Plastic pollution is a global problem that affects not only the oceans but also freshwater ecosystems. Microplastics, which are small plastic particles less than 5 mm in size, can be ingested by aquatic organisms, accumulate in food webs, and transport contaminants and pathogens.
Microplastics can also alter the physical and chemical properties of water and sediments, affecting the habitat and function of aquatic life.
A recent study by researchers from the University of Waikato and the University of Notre Dame, published in Nature, found that plastic pollution in some New Zealand lakes is comparable to northern hemisphere lakes in highly populated areas, despite much lower population densities.
The study is the first to develop a standardized protocol for looking at microplastics in lakes and across a range of environmental conditions.
How microplastics get into lakes
BEN STANSALL/AFP via Getty Images
The researchers collected samples from 38 lakes across 23 different countries and six continents, using the global lake ecological observatory network (GLEON), as per Phys.org.
They measured levels of small plastic particles, from microplastics to macroplastics, measuring 5-10 mm in diameter.
They found that all lakes in the study had microplastic pollution, but lakes in or near built-up areas were significantly more polluted than those in less populated areas.
The researchers identified two types of lakes that are particularly vulnerable to plastic contamination: those in densely populated and urbanized areas and large lakes with long water retention times.
These lakes receive more inputs of plastic debris from human activities, such as wastewater discharge, stormwater runoff, tourism, recreation, and agriculture.
They also retain plastic particles for longer periods, allowing them to accumulate and fragment into smaller pieces.
The researchers found that most of the microplastics were fragments and fibers of plastics that are generally considered easy to recycle, such as polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP).
These plastics are commonly used for packaging, clothing, and personal care products. The researchers suggested that these plastics may escape from recycling systems or degrade from larger items during transport or disposal.
The researchers found that plastic pollution in some New Zealand lakes is comparable to northern hemisphere lakes in highly populated areas, despite much lower population densities, as per The Conversation.
Of the three New Zealand lakes included in the study - Rotorua, Taharoa, and Wiritoa - microplastic pollution was highest in Lake Rotorua, equal to lakes such as Lake Erie in North America and Lake Geneva in Europe.
Lake Rotorua is a large lake with a long water retention time of about 11 years. It is also surrounded by intensive agriculture and urban development, which contribute to nutrient enrichment and algal blooms.
The researchers speculated that these factors may enhance the growth of submerged plants and algae that provide habitat and food for snails, which are known to ingest microplastics.
Snails can then transfer microplastics to higher trophic levels, such as fish and birds.
The researchers warned that microplastic pollution could have negative impacts on lake ecosystems and human health.
Microplastics can affect the feeding, growth, reproduction, and survival of aquatic organisms. They can also carry harmful substances, such as additives, pollutants, and pathogens, that can leach into water or be transferred to organisms.
Moreover, microplastics can alter the physical and chemical properties of water and sediments, affecting light penetration, oxygen levels, nutrient cycling, and sediment stability.
The researchers called for more research on the sources, pathways, fate, and effects of microplastics in freshwater ecosystems.
They also urged for more actions to reduce plastic consumption, improve waste management, promote a circular economy, and raise public awareness.
