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The messy, muddy work retrieving recorders from the sea floor

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They are moments of excitement mixed with relief when researchers pull up their mud and weed covered hydrophones and recorders which have spent months on the seafloor quietly capturing the sounds of weather, marine life, boats and ships.

The equipment used for the ‘Noise’ theme project in the WAMSI Westport Marine Science Program was put out three times over a year in Cockburn Sound and left under water for four months.

The research team carefully noted the coordinates of the devices when they lowered them under water and connected them by rope to weights to stop them drifting.

The underwater recorders contain enough batteries to sustain them through the months of data collection and are built to withstand the pressures of saltwater, sediment and sometimes rough weather conditions.

Because of the boating and fishing activity in Cockburn Sound the team decided not to attach the devices to floats which would increase the possibility of ropes becoming snagged in propellers.

When it comes time to retrieve the devices, the team takes its boat to the drop sites using the GPS coordinates and uses a hook to grab the line. It can feel like looking for a needle in a haystack.

When they are found, the recorders are usually covered in mud and some are tangled in seagrass but once they are cleaned the precious data is retrieved.

What’s downloaded are the sounds of the Sound. There are wind and bubbles, jet skis, boats, large ships but also fish, dolphins, crabs and many noisy shrimp.

 

 

 

Ship safety system helping Sound’s noise research

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A safety system that tracks ships and helps prevent collisions is being used as part of a study of noise levels in Cockburn Sound and their potential impact on marine life.

Cristina Tollefsen from Curtin University said researchers were using ship location information from the worldwide Automatic Identification System along with data from recorders on the seabed.

At the start of the project, researchers placed recorders with hydrophones (underwater microphones) at nine locations in and around the Sound.

“AIS gives us details of ships and their location which means we can attribute portions of the recording to certain vessel types,” Dr Tollefsen said.

“Because we can combine this information with data from the recorders, we have been able to measure the sound levels of all the different vessel classes from tugboats and the pilot vessel to the massive bulk carrier ships,” Dr Tollefsen said.

“Port activities require more than one vessel typically, so we wanted to capture a set of activities including the pilot boats meeting larger ships as they arrive and the tug boats assisting ships as they come into port.

“It’s less common in research to measure the combined noises but that is much more realistic.”

Dr Tollefsen, who is working on the project for the WAMSI Westport Marine Science Program, said there was growing awareness of the impact of noise on animals.

“Because light doesn’t penetrate very well under water, a lot of animals use sound to communicate,” Dr Tollefsen said.

“The best-known animals to do this are whales and dolphins but invertebrates and fish also use sound.

“If it’s too noisy from human activities, you can imagine that it’s harder for the animals to find a mate or find food.

“That’s why we’re doing this work is to understand the sounds in Cockburn Sound and whether there are ways to estimate a potential increase in noise or mitigate any increase if shipping traffic were to increase.”

Dr Tollefsen said a port in Vancouver, Canada had implemented a strategy to slow vessels on approach as a way of protecting the endangered population of orcas in the area.

She said by slowing the vessels, similar to a maritime equivalent of a traffic school zone, they had made the waters less noisy with the aim of reducing the impact of human-caused noise on the marine mammals.

Penguin ‘poop study’ to help unlock colony’s diet

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Researchers from The University of Western Australia and Murdoch University are analysing DNA from the excrement of little penguins in Cockburn Sound to find out what, other than fish, they are eating and whether it is affecting their breeding.

Penguin researcher Dr Belinda Cannell, from UWA, said analysing the animals’ diet in greater detail would provide an insight into their breeding and how it related to the availability of their primary diet, which is fish.

Little penguins in Cockburn Sound (their northern most range in Western Australia) primarily eat anchovies, pilchards, scaly mackerel and sandy sprat.

Penguins are known to also feed on crustaceans, cephalopods and even jellyfish.

“If it’s a poor year and there are not a lot of fish around, the little penguins may be feeding more on other things such as jellyfish,” Dr Cannell said.

