Research to inform seagrass restoration in Aotearoa

Abstract

An undergraduate summer report summarising research to inform seagrass restoration in Aotearoa

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REPORT NO. 3775
RESEARCH TO INFORM SEAGRASS RESTORATION
IN AOTEAROA
A CAWTHRON UNDERGRADUATE SUMMER SCHOLAR REPORT

CAWTHRON INSTITUTE | REPORT NO. 3775 NOVEMBER 2022
RESEARCH TO INFORM SEAGRASS
RESTORATION IN AOTEAROA
A CAWTHRON UNDERGRADUATE SUMMER SCHOLAR REPORT
BREANNA HINDMARSH*, RACHEL HOOKS*
*JOINT FIRST AUTHORS
Supervised by Dana Clark, Anna Berthelsen and Anaru Luke (Cawthron Institute)
Students funded by the Cawthron Institute, Nelson City Council and Ng Pae o te
Mramatanga
CAWTHRON INSTITUTE
98 Halifax Street East, Nelson 7010 | Private Bag 2, Nelson 7042 | New Zealand
Ph. +64 3 548 2319 | Fax. +64 3 546 9464
www.cawthron.org.nz
ISSUE DATE: 16 November 2022
RECOMMENDED CITATION: Hindmarsh B, Hooks R 2022. Research to inform seagrass restoration in Aotearoa. Prepared
for the Cawthron Institute. Cawthron Report No. 3775. 32 p. plus appendices.

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TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................................1
1.1. Background and project aim ...................................................................................................................... 1
1.2. Study locations and climate ....................................................................................................................... 2
2. INTERVIEWS TO INFORM SEAGRASS RESTORATION ..............................................3
2.1. Introduction and methods .......................................................................................................................... 3
2.2. The observed environmental changes ....................................................................................................... 3
2.3. Mtauranga Mori .................................................................................................................................... 4
2.4. Restoration views ..................................................................................................................................... 5
3. SEAGRASS GROWTH TRIALS ......................................................................................7
3.1. Current transplantation methods and aims of our growth trials .................................................................... 7
3.2. Methods ................................................................................................................................................... 7
3.2.1. Collection of plants .............................................................................................................................. 7
3.2.2. Laboratory growth trials ....................................................................................................................... 8
3.2.3. Statistical analyses .............................................................................................................................. 9
3.3. Results ..................................................................................................................................................... 9
3.3.1. Environmental conditions ..................................................................................................................... 9
3.3.2. Plant survival and growth ................................................................................................................... 10
3.3.3. Change in leaf counts ........................................................................................................................ 10
3.3.4. Percentage changes in shoot counts .................................................................................................. 11
3.3.5. Change in leaf and rhizome lengths ................................................................................................... 12
3.3.6. Summary of growth trials ................................................................................................................... 13
3.4. Discussion and applications for restoration .............................................................................................. 13
4. BROAD-SCALE SURVEYS OF FLOWERING ..............................................................15
4.1. Introduction and site selection ................................................................................................................. 15
4.2. Methods ................................................................................................................................................. 16
4.3. Results ................................................................................................................................................... 16
4.3.1. Nelson Haven .................................................................................................................................... 17
4.3.2. Waimea Inlet ..................................................................................................................................... 19
4.3.3. Wakapuaka/Delaware Inlet ................................................................................................................ 21
4.4. Discussion and application for restoration ................................................................................................ 23
5. FINE-SCALE SURVEYS OF FLOWERING AND SEEDS .............................................24
5.1. Introduction ............................................................................................................................................ 24
5.2. Methods ................................................................................................................................................. 24
5.2.1. Fine-scale survey .............................................................................................................................. 24
5.2.2. Processing of sediment cores ............................................................................................................ 26
5.2.3. Statistical analyses ............................................................................................................................ 26
5.2.4. Seed germination .............................................................................................................................. 27
5.3. Results ................................................................................................................................................... 27
5.3.1. Differences in flowering abundance between estuaries and tidal heights ............................................. 27
5.3.2. Differences in flowering abundance over time ..................................................................................... 28
5.3.3. Drivers of flowering abundance .......................................................................................................... 28
5.3.4. Seed germination .............................................................................................................................. 29
5.4. Discussion and application for restoration ................................................................................................ 29
6. SUMMARY....................................................................................................................31

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7. ACKNOWLEDGEMENTS .............................................................................................32
8. REFERENCES .............................................................................................................33
9. APPENDICES ...............................................................................................................35
APPENDIX 1. METHOD FOR MEASURING PREVALENCE OF FUNGAL WASTING
DISEASE. 35
APPENDIX 2. TOTAL NUMBER OF FLOWERS FROM EACH QUADRAT COUNTED
AT EACH TIDAL HEIGHT ACROSS THE SITES. .........................................................35
LIST OF FIGURES
Figure 1. An intertidal seagrass meadow providing habitat for a crab (left) and a juvenile
flounder (right) in Waimea Inlet, Aotearoa. (Photos: Rachel Hooks, Breanna
Hindmarsh and Dana Clark). ...........................................................................................1
Figure 2. Schematic diagram of seagrass growth trial set up. .........................................................8
Figure 3. The change in one directly harvested seagrass plant (left) after 6 weeks of growth
(right) in the recirculating treatment. .............................................................................. 10
Figure 4. Change in the number of leaves of beach-cast or directly harvested seagrass plants
(labelled as ‘transplant’) exposed to different ‘treatments’ – recirculating, static,
outside. ......................................................................................................................... 11
Figure 5. Change in shoot count as a percentage of initial shoot count of beach-cast or directly
harvested seagrass plants (labelled as ‘transplant’) exposed to different ‘treatments’ –
recirculating, static, outside. .......................................................................................... 12
Figure 6. Change in the maximum leaf length of beach-cast or directly harvested seagrass
plants (labelled as ‘transplant’) exposed to different ‘treatments’ – recirculating, static,
outside. ......................................................................................................................... 12
Figure 7. Change in rhizome length of beach-cast or directly harvested seagrass plants
(labelled as ‘transplant’) exposed to different ‘treatments’ – recirculating, static,
outside. Measurements were taken at the beginning of the trial and at week six............. 13
Figure 8. Left: Zostera muelleri inflorescence with exposed stigma (hook like appendages that
catch pollen from male flowers) (Photo: Rachel Hooks and Breanna Hindmarsh).
Right: Female and male flowers are encased in the spathe (leaf/protective sheath
surrounding the female and male flowers) (Photo: Phil Garnock-Jones). ........................ 16
Figure 9. Broad-scale mapping of seagrass flowers in Nelson Haven (survey 1 – left plot, survey
2 – right plot). ................................................................................................................ 18
Figure 10. Broad-scale mapping of seagrass flowers in Waimea Inlet (survey 1 – top plot, survey
2 – bottom plot). ............................................................................................................ 20
Figure 11. Broad-scale mapping of seagrass flowers in Wakapuaka/Delaware Inlet (survey 1 –
top plot, survey 2 – bottom plot). .................................................................................... 22
Figure 12. Flowering shoots from Wakapuaka/Delaware Inlet with multiple inflorescences.
(Photo: Rachel Hooks & Breanna Hindmarsh). .............................................................. 25
Figure 13. Fine-scale set up using quadrats to sample flowing abundance (left) and a core (right)
to sample for seeds in the sediment and seagrass length and biomass. ......................... 25
Figure 14. Number of flowering shoots per quadrat by estuary (left) and by tidal height (right). ....... 28
Figure 15. Scatterplots showing the relationship between above-ground seagrass biomass
(Above), average seagrass leaf length (AveLeaf), percentage cover of seagrass
(DORPctCover) and the number of flowering shoots per quadrat at
Wakapuaka/Delaware Inlet and Nelson Haven in November and December 2022. ........ 29
Figure 16. Two immature seeds and germinated seed with cotyledon. Photos by: Breanna
Hindmarsh and Rachel Hooks. ...................................................................................... 29

