The research team found small-spotted catshark eggs attached to plastic, which is something that has never been seen before. Photo: Arnau Subías
One of the identified species -the bryozoans Arbopercula tenella- is not native from the Mediterranean. Photo: Emanuela di Martino
A new study led by members of the Faculty of Earth Sciences of the UB and the Institute of Marine Sciences (ICM-CSIC) revealed that plastic debris in the sea could contribute to the introduction and transport of non-native marine species that attach to these particles of anthropogenic origins. As part of the study, published in the journal
, the scientific team identified several species attached to a series of plastic debris —both floating and present in beaches and seafloors— in the Catalan coast. Specifically, bryozoans —a group of invertebrates that are usually small— were the most diverse group with a total of 15 identified species. In particular, one of these species —bryozoan Arbopercula tenella— is not native from the Mediterranean although it had been previously detected in other marine areas of the Mediterranean.
"It is important to conduct a constant monitoring to confirm the establishment of A. tenella and other non-native species in natural and artificial habitats of the Catalan coasts since they can become invasive species in the future, and consequently contribute to reducing the natural biodiversity, so ecosystems can become less resilient to changes", notes the expert Blanca Figuerola (ICM-CSIC), member of the MedRecover research group.
Moreover, the team studied the different types of plastics they found, since they can "be relevant to differentiate the biofouling communities that adhere to plastics probably due to their chemical structure or the surface properties", notes Arnau Subías-Baratau, member of the Marine Geosciences Consolidated Research Group of the UB and ICM-CSIC.
The effects in the plastic's journey
The study reveals that all species of bryozoans found in plastics collected in the seafloor are typical from shallow areas. Also, most of these plastics have lower densities than seawater.
According to Figuerola, "this shows that the organisms' colonization of the plastic surfaces —biofouling— plays a relevant role in the sinking of plastic debris, thus the identification of these organisms can provide us with key information of the dispersal and movement processes of plastics in the oceans". Therefore, the low-density plastics would not reach the sediments in the seafloor if not for the added weight of the organisms that are adhered to the surface. According to lecturer Anna Sanchez-Vidal, expert on plastic marine pollution and member of the Department of Earth and Ocean Dynamics and the Marine Geosciences Consolidated Research Group of the UB, "the presence of several species attached to plastics found in the beaches suggests that this deposition is not permanent, and that these particles in the seabeds can be resuspended by currents and then and transported to the beaches as a result of the waves during storms".
"This supports the idea that an important amount of plastic that enters the ocean is temporarily stuck in the coastal areas, although it can be transported to great depths by energetic hydrodynamic currents", conclude the authors of the study.
The study highlights that plastics can act as dispersal vectors when providing substrates that can be used as habitats by a great variety of marine species, and as a result, they can alter the marine ecosystems. For instance, the team found for the first time small-spotted catshark eggs (Scyliorhinus canicula) adhered to plastics, which has not been documented but which could have an impact on the geographical distribution and the habitat of this fish species.
Reference article:
Subías-Baratau, A.; Sànchez-Vidal, A.; Di Martino, E.; Figuerola, B. «Marine biofouling organisms on beached, buoyant and benthic plastic debris in the Catalan Sea». Marine Pollution Bulletin, February 2022. Doi: 10.1016/j.marpolbul.2022.113405
