Credit By: OneGreenPlanet
Microscopic remnants of plastic have been identified in the fat and lungs of more than 65% of the marine mammals analyzed during a graduate student’s investigation into microplastics in the ocean. This finding suggests that microplastics can go beyond the digestive system and become embedded within the tissues of these animals.
The research, slated for publication in the Environmental Pollution journal on October 15, has been recently made available online.
The potential harms embedded microplastics might inflict on marine mammals have yet to be entirely ascertained. However, other studies have implicated plastics as potential hormone mimics and disruptors of the endocrine system.
Greg Merrill Jr., a fifth-year graduate student at the Duke University Marine Lab, highlighted the significance of this discovery: “This is an additional burden in addition to everything else they are contending with climate change, pollution, noise. Apart from ingesting plastic and dealing with larger pieces in their stomachs, they are also experiencing internalization.” Merrill emphasized that a portion of their body mass now comprises plastic.
The specimens examined in this study were sourced from 32 stranded or subsistence-harvested animals from 2000 to 2021 in Alaska, California, and North Carolina. The dataset encompasses twelve species, with one bearded seal also exhibiting plastic in its tissues.
Due to their lipophilic nature, plastics are attracted to fats. This characteristic draws them towards blubber, the melon responsible for sound production on toothed whales’ foreheads, and the fat pads along the lower jaw that focus sound towards the whales’ internal ears. The study analyzed these three types of fats and lung tissues, revealing plastics in all four tissue types.
The sizes of plastic particles identified within the tissues ranged from 198 to 537 microns. To provide a comparison, the diameter of a human hair is around 100 microns. Merrill underscored that apart from any potential chemical risks posed by the plastics, the physical presence of plastic fragments can lead to tissue tearing and abrasion.
Merrill is now poised to investigate the metabolic impact of plastic in these tissues through toxicology tests using cell lines cultivated from biopsied whale tissue.
The most frequently encountered plastic types in tissue samples were polyester fibers, commonly produced by laundry machines, and polyethylene, a component of beverage containers. Blue plastic was the predominant color found in all four tissue categories.
A 2022 study in Nature Communications estimated that a filter-feeding blue whale, based on microplastic concentrations off the Pacific Coast of California, could ingest as much as 95 pounds of plastic waste daily while consuming tiny organisms in the water column. Additionally, whales and dolphins preying on fish and more giant creatures may accumulate plastic by consuming contaminated prey.
Although a significant proportion of microplastics likely pass through the gut and are excreted, some portion finds its way into the animals’ tissues, underscoring the widespread and enduring nature of the issue.
Merrill summarized the gravity of the situation, stating, “For me, this just underscores the ubiquity of ocean plastics and the scale of this problem. Some of these samples date back to 2001. Like, this has been happening for at least 20 years.”