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LIST OF TABLES
Table 1. Light intensity data collected on 10 December 2021 in each system. ...............................9
Table 2. Summary of average environmental conditions each treatment was exposed to over
the 6-week trial. ............................................................................................................. 10
Table 3. Summary of average change in leaf count, shoot count and rhizome length across all
treatments. .................................................................................................................... 13
Table 4. Zostera muelleri survey locations, timings, and recorded presence of flowering plants. .. 15
Table 5. Total number of flowers from the quadrats (sum of three quadrats) counted at each
tidal height across the sites. .......................................................................................... 27

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1. INTRODUCTION
1.1. Background and project aim
Seagrass provides valuable services to coastal ecosystems. For example, it provides
an important habitat for many animals, including fish and birds (e.g., Figure 1, Orth et
al. 2006; Battley et al. 2005). Seagrass also stabilises the sediment, improves water
quality by filtering nutrients, and supports a high carbon uptake which helps to
mitigate climate change. Deposits of carbon within seagrass sediments are capable of
being preserved for millennia (Duarte et al. 2013). Zostera muelleri, also known as
karepo or nana, is the only species of seagrass here in Aotearoa.
Figure 1. An intertidal seagrass meadow providing habitat for a crab (left) and a juvenile flounder
(right) in Waimea Inlet, Aotearoa. (Photos: Rachel Hooks, Breanna Hindmarsh and Dana
Clark).
Due to the accelerated decline of seagrass meadows globally, restoration efforts are
being explored. To date, restoration efforts in Aotearoa have focused on transplanting
sods of intact seagrass from donor meadows to new sites for restoration (e.g.,
Matheson et al. 2017). This method can cause damage to existing donor meadows
and could be particularly destructive if carried out on a large scale.
Our study builds on a recent review of alternative techniques for seagrass restoration
that could have a lower environmental impact than traditional transplantation
approaches (Clark & Berthelsen 2021). The overarching aims of our project were to
engage with Nelson locals to gather information relevant to seagrass restoration and
to investigate less impactful methods of seagrass propagation.
Zostera species can reproduce asexually through a process known as fragmentation,
where a fragment of seagrass can break off and grow independently from its origin.
We hypothesised that these fragments may be collected from beaches and grown in a

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nursery to produce plants for restoration purposes in a way that does not damage
existing seagrass meadows. Through a series of growth trials, we aimed to determine
whether beach-cast fragments would grow as well as seagrass harvested directly
from a meadow.
As a marine angiosperm, Zostera also reproduces sexually through the pollination of
female flowers and the subsequent production of seed. Flowering was thought to be
uncommon in Aotearoa’s Z. muelleri until a recent study suggested otherwise (Dos
Santos & Matheson 2017). We wanted to determine whether seed-based restoration
could be a viable alternative for plant propagation with low environmental impact. Our
approach to help answer this question was to undertake a series of seagrass flower
surveys in local Whakatū/Nelson estuaries. The discovery of flowers in our broad-
scale surveys allowed us to undertake fine-scale surveys to quantify flowering
densities and seed presence over time.
Our project was therefore comprised of four main components:
• Interviews with locals to understand environmental changes in the estuaries,
mtauranga Mori associated with seagrass and views on seagrass restoration
• Seagrass growth trials in a nursery set up (beach-cast plants vs direct harvest)
• Broad-scale surveys of seagrass flower presence
• Fine-scale surveys of seagrass flowering (flower abundance, shoot density and
biomass) and seed abundance and germination.
Breanna Hindmarsh led the ‘interviews’ component of this study, Rachel Hooks led
the ‘growth trials’ component and both co-led the broad-scale and fine-scale surveys.
1.2. Study locations and climate
We studied three estuaries within the Nelson region that contained large intertidal
seagrass meadows. These were Nelson Haven (grid reference -41.2267, 173.3140),
Waimea Inlet (-41.2919, 173.2219) and Wakapuaka/Delaware Inlet (-41.1681,
173.4411). The research was undertaken from early November 2021 to the end of
January 2022. Over the summer of 2021/22, Aotearoa experienced La Niña
conditions. Furthermore, 2021 was officially declared the hottest year on record in
Aotearoa and marine heatwave conditions were observed in November and
December (NIWA 2022). Temperature data
1
collected between 26 December 2021
and 19 January 2022 showed average water temperatures of 22 °C (range 12 to
33 °C) in Nelson Haven and Waimea Inlet (Cawthron Institute, unpublished data).
1
Temperature loggers were positioned 2 cm above the sediment in intertidal sandflats close to the seagrass
meadows and logged the temperature every 20 minutes.

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2. INTERVIEWS TO INFORM SEAGRASS RESTORATION
2.1. Introduction and methods
By interviewing Nelson locals, we were able to collect knowledge on our study areas
to inform seagrass restoration. Most of this knowledge had been passed down
through oral history and or gained via personal observations. Ethics approval
2
to
interview people from the study areas (focusing on local iwi members) was obtained
from Cawthron Institute (Cawthron) following their policy on ethics in research
involving human participants. We recognise that it is important to consult with local iwi
before beginning any restoration projects, particularly in coastal regions where there
may be historical settlements or tapu sites (Department of Conservation 2015).
Interviews were conducted by Breanna Hindmarsh. The semi-structured interviews
had four main questions. These questions were open-ended with related sub-
questions to prompt building on the interviewee's answer. We were able to interview
three locals, two of which were from local hapū (Ngti Tama and one other) of our
study areas and one who was a former Department of Conservation (DOC) employee.
Each interview was approximately 45 minutes and was later transcribed.
The four main questions were:
• Question one: Introductory questions such as tell us about yourself, how long
have you been in Nelson, and do you undertake activities in the local estuaries?
• Question two: What are some of the main environmental changes you have
observed over your time in Nelson?
• Question three: What is your familiarity with seagrass and is there any
mtauranga you would like to share?
• Question four: Do you view seagrass restoration in Nelson estuaries as
beneficial and why?
The interview responses are summarised in the following sections.
2.2. The observed environmental changes
Discussing environmental changes with our interviewees was important to understand
observed changes and local opinions on the drivers of these impacts. As our Ngti
Tama interviewee exclaimed,
It's not looking at it as just an estuary, it is looking at it as a whole
ecology, if you're doing well in one area, then that overflows into
other areas.
2
Cawthron Ethics Approval Document Number F-RE05 dated 31 August 2020.

