Spatial Distribution and Biogeographical Patterns of Bacteria the Water Column and Sediments of the Northeastern Gulf of Mexico

Through their metabolic activities, marine microbes hold substantial influence on the biogeochemical reactions occurring in the world’s oceans. Charting their spatial distribution and biogeographical patterns is important in order to increase knowledge of key parameters that drive the structure of these microbial communities. We evaluated bacterial communities at 22 stations spanning the continental shelf to the continental slope and rise in the Northeast Gulf of Mexico during the summer months of 2013, covering an area of approximately 486,000 square nautical miles. This entailed collection of surface, deep chlorophyll maxima, and near bottom waters, surface sediments, as well as water laying directly over the benthos, totaling 91 samples. At each station samples were acquired with metadata and measurements of physical parameters. Seawater (~20L) was collected on Sterivex filters and stored at -80° C until gDNA extraction and subsequent Illumina sequencing (MiSeq), targeting the 16S rRNA gene. Based on sequences that matched known organisms in the database, over 700 genera were discernible. Bray-Curtis analysis performed on the classified sequences from all the sites identified 3 major clusters – surface water, deep, and benthos. Further multivariate analysis of dissimilarity between surface water and sediment samples showed 68.48% dissimilarity, with Prochlorococcus (8.25%), Thiorhodospira (5.64%) and Lacinutrix (5.17%) as the genera most responsible. Diversity analysis indicated higher richness in sediment samples compared to that of the surface waters (Sediment = 236, Sur The highest richness was found in the water over core samples which averaged 300 genera per sample. Differences were also noted when comparing surface samples with the deep water column (>200m) samples (58.38% dissimilarity), with the genera Lacinutrix (5.24%), Prochlorococcus (5.19%) and Alteromonas (4.28%) having the highest impact.