Comment: Marine sponges were thought to be more resilient to ocean warming than other organisms. But earlier this year, New Zealand recorded the largest-ever sponge bleaching event off its southern coastline.

While only one species, the cup sponge Cymbastella lamellata, was affected, a prolonged marine heatwave turned millions of the normally dark brown sponges bright white.

Subsequently, we reported tissue loss, decay and death of other sponge species across the northern coastline of New Zealand, with an estimated impact on hundreds of thousands of specimens. In contrast, we didn’t observe any bleaching or tissue loss in central areas of New Zealand’s coastline, despite extensive surveys.

Our latest research shows the most severe impacts on sponges occurred in areas where the marine heatwave was most intense. The loss of sponges may have major repercussions for the whole ecosystem.

Why should we care about sponges?

Sponges are among the most ancient and abundant animals on rocky reefs across the world. In New Zealand, they occupy up to 70 percent of the available seafloor, particularly in so-called mesophotic ecosystems at depths of 30-150m.

They serve a number of important ecological functions. They filter large quantities of water, capturing small food particles and moving carbon from the water column to the seafloor where it can be eaten by bottom-dwelling invertebrates. These invertebrates in turn are consumed by organisms further up the food chain, including commercially and culturally important fish species.

Sponges also add three-dimensional complexity to the sea floor, which provides habitat for a range of other species such as crabs, shrimps and starfish.

Sponge bleaching, tissue loss and decay

Like corals, sponges contain symbiotic organisms thought to be critical to their survival. Cymbastella lamellata is unusual in that it hosts dense populations of diatoms, small single-celled photosynthetic plants that give the sponge its brown colour.

These diatoms live within the sponge tissue, exchanging food for protection. When the sponge bleaches, it expels the diatoms, leaving the sponge skeleton exposed.

Tissue loss occurs when sponges are stressed and either have to invest more energy into cell repair or when their food source is depleted and they reabsorb their own tissue to reduce body volume and reallocate resources.

Tissue decay or necrosis on the other hand is generally associated with changes in the microbial communities living within sponges and growth of pathogenic bacteria.

Bleaching, tissue loss and decay in sponges have all previously been associated with heat stress, but didn’t necessarily result in sponge death. In other places where such impacts have been observed, they were much more localised, compared to what we saw in New Zealand.

Impact of marine heatwaves

Marine heatwaves are defined as unusual periods of warming that last for five consecutive days or longer. Some can last from weeks to several months and extend over hundreds or thousands of kilometres of coastline.

The sponge bleaching and tissue loss or decay in New Zealand matched the duration and intensity of marine heatwaves to the north and south of New Zealand during the summer of 2021/2022. The Hauraki Gulf, where sponge necrosis and decay was reported, was in a continuous marine heatwave for 29 weeks from November 2021 to the end of May 2022, with a maximum intensity of 3.77℃ above normal.

In Fiordland, a prolonged marine heatwave developed in early February 2022 and persisted for more than 16 weeks into May, with a maximum intensity of 4.85℃ above normal temperatures. In contrast, the Wellington and Marlborough Sounds regions experienced only short (weeks) marine heatwaves with a lower intensity and we did not observe any impacts on sponges.

These extreme heat events can result from a combination of changes in the heat exchange between the air and the sea, wind patterns and ocean currents. Their likelihood is also influenced by large-scale climate patterns such as the El Niño Southern Oscillation (ENSO).

What the future may hold

Most global research on climate change impacts has focused on experimental studies exposing organism to temperatures predicted for 2100, often 2-4℃ higher than current temperatures. But the occurrence of marine heatwaves means organisms are already experiencing these temperatures, sometimes for several weeks or months. By 2100, marine heatwaves will become even more extreme.

For bleached Cymbastella, recent anecdotal reports suggest many sponges have recovered their colour, which is good news. However, observations immediately after the bleaching indicate many sponges were being eaten by fish, possibly because their symbionts may provide chemical defences against predation.

For bleached corals, studies have shown impacts on spawning success for many years after the event, likely because their energy reserves have been depleted.

We don’t yet know if this is the case for sponges. For sponges with decayed tissue the outlook is even less clear, as many probably died.

Sponges are not the only species to be affected by marine heatwaves New Zealand experienced in 2021/2022. There were reports of seaweed die-offs and changes to normal distribution patterns of tuna and other ecologically and commercially important fish species.

Marine heatwaves should be front of mind when thinking about climate impacts. They are happening now, not in 50 years, and we don’t know enough yet to determine if sponges may be the canary in the coal mine.

This is especially important because New Zealand’s northern coastlines are already experiencing almost continuous marine heatwave conditions, with the ongoing event forecast to extend into the coming summer.

Read the original article at The Conversation.

