Production of tyrosine-like fluorescence and labile chromophoric dissolved organic matter (DOM) and low surface accumulation of low molecular weight-dominated DOM in a productive Antarctic sea

• Published in: Marine chemistry 2019-07, Vol.213, p.40-48
• Main Authors: Chen, Meilian, Jung, Jinyoung, Lee, Yun Kyung, Kim, Tae-Wan, Hur, Jin
• Format: Article
• Language: English
• Subjects: Amundsen sea; Chromophoric DOM production; Dissolved organic matter (DOM); Net DOC production ratio,EEM-PARAFAC; SEC-OCD
• ISSN: 0304-4203; 1872-7581
• DOI: 10.1016/j.marchem.2019.04.009

The Antarctic seas play critical roles in global carbon cycling. Yet, little is known about the dissolved organic matter (DOM) characteristics and the dynamics there. Here, we conducted an extensive study on the seawater DOM in the Amundsen Sea in the Pacific sector of the Southern Ocean. We found that low molecular weight fractions quantitatively dominated the DOM composition at the surface of the highly productive Amundsen Sea Polynya with the relative abundance reaching up to ~89%. Moreover, CDOM and tyrosine-like fluorescence generation were observed, with the average values of~2.4–2.6 m−1 (a254) and ~0.3 RU, respectively. While there is a net positive accumulation of dissolved organic carbon (DOC) at the ocean's surface, the net accumulation was negative for the chromophoric DOM (CDOM), which suggests a labile nature for the freshly produced CDOM. The estimated net DOC production ratio was only ~9 ± 6%, which was less than the global level (~17%). This finding signified a low surface accumulation of DOM in the austral summer, which is potentially explained by its nonlimiting nutrients, photo- and/or bio-labile nature of produced DOM, and long water residence time. [Display omitted] •Dynamics of DOM is extensively explored in a highly productive Antarctic sea.•The CDOM freshly produced by algae is labile in nature.•Low molecular weight DOM and tyrosine-like component are massively produced.•DOM accumulation at surface is very low despite its high primary productivity.