Study examines 30 years of seagrass restoration to find best methods

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A major review of seagrass programs in Cockburn Sound has helped identify the best methods for restoring large scale seabed meadows and found community involvement was a key to success.

Seagrass meadows were decimated from the 1950s and restoration attempts in the past three decades have included everything from sprig and seed-based methods to mechanical plantings, seagrass in sandbags being placed on the seabed and wire coils being used to fix small plants into the sediment.

The project, which is part of the WAMSI Westport Marine Science Program, looked at more than 110 restoration efforts since the 1990s and re-visited 31 sites to assess their success.

The study was led by Professor Gary Kendrick from The University of Western Australia and Professor Jennifer Verduin from Murdoch University.

Professor Verduin said sprig-based programs, where mature seagrass shoots were collected by divers from natural meadows, were found to have achieved high transplant success rates.

“Survival was as high as 90 percent on larger scale sprig-based restoration trials of up to three hectares,” Professor Verduin said.

“We found over a period of 15 to 20 years, the growth of sprigs resulted in the formation of new meadows.”

The study found both sprig-based restoration and seeding programs, such as Seeds for Snapper, had developed viable methods for revegetating large areas of bare seafloor. But large-scale sprig-based restoration programs, while labour intensive, were particularly efficient in quickly stabilising the sediment and creating almost instant meadows. This accelerated the formation of natural meadows.

“Cockburn Sound and Owen Anchorage suffered a major loss of seagrass from the 1950s to the 1990s and while there have been dozens of programs since to rehabilitate the area, there has been limited follow-up to gauge their success,” Professor Verduin said.

“Restoration programs are important and contribute to the rapid natural recovery of seagrass habitats by ameliorating loss and supporting the recovery of grasses.”

“Some of the projects in the past have been on areas of no more than three hectares and we wanted to see if we could recommend a restoration package that could be scaled up to ten times that area to enhance restoration success.”

One of the main findings of the review was confirmation that engaging with local communities was key to the success of large-scale seagrass restoration programs.

Community-based citizen science and restoration projects working with volunteers were recommended as cost-effective approaches to increase the scale of restoration.

“These transplanting projects have already been successful at Southern Flats, Cockburn Sound, and Oyster Harbour, Albany,” Professor Verduin said.

Seagrasses, sometimes referred to as the ‘oceans’ lungs’ are a vital part of the ecosystem. They reduce coastal erosion by stabilising sediment, provide critical habitat for marine animals and efficiently store carbon.

Dozens of recreational uses identified, valued and mapped in project surveys

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Researchers have used data from hundreds of community surveys to create ‘heat maps’ showing the popular spots for 31 recreational activities in Cockburn Sound.

Bird watching, kayaking, jet-skiing and snorkeling were among the many uses identified by almost 600 people who responded to questions as part of the WAMSI Westport Marine Science Program project, which looked at community values in the Sound.

Beach activities, walking, running and swimming were commonly reported forms of recreation and the survey revealed recreation in Cockburn Sound was most highly valued for its contribution to people’s ability to have fun, improve their physical health, socialise with others, and to relax.

Dr Abbie Rogers, a Premier’s Mid-Career Fellow from The University of Western Australia School of Agriculture and Environment, who is leading a theme of socio-economic research for the program, said Cockburn Sound was one of the most intensively used bays in WA.

“The Sound is highly valued by the community for its ecological and recreational values and it hosts a vital part of the State’s economy,” Dr Rogers said.

Woodman Point Reserve, at the northern end of the study area, was found to be the most frequently visited location and beach.

The results were used to create ‘heat’ or kernel density maps that showed activity density or occurrence using circular patterns. Economic valuations were also calculated for recreational use of various sites.

Murdoch University’s Dr Michael Hughes, the project’s lead investigator, said the area was important for recreation.

“The variety of non-fishing recreational activities and associated values that coexist in the Sound highlights the importance of this area for the public,” Dr Hughes said.

The area studied included the shore and waters between Woodman Point and Cape Peron along with Garden Island and Carnac Island. The entire study area was associated with one or more recreational activity values.  “Understanding how people use marine coastal areas for recreational activities and the values associated with such uses, are important considerations for the development and management of these areas,” Dr Rogers said.

