Modern science and technology are rapidly improving our understanding of how plastic pollution affects marine life, and a new study suggests that they can also be used to understand the plight of past organisms. Using museum collections, scientists looked at the guts of freshwater fish from the past century and found that not only have they been devouring plastic waste for decades but the concentration of plastic waste in their stomachs has risen sharply in recent years.
The study, from biologists at Loyola University chicago, focused on microplastics, which are small fragments smaller than 5 millimeters after shopping bags, beverage bottles and other plastic items break down. Recently, scientists studying the impact of microplastics on marine life have made some worrying discoveries, such as microplastics can cause fish aneurysms and reproductive changes, affect the cognitive ability of hermit crabs, and weaken the physical properties of mussels. They also found evidence of microplastics spreading along the food chain, while studies of potential effects on humans found that microplastics may alter the shape of lung cells.
The authors of the new study set out to study how microplastics have accumulated over the past century and what this meant for fish in the past. So they went to the Field Museum in Chicago, where about 2 million fish specimens are kept in alcohol and underground collections.
Tim Hoellein, an associate professor of biology at Loyola University Chicago, said: "Over the last 10 or 15 years, the public has become aware that there is a problem with plastic in the water. But in fact, since the invention of plastics, microorganisms have been exposed to plastic waste, and we don't know what the historical background looks like. Observing museum specimens is essentially a way for us to go back in time. ”
The study focused specifically on four species of fish: the largemouth bass, the spotted forktail catfish, the sand spotted fish and the round goby, all of which can be recorded from 2017 to 1900. To complete the study, the team also collected fresh samples of these same species.
Loren Hou, lead author of the paper, said: "We would take these jars filled with fish and find some ordinary samples, not the largest, not the smallest, and then we dissected their digestive tract with scalpels and forceps. We try to get at least 5 specimens every decade. ”
After treating these digestive tracts with hydrogen peroxide, the compound is able to break down all the organic matter but leaves any potential plastics behind. The scientists used microscopes to identify materials that might be the smooth and suspicious edges of microplastics, and then collaborated with researchers at the University of Toronto to confirm their chemical signatures through Raman spectroscopy.
This suggests that plastics did not appear until the middle of the last century, but when plastic manufacturing industrialized in the 1950s, the concentration of plastics began to soar. These plastics are found in the form of fibers, which come from polymers as well as a range of natural and synthetic textiles. The researchers described this discovery and the significant increase in attention as "alarm bells" and "alarm bells."
"We found that the amount of microplastics in the guts of these fish essentially increased as plastic production increased. This is the same pattern they found in marine sediments, which follows the general trend of plastics being ubiquitous," said Caleb McMahan, a ichthyologist at the Field Museum.