This could then have an impact on their ability to produce and raise young.

“This other food may not get them into the condition where they can breed and feed their young,” Dr Cannell said.

“It may be that the chicks don’t fatten up as quickly.”

She said diet made up one element of the project, which is part of the WAMSI Westport Marine Science Program.

Another methodology being used to determine diet composition is the analysis of stable isotopes of carbon, nitrogen and sulphur from the down of little penguin chicks and feathers from adults.

“Stable isotopes of carbon reflect primary production sources and is more enriched in inshore, seagrass dominated areas, compared to offshore food webs,” Dr Cannell said.

“The stable isotope of nitrogen increases up the food chain and can also increase between size classes of the same prey species.”

“Stable isotopes of sulphur can be useful to distinguish between offshore and inshore components in food webs and can also indicate if producers are using sulphur from seawater, which is more enriched, or from sediments which are less enriched.

“This gives us a better idea of the whole diet of these birds.”

Dr Cannell said stable isotopes assist with establishing diet composition.

“I presume little penguins are eating jellyfish, but we haven’t had stable isotopes for jellyfish until now.”

The Western Australian Museum provided samples to assist with the research.

Cockburn Sound research reports now online

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Cockburn Sound research teams have started delivering project reports for their work on the WAMSI Westport Marine Science Program.

These are now published on WAMSI’s Cockburn Sound webpage under ‘Research Themes and Reports‘.

More than 100 scientists and researchers are working across 33 projects, helping to build a picture of the Sound’s environment and provide key input into the port design.

In one of the latest reports to be released, scientists have carried out a detailed literature review identifying potential invasive marine species which may have become established in Cockburn Sound, with procedures to mitigate the risk of introducing these to future Westport facilities.

Another project explores the potential effects of suspended sediment on fishes from dredging, while a social science study has identified and mapped 31 non-fishing recreational activities and 11 associated values for the Sound.

Reports will continue to be published on our website over the next few months.

 

Eco-design and pre-seeding among options to encourage healthy port marine life

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Pre-seeding new port structures to encourage the colonisation of native species is one of the mitigation measures against invasive marine plants and animals, outlined in a new report prepared for the WAMSI Westport Marine Science Program.

The literature review by Curtin University School of Molecular and Life Sciences Adjunct Professor Fred Wells lists many of the invasive marine species that have been recorded in waters around Perth and mitigation measures that could be used during any port construction.

Pre-seeding works by attaching local, fast-growing species to a new structure. The common mussel is one option identified in the report.

Professor Wells said invasive marine species were a worldwide problem and shipping was the most common way they spread to coastal areas. Ninety-eight percent of trade in and out of Australia is on vessels.

“Invasive marine species are concentrated on artificial surfaces and eco-engineering is a new field that attempts to encourage biodiversity and prevent potential marine pests taking hold,” Professor Wells said.

“The risk of introducing new species is greatest during construction but experience during the construction boom in the Pilbara demonstrated the issue is manageable.”

Professor Wells said eco-design was a new and evolving field that could help improve the biodiversity of the marine community that develops underwater, while minimising the risk of invasive species.

“Current design procedures tend to create uniform habitats, such as seawalls with smooth vertical faces. The lack of habitat diversity reduces the biodiversity of the marine community that develops on the structure. “

“Increasing the habitat diversity of new immersed structures and pre-seeding them with native species appear to be the most promising ways for mitigating against species that can cause ecological harm and prove expensive.”

Professor Wells said the biggest threats from invasive species to marine ecosystems were introducing disease, displacing native species, changing the ecology of native communities, clogging pipes and damaging other critical infrastructure.

The report, which was done to understand potential risks, is a literature review of invasive marine species from Cottesloe to Cockburn Sound, including waters around Fremantle and the Swan River.

A comprehensive survey more than a decade ago recorded 60 introduced marine species living in WA waters. Three were on the national marine pest list. Four additional marine pests were subsequently recorded in WA.

