Microplastics in Maryland's Water
In 2019, Anacostia Riverkeeper staff put samples from various locations on the river under a microscope and discovered that each of the samples contained over 400 pieces of microplastics in each liter of water, with one sample even containing nearly 700 microplastic particles. High concentrations of microplastics had previously been found in water samples taken from the Back and Patapsco Rivers, near Baltimore’s Inner Harbor. The Chesapeake Bay watershed has a microplastics problem.
In a world where plastic trash has been found almost literally everywhere, even at the deepest parts of the ocean, it must not come as a surprise that the Chesapeake Bay is experiencing these issues, but that does not make it any less concerning. There are gaps in our waste disposal processes that allow for plastic trash to find its way from human hands into our oceans and waterways with ease, which leads to numerous environmental problems.
Plastic's Threat to Wildlife
Much of the country is now familiar with the striking images of sea turtles injured by plastic straws, which can get lodged in their nostrils. This has led to calls for individuals and businesses to refrain from using or offering plastic straws in order to decrease the number which enter into the waste stream and, eventually, the ocean. But effects such as those seen from this example do not constitute the full extent of the threats plastics pose to aquatic ecosystems. Plastics impact these systems in a number of complex ways, the details of which many scientists are still researching.
One such scientist is Christine Knauss, a graduate researcher at Horn Point Laboratory in Cambridge, Maryland. She is investigating how ingesting small plastic particles affects oyster larvae’s growth and fitness. This is research that she believes is especially important due to oysters’ environmental, economic, and cultural importance to the Chesapeake region.
She says that the issues all begin with poor waste management and human behavior, which leads to the introduction of plastic waste into the environment. For example, most plastic products are produced from small plastic pellets called “nurdles.” Nurdles are created in plastic production facilities and transported all over the world to various companies so that they can be manufactured into the products we buy in stores. However, “this supply chain is leaky and many nurdles are spilled and not recovered throughout this whole process, releasing microplastic into the environment,” Knauss claims.
There are no plastic production plants in Maryland currently, but the building of a new plant in Western Pennsylvania could have future negative impacts on the environment further down the coast and throughout the Chesapeake Bay watershed.
The negative impacts of the introduction of plastics into aquatic ecosystems are many and varied. Larger pieces of plastic, such as plastic bags from a grocery store or plastic lines, can entangle and smother plants and wildlife. Plastic bags, especially, have gotten a well-deserved bad reputation for causing injury to sea turtles who mistake the floating plastic sheets for jellyfish or algae, both common foods in a sea turtle’s diet.
Knauss explains that there are other less commonly-known issues associated with plastics. Firstly, they are able to act as a conduit for the introduction of invasive species. Species may cling onto the surface of pieces of plastic and travel long distances on currents. In a similar manner, plastic can harbor harmful bacteria. Vibrio, in particular, can be introduced into an ecosystem via plastic, leading to harm for oyster populations and humans as well.
Over time, plastics tend to break up into smaller pieces called microplastics -- those pesky particles that had been found in high quantities in rivers throughout Maryland. These are plastic particles that are sized from 5 millimeters all the way down to 1 nanometer. They can be both primary and secondary sources of pollution. The first refers to those bits of plastic that are small enough to be considered microplastics upon entering the environment, and the latter refers to the results of larger pieces of plastic breaking up into bits over time.
These small particles are ubiquitous throughout many waterways. They are so small that they are easily spread across a number of water depths -- they can even float or disperse into the sediment, making them easily exposed to a number of different aquatic species. Particles this tiny often appear similarly to organisms such as plankton and, as such, as easily consumed by larger organisms like oysters, crustaceans, and fish, as well as even larger mammals and seabirds.
In the laboratory, Christine Knauss feeds these particles -- in a variety of sizes, shapes, and polymers, and concentrations -- to baby oysters. From there, she tracks measurements such as growth, respiration, algal ingestion, and how much carbon the oysters incorporate into their own tissues from their food. Though she is still in the process of analyzing her data, it is clear that microplastic ingestion has effects on the physiology of the oyster larvae.
Other research has already been conducted on other animals such as the black sea bass, another creature commonly found in the Chesapeake Bay. Although the sea bass were found to discern between microplastics and food, the smaller organisms that they did choose to eat often had already ingested microplastics themselves. The microplastics then affect the next rung up on the food chain, causing the juvenile black sea bass to have affected respiration and immune responses.
This brings up another important point: if the effects of microplastics can be carried up the food chain, what impact do they have on humans? Researchers have discovered microplastics in many species of invertebrates, crustaceans, and fish intended for human consumption. Due to the chemical additives in plastic, there are concerns that these microplastics could transfer hazardous toxins to the fish that ingest them and, likewise, to the humans who consume the fish. However, the full extent of these effects on both animals and humans is not yet known.
So what can we do to fix this issue of plastic pollution in our waterways?
According to Knauss, our current technology is not capable of removing a majority of microplastics from environmental systems. Not only is separating microplastics from sediments, soil, or other organic particles time consuming, costly, and labor intensive, but microplastics are also the same size as oyster and blue crab larvae, so attempting to remove those particles would undoubtedly cause harm to those key organisms.
There is no clear way currently to reverse the damage already done, but Knauss cites better solid and water waste management systems as an important step to preventing the plastic pollution problem from getting worse. And there are many things that individuals can do to make a positive impact as well.We can decrease the amount of plastic pollution that continues to be fed into the environment by using less plastic -- especially single-use plastics.