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KUKURIKI REEF INTERTIDAL INSPECTION 2018
Prepared for:
OMV Taranaki Limited
167 Devon Street West
New Plymouth 4310
New Zealand
PREPARED BY
SLR Consulting NZ Limited
Company Number 2443058
6/A Cambridge Street
Richmond, Nelson 7020
New Zealand (PO Box 3032, Richmond 7050 New Zealand)
T: +64 274 898 628
BASIS OF REPORT
This report has been prepared by SLR Consulting NZ Limited (SLR) with all reasonable skill, care and diligence, and taking account of the timescale and resources allocated to it by agreement with OMV Taranaki Limited (the Client). Information reported herein is based on the interpretation of data collected, which has been accepted in good faith as being accurate and valid.
This report is for the exclusive use of the Client. No warranties or guarantees are expressed or should be inferred by any third parties. This report may not be relied upon by other parties without written consent from SLR.
SLR disclaims any responsibility to the Client and others in respect of any matters outside the agreed scope of the work.
Table of contents
  • 1 Introduction
1 Introduction
SLR Consulting NZ Limited (SLR) were engaged by OMV Taranaki Limited (OTL) to undertake a marine ecological inspection at a reef that is culturally important to Ngāti Mutunga in north Taranaki. Members of Ngāti Mutunga also participated in the reef inspection. OTL have a relationship with Ngāti Mutunga due to OTL operating the offshore Pohokura natural gas field and associated platform in north Taranaki, located approximately 8 km from the shoreline which is near the rohe of Ngāti Mutunga.
OTL have commissioned annual marine ecological assessments at three intertidal reefs along the Motunui intertidal area since 2010. These assessments have been undertaken in conjunction with members of the local hapu Ngāti Rāhiri which has proven beneficial to the monitoring programme as it enables the integration of both cultural and scientific perspectives.
The intention of the intertidal monitoring programmes along the Motunui coastline is to collect a data set of information from the three north Taranaki reefs, where the primary aims are to:
Establish a data history and further understanding of the marine communities present at the reefs
Gain an insight into the influence of naturally occurring sand inundation that occurs along the coastline and the effects that has on the reef communities
OTL suggested to Ngāti Mutunga that it would be beneficial to undertake a similar type of assessment within their rohe. SLR's role was to support the assessment and to develop a set of recommendations for future and ongoing monitoring that Ngāti Mutunga could implement themselves at a reef location that had cultural importance.
Ngāti Mutunga selected Kukuriki Reef (Figure 1) due to the kaimoana resource it provides to iwi members. Kukuriki Reef is located approximately 2 km southwest of the Waiiti Beach Camp and is the only rocky feature in an otherwise sandy beach, which has a back drop of large papa and sand stone cliffs along the upper shore. Kukuriki reef is utilised by Ngāti Mutunga and many other Taranaki locals for the large numbers of green lipped mussels (Perna canaliculus) that are present on the reef as well as an area for recreational fishing.
Figure 1 Location map of Kukuriki Reef
2 Taranaki Coastal Marine Environment
The Taranaki region has a coastline that stretches 295 km and is exposed to the Tasman Sea from the west; often resulting in high energy wind and large wave conditions. The Taranaki coastline is characterised by rocky shores, cliffs, sandy beaches, a marine protected area, two marine reserves, subtidal reefs as well as river mouths and estuaries; providing a wide range of ecological habitats for native plant and animal species. The rugged and exposed nature of the Taranaki coast, confers a distinctive natural character which supports numerous coastal processes and ecosystems. Taranaki people place a high value on the landscape, natural character, amenity and recreational values of the coast and it is particularly significant for local iwi and hapū as kaitiaki (guardians) of the coast.
Most of the intertidal reefs along the Taranaki coast are comprised of lahar conglomerate bedrock, andesitic boulders, rock pools and occasional sand patches. Rocky shores provide a three‐dimensional environment with cracks and crevices present, providing shelter and protection for a number of marine intertidal species. This environment allows intertidal species to live further up the shore profile than would otherwise be expected, as a result of the increased shelter, and protection from desiccation, afforded by this habitat. Larger rock pools are often dominated by brown seaweeds, whereas the lahar reef and boulders are mainly dominated by coralline paint and turf, mobile grazing animals, encrusting organisms and predatory species.
However, the intertidal coastline along the Waiiti coastline differs to the description above, where papa and sandstone cliffs and outcrops are present. This section of coastline is exposed to high wave energy and the cliffs are constantly eroding all the time, as a result the nearshore water is often very turbid.
