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.
The authors expected plastic to be the most commonly used octopus material, when, in fact, just over 40 percent of octopus interactions were with glass bottles, and these were predominantly used for shelter.
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,” the authors warn in the study, led by marine biologists from the Federal University of Rio Grande in Brazil.
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.
The authors note that some newly described species, like the pygmy octopus in Brazil (Paroctopus cthulu), have only ever been observed sheltering in litter. There are no official records of this species using natural items like seashells for shelter, probably due to a scarcity of that material in its environment.
The authors found records of octopus/litter interactions had increased in the last few years, with most records occurring between 2018 to 2021. That could be because underwater photographs are easier to take now than ever, but it could also be a sign that the problem of marine waste is getting worse.