Lilies’ impact in focus

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Pierra WillixBusselton Dunsborough Times
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Ecologist Dr Robyn Paice with some of the harvested lilies.
Camera IconEcologist Dr Robyn Paice with some of the harvested lilies.

A study is being undertaken in the lower Vasse River to determine how the abundance of waterlilies is affecting the quality of water.

The introduced Mexican waterlily has been present in the lower Vasse River and adjacent New River wetland for many years; however, in 2013 they went through a prolific growth and now cover large areas of open water.

The swarm has remained in areas colonised during the period of rapid growth, rather than continuing to spread throughout the river.

Ecologist Robyn Paice is comparing water quality within and outside the waterlily meadows, in particular algae, nutrients and oxygen levels.

“The lilies for the last few years have started to cover a huge area of the area and I am interested in how it is affecting the water quality,” she said.

“The blue-green algal bloom is restricted to an area downstream of the waterlilies, so it will be very interesting to understand why.”

Dr Paice said in between the patches of waterlily the water quality appeared better but she said oxygen levels could be very low in and around the lilies which was not good for aquatic fauna and also limited open-water habitat for some waterbirds.

Dr Paice said she was harvesting some of the lilies to compare the conditions inside and outside of them, and determine the level of nutrients being held within them.

“The results will provide recommendations for the control of the waterlily, considering their effects on water quality and fauna,” she said.

“It is also important to predict the potential negative effects of killing large areas of lily which would release nutrients and further decrease oxygen levels.”

“Aquatic plants can have a profound influence on ecology of our aquatic ecosystems and there may be some native alternatives we could use to improve the Vasse Rivers.”

City of Busselton Mayor Grant Henley said the City was following the study with interest after community concerns raised at a City of Busselton community workshop in March last year on the progress of this invasive plant and potential effects on the lower Vasse River.

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