Glitter, utilized in a diverse range of hues and forms, embellishes apparel, footwear, cosmetics, handbags, festive ornaments, artistic creations, and jewelry, among myriad other uses. During Carnival festivities, multitudes of Brazilians adorn themselves with it, adorning their bodies as they revel in street dances.
While its luminosity captivates, glitter poses a burgeoning environmental threat, as discerned by numerous scientists: akin to other microplastics (tiny plastic fragments measuring less than 5 mm), it evades filtration in wastewater treatment facilities, ultimately infiltrating rivers and oceans, thereby disturbing aquatic ecosystems in manifold ways.
A study conducted at the Federal University of São Carlos (UFSCar) has unearthed an additional concern: apart from plastic, glitter harbors metals, notably aluminum. As outlined in the New Zealand Journal of Botany, these metals impede the transmission of light underwater to such an extent that they impede photosynthesis and stifle the growth of aquatic plants.
The authors of the study zero in on Egeria densa, commonly known as Large-flowered waterweed, a macrophyte native to Argentina, Brazil, and Uruguay. Macrophytes, visible to the unaided eye, serve as vital resources for numerous species, offering nourishment and refuge, casting shade, and emitting oxygen. They constitute a pivotal element in biofiltration systems within phytoremediation initiatives, wherein plants are deployed to detoxify soil, water, or air.
Additionally, some species, including E. densa, are extensively utilized for oxygenation and aesthetic enhancement in aquariums and artificial lakes.
The researchers conducted meticulous analyses through laboratory experiments involving 400 fragments of E. densa. These fragments were incubated in flasks filled with water sourced from the Monjolinho reservoir on the UFSCar campus, along with standard glitter commonly found in retail stores, featuring an average particle surface area of 0.14 mm2.
The experimental design comprised four distinct combinations: E. densa exposed to glitter at a concentration of 0.04 grams per liter, both with and without light, and E. densa absent of glitter, again with and without light, serving as control groups. To gauge photosynthesis rates, they employed the “light and dark flask” methodology, a technique devised in 1927 and widely employed in such investigations. In the flask exposed to light, the plant engages in photosynthesis, consequently generating oxygen as a byproduct.
Conversely, the dark flask facilitates the measurement of respiration, where the plant consumes oxygen. The net photosynthesis rate is determined by comparing the gas exchange rates between the light and dark flasks.
The results of the experiment revealed that photosynthesis rates were 1.54 times higher in the absence of glitter. This discrepancy arose due to the microplastic particles diminishing the amount of light penetrating the water. While respiration was also impacted, its alteration was less pronounced.
“These findings corroborate our initial hypothesis, suggesting that glitter disrupts photosynthesis, potentially due to light reflection caused by the metallic surface of the microplastic particles,” remarked Luana Lume Yoshida, the primary author of the study. This research constituted a segment of her scientific initiation project at the Bioassay and Mathematical Modeling Laboratory (LBMM) within UFSCar’s Department of Hydrobiology. Presently, Yoshida continues her academic pursuits, undertaking research for a master’s degree in ecology and natural resources at the same institution.
Sustainable Carnival
The study’s implications extend beyond mere physical interference observed in a specific macrophyte species. It underscores broader concerns regarding water contamination and the ingestion of these particles by various aquatic organisms, as highlighted in existing scientific literature. By piecing together these insights, the researchers were able to elucidate the functioning of entire ecosystems and anticipate potential ramifications throughout the food chain.
“This ecological perspective is pivotal,” emphasized Marcela Bianchessi da Cunha-Santino, the article’s senior author and a principal investigator at LBMM. “With a comprehensive database, we can formulate public policies aimed at promoting more conscientious consumption of such materials. However, it’s crucial to alert society that alterations in photosynthesis rates, though seemingly distant from our daily lives, are intricately linked to other changes that directly impact us, such as diminished primary production within aquatic food chains.”
“Why hesitate to transition to more sustainable alternatives if they exist?” questioned Irineu Bianchini Jr., another co-author of the article and a fellow principal investigator at LBMM. This sentiment underscores the urgency of adopting environmentally friendly alternatives to mitigate the adverse effects associated with glitter usage.
More information: Luana Lume Yoshida et al, Interference of glitter with the photosynthetic rates of a submerged macrophyte, Egeria densa, New Zealand Journal of Botany (2023). DOI: 10.1080/0028825X.2023.2276284
