Three distinct hydrothermal plumes emanating from new lava flows of the 2015 Axial Seamount eruption were sampled. The samples were characterized and compared to one another and to background seawater samples to determine the influence of deep-sea eruptions on the overlying water-column. Deep-sea eruptions release reduced substrates that can fuel autotrophic processes. Therefore, deep-sea eruptions have the potential to impact deep-sea carbon cycling by shifting the microbial communities from heterotrophy-dominated to autotrophy-dominated. The samples collected for this study provide an initial survey of the shifts in microbial communities.