This coastline has extensive stretches of black iron sand present on the beaches, where very few species live in this beach habitat due to the mobile nature of the sand and the extreme temperatures that can result from solar irradiation; further stressing this already depauperate intertidal environment. When the tide is in along this section of coast it comes all the way up to the base of the cliffs, so there is no area of upper intertidal zone that remains dry during high tide due to the topography of the coastline. This feature can make access along this section of coastline dangerous for those that do not take the tide times or weather conditions into consideration.
3 Intertidal Ecological Assessment
The intertidal assessment at Kukuriki Reef was undertaken on 25th November 2018 over the spring low tide. Members of Ngāti Mutunga were present for the intertidal assessment, as they selected the reef location to be assessed.
As mentioned in Section 1, Kukuriki Reef was selected due to its importance of supplying green lipped mussels to Ngāti Mutunga iwi members. On the day of the inspection the low tide was 0.3 m above chart datum; however, there was a reasonable swell running which prevents the tide from dropping as quickly and as far as would be expected.
Given this was the first visit to Kukuriki Reef it was unknown what monitoring could be undertaken and this visit was intended to be more of an investigation to understand the reef, identify what species occupy the reef and surrounding areas and develop a set of recommendations for future monitoring that could be implemented. Ngāti Mutunga would like to undertake the monitoring so that it can be incorporated into Ngāti Mutunga's annual environmental monitoring programme.
Even though the first visit to Kukuriki Reef was intended to be observational, a qualitative ecological survey would be undertaken at the reef itself and at the various outcrops along the beach. A qualitative ecological survey involves assessing the ecological diversity of a reef community using species diversity and species abundance as indicators of water quality and the general health of the reef environment. Species diversity is the number of different intertidal species present within the intertidal community; whereas species abundance is the number of individuals of each species present on the reef. For this initial assessment to gain a general understanding of the types of species which are present along this part of the Taranaki coastline, each area of rocky outcrop was assessed to gain an understanding of the different communities present.
A general classification system was used for relative abundance which classified each species as present, common or abundant based on percentage cover (i.e. algae) or number present (marine fauna) (Table 1).
Table 1 Relative abundance classification for the Kukuriki Reef intertidal assessment
Each rocky outcrop that was present south of the Waiiti Beach Motor Camp, to Kukuriki Reef was inspected and all intertidal species observed were recorded and given an abundance classification. Due to the tide at Kukuriki Reef it was very hard to get to the reef itself but it was very clear that in parts it was almost 100% coverage of the green lipped mussels. For the purpose of this report, the species diversity and abundance of all of the outcrops from Waiiti Beach Camp to Kukuriki Reef have been pooled into one summary table (Table 2).
Table 2 Kukuriki Reef – Species diversity and abundance classification
3.1 Kukuriki Reef
On 25th November 2018 a qualitative ecological inspection was undertaken at Kukuriki Reef on the rocky outcrops from the Waiiti Beach Camp entrance down to the Kukuriki Reef. The main outcrops were predominately in two main areas; at the Waiiti Beach Camp end and around Kukuriki Reef itself. The 2 km section in between was largely iron sand beach with cliffs on the upper shore. A number of recent slips were evident along this section of coastline with lots of cliff and farmland still present on the upper foreshore. High iron levels were evident in the soil and cliffs due to the red discharge running onto the beach.
Nineteen species of marine flora and fauna were observed along this coastline during the 2018 intertidal inspection. This indicates a coastline and reef area that is restricted by habitat and influenced by sand from this exposed coastline. For comparison, Turangi Reef on the Motunui coastline, which is used as a control site by the Taranaki Regional Council for compliance monitoring of resource consents and for their State of the Environment Monitoring Programme, had 40 species of marine flora and fauna during the November 2018 intertidal inspections. However, this reef is classified as a large platform reef and is located within a large embayment which provides some form of protection from the littoral drift and transportation of sand up the Taranaki coastline. Turangi reef is also comprised of small rocks and rock pools which provide habitat and shelter for marine fauna and flora species to live higher up the reef.
This coastline around Waiiti and Kukuriki Reef is very different to most of the other parts of the Taranaki coastline located to the south, due to the nature of the large papa and sandstone cliffs which are constantly eroding (Photo 1). Over the years the coastal margin has retreated through continual erosion which is evident on some of the papa and sandstone outcrops that still remain (Photo 2). Where these hard rocky outcrops are present, marine life resides as it is the only stable substrate in the otherwise sandy environment.