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It has been observed in Wakapuaka/Delaware Inlet that one of the largest changes
has been increased recreational use, mainly due to the use of an informal boat ramp
and the development of roads. Our interviewee from this area found it hard to
understand the disregard around vehicle use on the estuary during low tide.
As soon as you're putting housing areas around estuarine
environments or native bush, you're desecrating it… and it can be
impacted upon by driving on it.
As well as direct human activities, seasonal floods over time have caused a change in
sedimentation in Waimea Inlet. The severity of floods being influenced by surrounding
human land use. The changes were explained to us by our former DOC employee
interviewee,
The biggest change came with the big floods and the major one in
2011… Reclamation and drainage of the freshwater wetlands joining
the estuary are a big issue and with sea level rise we're going to have
problems with coastal squeeze … stopbanks are going to be
maintained and the natural vegetation zones are not going to be able
to move inland.
2.3. Mātauranga Māori
The aim here was to engage with local iwi to understand any mtauranga (such as
pūrkau, tohu, rongo, whakapapa) that could inform seagrass restoration.
Mtauranga Mori spans Mori knowledge, culture, and world view (Hikuroa 2017).
History on Wakapuaka/Delaware was shared with us through pūrkau from our Ngti
Tama interviewee. Pūrkau is a traditional form of Mori narrative with philosophical
thought, tikanga Mori values and world views (Lee 2009; Hikuroa 2017). Pūrkau is
sometimes referred to as a story but the idea encompasses a deeper understanding
of topics. Our interviewee from this area explained to us that they knew of five historic
p sites located on the margin of the inlet. Further going into details of the p
locations, they said:
Rotokura was right on the edge of it going around into Cable Bay and
Ng Wakapakoko and kai tangata, they were right on the edge of the
estuary.
You have a place called Bishops Peninsula which is a Tūmatakōkiri p
site that stretches into the estuary. You have the other p site which
used to be even older than that one. I'm unsure of the iwi that would've
been, but it was on Horoirangi maunga which is next to the road
coming around to Cable Bay.

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They continued to explain the extent of the midden sites around the estuary,
describing the depth and size of the middens as extensive. This painted a picture of
the productivity in the Wakapuaka/Delaware area when Mori first settled there.
When you go down to the middens the depth and size of the middens
is unreal, when you go down there, you see the cooking stones on the
inside or the heating stones where they have worked and argillite
(pakohe).
The occupation and the habitat all along the kainga space down there
was for workings of kaimoana.
Our interviewee from the other local hapū was able to share with us the rongo on
seagrass. Although they had no experience in preparing seagrass for medicinal use,
they said they were aware it could be used as an antiseptic, and that it was known for
treating stingray stings and, when steeped into tea, for treating stomach pain.
2.4. Restoration views
During the interview with the interviewee from the other local hapū, we learnt of the
estuary monitoring they partook in. It is common during construction such as Boulder
Bank maintenance and general digger use around Nelson estuaries for koiwi (skeletal
remains) artefacts to be uncovered. Their participation in monitoring these activities
further reinforced the importance of working alongside iwi during restoration activities,
especially ones that alter the environment.
As well as the cultural importance, we have much to learn from mana whenua. When
discussing conservation, our Ngti Tama interviewee agreed on its importance,
Ae! Kaitiakitanga, when our fish were weak in one area we would
move to another area to fish or re-pasteurising pua from one area to
another.
All interviewees agreed restoration would be beneficial for the area but expressed
caution in different areas; some of our interviewees explained how they felt about
restoration:
I’m not going to say yes just so it can offset the vehicle activity
furthermore explaining,
if there are opportunities to propagate, to harvest seed, to do that such
activities I'd love to see this place (Wakapuaka) being one that could
be a source for material…Nelson Haven and Waimea, well that’s
where that material could possibly be put into to help those areas
come back to some sort of healthiness.

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The point made by this interviewee about why they valued seagrass restoration was
insightful and made us think through a different lens as to why it should be important.
Further points on the practicality of restoration were raised by another interviewee,
provoking the thought of whether there is enough evidence to show restoration would
be successful:
The whole time I worked for DOC we were told to be on more of the
business side of the footing, and unfortunately those financial aspects
can't be overlooked.
In order to justify spending money, you've got to provide some
assurance that you're actually going to get a good return for that
investment by the right of the taxpayer or whomever. That's when we
need science to provide the justification for it.

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3. SEAGRASS GROWTH TRIALS
3.1. Current transplantation methods and aims of our growth trials
Taking whole plants from existing meadows and transplanting them to a restoration
site is a common method of active restoration for seagrass (Ferretto et al. 2021). This
method has the potential to negatively impact the healthy ‘donor’ meadows, especially
on a large scale; however, it is the primary technique used in Aotearoa restoration
projects to date (Clark & Berthelsen 2021).
The main aim of this part of our study was to investigate methods of obtaining plants
for seagrass restoration that have a lower environmental impact. We wanted to
investigate methods that are inexpensive and simple, so that community groups can
replicate our trials and produce plants for their own restoration projects.
Collecting naturally uprooted seagrass fragments is an alternative method of obtaining
seagrass plants. Fragments are often washed up on the beach and therefore can be
referred to as beach-cast. These beach-cast plants are particularly common after high
winds, storms, or large tides (Ferretto et al. 2021). Fragments with healthy shoots can
naturally facilitate the colonisation of new areas. Utilising these fragments by
collecting them and on-growing them in a nursery environment (prior to
transplantation) could be a lower environmental impact alternative to transplanting
plants directly from meadows. Furthermore, community groups might be able to grow
beach-cast fragments with home set ups. In this context, it is also useful to compare
the performance of beach-cast fragments with plants directly harvested from donor
beds in nursery growth trials.
3.2. Methods
3.2.1.
Collection of plants
Eighteen 2-litre containers were filled with 5 cm of sediment collected from a single
area in Nelson Haven. Prior to filling the containers, macrofauna were removed from
the sediment by sieving the sediment on site. Sediment was then mixed to
homogenise it. Seventy-two seagrass plants were collected from Waimea Inlet, 36
plants were harvested directly from the seagrass meadow and 36 were beach-cast
fragments. The beach-cast fragments were collected at low tide from the edge of the
water, which meant they were unlikely to have experienced substantial desiccation. All
plants had some visible root and at least three leaves. Plants were taken back to the
laboratory in large containers of seawater.

