Many know that plastics in the ocean is a huge problem. They can accumulate in areas over twice the size of Texas, and microplastics in particular (plastics that break down into pieces of less than 5 mm) can harm marine organisms when ingested. However, while researchers have a good understanding of the role of plastics at the surface of the ocean, few have determined just how much plastic actually reaches the seabed of the ocean, a difficult and costly problem given the depth of the ocean.
Researchers Justine Barrett, Chris Wilcox, and their team at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), an Australian Government agency, quantified the amount of microplastics in the Great Australian Bight, a large ocean area south of Australia that is home to many marine species. The researchers utilized a remotely operated vehicle to collect samples from around 1600 to 3000 meters deep in the ocean. They then adapted a characterization technique to filter and purify these deep ocean samples to better evaluate the amount of plastic they contain.
Using careful microscope images, the CSIRO team counted the number of microplastic particles in different samples and estimated based on the counts from this region that 14 million tons of microplastic exist on the whole ocean floor. Previous comparable studies found higher microplastic estimates because they were conducted in coastal areas with higher population densities. This resulted in more pollution or contamination of the samples collected, and therefore was not representative of the majority of the ocean. Because this team’s microplastic count was collected from a more remote location, their total count was lower and provides a more conservative estimate.
This research from Barrett’s team has significant implications for understanding the gravity of the plastics problem in the ocean. Many before have focused on the idea that plastics float on the surface of the ocean, with researchers only beginning to explore the idea of their role in the deep sea. However, these findings show that the deep ocean can serve as a sink for plastics, with even this more conservative estimate revealing a serious problem. We need to act faster to ban plastic dumping to prevent such accumulations.
Corresponding Author: Eesha Khare (@eesha_khare)
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Original Article: Microplastic Pollution in Deep-Sea Sediments From the Great Australian Bight, Frontiers Microbiology 5 Oct 2020