Mar 17, 2023

Are There Microplastics in Our Estuary?

Header photo courtesy of Ashley Adams.   

Plastic pollution has been observed in the world’s oceans since the 1960s and since then has become more abundant in the marine environment. Larger pieces of plastic can be broken down into smaller pieces of plastic through mechanisms like wave action, animal grazing, or photo degradation. These smaller pieces of plastic are more appropriately termed microplastics and are smaller than 5mm in length and cannot be seen with the naked eye.

These microplastics are harmful to both humans and animals. Marine animals will often mistake both large and small plastics for food, which can cause false feelings of fullness. They can also become entangled in plastic debris and on a smaller cellular scale, can experience toxic effects from ingestion and exposure to the chemicals in microplastics. 

Cal Poly graduate student Ashley Adams, and senior Audrey, preparing a sample to determine if microplastics are present. Photo courtesy of Nikki Adams.

The Central Coast of California has absolutely gorgeous beaches and generally stays trash-free. However, microplastics are sneaky and can’t be seen easily. We already know that there isn’t a place on Earth that is completely plastic free as they’ve been found in the deepest part of the ocean in the Mariana Trench and on the top of the world on Mount Everest. Because of this, students in Dr. Nikki Adams’ lab at Cal Poly San Luis Obispo wanted to investigate if microplastics were present on the beaches in the Morro Bay estuary, and where in the estuary they were most abundant.

Microplastics Research Effort

We set out to answer our questions by collecting sediment (mud or sand) samples from three different beaches in the estuary: Coleman Beach, Windy Cove, and Pasadena Point. These locations all vary in proximity to creek drainage and businesses, human traffic, ecological tourism, and natural processes like wave action and water flow from currents. The diversity of these three beaches is important in helping us understand if any of these factors influence how microplastics accumulate in different sub-environments.  

Cal Poly students (left to right) Lillian, Annie, Abbi, and Elle at Pasadena Point. Once a month, our team would visit the estuary during a low tide to collect sediment samples that we would work on back on the Cal Poly campus. Photo courtesy of Ashley Adams.

Since April 2021, we’ve been coming to the estuary each month to collect sediment samples at each beach during a low tide. In our lab, we use a special fluorescence microscope and dyes to help us view and count microplastics that may be in our samples.  

Cal Poly senior Danielle preparing solutions to analyze sediment samples for microplastics. Photo courtesy of Ashley Adams.

What We Learned

So far, we have found that there are microplastics at all three beaches. The most common type of microplastic has been fibers. These plastic derivatives commonly come from clothing made from polyester, abrasion from tires, and natural degradation of materials that may already be in the water like synthetic ropes on boats. 

This is an example of what a microplastic fiber looks like. Our team views possible microplastic pieces on glass fiber filters using a fluorescence microscope on the Cal Poly campus. Photo courtesy of Ashley Adams.

Where Do We Go From Here?

While this news is not ideal, it also is not completely surprising considering we live in a plastic world. Fortunately, our beaches are much cleaner in comparison to beaches that have been surveyed for microplastics by other researchers in various parts of the world, and there are things we can do as individuals to help mitigate this issue. Some of these things can include participating in local creek and beach clean ups, reducing plastic usage by drinking from a reusable water bottle, or wearing clothes made from cotton and linen, among many others.  

We are continuing this microplastics monitoring work in Morro Bay with support from the Santa Rosa Creek Foundation.

Guest author Ashley Adams

Author Ashley Adams, a Santa Rosa Creek Foundation graduate fellow, is a 2nd year Biological Sciences graduate student at Cal Poly. She began working with the Estuary Program in November 2020 on her long-term microplastics monitoring program. In addition to overseeing this project, she also studies the effects of microplastics on the immune systems of marine invertebrates. In her free time she enjoys hiking, reading, and exploring the Central Coast. Photo courtesy of Crystal Castillo.


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Thank you for helping our beautiful, bountiful, biodiverse bay!