Persistent plastic in the mix
Following an investigation of the incident, Researchers at the Smithsonian Environmental Research Center’s Marine Invasions Lab
suggested that much of the debris that had arrived with the dock – mostly plastic items from fisheries, including ropes, oyster spacers, eel traps, and crates – had already been floating off the Japanese coast. It was the enormous energy of the tsunami that sent them on their way across the ocean. The event proved to be a significant eye-opener for scientists investigating the role of marine debris in transporting organisms between habitats, with over 300 non-native species washing up alive and well across North America and Hawaii.
“A tree or a branch or even a wooden ship would disintegrate and fall apart before a significant amount of it could cross the ocean, but now the plastic, fiberglass, concrete and steel objects that we make — they don’t disappear. They carry these [species] across,” said Professor Chapman.
The tsunami had shown that species could survive for years aboard floating debris, particularly plastic. Chapman is unsure about what this means for the world’s coastal ecosystems. “We don’t know what this is going to do, which is the worst thing of all perhaps, we just know that every place is connected with every other single place on the planet, and it’s [through] plastic trash.”
Plastic trash includes so-called “ghost nets
”, lost or discarded nylon nets from fishing that are well known to entangle dolphins and turtles (among other species). Nylon is plastic and does not decompose, so the ghost nets continue to float and catch marine creatures for many years. There are an estimated 640,000 tons
of abandoned nets across the world’s oceans, comprising up to 10% of all marine litter.
One such ghost net was encountered by the TOMRA-supported eXXpedition
, a series of sailing voyages investigating the impacts of plastic on the world’s oceans. As eXXpedition co-founder and director, Emily Penn, explained, “What we find is that the algae comes along, and then the little fish come along to eat the algae, and that attracts the bigger fish, and then the even bigger fish, and you have the sharks coming along as well. It’s actually quite common that we see entire ecosystems hanging off the bottom of these bits of debris like a coral reef. But then they move, thousands of miles across an ocean to a place that they don’t belong.”