Written on: September 17th, 2020 in Outreach
By Mike Mensinger, DNREC Coastal Programs
Humans rely heavily on plastics in the modern era. We produce and use plastics for many things in life including, but not limited to, product packaging, plastics bags, utensils and much more. Simply look around your current area and count the number of plastic products or components surrounding you. It’s quite likely more than you realize! Have you ever wondered what happens to plastic after fulfilling its original purpose? While recycling gives many plastic items a second use in life, vast amounts are discarded and make their way into the environment.
Microplastics are tiny plastic pieces less than 5mm in size. They may enter the environment in their original form like microbeads previously used in things like skincare products and commonly referred to as primary microplastics. They may also enter as larger pieces, called secondary microplastics. Secondary microplastics break down into small pieces over time due to degradation from light, wind, water, etc. Unintended consequences of microplastics include aquatic critters like zooplankton and fish mistaking them for food. This may be harmful to them and organisms that feed upon them.
Researchers from The Delaware Department of Natural Resources and Environmental Control’s (DNREC) Coastal Programs Section piloted a microplastics effort in 2016 using methods developed by the National Oceanic and Atmospheric Administration. The pilot paved the way for additional monitoring from 2017 to 2020. Environmental Scientists, Dr. Kari St. Laurent, Nicole Rodi, and Mike Mensinger along with dedicated interns, Rachael Faust and Sydney Hall investigated microplastics in the St. Jones River and nearby beach areas. While Nicole focused on river sediment and beach sand, Mike’s efforts focused on microplastics within the water itself as highlighted in this article.
Mike conducted sampling every other month at Scotton Landing, a dock sitting on the south side of the St. Jones River. He deployed a plankton net, a sampling device with an appearance similar to a large mesh ice cream cone, which remained submerged near the water surface for two minutes. The net captured floating particles that flowed into the net’s open mouth and were funneled through the net body into a collection cup located at the net’s end.
Upon completion, the net’s contents were rinsed into a container and returned to the lab for processing and analysis. Once in the lab, samples were dried and exposed to a chemical mixture which dissolved the majority of organic matter. Next, salt was added to each sample to change its density, which caused the plastics to float at the surface while other materials sank to the bottom. The settled portion of the sample was drained away and the remainder drained through a mesh filter to that captured the microplastics. Mike later viewed each sample under the microscope to count and categorize each piece.
Sample processing and analysis for this project’s 2018 and 2019 samples are currently nearing completion. Prior year results confirm presence of microplastics within the St. Jones River water. Detected microplastics include small broken pieces called fragments, thin hair-like pieces called fibers, and small round spheres called microbeads.
The project’s annual report will be available from the DNREC Division of Climate, Coastal and Energy’s Delaware Coastal Programs upon completion in the coming months, so stay tuned!
Click here to learn more about efforts to clean up marine debris, including microplastics, in Delaware!