A study from the University of Texas indicates a higher concentration of microplastics at the mouths of Austin’s major urban tributaries, like Shoal and Waller creeks. The majority of particles found in samples had tire and road origins, compared to lower numbers of plastic fibers or fragments broken off of other plastic products.
Last week, Dr. Brent Bellinger, who is the conservation program supervisor with the Watershed Protection Department (WPD), discussed the presence of microplastics in Austin’s reservoirs during an annual update to the Environmental Commission.
Scientists are still determining the full health impact of microplastics in waterways. Some companies have removed intentionally-created microplastics like exfoliant beads in skincare from their products, but particles are unintentionally sloughed off of everyday plastic or rubber materials as a result of friction. In waterways, microplastics have the potential to accumulate.
“You get something that’s less than 5 millimeters — it looks like a plankton, and it’s going to be eaten by something… and then they’re able to bio-accumulate moving up the food web… This is just another one of those checkboxes of the Anthropocene Epoch,” Bellinger told the commission darkly. He noted that the concentration of tire and road-related microplastics increased near Austin’s urban core.
“You can see in these dense areas just how much of our roadways is ending up in our reservoirs,” he added. Bellinger highlighted the potential for follow-up studies evaluating factors like particular roadway conditions and tire brands sold in Austin.
Commissioner Martin Luecke asked about efforts to capture road runoff containing these particles before it gets into Austin’s water systems. The Watershed Protection Department does implement stormwater control ponds, rain gardens and other filtration systems, and is currently working with TxDOT to treat stormwater before it enters the Colorado River during the I-35 Cap and Stitch project. However, Environmental Officer Liz Johnston noted that it is more difficult to implement these practices in already built-out landscapes.
“There’s not a lot of land so, as we can, we’re putting ponds in. But the problem is pretty big,” she said.
During the presentation, Bellinger also provided an overview of the health of Austin’s reservoirs — Lake Austin, Lady Bird Lake, and Lake Walter E. Long. The Austin Lakes Index quantifies an amalgamation of factors in lake health including algae, water quality, flows, sediment, biological communities and habitat for various species. Austin’s reservoirs typically rate between 45 and 65, which is considered fair to good.
Bellinger said managing aquatic vegetation is critical to maintaining a healthy lake. He also spoke about codes that regulate development around shorelines and riparian areas. He described the shore zone as the “last line of defense,” noting that the city’s term for the area — the Critical Water Quality Zone — highlights the importance placed on its protection. Development code changes introduced in 2010 included slope gradient requirements for bulkhead and shoreline modifications along Lake Austin and required plantings for developments in the area.
“What we’re looking for is the middle ground there: having your access, having your boat docks, but also providing a robust vegetated community — something a bit more natural at your shoreline… So you have these ecological functions being better preserved there,” Bellinger said.
A recent study evaluated the effectiveness of these efforts. Bellinger’s team revisited 84 closed development sites along the shoreline to evaluate whether the number and biodiversity of plants proposed in site plans from 2010-2020 had persisted. While a few sites had robust, well-protected plant populations, the majority did not.
Vice Chair Mariana Krueger asked about repercussions for sites that are out of compliance. The Watershed Protection Department does plan to revisit the sites, and next steps are to be determined.
Bellinger’s presentation pointed towards several difficult questions. With human-driven change, Austin is facing increasing threats of nutrients that contribute to algae and cyanobacteria growth, droughts that lead to less flushing of our reservoirs and severe floods that increase water turbidity. Commissioners considered how Austin should weigh factors that are non-natural but seem to be becoming more frequent or permanent when evaluating waterway health.
For instance, Bellinger noted that the 2018 influx of zebra mussels, a non-native species, actually had a positive effect on desired insect biodiversity and water clarity. However, the invasive mussels negatively impacted the lake’s algae makeup.
The commission also touched on some difficult conversations about overuse and recreation.
“Are we loving parks to death, loving water sources to death?” asked Commissioner Justin Fleury. “Do you ever recommend a reduction in recreation?”
Bellinger said the ideal would be not to limit people’s access, but to limit their impact on these systems.
“It’s important to utilize and to have an interaction with the natural environment. You’re going to be more invested in it, you’re going to want to actually protect it more if you understand it, if you’re out in it,” he added.
The presentation tied into several upcoming future topics. Johnston previewed additional updates coming soon regarding the use of artificial turf in the Critical Water Quality Zone.
“It’s always exciting and depressing when you come,” Chair Jennifer Bristol said to Bellinger.
The Austin Monitor’s work is made possible by donations from the community. Though our reporting covers donors from time to time, we are careful to keep business and editorial efforts separate while maintaining transparency. A complete list of donors is available here, and our code of ethics is explained here.