Toxic fish, ‘dead’ sand, plastic and mattresses: Sydney Harbour in all its gory

On the surface, Sydney Harbour is one of the world's beauty spots. Down below, not so pretty.

On the surface, Sydney Harbour is one of the world's beauty spots. Down below, not so pretty. Photo: Getty

Sydney Harbour might be coveted by other cities for its pretty, pristine splendour – when in fact it doesn’t do so well for cleanliness. Or even, in parts, able to support life.

According to a new short video – Sydney Harbour: Above and Below – 15 Olympic size swimming pools of gross pollutants enter Sydney Harbour each year.

And 70 per cent of this debris ends up lodged on the Harbour’s floor.

Most of this visible junk – cigarette butts, plastic bags and bottles, lost shoes and trousers, dead creatures – comes from stormwater runoff.

Pollutants washed from your front lawn

This runoff also includes invisible pollutants – the fertilisers from front lawns, paint fragments from houses, the metals and other chemicals perfuming our streets.

And this is where it gets creepy. The areas around storm water drains are dead, save for anaerobic bacteria that produce hydrogen sulfide which gives off a rotten egg smell and, in higher concentrations, induces shock, convulsions, rapid unconsciousness, coma, and death.

Dr Katherine Dafforn is Deputy Director of the Sydney Harbour Research Program at Sydney Institute of Marine Science.

Exploring the dead zones

Dr Dafforn and her colleagues have done extensive surveys of the sediment at the bottom of the harbour, using a device that looks like the mouth of an excavator. Having dragged up between five and 10 kilograms of sand and mud at a time, the researchers sift through the sediment, looking for signs of life under the microscope. Sometimes they don’t find any.

“We found that certain areas are very low in oxygen and we know they have high levels of metals and organic contaminants,” Dr Dafforn told The New Daily.

Dr Katherine Dafforn, an environmental scientist who investigates urban impacts in marine systems, has been surveying harbour floor sediments. Photo: UNSW


“In those spots we haven’t found any of the bristle worms, or little shrimp and crabs we normally find in the sediment. That’s in the the top five centimetres … which is generally very well oxygenated and has a lot of burrowing shrimp and shellfish.”

These dead zones are generally associated with stormwater drains or  pollution, notably where there’s been a long history of industry. They remain confined to a few square metres.

“As soon as you move 100 to 200 meters away from a stormwater drain, conditions start to improve. East of the bridge is generally well flushed  and the pollution is lower and sediment healthier,” she said.

Relatively benign until the rain comes

Is there an argument that if these dead spots are localised, that maybe they don’t really matter?

“Under dry conditions, maybe,” said Dr Dafforn.

“But as soon as you get a big rainfall event or disturbance from boats or really high winds disturbing the sediments, everything comes up in the water column and it can spread through the harbour.

People are warned not to fish west of the bridge, and to limit how much they eat of their catch from east of the bridge. Photo: supplied

“With storm events, we get nasty pathogens in the water and people worry about that when swimming. When these sediments get suspended, they get ingested by fish and other marine life: contaminants move up the food chain and they start to reach us.”

One of the key messages in the new video, in which Dr Dafforn features: “We need to find better ways to manage stormwater. Now industry is better controlled through regulation, 60 per cent of the contaminants come into the harbour is through stormwater drains. They’re driving the dead zones.”

How to get past entrenched complacency

Perhaps one problem that inhibits change is the false sense of security that comes with so much beauty. It’s been years since commercial fishing was allowed in Sydney Harbour because of elevated dioxins – a group of toxic chemical compounds that accumulate in fatty tissues and can cause problems with reproduction, development, and the immune system.

Just about everybody in developed nations accumulates dioxins as a matter of course – so there’s good reason to keep exposures to a minimum where possible.

Recreational fisherfolk have long been told to throw away any fish caught west of the bridge. The warnings go unheeded.

A 2014 map from the Sydney Institute of Marine Science showing where microplastics have accumulated in Sydney Harbour. Illustration: SIMS

The NSW government’s warnings have become subtly more hard-edged over the years. Parents are advised to limit what fish (caught east of the bridge) they feed to their children under six.

Microplastics are the new threat – or at least relatively new to public consciousness. Five years ago, the Sydney Institute of Marine Science (SIMS) raised the alarm that microplastics were being deposited in the Harbour floor sediment and could enter the food chain.

Still the rubbish accumulates.

The new video, which we have posted, was produced by global recycling company, TOMRA, and “documents the work of SIMS, Ocean Protect, Project Aware and Manly Dive Centre… to raise awareness about this problem and offers some solutions for Australians looking to do their part.”

Good luck to that.

Stay informed, daily
A FREE subscription to The New Daily arrives every morning and evening.
The New Daily is a trusted source of national news and information and is provided free for all Australians. Read our editorial charter.
Copyright © 2024 The New Daily.
All rights reserved.