Miranda Montenegro, Mario Luis and Mustaffa, Nur Ili Hamizah and Robinson, Tiera-Brandy and Stolle, Christian and Ribas-Ribas, Mariana and Wurl, Oliver and Zielinski, Oliver (2018) Influence of solar radiation on biogeochemical parameters and fluorescent dissolved organic matter (FDOM) in the sea surface microlayer of the southern coastal North Sea. Elementa: Science of the Anthropocene, 6 (1). p. 15. ISSN 2325-1026

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Abstract

We investigated the influence of solar radiation on biogeochemical parameters of the sea surface microlayer (SML), including the spectroscopic composition of FDOM, and biotic and abiotic parameters. We calculated the humification index, biological index, and recently produced material index from the ultraviolet spectra to characterize the dynamic environment of the SML. The humification index ranged from 4 to 14 in the SML and 14 to 22 in underlying water (ULW). An inverse relation for this index as a function of solar radiation was observed, indicating photochemical decomposition of complex molecules present in fluorescent dissolved organic matter (FDOM). The biological index (along Leg 2) ranged from 1.0 to 2.0 for the SML and 1.0 to 1.5 for ULW. The index for recently produced material ranged from 0.25 to 0.8 for the SML and 0.5 to 1.0 for ULW. The FDOM enrichment process of the SML was influenced by the photochemical decomposition of highly aromatic-like fluorophores, as indicated by the calculated indices. Fluorescence intensity increased for humic C peaks (>0.5 Raman units) in the North Sea samples and for humic M peaks (>1.0 Raman units) for Jade Bay. Spearman analysis for FDOM enrichment in the SML as a function of PAR (for Leg 2) showed a weak positive correlation (Rho = 0.676, n = 11, p = 0.022). Abundance of small photoautotrophic cells (Rho = 0.782, n = 11, p = 0.045) and of bacteria (Rho = 0.746, n = 11, p = 0.0082) also showed a positive correlation as a function of PAR. Overall, we found positive trends between the intensity of available light and the response of the constituents within the SML, highlighting the role of the surface microlayer as a distinctive habitat characterized by unique photochemical processes.

Item Type:	Article
Additional Information:	Publiziert mit Hilfe des DFG-geförderten Open Access-Publikationsfonds der Carl von Ossietzky Universität Oldenburg.
Uncontrolled Keywords:	SML; Solar radiation; fluorescent dissolved organic matter; BIX; HIX; Enrichment factor
Subjects:	Science and mathematics > Chemistry Science and mathematics > Earth sciences and geology Science and mathematics > Life sciences, biology
Divisions:	Faculty of Mathematics and Science > Institute for Chemistry and Biology of the Marine Environment (ICBM)
Date Deposited:	11 Sep 2019 07:22
Last Modified:	24 Jan 2020 10:42
URI:	https://oops.uni-oldenburg.de/id/eprint/4131
URN:	urn:nbn:de:gbv:715-oops-42120
DOI:	doi:10.1525/elementa.278
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