24-5 Metagenomic insights on biogeochemical cycling in Seneca Lake, NY

Session: Lake Sedimentary Records of Past Climate and Environment (Posters)

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Abstract:

Microbial communities drive essential biogeochemical cycles in freshwater lakes, yet their composition, diversity, and environmental controls remain poorly understood. Understanding these controls is critical for interpreting organic molecular and stable isotope data, predicting nutrient cycling, and assessing ecosystem responses to environmental change. This study characterizes archaeal and bacterial communities across Seneca Lake, NY using sediment and plankton samples collected along depth and chronosequence gradients. Twenty-six sediment samples were collected using a ponar dredge from sites spanning 7.9–115 m in depth, with three layers sampled per site (0–4, 4–8, and 8–12 cm). Sediments represented three lithofacies: pink Late Pleistocene proglacial clay, grey early- to mid-Holocene marl, and brown and black Holocene profundal laminated silts. Plankton samples were collected at a single limnetic site (100 m) using a 50 cm-diameter, 150 µm-mesh closing net at four depth intervals: surface (0–2 m), benthic (90–100 m), thermocline (24.5 ± 2.5 m), and one percent light penetration depth (9.85 ± 2.5 m). Illumina 16S metagenomic sequencing enabled taxonomic classification from phylum to genus. Preliminary analyses to characterize phylogenetic diversity employ alpha and beta diversity metrics, and normalized read comparison to assess relative abundance of highly relevant taxa. Sediment samples showed more archaeal diversity than plankton samples, although certain bacterial phyla such as Actinobacteria, Bacteroidota, and Cyanobacteriota were more prevalent in plankton tows. Sediment samples showed high archaeal diversity across sites, with exceptional relative abundance of Methanomethylovorans in sediments at some profundal sites, and high relative abundance of Candidatus Nitrosotalea exclusively in the pink proglacial clay. Functional predictions based on KEGG Orthologs and open reading frames identified in Geneious revealed metabolic potential for methane cycling, nitrogen transformation, and other key biogeochemical processes. Metabolic pathways are predicted by functional gene annotations using KEGG Orthologs, with open reading frames identified in Geneious. By quantitatively assessing the microbial community composition and diversity in Seneca Lake, we expect to reveal metabolic reconstructions for uncultured lineages with crucial roles in lacustrine biogeochemical cycles. These results will have implications for selecting future coring sites for organic molecular and stable isotope research, enabling more precise investigations of microbial contributions to freshwater ecosystem function.

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