Dr Hughes said the ability of the Sound to host such a diverse range of recreational activities suggested the social and physical carrying capacity was considerable.

“Furthermore, management decisions and planning will require engagement with a wide range of recreational activity representatives,” he said.

Of the recreational activities identified and mapped, 16 were land based and 15 water based. They did not include recreational fishing, which is the focus of another project in the program. Other socio-economic projects are measuring the Perth community’s values for Cockburn Sound’s natural environment and ecology.

Students take a dive into marine science with ‘Thinking Blue’

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Students in their final two years of high school are being given access to some of Western Australia’s top marine scientists in a series of lectures on topics ranging from artificial reefs and ecotourism to coral bleaching and aquaculture.

‘Thinking Blue’, which is the Western Australian Marine Science Institution’s school outreach program, lets students hear from inspiring experts across a range of specialist areas.  WAMSI runs the program with John Ryan, a Marine Science graduate who is now a science teacher at Sacred Heart College in Sorrento.

WAMSI CEO Dr Luke Twomey said Thinking Blue was about inspiring year 11 and 12 students as well as taking the latest scientific research into schools.

“The Thinking Blue lectures allow students to hear from people at our partner universities and organisations who are among the leaders in their field,” Dr Twomey said.

“Some students may be inspired to study marine science but all of them develop a greater understanding of the world’s oceans, the threats they face and the role of science in finding solutions.”

The topics for the next school terms include marine pollutants, ecotourism around marine mammals and whale sharks, marine ecosystems, aquaculture as a solution to declining fish stocks and seagrass meadows and mangroves.

The lectures are presented by video link to students at Sacred Heart College and the recordings are shared with other schools and online to the community through the WAMSI website.

John Ryan said the outreach program helped open students’ minds to the wonders of marine science.

“The impact of Thinking Blue extends far beyond the classroom,” Mr Ryan said.

“By connecting students with scientists, it ignites a spark of inspiration, paving the way for a new generation of marine enthusiasts.”

“It is heartening to see that several Sacred Heart College students, driven by their experiences in this program, have chosen to pursue marine-based tertiary education courses, furthering their understanding and commitment to the conservation of our oceans.”

Links to previous recorded lectures can be found here.

First major study of fish larvae in Cockburn Sound

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While fishers head out into Cockburn Sound in search of prized catches such as pink snapper, a team of scientists has been targeting fish larvae to better understand which species are in the area during their earliest life stage and where they are most abundant.

Since late 2021, they have recorded more than 12,000 larvae during monthly sampling.

The researchers say while Cockburn Sound is known to be an important spawning ground for key fishes such as pink snapper, local studies on the larval stage of their development have been limited until now.

Jake Nilsen, a Research Assistant at Curtin University, is part of the team working on the WAMSI Westport Marine Science Program project which also involves scientists from WA Museum Boola Bardip, CSIRO and the Department of Primary Industries and Regional Development.

“We haven’t known a lot about the larval fish in this system,” Mr Nilsen said. “There have only been a few studies and nothing as comprehensive or long-term as the current project. This is the first of its kind to be looking at Cockburn Sound in such detail.”

He said of the thousands of larvae recorded by the team, the most abundant were baitfish, dragonets and filefish, which have to be individually identified to species (if possible) using a microscope.

This was a difficult and time-consuming task given there are so few larval fish taxonomists in WA.

“Important fishery species have also been common, including whiting, trevallies and flatheads which is exciting as it gives new information about their early life stages we didn’t previously understand,” Mr Nilsen said.

“Pink snapper larvae abundance has been relatively low compared to previous studies but observations indicate their abundance is likely to increase following the spawning in October of this year.”

“We are seeing spikes in the number of pink snapper larvae in the most recent samples over the summer period.”

“We know pink snapper use these areas for nurseries and that’s been backed up by the data we’re collecting for the fish larvae.”

“Cockburn Sound is proving to be really important for fish larvae and they are quite vulnerable to environmental stressors.”

Mr Nilsen said two methods were being used to sample larvae.

“The main one is bongo tows which is a net with a small mesh size towed behind a small boat. It basically goes from the surface almost to the seabed and comes back up.”

“In collaboration with DPIRD, we are also using light traps over the summer period to capture larvae that are attracted to light, and just after the snapper spawning period.”

