Local environmental and sustainability leaders say they are devastated by research, which estimates up to 11 million metric tonnes of plastic pollution is sitting on the ocean floor.

CSIRO Senior Principal Research Scientist Dr Denise Hardesty says the research is the first large-scale estimate of how much plastic is at the bottom of the ocean.

While similar research has previously been limited to microplastics, this study used remote operated vehicles to look at larger plastic items.

“Because plastic, by nature and by design, tends to be quite lightweight the actual volume to comprise this much mass is pretty huge,” says Ms Hardesty.

Ms Hardesty says most of the items found at the bottom of the ocean likely hadn’t travelled far from their source.

“It’s going to be coming off of ships, vessels, and recreational marine users, or it’s going to be coming from our city centers along the coastal area or making its way out from rivers into the open ocean after major rainfall events,” she says.

The remote location of this plastic would make clean-up efforts difficult, with Dr Hardesty advocating for prevention methods instead.

“By design, it’s going to be not very effective and highly expensive to go out and try to clean up the ocean floor,” she says.

Sea Shepherd Australia’s Marine Debris Campaign Coordinator Karolina Strittmatter says this new research by the CSIRO is shocking and has disastrous consequences for marine wildlife.

“We need to take action today to make a difference,” she says.

Ms Strittmatter says if rates of plastic pollution don’t change soon, plastic will outweigh fish in the ocean by 2050.

Sea Shepherd’s Marine Debris Campaign is one of several initiatives across Australia working to reduce plastic pollution in the ocean.

The campaign has been operating since 2016 and has removed more than 7 million pieces of trash from Australian waterways, thanks to a dedicated team of volunteers.

Ms Strittmatter says during the clean-ups hosted by Sea Shepherd, the group commonly finds hard and soft plastic remnants and single-use plastic items littering our beaches.

Unfortunately, Ms Strittmatter says the plastic problem isn’t limited to highly trafficked areas.

“We have seen lots of food packaging, bottle tops, and other discarded fishing gear in our remote areas,” she says.

Plastic pollution is incredibly damaging to marine wildlife and ecosystems, Ms Strittmatter says.

Ms Strittmatter says change begins at a personal level and encourages people to look for ways to make a difference.

“We should refuse single-use plastic in our daily lives. We should start reusing products more and more in our daily life and when you are choosing products, take your time and look for reusable products,” Ms Strittmatter says.

“Come to our community beach clean-ups and help us to prevent rubbish from entering the ocean. Come together with your community to say no plastics entering the oceans.”

Chair of Toxic Free Australia, formerly the Alliance for a Clean Environment, Jane Bremmer says she was also saddened to hear the findings of this research.

“Any science that demonstrates the absolute pollution of our planet is very disorientating and depressing, but not unsurprising,” she says.

Ms Bremmer says keeping our oceans clean is vital.

“All life on the planet depends on the ocean. It’s part of the planet’s ecosystem to which humans are inherently connected to,” Ms Bremmer says.

“Plastics are petrochemicals, and so not only have plastics pervaded every aspect of the planet…but this study shows that those levels of plastic contamination in the sediment of the ocean are hugely significant. That has direct consequences for our life.”

Ms Bremmer says the study highlights the need for the community to rethink the systems that support human life.

“What this study is showing us is that over time, [these systems have] been extremely detrimental, and the legacy of that is sitting at the bottom of the ocean,” she says.

She would like to see significant action taken, including caps on production and the elimination of toxic substances in certain materials, which prevent them from being recycled.

“I think there is room for improvement in how the Australian government regulates and protects the environment and human health from plastic, throughout its entire lifecycle,” Ms Bremmer says.

Ms Bremmer says this research also highlights the importance of a global plastics treaty.

“The global plastics treaty is a really important step that we can take internationally to address this issue because no one country can resolve the plastic pollution crisis. It has to be at an international level,” she says.