CDOM Sources and Photobleaching Control Quantum Yields for Oceanic DMS Photolysis

• Published in: Environmental Science & Technology
• Main Authors: Galí, Martí, Kieber, David J., Romera-Castillo, Cristina, Kinsey, Joanna D., Devred, Emmanuel, Pérez, Gonzalo L., Westby, George R., Marrasé, Cèlia, Babin, Marcel, Levasseur, Maurice, Duarte, Carlos M., Agusti, Susana, Simó, Rafel
• Other Authors: Biological and Environmental Sciences and Engineering (BESE) Division, Marine Science Program, Red Sea Research Center (RSRC), Takuvik Joint International Laboratory (Université Laval - CNRS), Biology Department, Université Laval , 1045 Avenue de la Médecine, G1 V 0A6 Québec, Quebec, Canada., Department of Chemistry, College of Environmental Science and Forestry, State University of New York , 1 Forestry Drive, Syracuse, New York 13210, United States., Department of Limnology and Bio-Oceanography, Center of Ecology, University of Vienna , 1090 Vienna, Austria., Department of Marine, Earth and Atmospheric Sciences, North Carolina State University , 2800 Faucette Drive, Raleigh, North Carolina 27695, United States., Fisheries and Oceans Canada, Bedford Institute of Oceanography , Dartmouth, NS B2Y 4A2, Canada., Instituto INIBIOMA (CRUB Comahue, CONICET), Quintral 1250, 8400 S.C. de Bariloche, Rio Negro, Argentina., Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC) , Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalonia Spain.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Chemical Society (ACS) 2016
• Subjects: Southern Ocean
• Online Access: http://hdl.handle.net/10754/622757; https://doi.org/10.1021/acs.est.6b04278

Photolysis is a major removal pathway for the biogenic gas dimethylsulfide (DMS) in the surface ocean. Here we tested the hypothesis that apparent quantum yields (AQY) for DMS photolysis varied according to the quantity and quality of its photosensitizers, chiefly chromophoric dissolved organic matter (CDOM) and nitrate. AQY compiled from the literature and unpublished studies ranged across 3 orders of magnitude at the 330 nm reference wavelength. The smallest AQY(330) were observed in coastal waters receiving major riverine inputs of terrestrial CDOM (0.06-0.5 m3 (mol quanta)-1). In open-ocean waters, AQY(330) generally ranged between 1 and 10 m3 (mol quanta)-1. The largest AQY(330), up to 34 m3 (mol quanta)-1), were seen in the Southern Ocean potentially associated with upwelling. Despite the large AQY variability, daily photolysis rate constants at the sea surface spanned a smaller range (0.04-3.7 d-1), mainly because of the inverse relationship between CDOM absorption and AQY. Comparison of AQY(330) with CDOM spectral signatures suggests there is an interplay between CDOM origin (terrestrial versus marine) and photobleaching that controls variations in AQYs, with a secondary role for nitrate. Our results can be used for regional or large-scale assessment of DMS photolysis rates in future studies. We thank the NASA Ocean Biology Distributed Active Archive Center (OB.DAAC) for access to SeaWiFS datasets, Maxime Benoît-Gagné for assistance with radiative transfer computations, and three anonymous reviewers for their constructive comments that helped improve the manuscript. Funding was provided by the (former) Spanish Ministry of Science and Innovation through projects ATOS (POL2006-00550/CTM), SUMMER (CTM2008-03309/MAR) and Malaspina (CSD2008-00077) to RS, and through the National Science Foundation to DJK (ANT-0944686, OCE-0961831). MG acknowledges the receipt of a Beatriu de Pinós postdoctoral fellowship funded by the Generalitat de Catalunya. This is a contribution of the CERC in Remote Sensing of Canada’s ...