Identifying the Sources and Sinks of CDOM/FDOM across the Mauritanian Shelf and Their Potential Role in the Decomposition of Superoxide (O2-).

Heller, Maija I., Wuttig, Kathrin and Croot, Peter L. (2016) Identifying the Sources and Sinks of CDOM/FDOM across the Mauritanian Shelf and Their Potential Role in the Decomposition of Superoxide (O2-). Open Access Frontiers in Marine Science, 3 (Art. Nr. 132). DOI 10.3389/fmars.2016.00132.

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Abstract

Superoxide (O−2) is a short lived reactive oxygen species (ROS) formed in seawater by photochemical or biological sources, it is important in the redox cycling of trace elements and organic matter in the ocean. The photoproduction of O−2 is now thought to involve reactions between O2 and reactive reducing (radical) intermediates formed from dissolved organic matter (DOM) via intramolecular reactions between excited singlet state donors and ground-state acceptors (Zhang et al., 2012). In seawater the main pathways identified for the decomposition of O−2 into H2O2 and O2, involve reactions with Cu, Mn, and DOM. In productive regions of the ocean, the reaction between DOM and O−2 can be a significant sink for O−2. Thus, DOM is a key component of both the formation and decomposition of O−2 and formation of H2O2. In the present work we examined the relationships between O−2 decay rates and parameters associated with chromophoric dissolved organic matter (CDOM) and fluorescent dissolved organic matter (FDOM) by using the thermal O−2 source SOTS-1. Filtered samples (0.2 μm) were run both in the presence, and absence, of the metal chelator diethylenetriaminepentaacetic acid (DTPA) to determine the contribution from DOM. Samples were collected along a transect across the continental shelf of the Mauritanian continental shelf during a period of upwelling. In this region we found that reactions with DOM, are a significant sink for O−2 in the Mauritanian Upwelling, constituting on average 58 ± 13% of the O−2 loss rates. Superoxide reactivity with organic matter showed no clear correlation with bulk CDOM or FDOM properties (as assessed by PARAFAC analysis) suggesting that future work should concentrate at the functional group level to clearly elucidate which molecular species are involved as bulk properties represent a wide spread of chemical moieties with different O−2 reactivities. Analysis of FDOM parameters indicates that many of the markers used previously for terrestrial sources of DOM and FDOM are called into question as marine sources exist. In particular recent work (Rico et al., 2013) indicates that algal species may also produce syringic, vanillic, and cinnamic acids, which had previously been ascribed solely to terrestrial vegetation.

Document Type: Article
Keywords: reactive oxygen species, parafac, colored dissolved organic matter CDOM, Atlantic Ocean, excitation emission matrix fluorescence, fluorescence dissolved organic matter(FDOM), superoxide dismutase, hydrogen peroxide
Research affiliation: OceanRep > SFB 754 > B5
OceanRep > SFB 754
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.3389/fmars.2016.00132
ISSN: 2296-7745
Projects: SFB754
Expeditions/Models/Experiments:
Date Deposited: 23 Jan 2017 09:59
Last Modified: 01 Feb 2019 15:14
URI: http://oceanrep.geomar.de/id/eprint/35845

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