Plastics are the largest component of marine trash. They breakdown into micro-particles, but do not leave the ecosystem.
NPS/Chelsey Grobelny
Up to 90% of trash floating in the ocean and littering our shores is plastic.[1] While it is common knowledge that plastic persists indefinitely in the environment, until recently little was known about what happens as all this waste disintegrates.
Enter microplastics. These are tiny (under 5 mm, or about the size of a sunflower kernel) particles of plastic and fibers. Some result from the breakdown of trash already in the ocean. Others come from a variety of sources, both obvious, such as single-use plastics, and unexpected, like toothpaste, beauty products, and even synthetic clothing. They slip into our waterways through storm and waste water treatment systems, which are not designed to remove such miniscule, inorganic particles.
Whatever the source, microplastics pose an increasing threat to marine life. We are only now beginning to recognize the potential impacts of the breakdown of plastics in the marine ecosystem. Small organisms like zooplankton mistake microplastics for food and ingest them. As larger animals consume the zooplankton, microplastics work their way up the food chain. Harmful chemical pollutants, such as PCBs and heavy metals, can attach to these plastics and add to their toxicity. Once inside an organism, they block or irritate the digestive system and create a full sensation in the stomach, preventing the animal from seeking its natural prey. The resulting nutrient-poor diet lowers reproductive success, hinders predator avoidance, and can lead to starvation.[1]
But the breakdown process doesn’t stop there. Microplastics degrade into even smaller particles (<100 nm in diameter) known as nanoplastics. Evidence suggests that these microscopic fragments adhere to the surface of algae and are easily transferred up the food chain, where they pose their own set of health risks. One recent study found that nanoplastics had entered the liver and digestive organs, and had penetrated the embryo walls of freshwater fish. The study also saw behavioral changes in these fish including reduced feeding, vitality, and ability to avoid predators.[2] A separate study of scallops found that, after a brief period of exposure, billions of nanoplastic particles had accumulated in most major organs.[3]
Ultimately, micro- and nanoplastics are accumulating in the food chain, and are likely to wind up in the human food supply. As the amount of plastics entering the world’s oceans spirals upward, it becomes increasingly important to understand the risks to aquatic organisms and ecosystems, as well as to humans.
The National Park Service and Clemson University, with funding from the NOAA Marine Debris Program, conducted a study of microplastics in 35 national parks, including Sitka National Historical Park. How are they faring? While microplastics were detected on every beach surveyed, Alaska’s parks fared pretty well. Notably Sitka NHP beaches, with 21.3 pieces per kg of sand, had the lowest number of microplastics of all the parks surveyed. And among Alaska’s national parks, Katmai had the most, with 128.2 pieces/kg. Nationally, Hawaii’s Kalaupapa National Historical Park accounted for the greatest number of microplastics averaging 225 pieces/kg. What may be surprising to many, though is consistent with similar studies, is that fibers were the most common particles detected, making up fully 97% of the totals. For more in-depth detail, read the full study.
[1]Quantification of Microplastics on National Park Beaches 06/01/2015 - 05/31/2017; Principal Investigators: Stefanie L. Whitmire, Ph.D. Baruch Institute of Coastal Ecology & Forest Science, Clemson University Skip J. Van Bloem, Ph.D. Baruch Institute of Coastal Ecology & Forest Science, Clemson University