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3.2.2.
Laboratory growth trials
Each plant was photographed and measurements were taken of each leaf, root and
rhizome length using ImageJ. Shoot and leaf numbers were also counted for each
plant. Two of each type of plant (direct harvest and beach-cast) were then planted into
one of 18 ice cream containers and each container was randomly assigned to buckets
of seawater in one of three treatments (recirculating, static inside, static outside,
Figure 2).
The first two treatments were inside a laboratory environment where light levels and
temperature were relatively constant, with the initial light intensity measurements
shown in Table 1. Seawater in the buckets ranged from 16.5 to 19 °C and the lights
were on for 14 hours and off for 10 hours each day to emulate summer daylight
lengths. The first treatment (recirculating) had buckets filled with seawater
recirculating through a filtration system. The second treatment (static inside) had
buckets filled with static seawater that was constantly aerated via bubblers. The final
treatment (static outside) was located outside and subjected to ambient temperature
and light, with an initial light intensity much higher than the other two treatment types.
Buckets filled with static seawater were placed within larger containers filled with fresh
water to reduce temperature fluctuations. The seawater temperature in this treatment
fluctuated between 15 to 30 °C degrees during daylight hours. Initial light intensity
data were collected for each treatment using a photosynthetically active radiation
(PAR) light sensor. Light intensity of each treatment was measured in µmol m-2·s -1
and averaged over five hours.
Figure 2. Schematic diagram of seagrass growth trial set up. In each 2-L container there were two
‘direct harvest’ plants (T) on the left and two beach-cast plants (BC) on the right. Eighteen
of these 2-L containers were assigned randomly to one of the three treatments numbered
1–18 in red.

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Table 1. Light intensity data collected on 10 December 2021 in each system.
Treatment type
Photosynthetic photon flux density (μmol·m-2·s-1)
Recirculating
136.92
Static inside
125.98
Static outside
949.09
The buckets for all treatments were cleaned once every 10 days to control algal
growth. This was done by removing the ice cream container with the seagrass from
the bucket of seawater and using hot water to clean the bucket. The bucket was then
refilled with seawater and the ice cream container with the seagrass was replaced.
The recirculating system had prolific algae growth issues throughout the experiment.
Temperature, pH, dissolved oxygen, and salinity were measured daily. Reverse
osmosis (RO) treated water was added to replace evaporated water to maintain
salinity between 29–32 ppt.
After six weeks, seagrass measurements were repeated to assess growth. Root
length was determined to be unreliable for the assessment of plant growth due to the
fragility of the structure and the difficulty of extraction from sediment.
3.2.3.
Statistical analyses
We performed all statistical analyses in R Studio version 1.4.1717. In the lme4
package (Bates et al. 2013), we used generalised linear mixed models (GLMMs) to
test the growth of plants using treatment (recirculating, static inside, or static outside)
and type of plant (beach-cast or direct harvest) as fixed effects, and bucket (1–18) as
a random effect. The model specification was as follows: Growth Measurement ~
Treatment*Type + (1| Bucket), with the growth measurement substituted with the
different response measurements taken.
3.3. Results
3.3.1.
Environmental conditions
Temperature was more variable in the outside treatments (12.6 ˚C range in
temperature) compared to the inside and recirculating treatments (1.1–1.2 ˚C range in
temperature). Fluctuations in salinity were much slower than changes in temperature
and more easily controlled for by adding seawater or reverse osmosis water as
needed. However, salinity did get as low as 15 ppt and as high as 38 ppt on occasion
in the outside buckets and recirculating treatments, respectively. In all three
treatments, pH was kept relatively constant, varying between 7.9 and 8.6 pH across

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all treatment types. The average environmental conditions that each treatment was
exposed to through the 6-week trial period are summarised in Table 2.
Table 2. Summary of average environmental conditions each treatment was exposed to over the
6-week trial. Values are averages ± 1 standard deviation.
Treatment
Salinity
(ppt)
Dissolved
oxygen (%)
Dissolved
oxygen (mg/L)
Temperature
(˚C)
pH
Recirculating
34.2 (±1.4)
102.7 (± 7.9)
8.0 (± 0.2)
18.4 (± 0.3)
8.2 (± 0.09)
Inside buckets
33.0 (±2.0)
105.5 (± 10.7)
8.0 (± 0.4)
17.9 (± 0.2)
8.2 (± 0.08)
Outside buckets
31.8 (±2.8)
96.1 (± 18.8)
8.1 (± 0.6)
19.0 (± 2.7)
8.3 (± 0.11)
3.3.2.
Plant survival and growth
Seventy-one of the 72 plants survived the six-week growth trial, one beach-cast plant
in the outside treatment died. Most plants increased in all growth measurements
barring leaf length (see following result sections for individual analyses). An example
of the increase in rhizome length and the number of new shoots over the six-week
growth trial is shown in Figure 3.
Note that the random assignment of plants to containers resulted in no significant
differences in any initial measurements by treatment. However, plant type did have an
impact on initial measurements, with plants that were directly harvested having more
shoots, leaves and a longer rhizome than the beach-cast plants.
Figure 3. The change in one directly harvested seagrass plant (left) after 6 weeks of growth (right)
in the recirculating treatment.
3.3.3.
Change in leaf counts
Plant type and treatment were both significant in the change of leaf counts. Treatment
was significant in the recirculating system (beta = 6.833, t = 3.695), the inside

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treatment (beta = -6.500, t = -2.485) and the outside treatment (beta = -5.417, t
= -2.071) (Figure 4). The plant type ‘direct harvest’ increased in leaf count more than
beach-cast (beta = 6.000, t = 2.294) and the treatment type ‘recirculating’ had the
largest increase of leaves. No significant interactions between plant type and
treatment were observed.
Figure 4. Change in the number of leaves of beach-cast or directly harvested seagrass plants
(labelled as ‘transplant’) exposed to different ‘treatments’ – recirculating, static,
outside. Measurements taken at beginning of trial and at week six.
3.3.4.
Percentage changes in shoot counts
Treatment significantly affected the observed changes in shoot count. We have
presented results based on counts that were standardised by percentage growth to
account for relative growth rates (some plants had more shoot counts than others at
the start of the trial) (Figure 5). Plants in the recirculating system, regardless of type,
had a higher increase in shoot numbers than the two static systems (beta = 58.780, t
= 5.463). The inside treatment (beta = -38.958, t = -2.560) and the outside treatment
(beta = -57.966, t = -3.808) had similar changes in shoot counts. No plants in the
recirculating system decreased in shoot counts, compared to the other two static
systems in which some plants had a reduction in shoot number (i.e., shoots died
during the six-week growth trial).

