GeoHazards cover story
Our article on the impacts of sea-level change was unexpectedly chosen as the cover story for the latest issue of GeoHazards!
Check it out here https://www.mdpi.com/2624-795X/2/4
This paper evaluated the relationship between sea-level change and the severity of impacts on major habitat-forming seaweeds that sustain life on rocky shores. The vertical displacement of intertidal areas uplifted by the 7.8 Mw Kaikōura earthquake was assessed using LiDAR differencing analyses from the closest terrestrial surfaces coupled with controls on horizontal land movement and tilt. Seaweed cover measurements in equivalent intertidal zones found severe (>80%) losses at 9 of 10 sites and included the lowest uplift values (0.6 m). The results indicate major impacts beyond a functional threshold of one-quarter of the tidal range and considerable lag times in ecosystem recovery due to interactions with other stressors in the reassembly phase.
Relationship between sea-level change and loss of seaweed on a rocky shore
In this paper recent published in GeoHazards we evaluated the relationship between sea-level change and the severity of impacts in the major habitat-forming seaweed beds that sustain life on rocky shores.
Check out the open access paper here:
Threshold effects of relative sea-level change in intertidal ecosystems
The 7.8 Mw Kaikōura earthquake affected a large section of the South Island’s east coast and led to a major re-assembly of ecological communities and coastal resource use. To understand the drivers of change and recovery in nearshore ecosystems, we quantified the variation in sea-level change caused by tectonic uplift and evaluated relationships with ecological impacts with a view to establishing the minimum threshold and overall extent of the major effects.
For this assessment we needed to quantify the degree of vertical uplift from the earthquake as close as possible to our post-earthquake study sites in the new intertidal zone. Challenges for this included the availability of elevation data within this area since it was previously covered by water at high tide.We used a methodology based on LiDAR data from the closest adjacent areas to landward that also incorporated an assessment of tilt effects that could lead to uneven ground level displacements, and two time periods to address the potential for continued displacement subsequent to the main seismic event. We also included two different sensitivity analyses to validate the approach used, and assessed interactions with substrate types.
Findings
We found that co-seismic uplift accounted for the majority of the sea-level change at most locations. However, some changes were detected in the period after the initial earthquake that result from the effects of reef weathering and movement of mobile gravels along the coast.
Vegetation losses were evident in equivalent intertidal zones at all of the uplifted study sites. Nine of ten uplifted sites suffered severe (>80%) loss in habitat-forming algae and they included the lowest uplift values (0.6 m). The results indicate a functional threshold of approximately one-quarter of the tidal range above which major impacts were sustained. This pattern wasn’t entirely explained by the previous position of zone boundaries between the main habitat-forming species in relation to their intertidal position, suggesting that other factors (additional to sea-level changes) were involved.
One of the interesting effects involved previously subtidal algae such as bull kelp (Durvillaea spp.) individuals that were uplifted into the low intertidal zone where they ought to persist – but did not. This suggests that additional post-dearthquake stressors had contributed to the degree of impact, since otherwise we would have expected to find more survivors in our lower intertidal study areas. Similar effects were found for Hormosira in the mid-intertidal zone. Continuing research has been investigating the nature of these factors. These ‘double whammy’ situations are evidently important to the regeneration of ecosystems and ecosystem services following a major disturbance, and may also affect the severity of observed mortality events.
New Report on beach recovery in Marlborough
A new report covers some of our ongoing disaster recovery work on the Kaikōura and Marlborough coasts. It responds to a request from Marlborough District Council (MDC) for information on the coastal environment, with a particular focus on supporting the development of a bylaw to address changes in recreational use patterns that have occurred since the Kaikōura earthquake. In the report, we present a selection of information from our earthquake recovery research that has a focus on understanding the impacts and ongoing processes of change.
Major impacts of the natural disaster are associated with vertical uplift of the coastal environment, although ongoing erosion and deposition processes are important as well. Interactions with human activities are also important because they can exert strong influences on the reassembly of ecosystems which is a critical aspect of outcomes over the longer-term. Earthquake uplift caused widespread mortality of many coastal habitats and species (e.g., algal assemblages) that are adapted to a relatively specific set of conditions, often associated with characteristic locations in relation to the tidal range. In uplifted areas the intertidal zone has moved seaward leading to a physical widening of many beaches. This has provided greater opportunity for off-road vehicle access to the coast and has become particularly noticeable at headlands and other natural barriers that were previously impassable at high tide. Off-road vehicles pose threats to sensitive vegetation and wildlife unless appropriately managed. Achieving this is assisted by an understanding of the specific impacts of vehicle use, which in turn requires information on the location of sensitive areas.
