Document Type

Article

Publication Date

2015

DOI

10.1016/j.marchem.2015.06.016

Publication Title

Marine Chemistry

Volume

177

Pages

205-217

Abstract

This study investigates optical and high-resolution molecular signatures and photochemical degradation of DOM from the Barra Bonita Reservoir (BB-DOM), a tropical eutrophic lake, as well as from its dominant phytoplankton species, the cyanobacteria Microcystis aeruginosa (Microcystis-DOM). Consistent with a predominantly autotrophic source, BB-DOM and Microcystis-DOM exhibited high protein-like fluorescence and contained a large number of aliphatics. Microcystis-DOM was enriched in peptide-like formulae, while BB-DOM had higher chromophoric and fluorescent DOM(CDOM and FDOM) and was enriched in moderately unsaturated formulae, indicating additions of terrigenous DOM and/or in situ processing of autochthonous material in the lake. Consistent with its higher CDOM content, BB-DOM was more photoreactive than Microcystis-DOM. For both types of DOM, photodegradation resulted in loss of CDOM, FDOM, moderately unsaturated structures, high O/C and low H/C formulae, and preservation of aliphatics. The majority of photoproducts of 0.5 d irradiation were subsequently removed by day 7, and photoproducts represented a minor fraction of the photo-irradiated DOM. For BB-DOM, molecular formula photolability increased with increasing aromaticity index values, while for Microcystis-DOM, molecular formula photolability increased with molecular mass. Photodegradation increased the proportion of molecular formulae containing N (CHO + N) in BB-DOM, while the molecular mass and the proportion of CHO + N formulae decreased upon photo-irradiation of Microcystis-DOM. In concert, these molecular shifts due to photodegradation decreased the diversity of and increased the similarity between BB-DOM and Microcystis-DOM, suggesting the selective pressure exerted by photochemistry selects for the survival of similar compounds in both samples.

Comments

Web of Science: "Free full-text from publisher -- gold open access."

© 2015 Elsevier B.V. All rights reserved.

Original Publication Citation

Bittar, T. B., Stubbins, A., Vieira, A. A. H., & Mopper, K. (2015). Characterization and photodegradation of dissolved organic matter (DOM) from a tropical lake and its dominant primary producer, the cyanobacteria Microcystis aeruginosa. Marine Chemistry, 177, 205-217. doi:10.1016/j.marchem.2015.06.016

ORCID

/0000-0001-8089-6019 (Mopper)

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