No small rocks or boulders were present along the beach but some small pockets within the papa and sandstone has been eroded to form small pools which capture the seawater when the tide retreats. These pockets of water are full of marine life as it provides the only suitable habitat in an otherwise inhospitable environment (Photo 3).
Photo 1 Papa and Sandstone Cliffs at upper intertidal zone
Photo 2 Evidence of erosion on the papa and sandstone outcrops
Where cliffs or vertical rocks are present in the marine environment, vertical zonation patterns are often well defined. Different species will live at certain heights on the rock depending on where they are best adapted to live. The species present in Photo 4 are displaying forms of zonation but these species (i.e. Brown barnacle (Chamaesipho brunnea), Columna barnacle (Chamaesipho columna), little black mussel (Xenostrobus pulex), Snakeskin chiton (Chiton pelliserpentis)) are all resilient to being out of water for long periods of time and are often found high on the shore in the upper intertidal zone (Photo 5). These species can seal themselves to the rock and enclose themselves to retain enough moisture to protect themselves from the air environment to prevent drying out until the tide comes in again.
Photo 3 Small pockets of water within the papa outcrops provide habitat for marine communities | Photo 4 Vertical reefs often show clear patterns of zonation with resilient species | Photo 5 Intertidal species that are resilient to live out of the water for long periods of time
Kukuriki Reef as described above is very important to the people of North Taranaki, especially Ngāti Mutunga. It is used for a source of kaimoana, but it is also well used as a place to go recreational fishing. A lot of people will fish the low tide period to target snapper, trevally and kahawai, particularly to the north of the reef where there are some deeper holes in the surf zone, where the fish come in to feed.
It was evident that Kukuriki Reef can only be assessed on the spring low tide periods, and preferably when the weather is settled. Kukuriki Reef sits proud above the sand with one large main reef structure with a number of broken rocks and ledges that surround the main rock (Photo 6 & Photo 7).
Photo 6 Kukuriki Reef
Photo 7 Surrounding rocks and ledges at Kukuriki Reef
It was clear to see why Kukuriki Reef is highly regarded for its kaimoana resource, as the numbers of green lipped mussels present on the reef were very abundant (Photo 8). Even though this section of coastline is likely to receive high levels of suspended sediment from sand movement up the coast through the natural littoral drift, the position of the reef on the low intertidal, where the mussels are mostly under the water results in their survival in this location. However, higher on the reef, there was evidence of some sand inundation where sand levels were right up to the mussels growing on the rocks (Photo 9).
Photo 8 Green lipped mussels (Perna canaliculus) on Kukuriki Reef
Photo 9 Green lipped mussels (P. canaliculus) located higher on the reef with evidence of sand inundation
Pacific oysters (Crassostrea gigas) were observed on the reef among the mussels (Photo 10). During the 2018 intertidal reef assessments at the three reefs along the Motunui coastline the same observation was also made, which was the first time pacific oysters had been observed on the reefs in eight years. A recent settlement event has occurred, and it appears that oysters have also settled and survived at Kukuriki Reef as well. This observation was discussed with members of Ngāti Mutunga present on the survey, and no one had observed these oysters at Kukuriki Reef before; however, if you are not looking for them specifically they can be easily overlooked. The presence of the pacific oyster should be something that is incorporated into future monitoring, as they can provide competition for space with the green lipped mussel on the hard reef structure.
With the sea conditions at the time of the survey, there was a reasonably amount of surf coming into the reef due to the larger waves breaking offshore. As a result the survey team did not go too far into the water to have a detailed inspection of the entire reef, but given this initial inspection was to gain an understanding of the area and the reef and how it could be assessed in the future, that was not required on this visit.
Photo 10 Pacific oyster (Crassostrea gigas) among the green lipped mussels at Kukuriki Reef | Photo 11 Ledge running across front of Kukuriki Reef | Photo 12 Intertidal communities at Kukuriki Reef
4 Summary & Recommendations
This initial inspection of Kukuriki Reef provided an initial understanding of the reef, the environmental factors which may have an influence on the reef (i.e. sand inundation, high suspended sediments in water column), the external factors which affect the ability to survey the reef (i.e. access requirements, lack of external communication, tide and weather constraints) and the marine fauna and flora species that are present along this section of coastline (Table 2). These variables have been incorporated into the recommendations for the monitoring approach to best assess Kukuriki Reef over time going forward.
