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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.

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.

 

 

Underwater symphony of noisy shrimp and whistling dolphins

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Waves crashing, boats motoring and seabirds squawking are what we typically hear at the beach.

But a WAMSI research team at Cockburn Sound is listening to the soundscape underwater and recording everything from the ‘popping’ noise of tiny snapping shrimp to fish sounds and whistling dolphins.

Vessels travelling across the water are also picked up.

Dr Iain Parnum, from Curtin University’s Centre for Marine Science and Technology, is part of a research team that has been using underwater microphones, known as hydrophones, which are linked to a recording device and lowered into the water.

“We put them in the water and leave them on the seafloor for several months at a time, so we have this continual data,” Dr Parnum said.

“We are trying to understand the underwater soundscape of Cockburn Sound.”

“We want to characterise different sounds that can be heard, how loud they are and how that soundscape changes through the year.”

He said it was also useful for locating different species and information will be shared with other researchers involved in the WAMSI Westport Marine Science Program.

“Probably in coastal areas like this, one of the main sounds is anthropogenic or human caused.

“We are monitoring places where they have typically been finding dolphins but also areas where they haven’t.  We want to know what the overall sound levels in those areas are, if they are overwhelming and making it difficult for dolphins to communicate.”

“Everyone sees dolphins and it’s always nice to see them, but you also hear them chatting away underwater.

“We need to understand what the baseline sounds in the Sound are.”

The team is yet to record mulloway, but Dr Parnum said they’re a fish that has a distinctive sound.

“Sometimes if there’s enough of them, they like to gather together to do choruses particularly after sunset.”

Man with recording equipment on boat.

Research team member Malcolm Perry works on underwater sound recording equipment.

“That is something we have seen in other sites,” Dr Parnum said.

Other WAMSI Westport Marine Science Program scientists are doing related research on the hearing physiology of animals in the area including little penguins, and the behavioural response of fishes to underwater noise.