Proposed Extension to the Multi-purpose Berth at Port Chalmers:

Transcription

1 MPB Extension: Habitat Survey Habitat Survey: Proposed Extension to the Multi-purpose Berth at Port Chalmers: Prepared by Ryder Consulting April 2017

2 MPB Extension: Habitat Survey Habitat Survey: Proposed Extension to the Multi-purpose Berth at Port Chalmers: Prepared by Brian Stewart PhD Ryder Consulting April 2017 Ryder Consulting Ltd. PO Box 1023 Dunedin New Zealand Ph: Fax:

3 MPB Extension: Habitat Survey Table of Contents 1. Introduction 5 2. Methods 5 3. Results 7 4. Discussion Conclusions Acknowledgements References 17 Appendix 1 Subtidal Habitat 18

4 MPB Extension: Habitat Survey Executive Summary Port Otago Ltd (POL) has been granted consents to extend the multi-purpose berth at Port Chalmers. Conditions of the consents stipulate that POL undertake a habitat survey in the area likely to be affected. To this end rocky shore and soft bottoms were surveyed by Ryder Consulting Ltd. Surveys included the collection of photoquadrats and cores along randomly located transects at the proposed impact site and a nearby control site. Sheltered rocky shores within Otago are quite rare, but have been extensively studied. The communities encountered during this survey are flourishing and typical of those one would expect to find on sheltered rocky shores in southern New Zealand. The assemblages comprise largely foliose red and brown algae, sponges, ascidians and gastropod molluscs. Organisms living on rocky substrate are at risk of being covered by new rocky substrate and/or smothering by fine sediments. However, it is recognized that construction activity is unlikely to be the only source of such sediments, nor the most significant source. Overall, it is expected that hard substrate communities will recover within a two year timeframe, albeit with slightly reduced algal cover. It is recommended that POL consider a programme to relocate large invertebrates from the impact site to nearby sites with similar substrate.

5 MPB Extension: Habitat Survey Introduction Port Otago Ltd (POL) applied for and has been granted consents to erect structures within the coastal marine area for the purpose of extending the Port Chalmers Multi-purpose Wharf and supporting the existing wharves alongside the deepened berth (Consent No: VI). To facilitate this they have also been granted consent to disturb the foreshore and seabed and deposit up to 30,000 cubic metres of rock rip rap to form a rock buttress and revetment (if required) for the purpose of improving foreshore and seabed stability under the container wharf and the extended Multi-purpose Wharf and their associated berths (Consent No: VI). A third consent (No: ), granting permission to discharge contaminants to the coastal marine area for the purpose of depositing rock rip rap, extending the Port Chalmers Multipurpose Wharf and constructing a fishing jetty, has also been granted. Condition 8 of the Coastal Permit to Consent No: VI states that the consent holder shall undertake a habitat survey of the site to receive the rock rip rap and shall include a minimum area of 20 m surrounding the site, at least three months prior to commencement of work. To this end, POL has engaged Ryder Consulting Ltd (RCL) to carry out the habitat assessment. The following report presents the findings of the investigations carried out by RCL and comments on likely changes to habitat and possible outcomes. 2. Methods Methods for this survey are widely used in the assessment of subtidal marine habitats (Kingsford and Batttershill 1998). It is recognised that implementation of the proposed berth extension will result in the covering or removal of existing flora and fauna in the work area. As such, this survey is designed to provide a snapshot of the types and abundance of organisms present in the proposed work area, and in a nearby area that will be less affected by construction activities. Four shore-normal transects were surveyed at the proposed impact site and at a nearby control site (Figure 2.1.1). Transect locations were randomly selected at roughly equal spacing along each site. A weighted line was laid down the rip rap at each transect and at least 10 m out onto soft substrate at the base of the rock wall at each site. Divers then swam each transect taking photographs of a 0.25 m 2 quadrat at 5 m intervals until at least two photoquadrats had been obtained on soft substrate. Thus, at least 4, and as many as 6, quadrats were photographed along each transect. Once photoquadrats had been obtained the divers returned to the surface along each transect, ranging 2-3 m either side of the line making observations of the general flora, fauna, and substrate.

