That may seem resourceful, but it can sometimes have various negative consequences.

There was already anecdotal evidence that octopuses interact with the junk that ended up in the seas and oceans at our hands. However, systematic research into these interactions has never been done. “We didn’t know where they take place, how they take place or what kind of material the octopuses interact with,” said researcher Maíra C. Proietti. Scientias.nl† A new study on Proietti and her colleagues, published in the journal Marine Pollution Bulletin, is now changing that. Using 261 photos, the scientists describe the interactions of octopuses with waste. A large part of these photos were taken by citizen scientists: people who are not scientists, but who voluntarily made available image material obtained by them. There are also photos taken by scientists, sometimes with the help of underwater robots.

Multiple purposes

The photos reveal that octopuses use the junk on the seafloor for a variety of purposes. It turns out that many octopuses use (broken) glass bottles as shelter. Some even lay their eggs in it. Still others went for a walk with a plastic bottle in their arms that they used as camouflage when necessary. There were also octopuses hiding under a mix of shells and bottle caps.

Surprising

“What surprised me most was the sheer amount of photos we found,” says Proietti. “That was both surprising and worrisome,” she quickly adds. “I also found it surprising that octopuses that live at great depths and have been captured using underwater robots interact with waste.”

It does indicate that the problem does not only occur near the coast and in relatively shallow water. Waste is everywhere. And octopuses use it everywhere. In addition, there was one species that appeared remarkably often in the photos. And that was the coconut octopus. The mollusk owes its name to the fact that it naturally collects coconuts for shelter. But apparently he also exchanges those coconuts very easily for waste. In addition to the coconut octopus, the researchers were able to identify 23 other octopus species in the 261 photos.

An octopus lurks in a broken bottle. Image: John Paul Meillon.

“We can’t say much from these photos alone about how often octopuses interact with waste,” Proietti said. “But we can say with certainty that these interactions are widespread. We saw it in pictures taken in different places around the world. And we saw that different types of octopuses used different types of waste. And that certainly indicates that this is a widespread problem.”

A problem

At first glance, it may seem very imaginative that octopuses are giving our waste a second chance. But it is indeed a problem. “It’s extremely worrying that octopuses use our waste so much,” said Proietti. “It may seem positive that these organisms are adapting to a new environment where waste is abundant, but it mainly reflects how widespread waste is now and that waste can negatively affect octopuses in other ways as well.”

But even when they use the waste for shelter – and thus seem to take advantage of it – it cannot be ruled out that our junk still has a negative impact on the octopuses. “For example, the waste can have toxic components that leak out to the octopus. For example, we also saw an octopus that had made its shelter out of an old car battery, and such a battery contains many toxic substances.” In addition, the researchers also saw that octopuses like to lay their eggs in dumped bottles. “That could lead to smaller broods or affect the development of the eggs.” In addition, much of the waste used by the octopuses was already quite damaged. Glass bottles in which they regularly sought shelter were often broken. “And that broken glass can injure the animals.” These are just a few of the possible negative consequences that the interactions between octopuses and waste can have. “And we need to investigate them more closely to understand them better,” says Proietti.

Plastic versus glass
When it comes to water pollution, we hear a lot about plastic waste. The photos clearly showed that octopuses also do a lot with plastic waste. But strikingly enough, the molluscs worked with glass much more often. “We hypothesized that octopuses would interact more with plastic,” Proietti admits. “Since that is the most common type of waste in the ocean. So it’s a bit surprising to see that at least they’re more likely to interact with glass when they’re looking for shelter. But somehow it also makes sense, because on the seabed you will find more waste with a high density – such as glass. In addition, the glass bottles – the objects that the octopuses use most often – have properties that make them extremely suitable as shelter. They have a small opening and offer a lot of protection.”

Follow-up research

The research provides more insight into how octopuses deal with waste. But the research also raises new questions. “We would like to clarify what drives octopuses to use waste. More research is also needed into the possible negative consequences of the use of waste.” The latter does have priority, says Proietti.
“Because if there are negative consequences, we may be able to take measures to combat or limit them.”

An octopus is hiding in some plastic cups. Image: Claudio Sampaio.

In the meantime, there is no doubt that with our pollution we are radically changing the habitat of octopuses – even to great depths. “And while octopuses seem to adapt and, thanks to their impressive intelligence, see that they can use that waste for shelter, it mainly shows how much waste there is currently in the ocean. And that waste can negatively affect octopuses as well as other organisms in the water.”