The PLASDEEP project aims to shed light on deep-sea microbial communities associated with marine plastic waste in the deep ocean. These largely unexplored artificial habitats offer a unique opportunity to explore contributions of microbial biofilms communities to plastic fate, to uncover novel specific microbial diversity and functions, and to assess their potential polymer degradation capacity and impact on deep marine ecosystems.

This project relies on scientific research questions and corresponding research hypotheses that we will seek to demonstrate through a multidisciplinary and multiscale approach:
Research question 1: What is the diversity and composition of microbial communities associated with deep-sea conventional plastic waste and which environmental factors influence their distribution?
Hypothesis 1: Microbial communities on polymers are mostly influenced by the bathypelagic zone conditions: high hydrostatic pressure, darkness, cold temperature and oligotrophic environment (below 1,000m deep).
Research question 2: Do the type of polymers and associated composites (conventional or biodegradable) and their life history (initial colonization in sea surface, abiotic ageing during settling) influence the colonization process in the deep ocean?
Hypothesis 2. The colonization processes by bathypelagic microbial communities are influenced by the type of polymers, with biodegradable polymers being specifically colonized by microorganisms able to utilize them as carbon or energy sources, whereas conventional ones are probably inert substrate with the colonization speed which depends on the physico-chemical and mechanical characteristics of surfaces. The epipelagic initial plastisphere will become anecdotic with time when plastics settle, leaving only a small fraction of it.
Research question 3: Which microorganisms are actively engaged in the biodegradation of plastic substrates from sea surface to deep-sea waters?
Hypothesis 3. Only certain hydrocarbonoclastic bacterial, archaeal, and fungal taxa from the deep-sea microbial plastisphere possess specialized metabolic capabilities for plastic degradation and the utilization of polymers as a carbon or energy source.