Much of the focus on plastic pollution centres on our oceans. Emerging evidence shows it’s also a problem in freshwater, which may even be the source.
In 2016 a team of scientists scoured a dozen beaches around the shores of Lake Geneva in Switzerland – not for flora or fauna, but for litter. In particular, plastic litter.
It wasn’t hard for them to amass quite the collection of discarded common everyday objects. These included bottle tops, cotton buds, pens, toys and straws. They picked up lesser identified fragments too, such as blocks of polystyrene foam, the kind that keeps fragile goods soft in the post.
Collecting this debris wasn’t the team’s main goal, says Montserrat Filella from the University of Geneva. Instead, they wanted to assess whether chemicals emitted from these plastics were harmful.
Their analysis comes at a time when the world is uncomfortably waking up to the extent of human-caused plastic pollution – from islands of amalgamated plastic in our ocean to the smaller microplastics in riverbeds.
We have reached, as the UN has recently dubbed it, a “planetary crisis” that is ruining our ecosystem. Despite the increased awareness of its damage, plastic pollution is already everywhere. While potential solutions like a plastic-eating enzyme – announced in April 2018 – may someday help us cut down waste, there is no guarantee that it could tackle the millions of tonnes of waste already in nature.But marine plastic pollution is much better studied and understood than that found in freshwater sources. “Freshwater systems are increasingly studied but still at a much smaller scale than oceans,” says Filella. This may simple be due to the fact that initial studies focused on the ocean – and so research proposals and grants followed suit.
It didn’t take long for the Geneva team to find what they were looking for. Filella and colleagues collected over 3,000 samples. They went on to analyse 670 of these, revealing some worrying results.
Its effect on wildlife therefore remains a major concern. Plastic’s prevalence in water and on the shorelines of beaches, lakes and rivers, means that it can, and often is, ingested by wildlife. If an animal swallows it, their stomach acids might speed up how quickly the plastic degrades – potentially thereby also releasing the hazardous elements faster. Then there is the effect on the animal itself. Due to the lack of studies, it’s not yet entirely clear how freshwater organisms cope when they ingest plastic waste.
“You might need a lot of plastic to kill a water flea, but that does not tell you the long-term consequences and the ecological implications,” he says.
“Plastics will not go away. They are in the environment and will stay there for decades.”
Lake Geneva is not an outlier. Other lakes show similar levels of pollution. Italy’s Lake Garda, for example, also has high levels of plastic waste. A sample from the northern part of the lake contained 1,000 large plastic particles and 450 smaller particles (microplastics) per square metre.
Reducing our use of plastic may slow down the waste that washes up on beaches – and plastics we use today are less toxic than they were in the past. But as the insights into Lake Geneva reveal, for many decades, at least, the plastic at the bottom of lakes will continue to release toxic elements.
“It might take decades to get rid of the problem,” says Filella.