To ensure the best outcomes for earthquake recovery there is an urgent need to assess and respond to the new spatial patterns, and to make plans to avoid conflicts where possible. Although research is continuing, this report provides findings that include mapping of indigenous dune system remnants, recruitment of the indigenous sand-binders spinifex (Spinifex sericeus) and pīngao (Ficinia spiralis) on uplifted beaches, distribution of red katipō (Latrodectus katipo) within earthquake-affected dune systems, distribution of banded dotterel / pohowera (Charadrius bicinctus bicinctus) nesting pairs to determine important areas, and spatial overlaps with vehicle tracking measurements along the coast.
Find the full report here!
Ben Crichton M.Sc. Project: Whitebait fishery and populations dynamics of kōkopu
Ben’s research seeks to answer the elusive question of whether whitebaiting impacts the population dynamics of harvested kōkopu species and whether closing areas to whitebaiting contributes to species protection and increased production.
To achieve this, Ben will monitor banded, shortjaw, and giant kōkopu populations within whitebaited and legally closed waterways on the West Coast of the South Island each month for a year. Using spotlights, the nocturnal kōkopu are caught at night with hand nets and placed in buckets to be measured.
Environmental variables, such as pool volume and bank cover, are also likely to affect kōkopu abundance, so these are also measured at each site. This means the effects of whitebaiting can be more precisely evaluated. This research hopes to provide insight into the sustainability of the nationally significant, but highly controversial, whitebait fishery while ensuring that kōkopu and the whitebait fishery are preserved for future generations
Dr. Robyn Dunmore
Researcher Summary
Robyn is a marine ecologist at the Cawthron Institute who specialises in rocky shore ecology. Robyn has worked on a wide range of projects including impact assessments, resource consent monitoring and the experimental evaluation of a marine incursion response tool. She collaborates with MERG on the Kaikoura earthquake coastal recovery programme.
Field of Research
Resources
Subtidal research
Robyn Dunmore and PhD student Dan Crossett from the Cawthron Institute have been tracking recovery in the nearshore subtidal zone. This has involved largescale surveys and experiments in the field and lab. They found that initially, there was clear disturbance to areas with medium to high uplift, especially around Waipapa Bay but also including areas like Ward, Wharanui and Okiwi Bay. Bare rock had been uplifted through sand and gravel, and shifts in sand and gravel
into seaweed habitats had also occurred. More recently, they observed some declines in large brown algae across many sites (even those with low uplift), with changes from brown seaweed-dominated habitats to areas characterised by red seaweed.
These effects could result from a combination of a changing wave climate (from uplift and specific weather events) and stress from marine heatwaves.
After the earthquake, slips along rivers increased runoff of turbid water into the sea, and erosion from unstable rock along the coast also contributes to increased turbidity. Lab experiments were done to test the effects of temperature, light and turbidity on the early life stages of several species of large brown algae. These showed that some species can handle a range of temperatures, while others are restricted to growing only at cooler temperatures. Low light and turbidity also slowed growth in some species. Clearance experiments are helping us understand how seaweed recruitment is affected by substrate type, encrusting coralline algae and the presence of large brown seaweeds. Sites at Waipapa have had little or no recruitment of coralline algae and large brown seaweeds, but other sites with nearby reproductive adult plants are quick to recover. The information from the clearance and lab experiments is important to understand how these seaweeds will recruit into and grow in areas disturbed by the earthquake.
Prof. David R. Schiel
David is Distinguished Professor of Marine Science. He founded and leads the Marine Ecology Research Group. His primary research interests of late involve recovery of the North East coast of the South Island from the severe earthquake in 2016. His research interests include marine ecology, oceanography and fisheries. He has supervised around 70 postgraduate theses and works with collaborators across several universities and CRIs.
Dr. Mike Hickford
Mike is a long-standing Research Associate who has helped lead and manage the Marine Ecology Research Group for many years. His primary research interest is the whitebait fishery of New Zealand. He maintains strong collaborations with CRIs, governmental and management agencies. He co-supervises many of the post-graduate students in MERG.
Field of Research
- Fish biology
- Early life history of fishes
- Dispersal mechanisms
- Aquatic ecology
- Icthyoplankton
- Whitebait
Resources
Dr. Leigh Tait
Researcher Summary
Leigh is a marine ecologist at NIWA specialising in ecophysiology and the application of remote and in situ sampling techniques for better understanding spatial and temporal variation in ecological structure and the physiological functioning of diverse assemblages. He is collaborating with MERG on a wide range of coastal ecology projects, especially remote sensing applications for benthic ecology.