6 MPB Extension: Habitat Survey Figure Location of transects at (top) control site; and (right) impact site, Port Chalmers, Otago Harbour. Photographs were then viewed by experienced personnel and obvious flora and fauna identified and counted, or percentage cover estimated, as appropriate. As pointed out by Paavo (2009), algae typically form multi-species aggregations and it is not feasible to identify most individual algal taxa in some quadrats. Consequently, only large, well-documented taxa were identified individually. Similarly, colonial or cryptic animal species (particularly sponges, colonial tunicates, and bryozoans) cannot be reliably identified in the field and a best guess based on form and colour was made. Infauna were not counted unless they were clearly identifiable as individuals. A second diver obtained two replicate cores in soft substrate at the end of each transect. Cores were 85 mm in diameter and were collected to 200 mm depth using custom built corers (Figure 2.1.2).

7 MPB Extension: Habitat Survey Figure Core sampler used for deep channel core sampling. Cores were sieved on site and retained animals preserved and returned to the laboratory for identification and enumeration. 3. Results Sites were visited at mid ebb tide on 23 rd March Visibility was relatively poor at m. Photographs or example quadrats are presented in Appendix 1. There was moderate diversity of algae in the intertidal zones, with ten taxa observed at proposed impact site and seven taxa at the control site (Tables and 3.1.2). Cover was generally sparse except at the shallower quadrats, with quadrat b having the greatest algal cover at all transects. The visually dominant species present was Macrocycstis pyrifera, which was present in shallower water at every transect (Tables and 3.1.2). Cystophora and Ulva were also reasonably common. The species present, and cover, appear to be typical of sheltered intertidal rocky shores within Otago Harbour (Batham 1956; Probert and Jillett 1998; Stewart 2005, 2013).

8 MPB Extension: Habitat Survey Table Percentage algal cover within 0.25 m 2 quadrats along transects at the proposed impact site. Table Percentage algal cover within 0.25 m 2 quadrats along transects at the control site. Animals showed reasonable diversity with a total of 32 taxa observed at the proposed impact site and 27 taxa at the control site. It must be noted that these totals include animals from soft substrate cores. Abundance, however, was not particularly high, especially for fauna on hard substrate (Tables and 3.1.4). Exceptions were for barnacles (Chamaesipho columna) at Quadrat 1 for Transects T4 and C3 (Tables and 3.1.4). The results are generally consistent with other studies of rocky substrate within Otago Harbour (Batham 1956; Stewart 2005; Paavo 2009).

9 MPB Extension: Habitat Survey Table Animals encountered within 0.25 m 2 quadrats and core samples along transect at the proposed impact site. Shaded cells indicate soft substrate core samples. Note: there was insufficient soft substrate to obtain cores at the end to Transect 4.

10 MPB Extension: Habitat Survey Table Animals encountered within 0.25 m 2 quadrats and cores along transect at the proposed impact site. Shaded cells indicate soft substrate core samples. Multi-dimensional scaling was used to plot ordinations showing similarities in the faunal communities among sites at each quadrat. Invertebrate abundance data were first transformed (fourth root) to overcome the large number of zeros in the data. There is a high degree of overlap among symbols from both impact and control transect (Figure 3.1.1). However, some symbols are well removed from the others as a result of those particular quadrats containing species observed in none of the other quadrats. E.g. Scutus breviculus appears only in Quadrat T3c, Haliotis iris appears in just T3a and Chamaesipho columna is the only animal present at both C2a and C3a (Figure 3.1.1, Tables and 3.1.4). If these outliers are removed the pattern of symbols becomes more clear (Figure 3.1.2).

11 MPB Extension: Habitat Survey Figure Ordination plot for faunal communities within quadrats and cores along each transect. Green symbol = control; blue symbol = impact. Figure Ordination plot for faunal communities within quadrats and cores along each transect with outliers removed. Green symbol = control; blue symbol = impact. A dendrogram for the ordination clearly shows the separation of the four outliers to the right hand side (Figure 3.1.3). The remaining samples show relatively high compactness among clusters, and considerable intermingling, once again suggesting similarities in communities within the various quadrats. The soft substrate communities are grouped near the centre of the dendrogram (red rectangle, Figure 3.1.3).

12 MPB Extension: Habitat Survey Figure Dendrogram showing the relationship among communities in different quadrats at impact and control sites, proposed multipurpose berth extension, Otago Harbour. It can be seen from values for the indices of multivariate dispersion that the highest variability was encountered the proposed impact site. However, variability at the control site is not markedly lower (Table 3.1.5). Table Indices of multivariate dispersion calculated for different quadrats at assessment sites, Port Otago. Diversity indices calculated for animals within each quadrat show a high degree of variability with a range of 0.0, at quadrats where just one species was present, to at T3g where seven species were present (Table 3.1.5). Overall, however, there is little difference among diversity indices at proposed impact sites and control sites (Figure 3.1.4).

