Out of the 10 million tons of plastic waste that enters the ocean each year, we only see 1% of it – the portion that floats on the surface of the water. So, where is the other 99% of it? New studies show that ocean plastic is either pushed back inland where it gets trapped in vegetation or gradually broken down into tiny microplastics on the seafloor.
Plastic Pushed Onto Land
The researchers found around 90% of marine debris that enters the ocean remains within 8 km of the coast (in the “littoral zone”), so they set out to find out where it all ends up. New research shows that ocean plastic is transported back onshore and pushed via waves onto land away from the water’s edge, where it becomes permanently trapped in vegetation.
Between 2011 and 2016, the team went around 188 locations along the entire coast of Australia and collected data on the amount and site of plastic pollution every 100 km. Among the recorded debris, 10% was foam, 17% glass, and 56% plastic.
Areas towards the inland of the beach where vegetation begins had the highest concentrations of plastic waste. Smaller debris were found near the water’s edge, while larger items such as plastic containers, bags, drink bottles, and chips packets were found further back from the sea, trapped in vegetation.
Where the marine debris end up is influenced by coastal wave activity and, in some cases, wind activity. Densely populated areas, urban areas where rivers and creeks enter the ocean, and areas where the coast is easily accessible are hotspots for trapped plastics.
Microplastics On The Seafloor
Scientists discovered the world’s highest concentration of microplastics ever recorded near Italy. They found it on the seafloor, with 1.9 million pieces of microplastic in a five cm-thick layer covering just one square meter. New research shows that these microplastics end up on the seabed when powerful currents sweep them into large drifts, which accumulates them into massive quantities.
The researchers surveyed the Tyrrhenian Sea, off the western coast of Italy, and studied the currents that flow near the ocean floor. Differences in water temperature and salinity are what drives these currents, and it’s all part of a global system of ocean circulation.
In some areas, the currents lose their strength, forming seafloor drifts of sediments hundreds of meters high and many kilometers across. The researchers took sediment samples from depths of hundreds of meters and brought them back to the laboratory to analyze.
The team separated the microplastics from sediment and analyzed them using infra-red spectroscopy to learn what kinds of plastic polymers were on the seafloor. They found that the majority of microplastics were textiles and fiber from clothes.
These currents also carry oxygenated water and nutrients to deep-sea ecosystems and creatures, including coral reefs that depend on these flows. Now, instead of receiving flows of nutrients, it’s receiving streams of microplastics.
Solutions
These findings highlight the importance of studying coastal areas and deep-sea environments to understand better where and how much debris gets trapped. This information could help to target approaches to managing all the waste.
Plastic waste can be reduced in many ways, such as additional trash bins, water refill stations, container deposit schemes, awareness campaigns, and waste management policies to reduce, reuse, and recycle. However, in the end, the best way to keep plastic out of our ocean and land is to stop putting there in the first place.
