local recreational catch was not obtained during this review, but a number of targeted fish species were obtained during the collection of samples by Mutoro (2001), and in a baseline survey of non-indigenous marine species around the Port of Auckland (Inglis et al. 2006). Those and other potentially targeted, or incidentally caught, species are listed in Table 2. Fishers have also reported hooking great white sharks in the harbour (Anonymous 2014). Additional, non-targeted fish species found in the area include speckled sole (Peltorhamphus latus), anchovy (Engraulis australis) and goby (Favonigobius lateralis) (Mutoro 2001).

Table 2: Fish species potentially caught in and around Masefield Beach. Species listed by Mutoro (2001) and Inglis et al. (2006) are indicated.

Common Name Māori Name Scientific Name Mutoro Inglis et (2001) al. (2006) Yellow eyed mullet Aua Aldrichetta forsteri ✓ ✓ Snapper Tamure Chrysophrys auratus ✓ ✓ Sand flounder Pātiki Rhombosolea plebia ✓ Yellow-belly flounder Pātiki Rhombosolea leporina ✓ Kahawai Kahawai Arripis trutta ✓ Parore (Black snapper) Parore Girella triscuspidata ✓ Kingfish Haku Seriola lalandi Trevally Araara Pseudocaranx dentex ✓ Koheru Koheru Decapterus koheru ✓

Spotty Pākirikiri Notolabrus celidotus ✓ ✓ John dory Pukeru, Kuparu Zeus faber Leatherjacket Kōkiri Parika scaber Grey mullet Kanae raukura Mugil cephalus ✓ Pilchard Mohimohi Sardinops neopilchardus ✓ Jack mackerel Hauture Trachurus declivis ✓ ✓ Estuary stargazer Kourepoua Leptoscopus macropygus ✓ Shortfin eel Tuna Anguilla australis ✓ Long fin eel Tuna Anguilla diffinbachii ✓ School shark Mangō, Kapetā Galeorhinus australis Rig Mangō, Koinga Mustelus lenticulatus ✓ Hammerhead Ururoa, Kakere Sphyrna zygaena Bronze whaler Horopekapeka Carcharhinus brachyurus Short tailed stingray Whai, Pākau, Dasyatis brevicaudata Roha, Pakaurua Long tailed stingray Whai, Pākau, Dasyatis thetidis Roha, Pakaurua Eagle ray Whai keo Myliobatis tenuicaudatus

NIWA have also carried out a relatively extensive survey of fish in intertidal areas of the Waitemata Harbour in February 2001 using beach seine nets (Morrison & Francis, unpublished data (for further details, refer to Morrison et al. 2002; Francis et al. 2005)). Standardised fish count data originally provided by Mark Morrison (NIWA) showed that the occurrence and abundance of most fish species obtained with this method was very patchy (see Kelly 2008, Figure 3-22). None of the sampling sites were located in Masefield Beach, but other sites in the outer Waitemata tended to have relatively low counts of most fish species (highest counts tended to be obtained from sites in the Upper Waitemata Harbour and Whau Channel). Nevertheless, fish diversity in outer parts of the Harbour was similar to diversity in central and upper areas ( Figure 3-23). Waitemata Harbour is also regarded as a high value rig nursery due to the number of less than one-year-old rig caught during research surveys (Blackwell & Francis 2010, Francis et al. 2012).

A number of studies have also looked at fish health in the Waitemata Harbour. Findings of note include:

▪ Lowe (2013) examined the relationship between suspended sediment loads and juvenile snapper condition3 at sites in seven northern New Zealand harbours. Lowest water clarity, highest total suspended solids concentrations and lowest condition scores were recorded from the Waitemata Harbour site. However, a higher incidence of gill deformities was recorded in Manukau and Mahurangi Harbours. ▪ Mutoro (2001) examined yellow belly flounder from the Waitemata, Kaipara and Manukau Harbours and Tamaki and Waiwera Inlets for “pollution-related diseases”. 13.5% of fish from the Waitemata were found to display haemorrahagia, 6% were found to have skin infections,

3 Condition was determined using the ratio of the actual carcass weight to expected carcass weight, where expected carcass weight was taken from the weight of an average snapper of the same length.

and 4% had lesions. These incident rates were less than the Manukau Harbour, but much higher than fish from the relatively unpolluted Kaipara Harbour. ▪ Nenadic (1998) found that yellow belly flounder from two sites in the Waitemata Harbour had a greater prevalence and severity of pathological changes in the gills, blood, liver, kidney and gonads compared with fish from a single Whangaparoa reference site.

