What's really in our waters? Reef scientist reveals hidden pollutants reaching Pacific coral reefs
The medicine in your bathroom cabinet, the sunscreen you wear to the beach and the polyester shirt in your washing machine may all be ending up on Fiji's coral reefs.
That's the message from a CQUniversity water-quality scientist, who's shared his insights and solutions at a free public seminar hosted by the University of the South Pacific.
CQU Senior Lecturer in Chemistry and former Chief Scientific Officer of the Queensland Government's Office of the Great Barrier Reef, Dr Shaneel Chandra presented What's in our waters? Hidden pollutants, smarter sensors and the future of coral reefs on Monday 12 October 2026, as part of the USP Centre for Sustainable Futures (CSF) Seminar Series.
Dr Chandra was a lead author of the freshwater chapter of the United Nations' Global Environment Outlook (GEO-7). His seminar draws on two recent reviews he co-authored on emerging contaminants and microplastics.
"Before we can manage what is in our waters, we need to be able to see it – often enough, cheaply enough and close enough to where it matters," Dr Chandra said.
"Right now, a single nitrogen test can cost around A$40 and take two weeks to come back from the laboratory. By then the flood plume or the sewage overflow has long passed.
"For small island communities, comprehensive monitoring at that price simply isn't affordable."
Everyday products, hidden risks
The seminar followed everyday chemicals from the home to the reef. Pharmaceuticals, sunscreen UV filters such as oxybenzone, soaps and cosmetics enter wastewater after use. Conventional treatment plants do not reliably remove them at trace levels, so they flow on into coastal waters.
Because these products are used every day, they are replenished faster than they break down. Scientists call this "pseudo-persistence". Studies have reported 113 different pharmaceuticals and their by-products in coastal waters worldwide.
Laboratory studies show some of these compounds can harm corals. They have been linked to larval deformities, bleaching, reduced growth and disrupted microbiomes. One study found sunscreen-contaminated water killed up to 83 per cent of exposed corals of one species, and warmer water can make bleaching worse.
"These chemicals are not a replacement for the big pressures on our reefs – warming, nutrients, sediment and pesticides," Dr Chandra said.
"They are an additional, under-monitored pressure acting on reefs that are already stressed. Reefs near towns, resorts and ports are where we should be looking first."
Plastics that carry pollution
Microplastics were a major focus of the talk: Dr Chandra said a multi-country study found microplastic fibres in 83 per cent of tap water samples, and only 9 per cent of all plastic waste ever made has been recycled.
Microplastics also act as tiny rafts that can pick up other pollutants, from antibiotics to lead.
Even the best water treatment struggles with the smallest particles, removing less than half of those under 50 micrometres in some studies. That makes stopping plastics at the source essential.
Dr Chandra pointed to Fiji's ban on thin single-use plastic bags as an example of regional leadership. He also discussed what Pacific nations can borrow from successful global agreements such as the Montreal Protocol.
Smarter, cheaper sensors
The seminar also showcased a solution: small, low-cost electrochemical sensors that can run on solar power and send data in real time to a dashboard that managers and communities can read.
Dr Chandra's group has developed sensors for nutrients such as nitrate and trace metals such as lead, cadmium and arsenic.
"No routine, field-ready method yet exists to measure micro- and nanoplastics in water," he said.
"Affordable, validated sensors are how Pacific countries can build the evidence they need to protect their reefs."
The presentation was co-authored with researchers from CQUniversity, Alexandria University (Egypt), the Autonomous University of Barcelona (Spain) and the Indian Institute of Technology Delhi.
CQUniversity research is driving an economically and environmentally sustainable future for coastal communities, explore more at the Coastal Marine Ecosystems Research Centre.