“A promising finding from the light trapping method is the exceptionally high number of invertebrate larvae captured including the larvae of the blue swimmer crab.”

“Work is underway to determine the abundance of the early stages of this species, which remains largely unstudied.”

“Findings from this work may prove useful in restoring that fishery, which remains closed in Cockburn Sound because of concerns about declining numbers.”

He said there was a lot happening in the Sound that couldn’t be seen without a microscope.

“There is a lot going on in the water column.”

How does the ocean’s only flowering plant cope with being buried?

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In water tanks at Edith Cowan University, pots containing Posidonia sinuosa, the most widespread species of seagrass in Cockburn Sound, have been tested to see how much burial under sediment they can withstand. The research, part of the WAMSI Westport Marine Science Program, is looking at the resilience of the ocean’s only flowering plant, to dredging.

ECU researcher, Chanelle Webster, said seagrass was an important part of the ecosystem – providing not only food and habitat for marine animals but also stabilising the seabed and storing carbon which could help combat climate change.

Seagrasses tend to occur in the shallow waters along coastlines as they require a lot of sunlight, but they are easily affected by disturbances in the light reaching the plants.

“One of the main impacts of dredging is changing the amount of light plants receive when sediment is stirred up during operation,” Ms Webster said.

“Another effect of dredging on seagrass is when sediment gets moved and dumped in an area, the particles can settle on seagrass and bury it. This is where my experiment comes in.”

“There are about 10 different species of seagrass in the Sound but Posidonia sinuosa is the main species, you can find it in all areas of the Sound from Kwinana to Garden Island, and this is why we decided to do the experiment with this species.”

“We have been trying to understand how much burial Posidonia sinuosa can tolerate before you start seeing negative impacts to their growth or survival.”

Some of the potted seagrasses had no sediment added, others had up to 16 centimetres of sediment put on them in controlled conditions over four months.

The research team measured the amount the plants grew and noted cellular changes.

“From preliminary analysis, plants tolerate up to four centimetres of burial by sediment but with eight centimetres and more of burial they are impacted.

“When plants were buried by 8cm or more of sediment the growth was significantly less.”

The research indicated Posidonia sinuosa could tolerate burial of four centimetres of sediment for 16 weeks which was the duration of the experiment.

Ms Webster said while further analysis was still to be done, the preliminary results were promising in terms of being able to minimise impacts to seagrasses in the Sound.

WAMSI offering two free student registrations for lobster biology conference

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The Western Australian Marine Science Institution is offering two WA-based Honours, Masters or PhD students the chance to improve their understanding of rock lobster and crab biology with free registration for the International Conference and Workshop on Lobster Biology and Management (ICWL) in Fremantle this October.

The theme of the 12th ICWL is ‘Ecosystem-based fisheries management (EBFM)’ – an approach that recognises all interactions within an ecosystem rather than considering a single species or issue in isolation.

WAMSI is a Bronze Sponsor of the conference and has secured two student registrations to offer people undertaking study at any of our partner universities (Curtin University, Edith Cowan University, Murdoch University and The University of Western Australia) or working at our partner organisations while doing further studies. They must be WA based but can be enrolled at other universities.

WAMSI Research Director Dr Jenny Shaw said it was an opportunity for students to find out more about marine research and fisheries and explore career opportunities.

“The ICWL began in Perth more than 40 years ago. At the time, 37 biologists from six countries met to discuss and compare their work on a range of lobster topics,” Dr Shaw said.

“Since then, it has grown in popularity and prestige.”

“Given the WA rock lobster fishery is the largest single species fishery in Australia with a value of more than $450m annually and was the first in the world to achieve Marine Stewardship Council accreditation, this is a fabulous opportunity for students to learn more about the industry as well as science around the species.

“It’s also a terrific opportunity to network at a prestigious, international conference.”

Students who are interested in applying for WAMSI’s student registration offer are asked to:

Write a letter (maximum of one page) outlining their area of study, explaining how they would benefit from attending the conference and stating where they are enrolled.

Applications should be addressed to Dr Jenny Shaw and be emailed to info@wamsi.org.au by 5.00pm on Monday 4 September 2023. A decision will be made on Monday 18 September.

Details about the conference can be found here.