“Fortunately, most introduced marine species are apparently innocuous, causing no known adverse effects and we know only a small portion become pests,” Professor Wells said.

 

 

Sediment samples at the core of a model project

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Dozens of core samples, taken from sediment around Cockburn Sound, will play a crucial role in the creation of a model of the area’s ecosystem to help inform environmental assessment of the proposed port.

The work, being done as part of the WAMSI Westport Marine Science Program, involved divers collecting three sediment cores from 12 sites and scientists analysing them at a specially created laboratory nearby.

The project is being run by Professor Bradley Eyre from Southern Cross University and Professor Matthew Hipsey, from The University of Western Australia.

Professor Eyre said the tubes of sediment and water were set up in a laboratory, in the garage of a beachside home, where conditions simulated in situ temperature and changing light conditions between night and day, at the sediment surface.

“Some analysis is best done when we have fresh samples, so we wanted to avoid any delays,” Professor Eyre said.

“Other samples will be sent back to the Southern Cross University campus near Byron Bay, which has the only instrumentation in Australia for some of the analyses.”

The 12 locations in the Sound, represent different types of shallow and deep sediments including muds, seagrass meadows, and sandy areas.

“In the laboratory, we were measuring the flux of oxygen and nutrients in and out of sediment including nutrients such as ammonia and phosphate,” Professor Eyre said

“Some of the tubes contained sediment with seagrass growing in it.

“We are also measuring a critical process in the sediments called denitrification.

“Denitrification is a natural process by which ecosystems such as Cockburn Sound can remove nitrogen.”

“It is a really important cleansing process but if the carbon load gets too high the process can be reduced.”

The researchers said data from the sediment testing would underpin new water quality modelling of the Cockburn Sound ecosystem.

“The data complements other key experimental data being collected as part of the WAMSI Westport Marine Science Program on the chemical and biological conditions, allowing the development of Cockburn Sound Integrated Ecosystem Model platform to help manage the system,” Professor Hipsey said

“What we are measuring will reflect what is happening currently in the Sound and when used alongside the modelling we will be able to predict what will happen under future scenarios.”

High tech equipment collecting data beneath the waves

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Wave, current, sonar and camera equipment has been deployed underwater to allow researchers to track sediment flow in and around Cockburn Sound as part of a project which is expected to improve sand nourishment.

Research Fellow Dr Michael Cuttler, from The University of Western Australia’s Oceans Institute, said the research team had set up the high-tech instrument suites during dive trips to three sites.

“At each site, we have the same instrument packages which are designed to measure sediment transport,” Dr Cuttler said.

“They include acoustic instruments to measure waves and currents, and a three-dimensional scanning sonar and custom camera system to map and track seabed morphology.

“The instruments take measurements throughout the day and have already captured significant storm events this winter.”

The equipment is mounted on frames that are attached to steel poles which are fixed to the sea floor.

Dr Cuttler said the systems work to track how and where the sediment moves.

“A lot of our coastal processes work is focused on understanding the beach dynamics – are they accreting or eroding and under what conditions,” Dr Cuttler said.

Dr Cuttler said one of the key knowledge gaps researchers had been trying to fill was sediment transport from the offshore source to the beach.

“Some of the applications for this work is understanding the potential beneficial reuse of dredge material,” Dr Cuttler said.

“So, if they have excess material and want to use it for beach nourishment, where would be the best place to put it and then how long could we expect for that material to move onshore to act as sediment nourishment for the beach.

“One thought is that if you can understand the sediment transport pathways, you can optimise that nourishment, so it continually feeds the beach using natural processes.”

The Coastal Processes project, led by UWA’s Dr Jeff Hansen, is part of the WAMSI Westport Marine Science Program.

The equipment has been deployed three times since the start of the year during different seasons and a final deployment is planned for early 2024.

 

 

 

 

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.