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Pesticide pollution threatens shellfish safety

Shucked oysters


15 December 2023

Southern Cross University has found a cocktail of nasty pesticides in wild oysters and water from one of the NSW North Coast’s dominant rivers. In this video Professor Kirsten Benkendorff and Professor Amanda Reichelt-Brushett explain how the samples taken from the Richmond River estuary reveal 21 different pesticides, including a mix of herbicides, insecticides and fungicides.

Southern Cross University has led the most comprehensive investigation undertaken into the pesticides entering waterways from agricultural and urban run-off in northern NSW. The concentrations of several pesticides exceeded safe environmental guidelines. This study highlights the urgent need to manage diffuse source water pollution in the Richmond River. Further research is required to establish the magnitude of pesticide contamination in other estuaries with intensive agriculture and urban development.

We've been looking at pesticides in the New South Wales North Coast estuary, the Richmond River. And we've looked in both the oysters and the water and found in total 21 different pesticides which is quite a concern. They are actually more pesticides in the oysters than there are in the water. The oysters are filter-feeding organisms so they're pumping large volumes of water through their body. Part of our study on the Richmond River was using oysters as biomonitors and we were collecting oysters in the estuary. Oysters only grow in brackish water which means they need a little bit of salinity. We use conductivity as a measure of salinity and this will show us the range of where oysters grow and gives us some water quality information for our study as well. Having this accumulation of lots of different pesticides we don't know what the implications of that is. At the moment the regulations only regulate as if each pesticide occurs in isolation and we don't know where all the pesticides have come from but certainly likely to come from intensive agriculture, many different horticulture up the river but we've also got urban development and some of that could be using pesticides on sports fields for example or in urban gardens. The oysters accumulating so many pesticides are doing a really important ecosystem service cleaning up our rivers but we need to think about not collecting them from adjacent to agricultural areas where we might be getting a lot of that run-off. However I don't want people to not eat oysters. Farmed oysters are usually really high quality and the Australian quality assurance program means that they're only harvested during clean.

Media contact

Sharlene King, Media Office at Southern Cross University +61 429 661 349 or