Microplastics in Texas bays are being swept out to sea

(Press-News.org) From tiny pellets to creepy wave-battered baby dolls, the Texas coast is a notable hot spot for plastic debris.

But when researchers from The University of Texas at Austin went searching for microplastics in sediments pulled from the bottom of Matagorda Bay and its surrounding inlets, they didn’t find much.

Most of their samples contained only tens to hundreds of microplastic particles for each kilogram of sediment. This is hundreds to thousands of times less than other bayside environments around the world.

Their findings, which were published in Environmental Science & Technology, suggest that rather than settling at the bottom of the bay, microplastics are being swept out to the wider Gulf of Mexico.

That’s a problem, according to researchers at the UT Jackson School of Geosciences who led the research. Once in the open water, the microplastics can absorb chemicals from the surrounding environment and can build up in the bodies of migratory birds, sea life — and eventually humans.

“It’s good that the bay is not a microplastic dump or hotspot,” said study co-author Cornel Olariu, a research associate professor in the Jackson School’s Department of Earth and Planetary Sciences. “But the bad thing is they move around much easier than we thought … and they’re a threat to everything up to us.”

The study is the first time that researchers have examined the prevalence of microplastics in Texas bay sediments. The results provide important baseline data. They also show that since the bay is not retaining microplastics, more research is needed on where they’re off to next.

“We as geoscientists are applying our understanding of sediment transport to understanding where these contaminated particles are being deposited or concentrating in these coastal systems,” said the study’s lead author William Bailey, a graduate student at the Jackson School. “We can figure out where particles might be routed.”

Bailey is using the data collected in this study to make a model for where the microplastics from the Matagorda Bay area  may be heading.

The research is part of a new field of geosciences called “environmental sedimentology.” This field treats microplastic fragments like sediment grains from rock. Researchers in this field are interested in where the fragments originate, how they travel in the environment, and where they end up.

For this study, researchers took 122 sediment samples from Matagorda Bay, East Matagorda Bay., and San Antonio Bay. They then took the samples back to the lab to separate out microplastic fibers and fragments from the surrounding mud. Throughout the project, the researchers had to take care not to introduce plastic waste of their own. That involved wearing clothing made from natural fibers, lining sample bags with foil, and using custom-blown glassware for filtering the samples.

Humans produce a lot of microplastic waste. One microfiber fleece jacket sheds about 6 million fibers with every wash, said Bailey. What’s more, Matagorda Bay is home to a plastics factory that produces plastic pellets — commonly called “nurdles” — that serve as a feedstock for plastic products.

With that in mind, the researchers said it wasn’t surprising that they found the most microplastics in samples that were taken closer inland. However, the microplastics dispersed throughout the environment without a clear correlation to surrounding sediment grain size, organic matter, water depth or distance from the shoreline. These are factors that usually influence the transport of geologic sediments.

The researchers point to the plastic’s low density and the bay’s windy and shallow environment to explain why the microplastics are so easily swept out to sea. With water not much more than 13 feet deep, high winds and hurricanes are constantly reworking sediment at the bottom of the bay, the researchers said.

Microplastics are a ubiquitous global pollutant, and the scientific community is playing catch up when it comes to measuring their abundance and influence, said Jace Tunnell, the founder of the citizen science initiative Nurdle Patrol that tracks plastic pellets.

There is currently no standardized method for analyzing microplastics in environmental samples. Tunnell, who was not involved with the research, said that this study provides much-needed data about microplastics on the Texas coast.

“The work that UT and other research institutions are doing, it’s so important because if nobody’s looking into this stuff, there’s no way to ever say that there’s a problem,” said Tunnell, who also serves as the director of Community Engagement at Texas A&M University-Corpus Christi’s Harte Research Institute. “Hopefully, when we know there’s a problem, there are actual solutions that can be developed.”

The research was funded by the Matagorda Mitigation Trust and the Jackson School of Geosciences. Jackson School Professor David Mohrig is a co-author on the study. 

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