Figure 3-21: Positions of recreational fishing boats recorded during aerial surveys in 2011–12 (see Hartill et al. 2013 for details of the survey).

28 a. b.

c. d.

Figure 3-22: Examples of standardised fish counts (number per meter of beach seine towed) for commercially and recreationally fished species including a) snapper, b) yellow eyed mullet, c) yellow belly flounder and d) sand flounder in Waitemata Harbour (Morrison and Francis unpublished data, maps adapted from Kelly 2008).

Figure 3-23: Number of fish species obtained in 9 m wide beach seines in February 2001 (Morrison and Francis unpublished data, map adapted from Kelly 2008 ).

3.2.4 Birds A variety of coastal birds were observed during the surveys including: red billed gulls (Larus novaehollandiae), southern black-backed gulls (Larus dominicanus), kingfishers (Todiramphus sanctus) and variable oystercatchers (Haematopus unicolor).

4 Potential effects

Based on information provided on construction methods, ecological effects potentially include:

▪ The smothering and crushing of biota within the footprint of the temporary intertidal work platform and access ramp. A range of intertidal species will potentially be affected, including: native and Pacific oysters, little black, and blue mussels, barnacles, marine snails (black nerita, cat’s eye, spotted top shell), the snake skin chiton, and algae such as Neptune’s necklace, Codium fragile coralline turf. All of the potentially affected species are common and are likely to return to the site once construction is complete.

▪ The removal of scattered subtidal epifauna (emergent seabed species), infauna (species that dwell within seabed sediments) and potentially algae from along the trench excavation. It is likely that a high proportion of the plants and animals removed during excavation will be killed. A wide range of species will potentially be affected, including some species that form biogenic habitats and are considered to have relatively high ecological values (such as sponges

and horse mussels). Other species, including Mediterranean fan worm may be able to survive (see below). The excavated area will progressively be recolonised once construction activities cease.

▪ The smothering of subtidal seabed species beneath excavated material that is cast beside the trench. The species affected will be similar to those affected by trenching, and also similarly, this material will be progressively recolonised once construction activities cease. ▪ The total area directly affected by trenching and side casting will be approximately 3000 m2 to 3500 m2 (based on a 2.6 m wide by 450 m trench, and excavated material deposited along a 4 m to 5 m wide band along the trench). A smaller area will also be directly affected within the connection work site and access ramp areas.

▪ The crushing of organisms by machinery and their incidental removal during the demolition and extraction of the old outfall structure. Relatively few species were observed in this area, but they included cockles, crabs, chitons, oysters and algae (predominantly Neptunes necklace). The affected area will be progressively recolonised once demolition activities cease. ▪ Mediterranean fan worm Sabella spallanzanii and the clubbed sea-squirt Styella clava are present in the Masefield Beach area (Error! Reference source not found.), and potentially occur along the excavation footprint. Both species are classified as “Unwanted Organisms”, and are therefore managed under the Biosecurity Act 1993.

Section 52 of the Biosecurity Act 1993 states:

No person shall knowingly communicate, cause to be communicated, release, or cause to be released, or otherwise spread any pest or unwanted organism except— (a) in the course of and in accordance with a pest management plan; or (b) as provided in an emergency regulation made under section 150; or (c) for a scientific purpose carried out with the authority of the Minister; or (d) as permitted either generally or specifically by a chief technical officer. The Ministry for Primary Industries therefore requires permission to be obtained prior to moving unwanted organisms. Localised movement could occur within the construction site during the excavation of the trench, while broader scale movement could occur if side-cast material was removed and disposed of off-site.

Mediterranean fan worm is a prolific tube worm species that grows on most substrates in depths ranging from the low tide mark to 30m deep. They grow up to half a meter in length, with leathery tubes that look like a broken off kelp stalks. Their distinct fan emerges from their tubes when feeding, but is rapidly retracted when disturbed. Mediterranean fanworm can form dense mats, potentially outcompeting other species and altering the composition of benthic communities. Their ability to filter large volumes of water also means they have the potential out compete native filter feeders. Dense beds could also become a problem for marine farmers, fishers and other users, by clogging dredges and fouling equipment. Mediterranean fan worm have remarkable regenerative capabilities, with amputated body

fragments able to reform back to an entire worm (Licciano et al. 2012). This ability increases the risk of them being mobilised and dispersed to new areas when disturbed.

The clubbed sea-squirt is also a prolific species that grows on rocks, shells and hard structures in depths ranging from just below the low tide mark to 25m deep. They can reach around 10 cm in length, with a leathery body (that looks like a “warty” bulb) attached to the substrate by 1 -3 cm stalk. Clubbed sea-squirts also foul, smoother, outcompete important native species and habitats, with species such as scallops and horse mussels frequently being fouled (S. Kelly pers. obs., Figure 4-1).