Field of Research
Resources
Prof. Chris Battershill
Researcher Summary
Chris holds the inaugural Bay of Plenty Regional Council Chair in Coastal Science, based in Tauranga. He is Chair in coastal science at Waikato University. He specializes in marine ecology, chemical ecology and sponge taxonomy. Chris collaborates with MERG on earthquake impact recovery science.
Field of Research
Resources
Prof. Ian Hawes
Researcher Summary
Ian is at the Waikato University coastal lab in Tauranga. He specializes in Antarctic aquatic ecosystems, with expertise in geobiology, microbial ecology, plant physiology and limnology. Ian collaborates with MERG in estuarine ecology and photophysiology of algae.
Field of Research
Resources
Dr. Mads Solgaard Thomsen
Researcher Summary
My research focuses on how human stressors, such as bio-invasions, pollution, and climate change, impact the structure, productivity and biodiversity of aquatic ecosystems. I combine experiments, surveys, analysis of long-term dataset, modeling and meta-analysis, to test how patterns in biological communities are generated and maintained. My research provides predictions on how coastal habitats will respond to human stressors and recommendations for conservation strategies needed to ameliorate their impacts.
Field of Research
- Climate changes in marine ecosystems
- Impact of marine invaders
- Meta-analysis and cross-ecosystem comparisons
- Restoration of marine foundation species
- Marine biodiversity in a changing world
- Facilitation and mutualistic interactions
- Eutrophication in estuaries
Resources
Remote sensing coastal recovery using drones
Over the last summer our drone survey team was busy optimising methods for measuring change in the coastal environment change. We now have a comprehensive set of 3D models and imagery from 30+ field sites. Advantages of drone technologies include the ability to cover more ground and a greater range of habitats than we can manage in ground-based surveys alone, yet the resolution of these methods is impressive. Each model covers several hundred metres of coast and the size of each pixel is < 1 cm on the ground! We are using the drone data to assess intertidal area changes which are potentially some of the most important and long-lasting earthquake impacts e.g. where the area of characteristic zones has been reduced from their pre-quake size. Within these areas we are using photogrammetric methods to follow seaweed recovery, building on earlier trials of options for this type of analysis (see Recover issue 3).
Whitebait spawning sites in Kaikōura’s rivers
Early in 2019 we started work to fill a knowledge gap about whitebait in streams and rivers along the Kaikōura coast. For īnanga, which makes up the bulk of the whitebait catch, the spawning grounds are usually found close to the coast near the river mouths. Knowing where they are is useful for recovery planning in the same areas post-earthquake as well as for restoration projects in local waterways. Our survey programme started with fish trapping to find out which species were living in which rivers, after which we selected waterways that were suspected to have good īnanga populations. They included seven catchments close to Kaikōura (Oaro, Kahutara, Lyell / Waikōau, Middle, Swan, Harnetts and Blue Duck) as well as other sites in Marlborough. After four months of surveying we discovered at least one spawning event in all of these streams and rivers and were able to map the spawning locations including some large sites!
Spawning events often coincided with a rise in water levels due to rain events leaving the eggs high above the normal waterline where they can be easily disturbed. The spawning grounds themselves were not always in the same locations but we now have a better understanding of where they might be to make sure they are protected. We also followed the fate of some sites through to hatching… stay tuned for more on this in the next issue of Recover.
Tipping Point project
As part of the National Sustainable Seas Tipping Point Challenge, MERG joined a bunch of other scientists from all around New Zealand for a 10-day excursion into the Marlborough Sounds in 2018. On this trip, the teams conducted brief surveys of the Sounds rocky and sandy subtidal environments.
Check out our video below!
Lab studies on seaweed recovery
Following on from Recover issue 4, Dan Crossett and Robyn Dunmore from the Cawthron Institute have had some interesting results from lab experiments set up to test the effects of temperature, turbidity and light on juvenile large brown seaweed growth and survival. We found distinct differences in species’ early life stage responses. Landsburgia quercifolia was more tolerant
of a wider range of conditions, with similar growth and survival across treatments. In contrast, Durvillaea antarctica (rimurapa or bull kelp) was the least tolerant and was strongly affected by increases in temperature and turbidity, with high mortality and slow growth. While Lessonia variegata could survive in the full range of conditions, its growth was significantly constrained with increasing temperatures, and by the lowest light and highest turbidity treatments.