James Bell is a professor of marine biology at Te Herenga Waka—Victoria University of Wellington, Nick Shears is an associate professor in marine science at the University of Auckland and Robert Smith is a lecturer at the University of Otago.

Comment: Following the settlement of Aotearoa New Zealand, many native species were wiped from the mainland. It’s a familiar story—one that has affected species such as the iconic flightless kākāpō and the tuatara, a reptile in a category all its own.

As the New Zealand government moves towards the goal of Predator Free 2050, the reintroduction of native species back into predator-free areas on the mainland is becoming increasingly common.

However, these reintroductions from offshore islands to the mainland can have unexpected outcomes.

A recent study led by researchers at Te Herenga Waka—Victoria University of Wellington raises questions about the impact habitat differences will have when we are reintroducing taonga species of special cultural significance to Māori.

The study focused on tuatara, which have undergone extensive recovery efforts. But the process of reintroducing these reptiles back onto the mainland may not be as straightforward as previously thought.

An icon of Oceania

Tuatara are reptiles so unique they are the sole surviving species in Rhynchocephalia—one of the four reptile orders.

Long-lived, slow to reproduce, and laying their eggs in the ground, tuatara are vulnerable to predators such as stoats and rats. Natural populations of tuatara remain only on predator-free offshore islands.

However, tuatara have been settled back onto the mainland inside several fenced ecosanctuaries, a trend that’s likely continue as the impact of invasive mammals is reduced across the country.

New research on the diets of tuatara living on Takapourewa Stephens Island reveals that larger individuals are eating a surprising amount of seabirds—or at least seabird matter.

Using carbon signatures to assess diet, we found that as much as 40 percent of the dietary carbon in sampled tuatara had marine origins—explaining the headless seabird carcasses often encountered across the island.

For a tuatara with a mouth large enough to fit around a seabird, and a territory in the burrow-pocked forest floor, this might mean one fledgling head a week.

The seabird situation

Seabirds represent a crucial food source on offshore islands, providing the opportunity for animals that can consume seabird eggs, fledglings or adults with a boon of nutrients like polyunsaturated fatty acids (PUFAs).

These fatty acids are important for egg hatchability, embryo development, and juvenile growth in other reptile species.

However, seabird colonies like the ones found on the Takapourewa are absent from mainland New Zealand, which poses a couple of questions: what are populations of tuatara reintroduced to the mainland eating, and are there physiological implications from this dietary lack of seabirds?

We currently don’t know how much of a benefit to growth and development the large role of seabirds in the tuatara diet provides or what the lack of these nutrients may mean for tuatara living on the mainland.

In ecosanctuaries, where biodiversity is high, skinks, geckos and ground-nesting native birds may provide some supplementation of PUFAs. However, PUFAs trend higher in marine environments than terrestrial systems.

Dietary disparity

This new research sheds light on an important facet of reintroducing native species to the mainland.

The biological communities on offshore islands are often very different from those on the mainland and the species living there are part of a complicated, interwoven web of predator and prey interactions.

While New Zealand is the undisputed seabird capital of the world, the mainland is very different from the time when tuatara were widespread. Once covered in either seabird colonies or the guano from seabird colonies, the mainland is now a patchwork of bush, agriculture and urban areas.

This research supports the need for a holistic view of restoration and a measured approach to reintroductions.

For many mainland ecosanctuaries, the resources to restore seabird populations are extremely limited. Located near cities with large amounts of light pollution, and with poor or missing records of which seabirds historically inhabited the space, the possibility of large-scale seabird restoration to the mainland is difficult.

What will the lack of seabirds, which make up a significant portion of the diet of large tuatara on offshore islands, mean for mainland populations? And will we see physiological effects of this disparity at our ecosanctuaries?

With lifespans of well over 100 years, setting up tuatara restorations is aiming for success well beyond our lifetimes. While we don’t yet know how this dietary disparity is affecting the viability of tuatara populations, the sheer number of seabirds being consumed by large tuatara offshore makes it a pressing question for restoration—and raises questions about how we approach translocations in Oceania.

Read the original article at The Conversation.

Sarah Lamar is a PhD candidate, Diane Ormsby is a senior lecturer in Reproductive and Developmental Biology, and Nicky Nelson is professor of Conservation Biology at Te Herenga Waka—Victoria University of Wellington.

“Alpine ecosystems have historically been extreme environments, where only high alpine specialist plant species could establish and thrive,” Dr Deslippe says. “Climate change is rapidly impacting these extreme environments.”

As the climate warms, lowland species can expand their range upslope in alpine areas, putting pressure on the species that live higher in the mountains.

“While some alpine species may benefit from milder growing conditions, others may not, and all will have to contend with increased competition by the new plants moving upslope. This combination of climate change and species invasion potentially puts huge numbers of alpine species at risk of decline and extinction.”