▪ Effects on fish and other mobile fauna are uncertain and may vary among species and age classes. They could be:

o displaced during construction because of noise, the movement of machinery and equipment, and sediment plumes created during excavations;

o attracted by prey that are killed or injured during construction activities;

o unaffected by construction activities.

▪ Sediment plumes could be generated during excavation and infilling. However, the work will be done within a relatively short timeframe and the level of turbidity generated is expected to be no greater than that typically generated by runoff and waves during storm events (Hume 2017). The ecological effects arising from sediment plumes are therefore expected to be less than minor. Longer term effects potentially include changes in water and sediment quality at the existing and new outfall sites. Sediment concentrations of key metals and organic carbon around existing outfall are relatively low, but gross solids were observed during site visits. Water quality monitoring also indicates that copper and zinc concentrations tend to be low around stormwater outfalls discharging into St Mary’s Bay (although an isolated spike in zinc concentrations occurred on one occasion), while lead concentrations are slightly elevated (Walker & Kalbus 2017). Based on this, only minor changes in water and sediment quality (excluding microbial quality) are expected to occur around the existing and new outfall sites in the Masefield Beach area, with the quality around the existing outfall slightly improving, and quality in the immediate vicinity of the new outfall slightly declining. The changes are expected to have a less than minor effect on ecological values. The effects of gross solids associated on marine ecology are likely to be minor, given that discharges through the outfall will be screened at the weir to remove gross pollutants. Amenity and human health effects have not been considered in this report.

Figure 4-1: Unwanted organisms that could be disturbed during the construction of the outfall pipeline, a) Mediterranean fan worm and b) Clubbed sea-squirt (pictures taken from other areas in the Hauraki Gulf).

5 Conclusions and recommendations

Overall, available information and a detailed site inspection support the following conclusions:

▪ The intertidal area of Masefield Beach includes reef and sediment habitats with communities that are typical of those found in the broader area. Existing intertidal habitats are highly modified, and appear to have degraded ecological values with no ecologically “significant” or unique features. However, a flourishing seagrass bed is present in the bay to the west of Masefield beach and patches of seagrass were observed in the shallow subtidal areas just beyond the intertidal margin within Masefield Beach.

▪ A number of effects of the existing combined sewer outfalls are apparent on intertidal habitats of Masefield Beach. They include: the deposition of gross solids, localised scour (including scouring of cockle beds), and biofouling of deteriorating outfall structures. Analysis of zinc, copper and lead concentrations in the sediment around the existing outfall found that they were all below TEL concentrations. Total organic carbon concentrations in the sediment were also low. ▪ The subtidal area out from Masefield Beach contains habitats that are likely to be locally significant, particularly horse mussel and sponge beds. The subtidal benthic infauna community was also relatively diverse, with moderately high diversity and high evenness. Physical disturbance to those habitats during construction should be minimised. ▪ The seabed was predominantly mud to fine sand, and zinc, copper, and lead concentrations in the sediment around the proposed outfall were all below TEL concentrations. There is some indication that zinc and TOC concentrations around the proposed outfall were slightly higher than the existing outfall, but these differences were not significant. ▪ Masefield Beach and the surrounding area is intensively fished by recreational fishers, with a wide variety of species potentially being taken. Baited underwater video tows suggest that snapper are the most common targeted species likely to be present in the area. ▪ Research has been carried out that suggests some fish may be adversely affected by water quality in Waitemata Harbour, but the relative influence (if any), of the combined sewer system is unknown. Having said that, reducing overall discharges loads from that system would reduce the potential for effects on fish health. ▪ The potential adverse ecological effects from the proposed activities mainly relate to impacts associated with physical disturbance, smothering, and crushing. Effects will be significant within the construction and demolition footprints, but minor to less than minor at the scale of Waitemata Harbour, and negligible at larger scales. Efforts should be made to minimise the footprints of construction and demolition activities. ▪ The ecological effects arising from sediment plumes generated during the construction of the outfall are expected to be less than minor. ▪ Biosecurity risks should be considered through an application made under the Biosecurity Act. However, given that the unwanted species present around Masefield Beach are already widespread and abundant in the area, the biosecurity risks of the proposed construction activities are generally considered to be low. However, to avoid the potential for unwanted species to be transferred to un-infested areas, if material excavated from the pipe trench is to be removed from the site, it should be transferred to trucks within the Auckland Port area and disposed of to land.

