LB 5-39 - Metagenomes show that methane, nitrogen and sulfur biogeochemical cycles are differentially affected by soil and sediment environments

Human activities have caused important changes in climate that control the structure and function of ecosystems and the services they provide, specifically inducing great changes in rivers and forests. Microbial activities play a critical role in nutrient biogeochemical cycles and soil/sediment functions. It has been observed that harsh environmental changes, such as mining, fertilization, industry or PAH contamination, can alter microbial ecosystem services. Microorganisms can profoundly affect biogeochemical cycles including methane, nitrogen and sulfur cycles, thereby playing pivotal roles in feedback that magnifies the impacts of global warming. The Kanawha-New River watershed covers about 12000 square miles of forested mountains with a considerable amount of surface mining and industrial activities along the Kanawha River. Our long-term research seeks to understand the impact of land-use practices on riverine microbial biogeochemical cycles. This study compared methane, nitrogen, and sulfur-cycling gene abundance and diversity in forest soil and the upper mobile sediment layers in the Kanawha River watershed. We sampled sediment metagenomes from four locations along an 80 km section of the Kanawha River and three locations from forest soil in the watershed. Total DNA was extracted from 8 sediment and 3 soil samples. Shotgun sequencing was performed using Illumina HiSeq and 70 Gb of sequence was obtained. Chemical variables were measured with ICP-OES and Dionex Ion-Chromatography. Metagenome analysis was done with MG-RAST using RefSeq. Statistical analysis was done using STAMP and R. Chemical analyses of sediment revealed that ammonium concentration in sediment increased with depth. The abundance and diversity of methane, nitrogen, and sulfur-cycling genes among the metagenomes were investigated using KEGG Orthology database. Multiple group test (ANOVA, Benjamini-Hochberg’s FDR corrected, q < 0.05) showed a significant difference between methane and sulfur-cycling genes among the locations. However, there was no difference for the nitrogen-cycling genes abundance between forest soil and river sediment. Rhizobiales, Actinomycetales, Solibacterales, and Acidobacterales were the most abundant orders in soil samples, while Burkholderiales, Myxococcales, and Desulfobacterales were more abundant in sediment samples. In conclusion, this study showed that microbiome structure and the functions linked to some of the most important biogeochemical cycles in these two ecosystems are differentially affected by the environmental conditions associated with different human activities. Supported by USDA-NIFA-2019-38821-29065 and Evans Allen funds.