Our Seas Our Future founder and marine conservationist Noel Jhinku said the beans were spread across the footpath yesterday and were being blown and washed into the gutters.
From there, they could be washed down drains and into waterways, before floating out to sea.
He was extremely concerned about the environmental impact it would have on the local wildlife.
"The Leith is just right next to this area and these waterways will lead to the ocean.
"They just spread around and on a day like today, with the wind and the rain, they’re just everywhere.
"They’re small enough to be ingested by wildlife and they’re particularly difficult to collect once they’re in the environment.
"It’s going to just persist in the environment and break down into smaller microplastics. The flow-on effects are quite impactful.
"Bits of plastic are mistaken for food by birds, marine birds, coastal birds, as well as fish and marine animals.
"Research is already out there that shows that microplastics are in the food chain.
"They’re being found in all sorts of animals. A few years ago, there was some plastic found in an albatross’ guts."
He said it could prove fatal for a lot of wildlife because it could cause choking or get stuck in the gut and cause blockages.
"It can also have nutritional impacts as well, because obviously, plastic is not nutritious."
Mr Jhinku called on students and the wider Dunedin community to be more thoughtful about how they handled their waste, and consider the impacts of throwing things out.
"This was a case of just thoughtless dumping of the contents of a beanbag, and not actually thinking about the wider impact of where that trash goes.
"It’s sort of like an out-of-sight, out-of-mind mentality.
"This is not the first time I have seen the contents of a beanbag spilled like this in the student area here.
"I have seen this scene a number of times over the years.
"It’s actually quite sad to see."
While he was inspecting the beans, he was upset by a passing student who said, "It’s snowing on Castle St".
"I instantly just sort of reacted and said, ‘well, I wish it was snow’.
"It was sad to hear comments like that because it just sort of reinforces the fact that there is no thought of the impact beyond those sort of thoughtless actions."
Otago Regional Council (ORC) compliance manager Carlo Bell said the council’s pollution team received notification of the polystyrene beans on their Pollution Hotline yesterday, and staff attended the site.
"Staff have screened mud tanks in the immediate area using sorbent pads, so no further beans go into any mud tanks.
"The ORC have advised the Dunedin City Council, as the authority responsible for litter."