The study involved 20 collaborators from Aotearoa New Zealand, Australia, Switzerland, and China. The New Zealand branch of the project was led by Dr Deslippe with support from Professor Kath Dickinson from the University of Otago. The researchers each spent two summers tramping through mountain ranges to collect their data: “We wore out a lot of tramping boots,” says Dr Deslippe.

The data researchers collected in their respective countries showed similar types of alpine species are at risk of decline due to climate change.

“We found that plants that live at lower elevations and have a wider area in which they can grow are generally more resilient,” Dr Deslippe says. “Plants that grow higher on mountains and can only grow in a small area are more likely to suffer due to climate change.”

Climate change is associated with biodiversity loss in many ecosystems around the world. Dr Deslippe hopes the data collected in this study will help land managers identify the species that will likely require conservation interventions to survive, as well as help them support biodiversity and healthy ecosystems in alpine areas.

“Our work has provided broad and general guidelines for land managers about which species may be at risk. But local conditions, such as land use and management actions, are huge factors dictating the persistence of native plant communities in the face of emerging threats, such as climate change and species invasions.”

The research team now plans to collect data from other mountainous regions around the world.

“Globally there remains a lot of work to be done to secure the future of species that live in habitats at risk from human-induced climate change,” Dr Deslippe says.

“The UN has declared the 2020s as the Decade of Restoration. We must conserve and restore habitats, and take actions such as habitat protection, seed banking, captive breeding, and weed control to prevent species decline.”

The research, led by Professor James Bell from the School of Biological Sciences and Dr Riccardo Rodolfo-Metalpa from the Institute for Research Development, was recently published in Global Change Biology.

Professor Bell and his colleagues travelled to Papua New Guinea in 2019 to study sponges in coral reefs surrounding shallow water carbon dioxide seeps—places where carbon dioxide bubbles from the sea floor

“Sponges are very abundant near these seeps in the ocean floor,” Professor Bell says. “The carbon dioxide from the seeps makes the ocean more acidic in this area, which is something that will happen to all of Earth’s oceans due to climate change. That means we can use this area as a proxy to see how sponges might cope with more acidic oceans.”

Previous research has suggested that sponges are well-suited to surviving in acidic ocean conditions because of their higher tolerance for both acidic conditions and warmer temperatures. Many sponges also contain photosymbionts which could potentially thrive in more acidic oceans due to greater access to carbon dioxide for photosynthesis.

“We were able to show that sponges that contain photosymbionts in this area can offset the metabolic costs of dealing with ocean acidification,” Professor Bell says. “This means while the sponges might not thrive under climate change conditions, they will survive.”

Despite bleached sponges being reported in cold-water sponges in New Zealand last month, tropical sponges might fare better in changing ocean conditions, Professor Bell says.

Essentially, the sponges were still stressed by the acidic conditions. However, because the symbionts were more productive thanks to higher levels of carbon dioxide, the sponges could draw more energy from them to survive in the acidic water.

“Sponges are really important on current coral reefs and our research continues to support the hypothesis that sponges will still be found on future reefs, even if corals were to completely disappear,” Professor Bell says. “These changed ecosystems will have major consequences for the resources people take from corals reefs. Sponge-dominated reefs will not be able to provide as many resources as coral-dominated reefs, but it will be better than no resources at all.

“While our understanding of the impacts of climate change on marine organisms is increasing, we still have limited ability to manage these impacts. A global concerted effort to rapidly eliminate carbon emissions is the only way in which we will keep ocean acidification and warming to a level that won’t fundamentally alter marine ecosystems forever."

Dr Park first developed an interest in the outdoors and plants through a connection with a childhood neighbour, acclaimed botanist Tony Druce. This passion led him to Te Herenga Waka—Victoria University of Wellington (then Victoria University) in the mid-1960s, where he completed an undergraduate degree in Botany and Geology and a Master’s in Ecology and Soil Science.

Thirty years later, Tim Park also came to the University to study. Tim started his degree while also completing his last year of high school. His first papers were in religious studies, although he also studied geography, biology, and photography.

“I’ve always been interested in the link between nature and humans, especially the spiritual benefits people get from nature, and how we use spirituality to organise ourselves as humans,” Tim says.

Tim says this link between humans and nature was also central to his father’s study of ecology.

“Dad was studying old alpine beech forests in the Tararua ranges, and while he was studying he found evidence of old human firepits under the forest topsoil,” Tim says. “This really changed his life and the way he thought.

“Often we try and separate humans and nature and forget about the millennia of interplay between them, to the detriment of both humans and the natural world.”

Tim’s mother Lindsay also studied ecology and taught art classes, giving Tim another link between science and spirituality.

