- Published:
- Tuesday 9 June 2026 at 9:55 am
For 40 years, our team has monitored Victoria's coastal waters. To mark World Ocean Day, we’ve gone behind the scenes with the scientists in the field.
As the boat glides to a halt and the anchor rattles down, our water scientists are already preparing their gear.
At the stern, one is checking the ropes and harness on a device known as a CTD – a sophisticated sensor that measures temperature, salinity, dissolved oxygen, pH, chlorophyll levels and turbidity, which indicates how cloudy or clear the water is.
It’s a necessary precaution, given the sensor is worth more than $75,000. At the bow, our colleague is preparing a Niskin bottle to take a water sample for later analysis in the lab.
The sensor readings and water samples must be taken at the same time and depth, so there’s a high degree of coordination required, but the operation is smooth and well oiled.
Which is no surprise, since EPA scientists have been doing this six times a year for 40 years in Port Phillip Bay – the longest continuing coastal monitoring program in the state. The program also runs in the Gippsland Lakes and Western Port.
The results from the Port Phillip program have been published in the international scientific journal Marine and Freshwater Research, and the news is good: despite Melbourne’s booming population and the extra stressors that brings, key water quality indicators are better than they were in 1985.
Climate change is a major driver, particularly through reduced inflows. But EPA’s Water Operations Lead, Dr Kelly Zuccala said improved industry practice had helped offset pressures from rapid suburban growth.
“A lot has changed in the past 40 years – our climate has become more variable, inflows have declined, the population has grown by 75% and the urban footprint has tripled,” Dr Zuccala says.
“But our own behaviour, technology and practices have changed too. Wastewater treatment is far more effective at removing many traditional pollutants than it was 40 years ago. And more businesses and residents understand the impact of what they dispose of down the drain or gutter.
“Our 40 years of continuous testing helps us understand how these climate-drive pressures and system responses are playing out over time.”
EPA’s monitoring program tests surface water for salinity, dissolved oxygen levels, suspended sediments and nutrients such as nitrogen, phosphorous and silicon. In these categories, the results show clear improvement.
Since 1985 suspended sediments have fallen by 45 per cent. This is a positive outcome for the health of our bays. High sediments can harm aquatic plants (such as seagrass) by preventing light from penetrating through water.
Phosphate concentrations have dropped by 30 to 42 percent, depending on location. This is important as high phosphate and ammonia can trigger algal blooms.
Salinity has risen slightly (by around 1.5 parts per thousand), indicating lower river flows into the bay and greater evaporation.
Of note, ammonia levels offshore of the Western Treatment Plant at Werribee have fallen 78 percent since 1990, thanks to engineering improvements and controls.
Melbourne Water’s Executive General Manager of Service Delivery, Sue Jackman, welcomed the results.
“The improved ammonia levels highlight the impact of sustained upgrades, improved technology and smarter processes at the Western Treatment Plant,” she said.
“We’ll continue modernising the plant so the bay remains heathy, resilient and safe for the community and for the precious environment the bay sustains.”
Back out on the water, the team has gathered their samples and readings and are heading back in. Once on shore, some of the water is filtered on a portable lab table that folds out of the back of their ute, while another portion is frozen for later analysis.
The results gathered on this trip will be added to decades of data already on file. It all builds a crucial understanding of what is happening in our environment, and how it is changing.
Results are publicly available at data.vic.gov.au and annual Report Cards can be found on EPA’s website https://www.epa.vic.gov.au/water-quality-data-and-reports
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