TWEED River has shown signs of poor water quality and ecological health in the last five years, according to results of a water testing program across the estuary.
The main concerns included in a report to Tweed Shire councillors was with high nutrients, phytoplankton blooms, poor water clarity and low levels of dissolved oxygen.
"It must be stressed that these issues are not constant across all parts of the estuary and their occurrence is not static over time," the report stated.
"It is also worth noting that some periods of poor compliance relate to natural phenomena, for example floods, where even pristine waterways would "fail" some targets for ambient water quality.
"Despite this natural variability, there are significant periods when key water quality objectives are not met in the Tweed River, and there is a clear link between water quality problems and impacts of land use and pollutant discharge within the catchment."
Murwillumbah and Kingscliff waste water treatment plants had been identified as causing higher levels of nitrogen in the mid Tweed estuary.
"The release of effluent (from the Banora Point waste water treatment plant) to Terranora Creek has no impact on nitrogen concentrations in this location due to tidal flushing and the uptake of nutrients by benthic micro-algae," the report stated.
Experts were expecting a bad year for algae blooms because of high levels of nutrients in the water after the rain events of the past few years.
Tweed Laboratory Centre coordinator Paul Wright said there was a significant outbreak at Bray Park weir and it was only the start of the season.