Acute and Long-Term Impacts of Climate Change on the Microbial Community Structure within the Soil Treatment Area of Coastal Septic System.

Climate change may affect the microbial community composition within the soil treatment area (STA) of onsite wastewater treatment systems (OWTS), also known as septic systems, in the Northeastern United States. Higher temperatures and water tables from sea level rise in coastal regions due to the long-term effects of climate change can affect wastewater treatment by reducing the volume of unsaturated soil and oxygen available for treatment, which may result in a shift in microbial community composition. The acute effects of climate change, such as storm surges, may lead to more severe temporary shift in microbial community composition due to increased salinity levels and inundation and saturation of the STA. We used intact soil mesocosms and high throughput sequencing to quantify the long-term impact of climate change (30 cm elevation in water table, 5°C increase in soil temperature) and acute impacts (storm surge event) on the microbial community composition from a conventional and two types of shallow narrow STAs. A higher numbers of microorganism were observed under present climate conditions in comparison to long-term and acute climate change conditions for all STA types. Microbial communities shifted towards more archaea under long-term climate change conditions, while marine microorganisms dominated microbial communities after the storm surge event. Our results indicate that both the acute and long-term effects of climate change can affect microbial community dynamics within the STA of septic systems, and affect their treatment capacity.