They’re barely visible, only 1/8-inch or smaller, so it might not seem like a big deal. But it is. Microplastic particles are floating around in Tampa Bay in alarming numbers. In fact, research scientists from the University of South Florida St. Petersburg and Eckerd College estimate that there may be as many as 4 billion of these indestructible particles at the bottom of the Bay.
“When we look out at Tampa Bay, we can’t imagine it, but microplastic particles are ubiquitous,” says David Hastings, a recently retired professor of marine science and chemistry at Eckerd College and courtesy professor at the University of South Florida College of Marine Science.
Hastings was the principal investigator of a study on microplastics with Kinsley McEachern, the first author of the study. McEachern conducted the study as part of her master’s degree thesis in Environmental Science and Policy at USF St. Petersburg.
Results from the study were published online in late August in the Marine Pollution Bulletin and will appear in the print version in November.
McEachern grew up in Naples, FL, and says that watching documentaries and reading books on plastic pollution sparked her interest, especially in microplastics, a new and emerging field of study.
She points out that it’s easy to be disturbed by the large visible plastic items -- the bottles, Styrofoam cups, buoys, straws, and plastic bags that you might see littering the Gulf beaches, or floating in the water when you’re kayaking in places like Weedon Island.
It’s also easy to understand the harm that castoff six-pack rings from soda or beer cans, or fishing line, can do to marine life. That’s what beach cleanups are all about.
But microplastics may be even more insidious.
Billions of teeny, tiny pieces at core of the issue
The National Oceanic and Atmospheric Administration reports that microplastics are not a specific type of plastic, but represent any plastic fragment ranging in size from 1 nanometer to about 5 mm.
The fragments can come from the breakdown of large plastic items like plastic bottles or plastic bags. They can also come from tiny threads or strands released from synthetic fibers that are in clothing, fishing line, or fishing nets.
Even just washing clothing made from petroleum-based synthetic fabrics like polyester, nylon, or rayon can release thousands of microfibers.
“As we wash our clothes, they shed tiny synthetic fibers that are actually microplastics,” says McEachern. “These go down the drain and through the sewer system to the wastewater treatment system, and eventually come out as discharge to the Bay.”
Microplastic particles are so tiny that they easily pass through water filtration systems.
“The new realization is that plastic keeps breaking down into smaller and smaller pieces. But unlike a leaf breaking down, the plastic doesn’t go away. It’s always there,” says Hastings. “Just because we can’t see it doesn’t mean it isn’t there.”
Even more unsettling, Hastings points out, is more plastics particles that we didn't know existed are being found as technology gets more sophisticated in allowing scientists to see extremely tiny particles. “The smaller we can see, the more we can identify,” he says.
To conduct the study, McEachern and Hastings collaborated with USFSP Association Professor of Chemistry Henry Alegria and the Environmental Protection Commission of Hillsborough County.
Over a 14-month period, the team counted the number of microplastic particles in water and sediment samples taken at 24 collecting stations located throughout Tampa Bay, from the Oldsmar area to the north in Old Tampa Bay, to Hillsborough Bay, St. Petersburg and south, near Egmont Key and Fort DeSoto.
They also sampled water and sediment from a range of ecosystems -- coastal mangroves, the mouth of major rivers emptying into the Bay, and near industrial facilities.
In the lab, the team looked at samples under the microscope, using a variety of standardized guidelines and techniques to help them identify the particles. A hot needle probe placed near a fragment will make the plastic melt and curl; biological organisms will burn, says McEachern. Plastic tends to be consistent in color throughout, and it’s flexible and won’t break when examined, unlike sand or salt crystals.
The most prevalent type of marine debris
To help keep the study 100 percent accurate and avoid contamination, Hastings said that researchers wore cotton clothing when obtaining water samples and made sure the lab where they were working was very clean.
Results from the study were interesting or alarming depending on your point of view.
On average, the researchers identified four particles of microplastics per gallon of water and more than 600 particles of microplastics per pound of sediment. Those findings were then extrapolated to estimate the total amount of microplastic pollution in the water at 4 billion particles and more than 3 trillion pieces in surface sediment.
The majority of microplastics in the Bay come from clothing, fishing lines, and fishing nets, rather than the breakdown of larger plastics. They’re concentrated fairly evenly from one end of the Bay to the other. But there are significant seasonal differences related to heavy rainfall.
“A large seasonal rainfall event correlated with higher microplastic concentrations, showing the potential for more debris to be washed out into the Bay during stormwater runoff, “ says McEachern.
Although the focus of the study was to establish a baseline for the amount of microplastic in Tampa Bay, the researchers expressed concern for the potential harm to both the environment and human health.
“It was unbelievable to realize our findings,” says McEachern. “We’re just beginning to learn about the impact microplastics might have on marine animals, from the smallest organism all the way up the food chain. It’s very concerning to me.”
“A lot of marine life doesn’t discriminate in choosing food, they simply filter everything in the water,” says Hastings. “An oyster can filter 50 gallons of water a day. During that process, they get a lot of food. But they also suck up whatever is in the water, including plastic. So they can get full ingesting plastic, which of course has no nutritional value.”
In addition, microplastics could cause internal blockages or fail to be excreted by the marine animal, says McEachern.
She also points to another concern. Because the surface of plastic is different from other materials, toxic pesticides, herbicides, and metals can stick to the plastics, making it even more harmful and potentially damaging to marine life.
“The plastics themselves contain a whole host of chemicals that can cause problems, and then you add in the potential for more toxins that are stuck to the item’s surface,” says McEachern.
The Tampa Bay researchers aren’t alone in discovering the extent of plastic pollution in oceans and waterways. NOAA reports that plastics are the most prevalent type of marine debris found in oceans and lakes worldwide.
“In the 70s we shifted toward a plastic-based economy,” says Hastings. “Think about it. Everything is wrapped in plastic these days, even a single cucumber that we buy at the grocery store. We think it’s not important, but plastic lasts a lifetime.”
But despite the challenge, he sees potential solutions.
“If there is a positive path here, it’s that we are recognizing the role of single-use plastics in harming the environment and that we can enact policies that change our behavior,” says Hastings.
McEachern agrees. “We can take a stand by voting for legislators who prize environmental interests and supporting businesses and retailers for taking a positive stand.”
Several bills already introduced for the 2020 Florida Legislature would ban plastics in different forms and under a variety of circumstances. You can track plastic-related bills in both the Florida Senate
and the Florida House
For more information, follow these links: