Elevated B‐vitamins within a temperate estuary: Strong spatiotemporal dynamics and links to microbial plankton communities

Abstract

B‐vitamins are organic cofactors required by prokaryotic and eukaryotic planktonic cells; their availability impacts aquatic microbial communities and associated biogeochemistry. Despite their ecological importance, B‐vitamin dynamics and their relationships to plankton composition in estuaries are unclear, limiting our understanding of estuary biology in general as well as how B‐vitamins are distributed in marine systems. Here, we simultaneously quantified multiple B‐vitamins and their vitamers (vitamin related compounds, e.g., precursors for de novo synthesis) in particulate and dissolved phases. Alongside, we characterized the prokaryotic and eukaryotic microbial communities across freshwater to polyhaline zones of the Neuse River Estuary (NRE), North Carolina, USA from summer to fall. We found notable autochthonous B‐vitamin production in the estuary, and the mid‐estuary emerged as a zone of increased levels of B‐vitamins fueled by algal growth. B‐vitamin and vitamer concentrations were highly dynamic on short time scales (weeks) and we identified two specific dynamic modes. Moderate concentration changes likely driven by production/consumption and sporadic rapid concentration peaks presumably driven by shifts in plankton community composition. We identified vitamin B ₁ , B ₁₂ , psB ₁₂ (pseudocobalamin), and B ₃ as key explanatory variables for change in prokaryotic and eukaryotic NRE plankton, revealing B‐vitamins as important compounds for resolving variability of plankton communities in estuaries. Our study provides insights into the dynamic concentrations of B‐vitamins and vitamers across zones of estuaries and provides new evidence of B‐vitamin influence upon plankton community composition.