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Figure 5. Change in shoot count as a percentage of initial shoot count of beach-cast or directly
harvested seagrass plants (labelled as ‘transplant’) exposed to different ‘treatments’ –
recirculating, static, outside. Measurements taken at beginning of trial and at week six.
3.3.5.
Change in leaf and rhizome lengths
The type of plant was significant for leaf length, with beach-cast plants doing better in
this aspect of growth than directly harvested plants (beta = -1.951, t = -2.174),
regardless of whether change was measured as a percentage of initial length (Figure
6). Treatment was not significant and there was no interaction between treatment and
plant type. When looking at the change in rhizome length, treatment was found to be
significant while type was not significant (Figure 7). The recirculating treatment had
the largest increase in rhizome length (beta = 4.641, t = 5.333) compared to inside
(beta = -2.6273, t = -2.135) and outside (beta = -3.481, t = -2.828) (Figure 6).
Figure 6. Change in the maximum leaf length of beach-cast or directly harvested seagrass
plants (labelled as ‘transplant’) exposed to different ‘treatments’ – recirculating, static,
outside. Measurements were taken at the beginning of the trial and at week six.

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Figure 7. Change in rhizome length of beach-cast or directly harvested seagrass plants (labelled as
‘transplant’) exposed to different ‘treatments’ – recirculating, static, outside.
Measurements were taken at the beginning of the trial and at week six.
3.3.6.
Summary of growth trials
Seagrass plants in the recirculating system showed a greater increase in growth (leaf
counts, shoot counts, rhizome length) than in either of the static systems (Table 3).
The change in leaf count in the recirculating system was approximately double that of
the static systems. Plant type was only significant for changes in leaf count and leaf
length. Directly harvested plants increased their leaf number significantly more than
beach-cast plants. However, beach-cast plants increased their leaf length significantly
more than directly harvested plants, even when accounting for initial length (i.e.,
percentage increase in length).
Table 3. Summary of average change in leaf count, shoot count and rhizome length across all
treatments.
Treatment type
Change in leaf
count
Change in shoot
count
Change in rhizome
length (cm)
Recirculating
9.83
4.36
4.29
Static inside
4.71
2.50
2.41
Static outside
4.96
1.83
1.65
3.4. Discussion and applications for restoration
The results of our growth trials indicated that Z. muelleri (both beach-cast and directly
harvested plants) can be grown in simple aquarium setups but that the growth rate is
likely to be increased with more sophisticated methods (e.g., recirculating systems, in
comparison to static systems). The addition of aeration pumps to aquaria was shown
to be an important parameter to control for. When aeration pumps were removed from
outdoor setups, the drop in dissolved oxygen resulted in a visible degradation in the

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health of the seagrass after one day. Our finding that beach-cast plants can be grown
in a range of aquaria conditions, both static (inside and outside) and recirculating
systems trialled, increases the feasibility of growing plants in such setups as stock for
future low environmental impact restoration projects.

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4. BROAD-SCALE SURVEYS OF FLOWERING
4.1. Introduction and site selection
Until recently, flowering was thought to be rare in Z. muelleri in Aotearoa. However,
work by Dos Santos and Matheson (2017) and Zabarte-Maeztu et al. (2021) has
indicated that flowering may be more common than expected. Our broad-scale
mapping survey aimed to assess whether flowering was occurring in the Nelson
region and if so, whether there were spatial or temporal patterns that might inform
where and when seagrass flowering is likely to occur in this region and in other
estuaries in Aotearoa.
Table 4. Zostera muelleri survey locations, timings, and recorded presence of flowering plants.
Location
Latitude
Longitude
Survey #1
date
Flowers
Survey #2
date
Flowers
Nelson Haven
-41.2267
173.3140
17.11.21
Present
9.12.21
Present
Waimea Inlet
-41.2919
173.2219
24.11.21
Present
16.12.21
Present
Wakapuaka Inlet
-41.1681
173.4411
18.11.21
Present
13.12.21
Present
We selected three estuaries in the Nelson region (Nelson Haven, Waimea Inlet and
Wakapuaka/Delaware Inlet) for surveying (Table 4). Portions of these estuaries
containing seagrass beds accessible by foot were surveyed for flowers in mid-
November and mid-December 2021. Flowers were identified by the presence of
inflorescences, which is the botanical term name for a cluster of female and male
flowers encased in a spathe (Figure 8).

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Figure 8. Left: Zostera muelleri inflorescence with exposed stigma (hook like appendages that
catch pollen from male flowers) (Photo: Rachel Hooks and Breanna Hindmarsh). Right:
Female and male flowers are encased in the spathe (leaf/protective sheath surrounding
the female and male flowers) (Photo: Phil Garnock-Jones).
4.2. Methods
Using ArcGIS software, a grid (50 x 50 m for Wakapuaka/Delaware Inlet, 100 x 100 m
for Nelson Haven and Waimea Inlet) was overlaid onto recent maps of seagrass
meadows in each estuary. A survey site was randomly selected within each grid cell.
A total of 29 different sites were surveyed in Nelson Haven, 29 different sites in
Waimea Inlet and 16 different sites in Wakapuaka/Delaware Inlet. We used ArcGIS
Collector, to record the presence or absence of seagrass flowers within a 1 m radius
of each site. Collector allowed us to navigate to the same points surveyed in
November again in our second survey in December 2021 (where possible). Marked
points that were inaccessible due to channel depths (Wakapuaka/Delaware Inlet) or
water immersion (Waimea) were not surveyed.
4.3. Results
Seagrass flowers were identified in all three survey locations in both November and
December 2021 (Table 4 and Figures 9, 10 and 11). Using the field data collected on
ArcGIS Collector, we were able to produce maps to indicate which sites were
flowering in November and December.

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4.3.1.
Nelson Haven
Nelson Haven had a similar presence of flowering in November and December, with
no temporal patterns observed. In the November survey, 71% of the 28 sites had
flowering shoots present (Figure 9). In the December survey, there was a slight
increase, with 76% of the 29 sites observed to have flowering shoots present.

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Figure 9. Broad-scale mapping of seagrass flowers in Nelson Haven (survey 1 – left plot, survey 2 – right plot).

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4.3.2.
Waimea Inlet
We observed no obvious temporal patterns of flowering in Waimea Inlet (Figure 10).
In November, 45% of the 29 sites had flowers present and 47% of the 19 sites had
flowers present in December. We observed spatial patchiness in flowering on both
occasions, also a large absence of flowering on the western side of the meadow.

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Figure 10. Broad-scale mapping of seagrass flowers in Waimea Inlet (survey 1 – top plot, survey 2 –
bottom plot).

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4.3.3.
Wakapuaka/Delaware Inlet
In Wakapuaka/Delaware Inlet, 78% of the nine sites had flowers in November and
56% of the nine sites in December (Figure 11). However the small sample sizes do
not provide robust evidence of flower distribution here and only two sites were
sampled more than once. Fewer sites were surveyed in this estuary to a deep channel
restricting access to the far side of the seagrass meadow.