6 Acknowledgements

Many thanks to Rod Asher from Biolive Ltd for the taxonomic identifications.

7 References

Anonymous (2014) Great white shark hooked in Auckland's Waitemata Harbour. Stuff. Available at: http://www.stuff.co.nz/national/64572915/Great-white-shark-hooked-in-Aucklands- Waitemata-Harbour [Accessed: 28/3/2017] CCME (1999) Canadian environmental quality guidelines. Canadian Council of Ministers of the Environment, Winnipeg. Francis, M.P., Morrison, M.A., Leathwick, J., Walsh, C., Middleton, C. (2005) Predictive models of small fish presence and abundance in northern New Zealand harbours. Estuarine, Coastal and Shelf Science, 64: 419-435 Hartill, B., Bian, R., Rush, N., Armiger, H. (2013) Aerial-access recreational harvest estimates for snapper, kahawai, red gurnard, tarakihi and trevally in FMA 1 in 2011–12. New Zealand Fisheries Assessment Report 2013/70, Ministry for Primary Industries. 44 pp. Hume, T.M. (2017) Combined sewer diversion and outfall reconfiguration: Masefield Beach coastal physical processes. Client report for Auckland Council, Hume Consulting Ltd., Auckland. 13 pp. Inglis, G., Gust, N., Fitridge, I., Floerl, O., Woods, C., Hayden, B., Fenwick, G. (2006) Port of Auckland baseline survey for non-indigenous marine species (Research Project ZBS2000/04). Biosecurity New Zealand Technical Paper 2005/08, Biosecurity New Zealand, Wellington. Keeley, N., Forrest, B.M., Crawford, C.M., MacLeod, C.K. (2012) Exploiting salmon farm benthic enrichment gradients to evaluate the regional performance of biotic indices and environmental indicators. Ecological Indicators, 23: 453–466 Kelly, S. (2008) Environmental condition and values of Mangere Inlet, Whau Estuary and Tamaki Estuary. ARC Technical Report 2008/031, Auckland Regional Council, Auckland. 130 pp. Licciano, M., Murray, J.M., Watson, G.J., Giangrande, A. (2012) Morphological comparison of the regeneration process in Sabella spallanzanii and Branchiomma luctuosum (Annelida, Sabellida). Invertebrate Biology, 131: 40-51 Lowe, M.L. (2013) Factors affecting the habitat usage of estuarine juvenile fish in northern New Zealand. PhD Thesis, University of Auckland MacDiarmid, A., Bowden, D., Cummings, V., Morrison, M., Jones, E., Kelly, M., Neil, H., Nelson, W., Rowden, A. (2013) Sensitive marine benthic habitats defined. Client report prepared for the Ministry for the Environment, NIWA. 72 pp. MacDonald, D.D., Carr, R.S., Calder, F.D., Long, E.R., Ingersoll, C.G. (1996) Development and evaluation of sediment quality guidelines for Florida coastal waters. Ecotoxicology, 5: 253-278 Morrison, M.A., Francis, M.P., Hartill, B.W., Parkinson, D.M. (2002) Diurnal and tidal variation in the abundance of the fish fauna of a temperate tidal mudflat. Estuarine, Coastal and Shelf Science, 54: 793–807 Mutoro, D.B. (2001) Life of a flatfish, the yellowbelly flounder, Rhombosolea leporina Günther, 1873, in Auckland's sheltered waters. PhD Thesis, University of Auckland, Auckland. Nenadic, A. (1998) The health of yellowbelly flounder (Rhombosolea leporina) from the Waitemata Harbour. PhD Thesis, University of Auckland, Auckland. Walker, J., Kalbus, E. (2017) St Mary’s Bay Auckland: Assessment of recent water quality monitoring initiatives. Working Report WR2017/004, Auckland Council, Auckland.

8 Appendices

Table 3: Taxa found in the sampled sites around the proposed outfall.

Taxa Common Name Site 1 Site 2 Site 3 Site 4 Site 5 Site 6 Site 7 Site 8 Site 9 Site 10

