Author: Kristan Reynolds
Date: 7/17/2025
Plastic Free July is a global movement that challenges and inspires people to reduce their plastic consumption for one month — or even longer. By taking on the challenge, we can cut down on plastic waste which, research shows, is harmful to the environment and especially devastating to marine life.
At the Florida Atlantic Marine Science Laboratory, scientists are not only participating in the plastic-free challenge but are also conducting pioneering research on how plastics affect sea turtles. Dr. Sarah Milton’s lab is focusing on identifying and measuring those effects. Here we highlight the research of her student, Ph.D. Candidate Heather Seaman.
Heather is studying the impact of plastic ingestion on sea turtles by examining the gastrointestinal tracts of deceased sea turtles that strand (wash up, usually weakened or dead) on Florida’s beaches. Out of the 200 deceased sea turtles she analyzed, Seaman discovered that around 60% of them had ingested plastic. Additionally, those that didn’t have physical pieces of plastic left in their digestive tract, Seaman still retained physical or chemical evidence of having ingested plastic at some point during their lifetime. Her findings also show that smaller sea turtles are more likely to contain plastic; nearly all of them were found to have ingested plastic. Those findings suggest that many young turtles, recently recruited into the population, will not survive.
Plastic is not only “killing sea turtles, but also changing their physiology,” Seaman said. “And, that is happening to other organisms, like the many fishes that also ingest the plastic.” According to Seaman, the chemicals linked with plastic ingestion can have feminizing effects when transferred from mother to their eggs, and eventually to their developing embryos. This is particularly concerning because sea turtles exhibit temperature-dependent sex determination — warmer nest temperatures produce more females, while cooler nest temperatures produce more males. With temperatures on the rise already causing a strong female bias in hatchlings, the addition of feminizing chemicals significantly adds to those risks. The production of too many females can, over many generations, lead to the extinction of the population.
However, the environmental impacts of plastics extend far beyond initial ingestion and chemical exposure. Since plastic takes hundreds of years to break down, it gradually fragments into smaller and smaller pieces known as microplastics. These particles are 5 millimeters — the length of a grain of rice — or smaller. These small plastic pieces are now ubiquitous, polluting beaches, estuaries, and oceans.
With relaxing beach days in the summer, there are other options available besides single-use plastics. Switches to reusable options like water bottles, cutlery, and grocery bags can go a long way. While multi-use plastic has a lower environmental impact compared to single-use plastics – especially when recycled or disposed of correctly, Seaman adds that you can reduce your own exposure to plastic by switching to alternatives like wooden and glass cutting boards. Our researchers encourage you to take on the challenge and avoid single-use plastics for at least one month, or for whatever extended time period you choose. Doing so will reduce the amount of plastic pollution entering our oceans. A little bit of conscious work now can become a habit that becomes second nature each day.
By taking intentional steps in our daily lives, we can help reduce the plastic pollution that threatens marine ecosystems. The Florida Atlantic Marine Science Laboratory researchers are doing their part and encourage you to join in!
