Notes From the Field: Microplastics Found in Bald Head Island Sand
December 17, 2022
by Katie Knotek, Fall 2022 Intern
Every Thursday, I make the reverse commute of many BHIC staff members and leave the island for Wilmington, NC. My destination is the Plastic Ocean Project (POP), where I am working on my intern research project on microplastics. Microplastics are abundant in marine environments and can be found worldwide, even on remote islands and in the middle of the ocean. The goal of my project is to determine if microplastics are present in sea turtle nests on Bald Head Island.
In order to determine if microplastics are present, the first step is to collect a sample. Three days after a nest hatches, the sea turtle team does an excavation and digs up the nest to count the number of egg shells. After excavations are complete, they collect a small tube of sand from the bottom of the nest. The next step is to dry the sand in our lab oven so it is ready for processing.
This is where my trips to POP come in. I have been working with POP scientist Kayla West and UNCW student Bo Huff to process sand samples and look for microplastics. Once I am at POP, I grab a lab coat and gloves and start looking through the sand samples under a microscope. As I am picking through the samples, I remove any suspicious looking particles or fibers that I think could be microplastics. I put these aside and save them for later.
Once I am done sifting through the dry sand, I do a process called density separation using Zinc Chloride to find any particles that I may have missed. The Zinc Chloride is added to the sand sample and stirred for fifteen minutes before being left to settle for twenty-four hours. After twenty-four hours, the top liquid layer is put through a filter using vacuum filtration. The filter collects any particles or fibers left in the sample, and I examine it to remove any remaining particles or fibers that could be microplastics.
The final step is to use a fascinating machine called a Fourier-transform infrared spectroscopy (FTIR) machine. The suspicious particles and fibers are put in the machine one at a time, and an infrared absorption spectrum is created. This is a unique signature that is compared to a database of previously sampled materials through a computer program. A list of the most similar materials is generated, and I can determine if the particle or fiber is actually made of plastic, or if it is harmless organic matter.
Understanding what can be found in our sand is important because microplastics have the potential to impact our endangered sea turtles. Sea turtles have temperature-dependent sex determination, which means that the temperature that the eggs are exposed to in the sand determines if the hatchlings are male or female. Climate change is already impacting the sex ratio of sea turtles further south where rising temperatures are creating more females than males. Microplastics have the potential to exacerbate this problem because plastics can trap heat, making the sand even hotter during incubation. Additionally, plastics have the potential to leach toxins into the environment. Currently, it is unknown how these toxins would impact developing turtle eggs. More research is necessary to determine the impacts of microplastics on incubating sea turtle eggs.