13 MPB Extension: Habitat Survey Table Diversity indices calculated for each quadrat at assessment sites, Port Otago. Figure Mean diversity indices at proposed impact sites and control sites. Error bars indicate 1 standard deviation. Beyond the marked transect lines the divers observed a variety of flora fauna that did not appear in quadrats. The invasive brown alga Undaria pinnatifida was present at both proposed impact and control sites and the green Enteromorpha intestinalis was present in localised patches at shallow depths. Soft substrate showed evidence of abundant burrowing crabs, gastropods, polychaetes and amphipods, horse mussels (Atrina zelandica) and cushion stars (Patiriella regularis). Rocky substrate was observed to host additional Scutus breviculus, kina

14 MPB Extension: Habitat Survey (Evechinus chloroticus), seahares (Chromodoris aureomarginata), anemones, variable triplefins (Tripterygion varium) (Figure 3.1.5), seven armed starfish (Astrostole scabra), mussels, oysters, and numerous crayfish (Jasus edwardsii) (Figure 3.1.6). Figure Anemones (Bunodactis chrysobathys and Actinothoe albocincta) and variable triplefins. Figure Abundant crayfish at base of rip rap.

15 MPB Extension: Habitat Survey Discussion This survey was designed to survey habitats at the site of the proposed extension to the multipurpose berth at Port Chalmers. Sheltered rocky shores within Otago are quite rare, with the majority of rocky substrate being on exposed coasts and other inlets having practically none (e.g. Stewart 2007). However, rocky shores within Otago Harbour have been extensively studied. The existence of the Portobello Marine Laboratory directly across the harbour from Port Chalmers ensures a steady flow of both amateur and professional scientists keen to document what lives on the shore. The communities encountered during this survey are flourishing and typical of those one would expect to find on sheltered rocky and soft substrate shores in southern New Zealand (Batham 1956, Morton and Miller 1973). The assemblages are very similar to those observed by Paavo (2009) and comprise largely foliose red and brown algae, sponges, ascidians, and gastropod molluscs. As one would expect, there is a gradient of both diversity and abundance moving from the shallow subtidal zone to deeper water. This is almost universal among rocky shores and well recognized (Clayton 1982, Raffaelli and Hawkins 1996, Ricketts 1997). It is worth noting that organisms living on rocky substrate are particularly prone to smothering by fine material (Brosnan 1999, Stewart 2001). While it is appreciated that hard substrate in the construction (impact) area will be covered or removed, communities on nearby rock substrate may also be affected, especially by any activity that generates fine sediments in the water column. However, it needs to be recognized that construction activity is unlikely to be the only source of such sediments, nor the most significant source. Ongoing road improvements, property development, heavy rain events, the Water of Leith and land subsidence all contribute varying, and sometimes considerable, amounts of sediment to the harbour. Soft substrate communities will, of course, be affected by any dredging activities to deepen the berth. Although soft substrate was not extensively surveyed, result indicate that the species encountered were not unique to the site and most are common to soft bottoms in other parts of the harbour (Ralph and Yaldwin 1956, Grove 1995, Paavo et al. 2008). In previous studies marine benthic communities have been found to re-establish within relatively short time frames of 30 days to 2 years (Brosnan 1996, Irwin 1999, Stewart 2010). It is expected that the organisms present at the surveyed sites at Port Otago will do likewise, with a similar suite of organisms establishing within a two year period. However, it is likely that algal communities at sites under the proposed berth extension will be light limited and will likely not return to the current diversity and abundance.

16 MPB Extension: Habitat Survey Conclusions The level of sampling carried out during this survey is believed to be adequate to provide a reliable snapshot of the type and abundance of organisms present at the proposed construction site and an adjacent control area. The epifaunal and infaunal communities encountered during this habitat survey are typical of those encountered in sheltered inlets and harbours around southern New Zealand (Morton and Miller 1973, Batham 1956). The invertebrate and macroflora assemblages encountered show considerable similarity to those observed in previous studies within Otago Harbour with minor differences attributable to differences in sampling techniques and taxonomic rigor (e.g. Ralph and Yaldwyn 1956, Rainer 1980, Grove 1995, Paavo and Probert 2005, Paavo et al. 2008, Paavo 2009, Stewart 2013). It is reasonable to expect that these assemblages will remain essentially unchanged at the control site, unless sediment generated during the construction phase, or some other extrinsic factor, has some discernible impact on the communities. The community at the construction (impact) site will be covered or removed, but is expected to recover within two years, likely with less algal cover. Bearing in mind the reasonably rich variety of larger organisms present and the fact that earthworks will effectively cover existing hard substrate habitat, Port Otago may wish to consider a programme designed to relocate easily accessible animals to similar habitat nearby. 6. Acknowledgements Ryder Consulting Limited would like to acknowledge the assistance of Robert Feist, Murray Robertson and Andrew Tuaine from Divepro Ltd.