As well as studying at Te Herenga Waka, Tim also made a connection to the University in other ways, including with Salient, and involvement with the campus environment group. He worked at the university library and made connections he has maintained to this day with landscape architects.

Tim also remembers covering several protests, as well as a number of controversial issues in Salient. Protest is also somewhat of a family legacy, with Dr Park acting as the first president of radical student protest group Ecology Action, as well as leading a group of Hutt Valley High School students to protest the widening of SH2 through native bush near Silverstream, ultimately leading to the preservation of much of that bush through the creation of the Keith George Memorial Park.

After graduating (Tim finished his degree at Lincoln University), Tim went straight into an extensive career in ecology. First, he started work with the Department of Conservation (DOC), “getting paid to tramp around and ID plants.

“We were paid to boat and helicopter around Stewart Island and identify the plants there, which was a fantastic experience and not something many people get to do.”

Here lies another family connection—Dr Park founded and led the New Zealand Biological Resources Centre, which was incorporated into the Conservation Department (that would become DOC) in 1986.

After working with DOC and with several regional Councils, Tim joined the team at QEII National Trust. The Trust helps people who own private land to protect natural areas of significance by putting them under a legal covenant that preserves them in perpetuity.

Tim says they were able to protect over 1500 different natural areas during his time there, with the average size of each area being 50 hectares (about 50 rugby fields in size, to put it into a New Zealand perspective).

“Both the government and private landowners really wanted to invest in protecting natural areas at the time, so we were able to achieve a lot,” Tim says. “It was a real privilege to be able to help protect these amazing places forever.”

After doing similar work for the Kāpiti Coast District Council, Tim took his expertise to a completely different part of the world, volunteering with an ecological organisation in Tanzania to grow eco-tourism.

“It was an incredible place to work—we were near the border with Kenya, so we were close enough to visit the Serengeti and climb Kilimanjaro on the weekends.”

After that it was back to Wellington, where Tim joined Wellington City Council. During his time there, Tim was involved with several new projects and partnerships including the WellyWalks—which help Wellingtonians get out and walk in the city and surrounding areas—and helping the Conservation Volunteers get established locally. Perhaps his best-known achievement, however, was enabling the establishment of Predator Free Wellington in 2016.

Tim is now the manager at Ōtari Native Botanic Garden and Wilton's Bush Reserve.

Throughout his career, Tim has maintained his connection with Te Herenga Waka. Alongside the Sustainability Office, Tim helped establish the Growing Futures programme, which allows staff and students to volunteer in an environmental setting.

“It was a great challenge to create a programme where staff and students could get hands-on experience in the environment, and that also could help the University off-set its carbon emissions,” Tim says. “This was a complex project to set up and deliver, but it’s going to leave an amazing legacy for Wellingtonians.”

Tim also works closely with the Landscape Architecture staff and students at the Wellington School of Architecture.

“I aim to challenge students to think different about plants and landscapes, especially how we can effectively integrate native plants and the urban environment,” he says.

As well as guest lecturing, Tim has also been involved in several Summer Research Scholarships, including one on the Pā Harakeke at Te Papa Tongarewa that was one of the Summer Gold award winners for 2022.

Dr Park also maintained a connection with Te Herenga Waka. After graduating, he worked first at the DSIR (now divided into Crown Research Institutes, including NIWA and GNS Science), and then at the New Zealand Biological Resources Centre (now part of DOC). He then returned to Te Herenga Waka as a Stout Research Fellow. It was during this time that he began research on perhaps one of New Zealand’s best-known ecology texts: Nga Uruora: The Groves of Life, Ecology and History in a New Zealand Landscape.

Beginning with James Cook's Endeavour party on the Hauraki Plains, and then covering the New Zealand Company's arrival in the valley that became the Hutt, the book covers how colonial settlement transformed the original forests and swamps in these and other river flatlands in New Zealand. Apart from small reserves and parks, New Zealand bears very little resemblance to the country colonial settlers first saw.

Dr Park also published Theatre Country Essays on Landscape and Whenua with Victoria University Press in 2006.

Dr Park passed away in 2009. Tim remembers one moment in particular from his father’s funeral, when Te Herenga Waka Religious Studies Emeritus Professor Paul Morris—who taught Tim when he was a student—commented on Dr Park’s legacy.

“Paul said Dad contributed a lot to our identity and spirituality as New Zealanders, and our relationship to the bush, particularly for New Zealand Europeans,” Tim says. “It was really special to have my father respected by Paul in this way.”

So, what is next for the Park family and ecology? Tim is currently focusing on his work at Ōtari, but as for the future, he says they’ll just wait and see.

“I’m not sure if my kids will continue the legacy—we’ll see. But they certainly get their dose of nature.”

Find out more about Ōtari Wilton's Bush.