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Figure 11. Broad-scale mapping of seagrass flowers in Wakapuaka/Delaware Inlet (survey 1 – top
plot, survey 2 – bottom plot).

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4.4. Discussion and application for restoration
Our study provides the first record of seagrass flowering in Nelson Haven, Waimea
Inlet and Wakapuaka/Delaware Inlet. This knowledge builds on the recent work
published by Zabarte-Maeztu et al. (2021) for other estuaries in the Te Tau Ihu ‘Top of
the South’ region (in Marlborough, the Abel Tasman and Golden Bay). Additionally,
our survey results indicated that the potential for seed-based restoration (which relies
on sexual seagrass reproduction through flowering) is worth investigating further. In
terms of comparing flowering presence between estuaries, comparisons between
Nelson Haven and Waimea Inlet indicate that flowering was more evenly distributed in
Nelson Haven, whereas Waimea Inlet had large areas where flowering was absent.
Wakapuaka/Delaware Inlet had only nine points surveyed each time, and therefore
this sample size was too small to draw any conclusions from. We did not observe
differing patterns in flower distributions at the three estuaries between the two survey
times. The abiotic factors that promote flowering in Z. muelleri were not able to be
determined in our broad-scale study—but see our fine-scale survey results.

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5. FINE-SCALE SURVEYS OF FLOWERING AND SEEDS
5.1. Introduction
Following our discovery of seagrass flowers during the broadscale surveys (refer
Section 4), we conducted fine-scale surveys to quantify the density of flowering shoots
and the number of inflorescences per flowering shoot. We also recorded information
that could help to explain any variation in flowering.
5.2. Methods
5.2.1.
Fine-scale survey
A fine-scale site was selected in each of the three estuaries: Nelson Haven, Waimea
Inlet and Wakapuaka/Delaware Inlet. At each site, a 100-metre transect line was laid
across the seagrass meadow, starting at the highest tidal height and ending at the
lowest tidal height. Three replicate 0.25 m2 quadrats were marked out at each tidal
height (lowest, middle and highest). At each quadrat, we looked at the number of
flowering shoots
3
, the number of inflorescences per plant, percent cover of seagrass
and percent cover of macroalgae cover (Figure 12). For the November and December
surveys, a sediment core (6.5 cm diameter by 10 cm length) was taken adjacent to
each quadrat and stored for further analysis of seagrass seeds, above and below
ground seagrass biomass and leaf lengths and percent cover of fungal wasting
disease (Appendix 1).
Fine-scale sites were surveyed three times (November 2021, December 2021 and
January 2022) and marker pegs ensured the same quadrat location was surveyed
each time. Unfortunately, the marker pegs were removed from the Wakapuaka/
Delaware Inlet site after the second survey because we did not expect to return. Thus
during the third survey, quadrats were placed within 3 m of the original locations but
not necessarily in the exact same location; refer to Table 5 for fine-scale survey dates.
3
Flowering shoots: a shoot that contains inflorescences, which are female and male flowers covered in a spathe.
Refer to Figure 8 for further reference.

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Figure 12. Flowering shoots from Wakapuaka/Delaware Inlet with multiple inflorescences. (Photo:
Rachel Hooks & Breanna Hindmarsh).
The quadrat and sediment core we used in our fine-scale surveys are shown in Figure
13. We started at high tide, where three of these quadrats and sediment cores were
spaced 2 m from each other, parallel with the tidal line. This process was then
repeated at mid-tide and low tide, resulting in data being collected from a total of nine
quadrats and nine sediment cores being taken back to the Cawthron laboratory for
analysis (from each survey location).
Figure 13. Fine-scale set up using quadrats to sample flowing abundance (left) and a core (right) to
sample for seeds in the sediment and seagrass length and biomass (Photos: Breanna
Hindmarsh and Rachel Hooks).

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5.2.2.
Processing of sediment cores
Sediment cores were processed to sieve out any seagrass seeds and remove
macrofauna from the sample. Four sieves were layered in decreasing mesh sizes,
ending with a 1-mm mesh size, in which seeds were retained. Seagrass from the top
of the sediment core was removed and analysed for percentage cover of fungal
wasting disease, above ground biomass and leaf length.
The seagrass at the top of the sediment core was analysed by randomly selecting ten
leaves which were measured to calculate an average leaf length. The same ten
leaves were used to estimate percent cover of fungal wasting disease, which was also
averaged. Biomass was measured by separating above ground biomass (seagrass
leaves) from below ground biomass (roots and some rhizome) and dried in the
laboratory oven at 60 °C. The seagrass was considered dehydrated/dried when a
constant weight was achieved, and this took approximately 48 hours. The dried
biomass was then weighed immediately to avoid measuring absorbed moisture. The
weight was recorded to the nearest three decimal places.
5.2.3.
Statistical analyses
No flowers were observed in quadrats during the fine-scale surveys in Waimea Inlet,
despite the presence of flowers in other parts of this seagrass meadow over the same
period. As such, Waimea Inlet is excluded from our data analysis and results.
Differences in the number of flowering shoots per estuary were assessed using
Kruskal-Wallis. Due to significant differences in the number of flowering shoots in
each estuary, further analysis was undertaken on each estuary separately. Kruskal-
Wallis was used to investigate whether time or tide level had a significant effect on
the number of flowering shoots. If significant results were observed, Wilcox pairwise
tests were undertaken.
Multiple regression was undertaken for the first two sampling periods (November and
December) to investigate the effect of several factors (above ground seagrass
biomass, below ground seagrass biomass, percent cover of seagrass, percent cover
of fungal wasting disease and average leaf length) on the number of flowering shoots
on each estuary separately. The January sampling period was not included in the
multiple regression because above and below ground seagrass biomass, leaf lengths
and percent cover of fungal wasting disease were not recorded. Very little
macroalgae was observed in the quadrats (n = 9 of 81 quadrats, ≤ 7% cover) so this
variable was not included in the analysis. In the case of Wakapuaka/Delaware, a
polynomial equation (degree = 2) was used for the factor above ground biomass as
this fit better than a linear effect.

