Cassy Tzoutzias spends her Sunday mornings shoulders deep in dirty creek water.She is on a mission to retrieve shopping trolleys dumped into a creek flowing through Stockland Shopping Centre in Rockhampton's north.Cassy Tzoutzias in Moores Creek. (ABC Capricornia: Jacob Gamble)Ms Tzoutzias has been volunteering since December and says she has removed more than 300 trolleys."These are so rusted that they've been here for goodness knows how long," she says, pulling out a blackened trolley."The wildlife, they have to live with this. I have found dead cane toads, that just goes to show how putrid the water is."Volunteers say Coles, Woolworths and Big W are the main culprits. (ABC Capricornia: Jacob Gamble)Behind the rust and gunk are the logos of major brands, including Coles, Woolworths and Big W, whose stores are only metres away."We do not find Aldi trolleys or Kmart trolleys in here at all; they are coin-returned trolleys," Ms Tzoutzias said."It sort of goes to show you that if people have to be responsible to return these trolleys, they possibly will not end up in our waterways."Platypus have been spotted around Rockhampton's waterways. (ABC Capricornia: Jacob Gamble)Chair of Capricornia Catchments Michelle McCrae said the trolleys were inhibiting fishways and harming animals that rely on the movement of water, while encouraging further pollution of the creek."If a place looks unloved, it's out of sight, out of mind, and they continue down the same track with bad habits, throwing rubbish into the creek systems," she said."Once it's been thrown into a creek, a lot of the trolleys are no longer usable, then the only place for them to go is landfill."Murky governanceThe question of who is responsible for the clean-up effort depends on who you ask.Further up the creek, Rockhampton Councillor Elliot Hilse is collecting rubbish at a burnt-out homeless encampment.The stench of burnt plastic is thick in the air, the site is littered with blackened wooden crates, melted plastic trolleys, and the remnants of tents strung up on trees.Elliot Hilse cleans up a burnt-out homeless encampment. (ABC Capricornia: Jacob Gamble)"It's a tough one, up until the high water mark is state government, the banks is council, but also this is between two shopping centres that is the same shopping centre that goes over the creek," Cr Hilse said."It's probably a three-way thing."Rockhampton Regional Council told the ABC responsibility for dumped trolleys sits with the state government.In a statement, a spokesperson for Queensland's Department of Natural Resources said it was the supermarkets.Moores Creek runs between two buildings in Stockland Rockhampton. (ABC News: Peter Mullins)Ms McCrae said these issues of complex governance were commonplace, but ultimately it fell to the supermarkets."Generally speaking, it's their asset that they need to retrieve," she said.Coles and Woolworths both said they were investing in collection and maintenance services. In separate statements, each pointed to online systems where users can report abandoned trolleys.Coles and Woolworths do not have coin-return trolleys at Stockland Rockhampton. (ABC Capricornia: Jacob Gamble)Trolley troublesFurther north, Mackay Council has introduced fines for the major supermarkets of $183 per abandoned trolley.Cr Hilse said he would support a fine in Rockhampton, but only as a last resort."I think fines are okay, but if we can sit down and organise a solution without going to that extreme, it's going to be a lot better.""Any fines that Stockland have to pay or any other shopping centre, they're going to have to pass that cost on," he said.Capricornia Catchments says issues of governance are not uncommon for environmental issues. (ABC Capricornia: Jacob Gamble)Ms McCrae said the supermarkets needed to consider wheel locks and user pay systems to incentivise people to return the trolleys."Obviously, something needs to be done, and it's only through a collaborative effort with the community, business and council that we'll be able to get anything to happen," she said.Cassy Tzoutzias and Cheryl Dolan retrieve rubbish from the creek. (ABC Capricornia: Jacob Gamble)For now, the clean-up effort relies on the goodwill of volunteers."Moores Creek doesn't own them; someone owns them, and they need to be responsible," Ms Tzoutzias said.