These species-specific responses are important for understanding not only how areas around Kaikōura may recover post-quake, but also how these species may respond to an altered environment under climate change, with higher temperatures, and potentially increased sedimentation and associated lower light levels due to more storm events. In the next step we want to see how different juveniles raised in stressed conditions respond once transplanted into the natural environment, in aspects such as growth and survival.
Pr. David R. Schiel
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Can’t think how to get started? Just write the first thing that pops into your head. Anne Lamott, author of a book on writing we love, says that you need to give yourself permission to write a “crappy first draft”. Anne makes a great point — just start writing, and worry about editing it later.
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Introduce Yourself (Example Post)
This is an example post, originally published as part of Blogging University. Enroll in one of our ten programs, and start your blog right.
You’re going to publish a post today. Don’t worry about how your blog looks. Don’t worry if you haven’t given it a name yet, or you’re feeling overwhelmed. Just click the “New Post” button, and tell us why you’re here.
Why do this?
- Because it gives new readers context. What are you about? Why should they read your blog?
- Because it will help you focus your own ideas about your blog and what you’d like to do with it.
The post can be short or long, a personal intro to your life or a bloggy mission statement, a manifesto for the future or a simple outline of your the types of things you hope to publish.
To help you get started, here are a few questions:
- Why are you blogging publicly, rather than keeping a personal journal?
- What topics do you think you’ll write about?
- Who would you love to connect with via your blog?
- If you blog successfully throughout the next year, what would you hope to have accomplished?
You’re not locked into any of this; one of the wonderful things about blogs is how they constantly evolve as we learn, grow, and interact with one another — but it’s good to know where and why you started, and articulating your goals may just give you a few other post ideas.
Can’t think how to get started? Just write the first thing that pops into your head. Anne Lamott, author of a book on writing we love, says that you need to give yourself permission to write a “crappy first draft”. Anne makes a great point — just start writing, and worry about editing it later.
When you’re ready to publish, give your post three to five tags that describe your blog’s focus — writing, photography, fiction, parenting, food, cars, movies, sports, whatever. These tags will help others who care about your topics find you in the Reader. Make sure one of the tags is “zerotohero,” so other new bloggers can find you, too.
Dr. Tommaso Alestra
Researcher Summary
I am a marine ecologist with 13 years of research experience in intertidal and subtidal benthic systems. I have developed and pursued marine ecological research both independently and in response to clients’ requests. I have worked on a variety of consultancy projects, for example quantifying impacts of the Kaikōura earthquake for the Ministry for Primary Industries, monitoring patterns of biodiversity in the Lyttelton Harbour/Whakaraupō for Environment Canterbury, and assessing effects of marine reserves for the Department of Conservation. I am equally at home in research design and planning, carrying out technical work in the field, and interpreting complex results. I am responsible for coordinating teams of researchers based at different institutions, ensuring project objectives are met, and reporting on results to clients, industry and community stakeholders, and the public.
Filed of research
Ressources
How much of the coast was uplifted by how much?
Although Covid19 set back some of our planned fieldwork, we put the lockdown period to good use to characterise some of the core earthquake impacts on the coast. One key questions is ‘how much of the coast was uplifted and by how much?’. Knowing this helps us to extrapolate the results from small-scale field surveys to the wider coast, which in turn is the best method for gauging the extent of impacts and how the recovery is looking overall. Being able to report the results as the ‘length of coastline’ affected is an intuitive option for comparing one place to another, but have you ever heard of the ‘Infinite coastline paradox’? Google it up!
In our case we have some very high resolution data for the whole coast, which means we can take into account all of the nooks and crannies. This is important because if you’re a small guy, like a paua, all of those intricacies are relevant to your available space. Another aspect is which part of the shoreline we’re talking about, and in this case we did the assessment for the position of Mean High Water Springs (MHWS). We also looked at two periods of time—the immediate earthquake effects and whether there have been any changes since. This is important since our RECOVER project began two years after the quake and we have been following changes since. The results can be shown lots ways, as in Figure 1. This shows the degree of uplift within four major substrate types that are associated with characteristic habitats and together make up the whole coast.
In the coming months we will be interpreting results from our field survey sites against these ‘big picture’ trends to evaluate how the recovery is going. We also confirmed that most of the changes have occurred during the initial earthquake, at least south of Waipapa Bay. However, in other work we are following the erosion of uplifted reefs—which is significant in some areas. See the next issue of Recover for an update!