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5.2.4.
Seed germination
We attempted to germinate seeds found in sediment cores during the fine-scale
surveys. We followed the germination process as outlined in Stafford-Bell (2016). The
process required the seeds to be sterilised and then triple washed with distilled water.
The seeds were covered for two weeks in a light concealed container at a
temperature of approximately 17 °C.
5.3. Results
5.3.1.
Differences in flowering abundance between estuaries and tidal heights
The number of flowering shoots was highly variable (Table 5, Appendix 2). Some
quadrats at the Wakapuaka/Delaware low tide sites had flowering shoot abundances
well above 100, whereas no flowers were found at the fine-scale sites in Waimea.
There were significant differences in the abundance of flowering shots between the
two estuaries (Kruskall-Wallis chi-sq = 10.49; p = 0.001), with Wakapuaka/Delaware
having a substantially higher number of flowers compared to Nelson Haven (Figure
14). In Nelson Haven, no significant difference (Kruskall-Wallis chi-sq = 1.91; p =
0.38) was observed in the number of flowers at the different tidal zones. In
Wakapuaka/Delaware, a different pattern was observed with a significant difference in
the number of flowers amongst tidal zones (Kruskall-Wallis chi-sq = 22.02; p < 0.001).
Pairwise comparisons indicated that there were significant differences (p < 0.001)
amongst all zones with the highest number of flowers being observed in the low tide
zone in this estuary.
Table 5. Total number of flowers from the quadrats (sum of three quadrats) counted at each tidal
height across the sites.
Tidal Height
Estuary
Date
High
Mid
Low
Nelson Haven
17/11/2021
8
3
5
Nelson Haven
9/12/2021
7
0
3
Nelson Haven
20/01/2022
0
0
0
Wakapuaka/Delaware
18/11/2021
0
7
279
Wakapuaka/Delaware
13/12/2021
0
17
323
Wakapuaka/Delaware
20/01/2022
3
11
112
*Waimea Inlet was excluded as no flowers were present in the fine-scale surveys.

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Figure 14. Number of flowering shoots per quadrat by estuary (left) and by tidal height (right).
5.3.2.
Differences in flowering abundance over time
In terms of time, there was a significant difference in the number of flowers present in
Nelson Haven over the course of the three months (Kruskal-Wallis chi-sq = 7.76; p =
0.02) with pairwise tests indicating a significant decline between November and
January (p = 0.016; Table 5, Appendix 2) when no flowers were observed. In
Wakapuaka/Delaware, there was no significant difference in the number of flowers
over the three months (Kruskal-Wallis chi-sq = 0.23; p = 0.89), although a decline was
observed in the total flowers observed in January. However, this could have been
influenced by the quadrats being in a different position in the January sampling.
5.3.3.
Drivers of flowering abundance
In Wakapuaka/Delaware only above ground biomass and average leaf length were
found to be significant predictors of flowering shoot abundance. The results showed a
negative relationship between the number of flowers and above ground biomass,
while a positive relationship was observed for flowers against average leaf length
(Figure 15).
In Nelson Haven, the factors above ground biomass, seagrass percent cover and
average leaf length were found to be significant in determining the number of flowers.
Different patterns were observed in comparison to Wakapuaka/Delaware with a
positive relationship between the number of flowers and above ground biomass and
negative regressions between flowers and average leaf length and percentage cover
(Figure 15). The differences could be due to the substantially lower number of flowers
observed in Nelson Haven making trends hard to ascertain. Further the assumption of
homoscedasticity was violated due to the high numbers of samples with low (or zero)
numbers of flowers so care should be taken in making conclusions from these results.

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Figure 15. Scatterplots showing the relationship between above-ground seagrass biomass (Above),
average seagrass leaf length (AveLeaf), percentage cover of seagrass (DORPctCover)
and the number of flowering shoots per quadrat at Wakapuaka/Delaware Inlet and
Nelson Haven in November and December 2022.
5.3.4.
Seed germination
We found approximately 20 seeds in the collected sediment cores, some of which
varied in size and shape. We attempted to germinate the seeds and, following the
2-week incubation, one seed germinated successfully. Germination was determined
by the emergence of a single cotyledon as seen in Figure 16 on the right.
Figure 16. Two immature seeds and germinated seed with cotyledon. Photos by: Breanna
Hindmarsh and Rachel Hooks.
5.4. Discussion and application for restoration
Our discovery of seagrass flowers and seeds in the sediment was an exciting find and
suggests that seed-based restoration may be possible in Aotearoa. Seagrass seeds
have only been documented once before in Aotearoa (by Ramage & Schiel 1998) and

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to our knowledge there are no records of successful germination in the laboratory.
Successful seed germination indicated that the seagrass flowers were producing
viable seeds. However, the process of collecting seeds from the sediment was very
time-consuming and not feasible on a larger scale for restoration. We sieved through
approximately 57 L of sediment to get a return of 20 seeds. The process of sieving
one of the 54 sediment cores was estimated to take 40 minutes. Furthermore, to use
this method for restoration, sediment collection would need to occur on a much larger
scale resulting in damage to existing meadows. Therefore, we conclude that sediment
collection is not a viable option for seed-based restoration based on the abundance of
seeds that we observed. Alternatives to sediment seed collection include collecting
flowers from wild populations in local estuaries or nursery broodstock and leaving
them in tanks of seawater to drop out. Both methods would produce seeds for
restoration projects with minimal impact on existing meadow and can be
complementary to each other. It was not clear from our study what was driving spatial
and temporal differences in flowering and further work is required to understand these
variations.

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6. SUMMARY
Seagrass is important for the benefits it provides to the environment and people.
Through the four components of our study, we determined that methods for seagrass
restoration with lower environmental impact than approaches used previously in
Aotearoa are feasible.
The interview component of our study emphasised the value of mtauranga Mori in
restoration projects and that local knowledge can contribute important information to
seagrass restoration. The growth trial component demonstrated that beach-cast
fragments can be successfully collected and grown in a range of aquaria conditions,
helping to pave the ways for citizen scientists and community groups to do this.
However, a long-term study would be required to determine whether these plants
could continue to grow throughout different seasonal conditions and then be
successfully transplanted.
We made the first records of seagrass flowering in Nelson Haven, Waimea Inlet and
Delaware/Wakapuaka Inlet. Our broad- and fine-scale surveys demonstrated that
seagrass flowering was highly patchy in space and somewhat variable through time.
We found significant differences in flowering abundance between estuaries, tidal
heights and survey dates. Flowering also co-varied with above ground biomass,
percent cover of seagrass and average leaf length. However, these trends were not
consistent, therefore, further research is required to ascertain the drivers of variation
seagrass flowering abundance.
We showed that seagrass seeds can be found in the sediment and successfully
germinated, indicating that the flowers can produce viable seeds. However, we
concluded that the damage to existing meadows and the low output of germinated
seeds means that sieving sediment to collect seeds is not feasible on a large scale. A
more likely source of plants for future restoration projects will be from seeds from
pollinated flowers collected from healthy estuaries (potentially by citizen scientists) or
from brood stock plants maintained in a specialised facility. However, even with a
robust production of seagrass plants or source of seeds, issues that caused (and are
continuing to cause) declines will need to be addressed prior to restoration, to
facilitate the survival of seagrass in that area in the future.

