PLASMAR: New pathways of marine plastic biodegradation through leachates and their interaction with microorganisms

Cristina Romera Castillo holds a degree in Chemistry from the University of Jaén. She carried out her doctoral thesis at the Institute of Marine Sciences of the CSIC in Barcelona on dissolved organic matter (DOM) in the ocean and its interaction with microorganisms. Between 2012 and 2017 she did her post-doctoral stage abroad working in different universities in the USA and Austria, during which time she published several scientific articles in high-impact journals. Thanks to a grant from the Government of Catalonia she worked at Florida International University (Miami, USA) studying the isolation and chemical composition of DOM. In 2014 she was contracted by the University of Miami to study the distribution of dissolved organic carbon in the ocean and the main factors controlling it. In 2016 she was hired by the University of Vienna where she conducted a study on organic carbon released from marine plastic and its effect on micro-organisms. In 2017 she returned to the Institute of Marine Sciences with a Juan de la Cierva-Incorporación grant. Since September 2018 and until 2021, she was a ComFuturo researcher in this institute where she carried out her ComFuturo project “New routes of marine plastic biodegradation through leachates and their interaction with microorganisms“. After ComFuturo, she was awarded with a Ramón y Cajal position.

Project Summary

It is estimated that there are more than 5.25 trillion pieces of plastic floating on the surface of the sea. Plastic waste, deposited on beaches or floating in the sea, is exposed to UV radiation and oxidation, which causes fractures on its surface and the progressive fragmentation of the plastic into smaller particles reaching microscopic sizes (< 5mm, microplastics). It has been shown that plastic can release organic compounds into the aquatic environment (leaching). The smaller the chunk, the greater the surface:volume ratio and the greater its leaching capacity. A recent study proposes that, through this process, microplastics can be gradually dissolved into dissolved organic carbon (DOC) by the action of solar radiation and rapidly consumed by marine bacteria. On the other hand, some of the DOC released by the plastic is volatile and could be released into the atmosphere. Could these processes be potential pathways for eliminating plastic in the ocean? The objective of this project is to study the environmental conditions that favour the migration of microplastic organic compounds into the marine environment and their subsequent fate (e.g. consumption by bacteria, venting to the atmosphere). Thanks to massive sequencing techniques of the 16S rRNA gene (16S Tags amplicons), we will also be able to know which microorganisms degrade the DOC released by the plastic and could be used in large-scale biodegradation. This will contribute to finding new pathways for biodegradation of plastic in the ocean. In addition, the effects of plastic leachates on marine microorganisms will be studied. Plastic debris in the ocean is a planetary-scale threat whose consequences are only beginning to be seen. The results of this project will contribute to improving the management of plastic waste and to finding a solution to the persistence of plastic in the ocean by improving its biodegradation.

Application: The project aims to study the environmental conditions that favour the migration of organic compounds from microplastics to the sea and to understand their effects on marine microorganisms, such as bacteria and phytoplankton. It also aims to understand which bacteria degrade the dissolved organic carbon released by plastic, as the results will help to open up an alternative pathway to the biodegradation of this material in the ocean and to waste management. It will also help plastic companies to choose materials with less environmental impact.

Scientific production derived from the ComFuturo PLASMAR Project

Scientific articles

Y. K. Lee; C. Romera-Castillo; S. Hong; J. Hur (2020). Characteristics of microplastic polymer-derived dissolved organic matter and its potential as a disinfection byproduct precursor. WATER RESEARCH. DOI:10.1016/j.watres.2020.115678


Book chapters

Co-author Chapter 3 “T13. Océano” of Libro Blanco de Desafíos Científicos CSIC 2030.


Works presented at conferences

C. Romera-Castillo. Dissolved organic carbon leaching from plastics stimulates microbial activity in the ocean. Ocean Sciences Meeting (ASLO). Invited oral presentation. San Diego, USA. 16/02/2020-21/02/2020


C. Romera-Castillo. Contribution of marine plastic debris to dissolved organic carbon pool. Banyuls-Barcelona bianual meeting. Platja d’Aro, Girona, Spain. 2/05/2019-3/05/2019


C. Romera-Castillo; M. Pinto; T. Langer; X.A. Álvarez-Salgado; G. Herndl. Dissolved organic carbon leaching from plastics stimulates microbial activity in the ocean. MICROS2018. Lanzarote, Spain. 19-11/2018-23/11/2018