Environmental Gradients Shape the Hydrocarbon-Degrading Microbiome in Two Mid Atlantic Bays

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Ecosystem resilience

Background:

• Coastal estuaries receive continuous hydrocarbon inputs, posing environmental contamination challenges.
• Microbial communities are key to hydrocarbon breakdown, but predicting their activity and resilience is difficult.

Purpose of the Study:

• To investigate factors influencing hydrocarbon degrader abundance and activity in Delaware and Chesapeake Bays.
• To understand microbial metabolic strategies for hydrocarbon degradation under varying environmental conditions.

Main Methods:

• Analysis of metagenomes, metatranscriptomes, and metagenome-assembled genomes (MAGs).
• Identification of key genes in hydrocarbon degradation pathways.
• Statistical analysis of environmental factors (salinity, temperature, nutrients) and microbial community structure.

Main Results:

• Aerobic aromatic and alkane degradation pathways were predominant, with higher gene abundance in low-salinity spring/summer samples.
• Hydrocarbon degrader MAG abundance was structured by salinity, temperature, nitrate, and silicate.
• Delaware Bay showed higher expression of degradation genes than Chesapeake Bay, especially under low-salinity spring conditions.
• Functional redundancy varied, with catechol degradation pathways being highly redundant and naphthalene degradation restricted.
• Distinct metabolic strategies were observed in *Burkholderiales* and *Pseudomonadales*, contributing to ecosystem resilience.

Conclusions:

• Environmental gradients and specific microbial metabolic strategies jointly control hydrocarbon degradation potential in estuaries.
• Findings aid in predicting ecosystem responses to hydrocarbon inputs under changing environmental conditions.
• Understanding these processes informs nature-based bioremediation strategies for contaminated coastal systems.