A new study carried out by ICM researchers proves the existence, at a depth of 700 meters in the Blanes canyon, of carnivorous sponges that have grown on nylon ropes and other plastics.
Every year, about 12 million tons of plastic are dumped into the world's seas and oceans at a rate of 200 kilos per second. When talking about marine plastic pollution we usually think of 'plastic islands' and floating debris, but the truth is that the seabed is not free from this epidemic.
Underwater canyons are one of the main entry routes of this marine litter to the deepest areas of the ocean, where darkness and low temperatures prevent the degradation of plastic.
This emerges from a study published this August in the specialized journal Marine Pollution Bulletin that proves the existence, 700 meters deep in the Blanes canyon, of carnivorous sponges that have grown on nylon ropes and other plastics.
According to the authors, from the Coelenterate Ecology Group at the Institut de Ciències del Mar (Institute of Marine Sciences, ICM) in Barcelona, the presence of plastic does not seem to have a detrimental effect on the sponges’ growth, although it shows that plastic reaches the deep ocean through underwater canyons and other areas of steep slope.
"This is a surprising fact, as the presence of carnivorous sponges in marine litter has never been detected before", states Andreu Santín, researcher at the ICM’s Coelenterate Ecology Group who adds that "one of the things that surprised us the most it is the high density of individuals -30 in 10 cm2- over the plastic surface", a fact that has been observed rarely in other natural populations.
The thirty individuals discovered in the Blanes Canyon belong to the species Lycopodina hipogea, which feeds on small crustaceans. In the ‘90s there was already evidence of the existence of carnivorous sponge species, but this is the first time they are seen on the Catalan coast.
Speaking about plastic, Santín explains that "although marine debris has turned out to be an optimal substrate for the growth of these sponges, it must be kept in mind that these materials release pernicious compounds to the environment, and we are still far from knowing the real gravity of what this means for marine biodiversity".
Previous studies prove that floating debris is a dispersal vector for marine biota, including invasive species. However, and although there is increasing evidence of the use of marine litter as a substrate by marine organisms, the role that this debris may have as a dispersal vector in the deep sea has hardly been studied.
The completely fortuitous finding took place in late February during a campaign of the ABRIC project, led by ICM researcher Pere Puig. This project studies the impact of trawling on the marine ecosystems of the Blanes Canyon and aims to help establish co-management measures that make fishing compatible with the conservation of ecosystems.