17 MPB Extension: Habitat Survey References Batham, E.J. (1956). Ecology of southern New Zealand sheltered rocky shores. Transactions of the Royal Society of New Zealand, 84: Brosnan, B.C. (1999). Recovery of terrestrial and marine communities in a New Zealand fiord after large-scale disturbances. Unpublished MSc thesis. Dept. of Marine Science, University of Otago. pp 137. Clayton, S.M. (1982). A biologically defined wave exposure scale for the Otago Peninsula. Unpublished BSc (Hons) thesis. University of Otago. Grove, S.L. (1995). Subtidal soft-bottom macrofauna of the upper Otago Harbour. Unpublished MSc thesis, University of Otago. Irwin, C.R. (1999). The effects of harvesting on the reproductive and population biology of the New Zealand Littleneck Clam (Austrovenus stutchburyi) in Waitati Inlet. Unpublished Msc thesis, University of Otago, Dunedin, New Zealand. Kingsford, M. and Battershill, C. (1998). Studying temperate marine environments: A handbook for ecologists. Canterbury University press. Morton, J. and Miller M. (1973). The New Zealand Sea Shore. Collins, Auckland. 653 pp. Paavo, B.L. (2009). Observations of Rocky Shore Habitats in Lower Otago Harbour. Report to Port Otago Ltd, 46 pp. Paavo, B.L.; Probert, P.K.; James, M.R. (2008). Benthic habitat structures and macrofauna of Lower Otago Harbour. Report to Port Otago Ltd, 52 pp. Probert P.K. and Jillett, J.B. (1998). Proposed Vauxhall redevelopment: Marine environmental aspects. A report for Incite Ltd, Dunedin. pp. 11. Raffaelli, D. and Hawkins, S.J Intertidal Ecology. Chapman and Hall, London. pp.356. Ralph, P.M. and Yaldwyn, J.C. (1956). Seafloor animals from the region of Portobello Marine Biological Station, Otago Harbour. Tuatara 6(2): Ricketts, E.F., Calvin, J., Hedgepeth, J.W. and Phillips, D.W. (1997). Between Pacific Tides. 5 th edition. Stanford University Press. pp.652. Stewart B.G. (2001). Assessment of Effects of Sediment Discharge from Excavation of the Proposed Deepwater Basin Marina on the Biota within Milford Sound. Report prepared for Tyndall and Hammond Ltd. Stewart B.G. (2005). Peninsula Road Improvements Projects: Ecological Impact Assessment. Report prepared for OPUS International Consultants Ltd by Ryder Consulting Ltd.

18 MPB Extension: Habitat Survey Appendix 1 Subtidal Habitat Proposed Impact Sites (Quadrats are 0.5 m x 0.5 m. Small square is 10 cm x 10 cm) Transect 1 Qa Transect 1Qb Transect 1 Qc Transect 1 Qd Transect 2 Qa Transect 2 Qb

19 MPB Extension: Habitat Survey Transect 2 Qc Transect 2 Qd Transect 2 Qe Transect 3 Qa Transect 3 Qb Transect 3 Qc

20 MPB Extension: Habitat Survey Transect 3 Qd Transect 3 Qe Transect 4 Qa Transect 4 Qb Transect 4 Qc Transect 4 Qd

21 MPB Extension: Habitat Survey Transect 4 Qe Transect 4 Qf Control Sites (Quadrats are 0.5m x 0.5m. Small square is 10cm x 10cm) Transect 1 Qa Transect 1 Qb Transect 1 Qc Transect 1 Qd

22 MPB Extension: Habitat Survey Transect 1 Qe Transect 2 Qa Transect 2 Qb Transect 2 Qc Transect 2 Qd Transect 2 Qe

23 MPB Extension: Habitat Survey Transect 2 Qf Transect 3 Qa Transect 3 Qb Transect 3 Qc Transect 3 Qd Transect 3 Qe

24 MPB Extension: Habitat Survey Transect 3 Qa Transect 4 Qb Transect 4 Qc Transect 4 Qd