Nitrifying niche in estuaries is expanded by the plastisphere

Area of Science:

• Environmental Microbiology
• Marine Biogeochemistry
• Anthropocene Ecology

Background:

• The estuarine plastisphere, a biofilm on plastic debris, is a novel habitat. Its role in nitrogen biogeochemistry is poorly understood but potentially significant.
• Plastic pollution is a growing global concern, impacting marine ecosystems and biogeochemical cycles.

Purpose of the Study:

• To investigate the biogeochemical significance of the estuarine plastisphere in nitrogen cycling.
• To elucidate the mechanisms by which the plastisphere regulates nitrogen cycling, particularly nitrification.

Main Methods:

• Utilized stable isotope probing with 15N and 13C.
• Employed metagenomics and metatranscriptomics to analyze microbial communities and gene expression.
• Compared nitrification activity within the plastisphere to surrounding seawater and other natural biofilms.

Main Results:

• The plastisphere exhibited significantly higher bacteria-mediated nitrification rates (0.9–12-fold) compared to seawater and stone, wood, or glass biofilms.
• Identified a shift in dominant nitrifying bacteria within the plastisphere, favoring those with versatile metabolic capabilities over oxygen-sensitive types found in seawater.
• Observed potential interspecific cooperation among nitrifiers in the plastisphere, possibly involving substrate exchange.

Conclusions:

• The estuarine plastisphere functions as an underappreciated nitrifying niche, distinct from surrounding environments.
• Microbial community structure and metabolic adaptations within the plastisphere create a unique environment for enhanced nitrification.
• This research deepens the understanding of the plastisphere's contribution to estuarine nitrogen cycling and marine biogeochemistry.