Multiple pesticides have been found in water samples taken from creeks and rivers running into the Great Barrier Reef, raising greater concerns about land management.
The University of Queensland project analysed 2600 water samples from 15 waterways that discharged into the reef lagoon over a four-year period.
Associate Professor Michael Warne said 99.8 per cent of the samples contained pesticide mixtures, with up to 20 pesticides in any single water sample.
He said a cocktail of pesticides generally increased the impact on the aquatic ecosystems.
The research did not take into account the concentration levels of the pesticides detected, although additional studies were now underway to look at this impact on the reef.
"That wasn't the purpose of the paper; it was to emphasise that we are not dealing with individual pesticides but complex mixes," Mr Warne told AAP on Tuesday.
"Looking at what the impact is likely to be, it is about the number of chemicals present, the concentration levels and the duration of the exposure."
Mr Warne says subsequent papers are coming out which will do that, with the current data saying further examination is needed of the mixes and how complicated those mixes are.
He says the study's findings strongly support the pesticide reduction target in the Reef 2050 Water Quality Improvement Plan, which aims to protect at least 99 per cent of aquatic organisms at the mouths of rivers from the adverse effects of all pesticides.
Mr Warne says the best way to address the issue of pesticide run-off is to work with farmers to help them to improve their land management practices, adding 70 sugar cane farmers in the Barratta Creek and Plane River catchments along the central coast region are already working towards this goal.
"We have found the farmers involved to be very eager to engage with the science - they have embraced the challenge and are making significant steps toward improvement," he said.
Queensland peak agricultural body says they have worked hard to protect the Reef and their efforts are not being recognised.
Chair of AgForce's Reef Taskforce Alex Stubbs, while not referring to the UQ research, said activists painted farmers as the bad guys when they were not.
"Farmers are committed to doing whatever we can to preserve the Reef for future generations - we just ask that regulations imposed on agriculture and other essential industries be based on credible science, not ideology and self-interest," he said in a statement.
Australian Associated Press