Researchers found microplastics in each of the 53 waterways they sampled throughout 2020, a survey that reveals the impact of these long-lasting pollutants on the entire Delaware Estuary.
“The staggering amount of microplastics we found likely means that no river, lake or stream is safe from this increasingly common contaminant,” said Faran Savitz, one of the project’s researchers, in a news release about the study.
The project by PennEnvironment, a nonprofit environmental research group, is just one of many efforts initiated in the last several years to develop a better understanding of just how bad microplastic pollution is in the Delaware Estuary system. Other groups currently conducting research in the region include the Environmental Protection Agency, United States Geological Survey, Delaware River Basin Commission, Philadelphia Water Department, Rutgers, and University of Delaware.
Any plastic debris that is five millimeters — about the size of a pencil’s eraser tip — or smaller is considered microplastic. Often, these particles are pieces of larger plastics that have been broken down over time by water and weather. But they can also be original products, like the microbeads found in cosmetics, toothpaste and other personal care products; abrasives used in cleaning compounds; polyester and nylon microfibers woven into clothing; and pellets for plastics manufacturing.
Microfiber is a common culprit
“We most commonly find microplastic fragments and microfibers,” said Jonathan Cohen, a professor of marine science and policy at the University of Delaware who has been studying microplastics in the Delaware Bay since 2016. “Polyethylene and polypropylene are common plastic polymers in our samples, as are polyester and rayon.”
Cohen was among the first researchers to begin mapping microplastics in the Delaware Bay. In 2016, while conducting a bay-wide study comparing zooplankton distributions to those from the 1950s, when water quality was much poorer than it is today, Cohen and his team decided to add microplastics sampling into their work.
That research resulted in the first published report on microplastics in the Delaware Bay, in 2019, which looked at particle concentrations and distribution, and how they are impacted by wind, tides, currents, and other factors that influence water movement.
While Cohen and his team found microplastics in each of the 16 sampling stations they established throughout the bay, they also found several “hot spots” for particle accumulation.
“Fresher river water is less dense and floats above the more salty ocean water,” Cohen said. “This layering is very distinct around the area where we see the most microplastics in the Delaware Estuary.”
Industrial and open water areas
Not surprisingly, the stations closest to industrial areas recorded higher than average microplastic densities, but, somewhat notably, open water areas around the mouth of the bay did, too. Additionally, microplastics concentrations vary vertically, since water stratifies based on salinity, temperature and other factors.
“We were surprised by the variability in microplastic concentrations across Delaware Bay,” said Cohen. “We’re still getting a handle on how much microplastic there is in the system, and how it is distributed in space and time.”
The research project Rutgers is currently conducting is also looking at how microplastics are distributed as they move from the upper Delaware Bay to its mouth and the adjacent coastal ocean. But the researchers at Rutgers also are studying how microplastic is ingested and digested by zooplankton, and how that may impact humans.
Like Cohen and his team, the Rutgers researchers have identified concentrations of microplastics in the region where fresh and salt water collide. “These boundaries, or ‘river plume fronts,’ accumulate materials, such as microscopic larvae, phytoplankton, and other floatables where marine species gather to feed,” Robert Chant, the study’s oceanographer, wrote in a blog post about the project. “Because of these characteristics, river plume fronts are likely to be regions where microplastics enter the food chain.”
By identifying the places in the estuary where microplastics are most dense, and how zooplankton are consuming them, it is possible to begin mapping the impacts on marine species that are regularly consumed by humans, like blue crabs, oysters and bass, to name a few. “Given trends in plastic production and use, microplastics are a pollution issue that will only increase in the years to come if left unchecked,” said Cohen. “If we can understand and manage it as a pollutant, we will be in a better position to achieve levels of water quality that support both ecological and human health.”
In his blog post, Chant pointed out that garbage patches — the large gyres of plastic trash that can be found in each of Earth’s five oceans — garner the most media attention. But it is in water systems like the Delaware Estuary, where the human and marine ecosystems must coexist, that microplastic concentrations are significantly higher. About 8 million metric tons, the equivalent of 285,000 Statues of Liberty, enter the ocean every year, an estimated 80% of that directly from land.
Spurring legislation and land-use policy?
This reality, coupled with the difficulty of delegating cleanup efforts in the middle of the ocean, where jurisdictional boundaries are blurred, emphasizes the importance of enacting legislation and land-use policy that focuses on the points where plastic pollution enters local waterways.
In 2015, the Microbead-Free Waters Act was signed into federal law, ending the addition, manufacture and sale of microbeads in some personal care products, like toothpastes and face washes. In November, Gov. Phil Murphy signed legislation (S-864) that is considered one of the strictest single-use plastics bans in the country.
What makes plastic a miracle product also makes it one of humanity’s most intractable problems. Speaking of the Microbead-Free Waters Act specifically, Cohen said, “Microbeads already in the environment don’t disappear. While some may be flushed from the estuary, others can be trapped in beach sand or sediment and become re-suspended over time.”
Research like that by Cohen and Chant, which is working toward pinpointing the locations where plastic waste is entering the Delaware Estuary, could help shape legislation and land-use policies at the municipal level.
“We’re hoping that our studies now and going forward can help communities make decisions on where to allocate resources for addressing plastic pollution,” Cohen said. “By understanding which sub-watersheds contribute the most plastic to the Delaware Estuary, and what that plastic is, we hope to allow for scientifically-based decision making that can target approaches addressing those plastics and pathways into the estuary.”