Sponge Unid. Encrusting Unidentifed encrusting sponge 1 1 1 1 Callyspongia sp. Erect sponge 1 Bryozoa (encrusting) Bryozoa 5 1 1 1 1 1 1 1 1 Bryozoa (solid stalked) Bryozoa 1 1 1 Hydroida (thecate) Hydroid colony 2 1 1 1 5 1 5 1 1 1 Hemichordata Acorn worm 2 1 Aspidosiphon sp. Peanut worm 1 2 1 1 1 Phoronus sp. Horseshoe worms 15 1 Oligochaeta Oligochaete worms 5 1 3 2 2 1 4 Nemertea Proboscis worms 1 1 2 1 2 Terebellides stroemi Polychaete worm 3 3 1 Terebellidae Polychaete worm 4 3 1 2 Sphaerosyllis sp. Polychaete worm 1 2 1 1 1 4 1 1 Syllidae Polychaete worm 2 1 1 1 Spirobinae Polychaete family 3 Prionospio multicristata Polychaete worm 1 1 3 1 3 1 Boccardia sp. Polychaete worm 2 2 2 Hydroides norvegicus Polychaete worm 1 Sabellidae Umbrella worms 1 2 Euchone pallida Fan worm 2 Polynoidae Scale worms 1 1 Paraonidae Polychaete worm 1 4 1 11 Myriochele sp. Polychaete worm 9 4 Owenia petersenae Polychaete 1 1 1 4 Orbinia papillosa Polychaete worm 1 1 1 1

Taxa Common Name Site 1 Site 2 Site 3 Site 4 Site 5 Site 6 Site 7 Site 8 Site 9 Site 10 Armandia maculata Polychaete worm 3 1 1 Nereidae (juvenile) Rag worms 1 Maldanidae Bamboo Worms 1 Magelona dakini Polychaete worm 1 Lumbrineridae Polychaete worm 1 Marphysa depressa Polychaete worm 1 Hesionidae Polychaete Worm 1 Goniada sp. Polychaete worm 1 1 1 Glyceridae Polychaete worm 2 2 Flabelligeridae Polychaete worm 1 Dorvilleidae Polychaete worm 1 9 1 Cossura consimilis Polychaete worm 1 Cirratulidae Polychaete worm 1 1 7 Heteromastus filiformis Polychaete worm 11 2 5 10 12 6 9 11 9 9 Amphinomidae Polychaete worm 1 Leptochiton inquinatus Chiton 1 3 1 Sigapatella tenuis Small circular slipper shell 1 1 Zeacolpus sp. Turret shell 1 Theora lubrica Window shell 1 2 1 2 7 1 2 3 Monia zelandica Window oyster 1 3 2 Felaniella zealandica Bivalve 2 1 Bivalvia unid. (juv) Unident juvenile bivalve 1 1 Leptomya retiaria retiaria Small bivalve 1 1 Arthritica bifurca Small bivalve 1 Limaria orientalis File Shell 1 Scintillona zelandica Small bivalve 1 Varinucula gallinacea Nut shell 1 Balanus sp. Barnacle 1 Phoxocephalidae Amphipod (family) 2 2 4 5 10 6 1 6 1 6 Amphipoda unid. Amphipod 1 1 6 1 12 14 2 2

Taxa Common Name Site 1 Site 2 Site 3 Site 4 Site 5 Site 6 Site 7 Site 8 Site 9 Site 10 Lysianassidae Amphipod (family) 2 1 2 2 Caprellidae Caprillid amphipod 1 Corophiidae Amphipod (family) 1 Scleroconcha arcuata Ostracod 3 1 2 5 Diasterope grisea Ostracod 2 1 1 1 2 2 Rutiderma sp. Ostracods 1 2 2 Phylctenophora zealandica Ostracod 2 2 Trachyleberis lytteltonsis Ostracod 1 1 1 1 Euphilomedes agilis Ostracod 2 Scleroconcha sp. Ostracod 1 Tanaid sp. Tanaid shrimp 2 2 1 Mysidacea Mysid shrimp 1 1 1 Anthuridea Isopod 1 3 1 1 Pycnogonidae Sea spiders 1 Pagurus sp. Hermit crab 5 1 1 13 2 Petrolisthes novaezelandiae Red false crab 4 Palaemon affinis Estuarine prawn 1 1 Liocarcinus corrugatus Swimming crab 1 Upogebia danai Mud shrimp 1 Cumacea Cumaceans 1 1 1 1 1 Nebalia sp. Small crustacean 2 3 Trochodota dendyi Sea cucumber 1 1 1 1 1 2 1 Echinocardium spat Heart Urchin 1 Ophiuroidea Brittle stars 10 3 1 11 1 14 88 9 Count: No of Individuals 52 53 26 35 74 67 75 73 153 50 84 Count: No of Taxa 18 20 20 27 27 27 28 29 18 33 Diversity (H’) 2.5154 2.9181 2.7956 2.9315 2.8067 2.8521 2.7977 1.8827 2.3432 3.1426 Evenness (J’) 0.8703 0.9741 0.9332 0.8895 0.8516 0.8654 0.8396 0.5591 0.8107 0.8988