Mussels ‘doing the dirty work’ to keep waters clean

Mussels may well be coastal waters ‘best new friend’. Scientists at the Nelson-based Cawthron Institute have been exploring an innovative way to improve coastal water quality using live Greenshell mussels.

The project aimed to tap into the mussels’ natural ability to filter and clean water, offering a nature-based solution to poor water quality caused by pollution, sedimentation, and nutrient loading from human activities.

Cawthron aquaculture scientist Dr. Jess Ericson explained: “The project took place at Port Nelson, where we placed 29,000 juvenile mussels on a large frame in the ocean. A single mussel can filter 200 litres of water per day—about the size of a bathtub—so our 29,000 mussels were able to filter 5.8 million litres of seawater daily.”

The mussels were closely monitored and a subset of 12 mussels had a sensor attached to their shells, tracking their growth and behaviour. In addition, water and mussel tissue samples were collected and analysed to determine the types of pollutants the mussels were filtering.

“The mussels survived really well. We were concerned that it might be too warm for them at the port over the summer, but we were all pleasantly surprised by their performance,” said Dr. Ericson.

Similar efforts are underway at the Ports of Auckland, where mussels are being used to improve water quality in the Hauraki Gulf.

The project was an initiative between Cawthron, MacLab, Port Nelson, and the Moananui blue economy cluster, with some funding from the Sustainable Seas National Science Challenge. The project, which began in January 2024, was a pilot study and the group are hoping to scale it up if further funding is secured.

“Imagine thousands of mussels out there happily cleaning the water,” Dr. Ericson says.

The ‘Living Filters’ initiative could be a natural solution to reduce contaminants, boost marine life, and create more resilient ecosystems—providing hope for cleaner, healthier coastal environments in the future.