Fig. 8: Conceptual model of carbon, nitrogen, and sulfur cycling driven by dominant MTB (Deltaproteobacteria and Alphaproteobacteria) members near the oxygen-stratified water column.

The model illustrates the oxygen-stratified water column on the left, with oxic, hypoxic, and anoxic layers indicated by gray dashed lines. Nutrient concentration trends with depth are shown with colored dashed lines on the right side of the water column. Key carbon, nitrogen, and sulfur cycling processes are depicted, and different dominant MTB members with specific metabolic characteristics are indicated. The vertical distribution of dominant MTB members is illustrated on the right side of the figure.