Young pāua growing well
Our work monitoring the juvenile pāua around Kaikōura has shown encouraging signs of recovery of this hardhit population. Wild pāua tagged a year ago have had excellent growth rates and survival. They’re quickly advancing through the size classes and will soon migrate to deeper waters and join the adult spawning groups, a key step in recovery. The abundance of pāua at our sites is increasing significantly through time, and we are seeing much higher numbers than we did in the
early days after the earthquake. Hatchery-raised reseed pāua planted in 2018 by the Pāua Industry Council have also shown excellent survival and growth. While things are looking good overall, some sites have been significantly impacted by large gravel movement, erosion and sedimentation, which can compromise pāua habitat and cause mortality.
Seed pāua found within groups of large wild pāua seemingly naturalised and behaving like their wild relatives.
Pictures by Shawn Gerrity.
Whitebait hatching experiment with Environment Canterbury
Our discovery of whitebait spawning sites in Kaikōura streams (see Recover Issue 3) ended with a twist in Waikoau / Lyell Creek when we realised that the eggs were unlikely to hatch. Thanks to Pete Adams at Environment Canterbury we came up with an engineering experiment in the form of a temporary closure — the reverse of mechanical stream openings that are routinely used to alleviate flood waters backing up after natural river mouth closures. In this case we temporarily blocked the mouth with gravel to raise the water level around 40 cm for just a few hours. That was enough to hatch out our īnanga/whitebait eggs that had been found four weeks previously, high on the river bank. This very simple experiment would not be feasible in most rivers but did demonstrate a successful rescue plan to give some stranded fish eggs a much needed helping hand!
Read more on the Environment Canterbury site here
Kelp and seaweed recovery
In the summer of 2019 NIWA and the University of Canterbury completed aerial drone surveys of many sites along the Kaikōura coast to examine the survival of vulnerable kelp species such as bull kelp (Durvillaea spp). This included testing the relative accuracy of readily available “RGB” cameras, and enhanced spectral cameras (multispectral cameras). This research revealed that both RGB and multispectral cameras can be used effectively for mapping broad scale distribution of marine vegetation (i.e., kelp), but multispectral cameras can be used to examine species biodiversity at higher taxonomic resolution. NIWA and UC researchers will now be examining kelp and seaweed distribution across a broader range of locations, and tracking the recovery through time.
Stuff article on Kaikōura whitebait
Great article by Sophie Trigger at the Marlborough Express that features our recent work investigating earthquake impacts on river mouths along the Kaikōura coast.
We were able to locate several whitebait spawning sites and made some interesting discoveries with many of them occurring on flood events. Read more about an ecological experiment to rescue eggs stranded high on the riverbank with the help of the Environment Canterbury flood management team here
Whitebait spawning in Lyell Creek Waikōau
Nice article in the Kaikōura Star on our surpise finding of whitebait spawning sites in downstown Kaikōura.
The spawning habitat in this area has benefitted from riparian restoration work in Lyell Creek / Waikōau since the earthquakes.
Beach birds: mapping hotspots for banded dotterels
Our beach birds study got underway this year on the uplifted Marlborough and Kaikōura coast beaches. In early December we completed a baseline survey of where Banded Dotterel nesting grounds are found, all the way from Oaro in the south to Marfells Beach in the north. That was a lot of walking for our team of three! The beach birds study aims to identify the most important nesting locations and assess interactions with human activities along the earthquake-affected coast. Knowledge of these sites fills a gap for coastal planning, especially where the beaches have changed. One of the best known locations is in South Bay where local researcher Ailsa Howard has been conducting a study on breeding success. Ailsa has found that the success rate is very low, suggesting that more needs to be done to help these birds!
The whole-coast survey has found that hotspots occur throughout the study area, but are very patchy in their distribution. Protecting these areas is important since the ground-nesting birds are extremely vulnerable to threats. Future studies will characterise the types of threats that occur at representative locations to identify conservation needs and practical strategies for protecting nesting grounds across the wider coast.
Seaweed recovery experiments
Before the earthquake, several reefs around the Kaikōura Peninsula and in the Cape Campbell area used to be covered by the seaweed Hormosira banksii (also known as Neptune’s necklace), but these lush algal forests were almost completely lost as a result of the uplift. It was shown by previous studies of MERG that these algal beds supported much of the biodiversity of intertidal reefs, which are now depauperate of other algae and small animals. We are now trying to aid the recovery of Hormosira by creating “oases” with shade and moisture in the middle of the hot, bare reefs. These are created by installing shade cloth canopies on top of water pools chiselled into the rock. We hope that they will gradually be colonized by Hormosira and that this could be a good starting point for this species to spread to wider areas of reef. This experiment was set up in December 2018 at Wairepo reef in Kaikōura (between Jimmy Armers beach and the seal colony on the northern side of the peninsula) and will be replicated at other sites if successful.
