Octopuses are increasingly using garbage in the ocean floor for shelter, study finds

Glass objects were present in over 40 per cent of interactions and plastic in about 25 per cent

(Roy Caldwell/UC Berkeley)

Scientists have documented a likely increase in the use of litter on the ocean floor by octopuses for shelter, findings that may help mitigate the impacts of trash on the cephalopods.

The research, published last month in the journal Marine Pollution Bulletin, assessed a trove of underwater images taken by citizen scientists across the world, to determine how octopuses interacted with marine litter, and to identify the affected species and regions.

Scientists, including those from the Federal University of Rio Grande in Brazil, assessed over 260 underwater images from citizen science records, and identified 8 genera and 24 species of octopuses living close to the ocean floor interacting with litter.

Most of the images and videos analysed in the study were gathered from social media with the permission of the original authors, while some were provided by scientists.

The findings revealed that glass objects were present in over 40 per cent of the interactions, and plastic in about a quarter of the cases.

The increased use of glass compared to plastic and other types of waste for shelter may be due to the former being more similar than plastic to the internal texture of seashells, researchers say.

“Asia presented the highest number of images, and most records were from 2018 to 2021,” scientists wrote in the study.

Scientists and deep-sea divers have documented octopuses interacting with marine litter such as abandoned fishing gear and glass bottles, and turning them into artificial shelters for decades.

Researchers have also found the molluscs using discarded objects like metal pipes, cans, and plastic cups for shelter.

Several studies, now suggest that tool use – once thought to be a defining feature of humans – is a complex trait also commonly exhibited by octopuses with their unique invertebrate nervous system.

In the new study, scientists suggest that in areas where human tourists have collected too many seashells, cephalopods – the family that includes, octopuses, and squids– have been forced to adapt.

While human waste has become a useful alternative to these creatures, they express concern that the clever octopuses adapted to using litter may become too dependent on it.

“Any apparent positive effect could also have several detrimental and indirect consequences,” scientists say.

They are also concerned that some of the litter the octopuses get accustomed to maybe toxic with heavy metals or may cause physical damage to the creatures.

Some species such as the pygmy octopus in Brazil, researchers say, have only been documented using litter for shelter with no official records of these octopuses using natural items like coconut shells or seashells for shelter.

While the study found an apparent increase in the use of ocean floor litter by octopuses from 2018 to 2021, they say this may also be because underwater photographs are easier to take now than ever.

However, they say it may also indicate that the problems posed by marine waste could be getting worse.

“Citizen science provided important evidence on octopus/marine litter interactions, highlighting its value and the need for more investigations on the subject,” researchers wrote in the study.

“This information is fundamental to help prevent and mitigate the impacts of litter on octopuses, and identify knowledge gaps that require attention,” they added.