Compared to other reefs around the Taranaki coastline, Kukuriki Reef is very small, it is confined to a limited area and it is bound by sand on either side. Given the location of Kukuriki Reef on the shoreline, the reef is only accessible for a very short period of time at the bottom of the spring low tide. If adverse weather conditions are present such as strong onshore winds or a large swell, monitoring will be difficult or potentially hazardous.
As such, it is recommended that any future monitoring that is undertaken at Kukuriki Reef going forward is done so with the development of a robust health and safety plan that is specific to each monitoring event. Some of the recommendations that should be included to mitigate potential risk to personnel from the environmental conditions that are present include:
All personnel involved in the survey should be wearing life jackets and/or wetsuits
A personal locator beacon or satellite phone should be part of the survey equipment given mobile phone coverage is limited and beach access is restricted to a small window either side of low tide
A communication plan should be developed so that once the survey is complete and all personnel are safely off the beach, and back past the headland near Waiiti Beach Motor Camp, which is where the tide first cuts off the access, the onshore team are stood down from mobilising any assistance if required
Kukuriki Reef is comprised of one main rock with a number of smaller boulders and rocks with a ledge which runs parallel to the shoreline and is covered in green lipped mussels (Photo 11). However, there are other species present on these hard structures such as sea lettuce (Ulva lactuca), oyster borer (Lepsiella scobina), little black mussel (Xenostrobus pulex), pacific oyster (Crassostrea gigas), Columna barnacle (Chamaesipho columna), and brown barnacle (Chamaesipho brunnea) (Photo 12).
From the initial observations at Kukuriki reef and review of available literature, a proposed methodology to monitor Kukuriki Reef to assess the different marine communities that are residing on the reef has been developed. There are two components to the recommended monitoring approach, a semi‐qualitative assessment and placement of fixed quadrats to assess the different communities present within the quadrates over time, and these are discussed in the sub‐sections below.
4.1 Semi‐quantitative Assessment
This methodology involves photographing the wider sampling area and recording the relative abundance of mussels and other marine fauna and flora, particularly pacific oysters in different areas of the reef. This approach is primarily used to guide the positioning of the fixed quadrats (Section 4.2) prior to the first sampling occasion. Photographing the reef over time and taking note of the broad relative abundances also provides an overarching view of the broad temporal changes that are occurring on the reef over time.
It is advised to record as many other observations at this time as possible, such as sand levels, weather conditions, signs of harvesting pressure, and whether there are signs of sand inundation on the reef.
4.2 Fixed Quadrats
The semi‐quantitative assessment will be utilised to guide the placement of the fixed quadrats. The number of fixed quadrats used will depend on the size of the reef. Kukuriki Reef is not a large reef so a large number of quadrats is not likely to be required, but it is recommended that as many quadrats that can be sampled within the available timeframes with the tidal constraints are undertaken. There are notably different habitats present across the reef such as the ledges and the main rock reef with vertical walls, and the smaller rocks. It would require further investigation, but it is possible that six fixed quadrats at each of these three different sites could be assessed.
Where possible the position of the quadrats should be chosen so that each quadrat has similar physical characteristics, and are positioned in locations that are relatively sheltered from the direct effect of prevailing wind and waves and where possible so that sampling can be undertaken safely. However, given the size of the reef this is unlikely to be possible. Given the primary focus of the monitoring is to examine any potential change in abundance of mussels and/or pacific oysters over time, the placement of the quadrats should be in areas where these species are present, as opposed to random allocation.
Within each quadrat the mussels and oysters should be counted and size classes should be estimated, this will then allow classification tables to be developed for densities and abundances, and will also allow the observations of different size classes moving through over time.
Using fixed quadrats over random allocation for this application has its advantages. It will speed up the sampling process given time is limited due to the tidal access, it eliminates the variation from microhabitat changes, and it will form a record of sequence of change within a defined area of the reef. However, a disadvantage to this approach is that the quadrat area may not truly represent the reef community as a whole and needs to be considered when selecting the quadrat locations.
4.3 Timing
To firstly gain an understanding into some of the seasonal and temporal changes that may occur on the reef in terms of the communities and environmental factors, it is recommended that a number of surveys are taken initially to capture some of the natural temporal variability that may exist. It would be beneficial to have a representative survey undertaken in summer, autumn, winter and spring to start with, and then it could go back to annual surveys thereafter once that baseline set of data is gathered.