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7. ACKNOWLEDGEMENTS
Supervisors and funding
First, we would like to thank our supervisors Dana Clark, Anna Berthelsen and Anaru
Luke (Cawthron Institute). Their endless support and organisational skills were
invaluable to us throughout our 10 weeks at Cawthron Institute. The funding of this
project was thanks to the Cawthron Institute, Nelson City Council (particularly Vikki
Ambrose), and Ng Pae o te Mramatanga. We would like to extend our gratitude to
Elizabeth Bean (Cawthron Foundation) for facilitating these scholarships for us.
Additional Cawthron acknowledgements
For their help in the interview process, we would like to thank Marc Tadaki and Jim
Sinner. For their assistance in the growth trials, we are most grateful to Tim
Dodgshun, Olivier Champeau, Daniel Crossett and the Tech team. Thank you for your
endless problem solving and advice. Lisa Floerl was indispensable for our broadscale
survey, particularly the technical aspects of ArcMap and Collector. We would also like
to thank Fiona Gower and Paul Wolf for sharing their space in the sieving,
microscopy, and taxonomy aspects of this study (and for sharing their lollies and
lunch). Thank you to Veronica Beuzenberg for helping with the germination process.
For the report write up we would like to thank Paula Casanovas for her statistical
advice and Gretchen Rasch for her guidance in our writing. Furthermore, John
Pearman carried out the statistical analysis for the fine-scale flowering survey.
Finally, we would like to extend our thanks to the remaining Cawthron staff who made
us feel very welcome and were always willing to help us and share their extensive
knowledge throughout our time at Cawthron and to fellow summer students Emma
Warmerdam and Layla Sudol for their support and friendship.
Other personnel acknowledgements
Thanks to our three interviewees, who volunteered their time and knowledge. Thanks
also to Phil Garnock-Jones for sharing his knowledge on plant taxonomy as well as
his detailed photos of seagrass flowers, which he generously allowed us to use in this
report. We would also like to thank Emma Jackson of Central Queensland University
for taking the time to share the projects and knowledge that they have in the seagrass
restoration area.

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8. REFERENCES
Bates D, Maechler M, Bolker B, Walker S, Christensen RHB 2013. lme4: linear mixed
effects models using Eigen and S4. R package version 1.0-5. http://CRAN.R-
project.org/package=lme4
Battley PF, Melville DS, Schuckard R, Balance P 2005. Quantitative survey of the
intertidal benthos of Farewell Spit, Golden Bay. Marine Biodiversity Biosecurity
Report No. 7. Ministry of Fisheries, Wellington NZ.
Central Queensland University Australia. (n.d). Restoring the ‘kidneys’ of the Great
Barrier Reef. Retrieved from CQL Website.
Clark D, Berthelsen A 2021. Review of the potential for low impact seagrass
restoration in Aotearoa New Zealand. Prepared for Nelson City Council.
Cawthron Report No. 3697. 53 p. plus appendices.
Department of Conservation 2015. Waimea Inlet restoration. Retrieved from
https://www.doc.govt.nz/Documents/our-work/waimea-inlet-restoration-
resource.pdf
Dos Santos VM, Matheson FE 2017. Higher seagrass cover and biomass increases
sexual reproductive effort: a rare case study of Zostera muelleri in New
Zealand. Aquatic Botany 138: 29-36.
Duarte CM, Losada IJ, Hendriks IE, Mazarrasa I, Marba N 2013. The role of coastal
plant communities for climate change mitigation and adaption. Nature Climate
Change 3(11): 961-968.
Ferretto G, Glasby TM, Poore AGB, Callaghan CT, Housefield GP, Langley M,
Sinclair EA, Statton J, Kendrick GA, Vergés A 2021. Naturally-detached
fragments of the endangered seagrass Posidonia australis collected by citizen
scientists can be used to successfully restore fragmented meadows. Biological
Conservation 262: 109308.
Hikuroa D 2017. Mtauranga Mori—the ūkaipō of knowledge in New Zealand,
Journal of the Royal Society of New Zealand 47(1): 5-10.
Lee J 2009. Decolonising Mori narratives: Pūrkau as method. MAI Review 2(3):1–
12.
Matheson FE, Reed J, Dos Santos VM, Mackay G, Cummings VJ 2017. Seagrass
rehabilitation: successful transplants and evaluation of methods at different
spatial scales. New Zealand Journal of Marine and Freshwater Research
51(1): 96-109.
National Institute of Water and Atmospheric Research (NIWA) 2022. 2021 Annual
Climate Summary Report.
https://niwa.co.nz/sites/niwa.co.nz/files/2021_Annual_Climate_Summary-
NIWA.pdf

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Orth RJ, Carruthers TJ, Dennison WC, Duarte CM, Fourqurean JW, Heck KL, ...
Williams S L 2006. A global crisis for seagrass ecosystems. Bioscience 56(12):
987-996.
Stafford-Bell RE, Chariton AA, Robinson RW 2016. Germination and early-stage
development in the seagrass, Zostera muelleri Irmisch ex Asch. in response to
multiple stressors. Aquatic Botany 128: 18-25.
Ramage DL, Schiel DR 1998. Reproduction in the seagrass Zostera novazelandica on
intertidal platforms in southern New Zealand. Marine Biology 130(3): 479-489.
Zabarte-Maeztu I, Matheson FE, Manley-Harris M, Hawes I 2021. Sexual reproduction
of seagrass Zostera muelleri in Aotearoa New Zealand: are we missing a
restoration opportunity? New Zealand Journal of Marine and Freshwater
Research in press.

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9. APPENDICES
APPENDIX 1. METHOD FOR MEASURING PREVALENCE OF FUNGAL
WASTING DISEASE.
From: Clark D, Crossett D 2019. Subtidal seagrass surveys at Slipper and Great
Mercury Islands. Prepared for Waikato Regional Council. Cawthron Report No. 3347.
32 p. plus appendices.
A semi-quantitative scale for estimating severity of fungal wasting
disease known as the wasting index method was developed by Burdick
et al. (1993) as a rapid visual determination of the amount of necrotic
tissue on seagrass shoots infected with fungal wasting disease
(Labyrinthula).
Figure A1.1 Ranks corresponding to the Wasting Index Key developed by Burdick et al. (1993).
APPENDIX 2. TOTAL NUMBER OF FLOWERS FROM EACH QUADRAT
COUNTED AT EACH TIDAL HEIGHT ACROSS THE SITES.
Table showing the total number of seagrass flowers from each quadrat counted at each
tidal height across the sites.
High
Mid
Low
1
2
3
1
2
3
1
2
3
Haven 1
3
0
5
0
2
1
0
1
4
Haven 2
4
3
0
0
0
0
3
0
0
Haven 3
0
0
0
0
0
0
0
0
0
Delaware 1
0
0
0
0
6
1
136
60
83
Delaware 2
0
0
0
2
6
9
187
66
70
Delaware 3
3
0
0
4
4
3
61
18
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