Beach wracks microbiome and its putative function in plastic polluted Mediterranean marine ecosystem

Area of Science:

• Marine microbiology
• Environmental science
• Coastal ecology

Background:

• Coasts accumulate diverse beach wracks, including organic matter and plastic debris.
• Beach wrack microbiomes (MB) are crucial for decomposition but can harbor pathogens.
• Understanding MB composition is vital for coastal ecosystem health and plastic pollution research.

Purpose of the Study:

• To characterize beach wrack microbiome composition in relation to beach exposure, sediment type, and plastic pollution.
• To investigate the influence of environmental factors on the microbial communities associated with beach wracks and microplastics.

Main Methods:

• Interdisciplinary approach combining geological sediment analysis, plastic debris composition analysis (ATR-FTIR), and 16S rRNA gene metabarcoding of beach wrack MB.
• Comprehensive sampling design across different coastal environments.

Main Results:

• Proteobacteria, Bacteroidetes, Actinobacteria, Planctomycetes, Verrucomicrobia, and Firmicutes were major MB contributors.
• Significant dissimilarities in MB were observed between exposed and sheltered beaches, with distinct bacterial groups dominating each.
• Plastisphere MB was primarily shaped by beach exposure, seagrass type, sediment, and naturalness, showing no significant dissimilarity across various microplastics (MP).
• Functional analysis detected plastic degradation capabilities and potential human pathogens within beach wrack and seawater MB.

Conclusions:

• Beach exposure is a significant factor shaping beach wrack microbiome composition, more so than plastic pollution itself.
• Seawater MB composition heavily influences plastisphere MB.
• The study highlights the dual role of beach wrack MB in decomposition and potential pathogen dissemination, emphasizing the need for further research into their functional roles.