Conservation Matters July 2013

The Texas Land, Water and Wildlife Connection

Invasive aquatic species: a concern even abroad

By Katie Heinrich

Invasive aquatic species: a concern even abroad

Giant salvinia, water hyacinth and other invasive aquatic plants are a problem not only in some of Texas’ water bodies, such as Caddo Lake, but worldwide as well. 

Elizabeth Edgerton, a master’s student in the Department of Wildlife and Fisheries Sciences at Texas A&M University, said the native wetlands and freshwater ecosystems in Australia and New Zealand are also suffering from the growth of these invasive species.

Edgerton saw the damage first-hand during her recent 5-week study abroad trip to Queensland and Sydney, Australia, and the north island of New Zealand. She is currently working on developing a risk assessment model for identifying potential invasive aquatic weeds in Texas for her master’s degree. Edgerton is also a research assistant for the Texas A&M Institute of Renewable Natural Resources and Texas Water Resources Institute (TWRI). 

While attending the International Conference on Aquatic Invasive Species this April in Niagara Falls, Edgerton had the opportunity to meet New Zealand researcher Paul Champion, who developed the New Zealand Risk Assessment Model for invasive aquatic weeds and currently works for the National Institute of Water and Atmospheric Research in New Zealand.

After learning that Edgerton was already going to be nearby in Australia and that her topic of research followed his risk assessment model, Champion invited her to extend her study abroad trip and come to New Zealand, she said.

“I wanted to go and see the kind of work that has been done — see it firsthand,” Edgerton said. 

While there, Edgerton said she also had the opportunity to meet John Clayton, who co-authored New Zealand’s Risk Assessment Model, tour the institute’s quarantine facilities and visit the lakes used for invasive species research.

She was also able to see directly how invasive giant salvina has become in Queensland’s freshwater wetlands and learn from an aboriginal group, the Nywaigi people, about their control methods.

Currently, the Nywaigi people are trying to control giant salvinia by applying a herbicide treatment. Since 90 percent of the wetland is already being choked by a variety of invasive aquatic plants including giant salvinia, water hyacinth and hymenachne, Edgerton said they are now planning to remove a berm that was built years ago to stop the seawater from flowing into the wetland.

“The hope of trying this method is to see if the saltwater will kill the freshwater invasive plants and restore the wetland,” she said. “I was also able to talk with them about some of the successes and not so successful attempts they have had in controlling the species.”

To watch in real-time the progress they are making in removing these invasive species in the wetland on the Nywaigi property, called Mungalla Station, see

The risk assessment model Edgerton is working on is beneficial for research on current invasive species, along with up-and-coming invasives, she said.

Her model uses a question and answer format, she said. Each question is weighted, and at the end, the points from each question are totaled. The higher the point value, the more likely it is to be an invasive species.

“By developing the risk assessment model, we will be able to predict potential future invasive species as well as prioritize current invasives for control,” Edgerton said.

Giant salvinia (salvinia molesta) is a small free-floating plant that grows in clusters and develops into dense, floating mats, and is one of the most challenging aquatic plants in Texas. It can spread rapidly due to its invasive nature and fast growth, even doubling in size in as few as 4 days under ideal conditions, Edgerton said.

To learn more about TWRI’s giant salvinia research, see the website, project blog and Facebook page.

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