Optical properties of marine DOM in the NW Iberian coastal upwelling system

International DOM Spectroscopy Workshop, 19-21 May 2010, Granada, SpainCoastal upwelling areas are highly dynamic marine environments where the production, consumption, transformation and export of dissolved organic matter (DOM) are magnified. The coloured fraction of DOM (CDOM) represent 36 ± 20% of the bulk DOM in the large coastal embayments of the NW Iberian upwelling system, where 2/3 of the CDOM exported to the adjacent ocean are autochthonous materials produced in situ and 1/3 are allochthonous materials introduced by continental runoff. Both in situ and in vitro approaches have been applied in this coastal upwelling system to objectively separate and quantify the effect of water mass mixing from biotic (microbial) and abiotic (photochemical) processes on the absorbance and induced fluorescence spectra of CDOM. The potential of protein- and humic-like fluorophores to trace the dynamics of the labile and refractory CDOM pools and the microbial transformation of the former into the latter have also been examinedN

Optical properties of marine high molecular weight dissolved organic matter and their transformation by heterotrophic activity in the oceans

The First Meeting of SCOR WG 134, Microbial Carbon Pump in the Ocean, October 27-30, 2009, Xiamen, ChinaThe transformation of labile LMW–DOM into refractory HMW–DOM by the marine microbial food web is a key component of the recently defined “microbial carbon pump” that occurs in ocean margins as well as in epi– , meso– and 20 bathypelagic open ocean waters. Recent methodological advances have enabled to trace this transformation on basis of the optical properties of DOM. The coloured fraction of DOM (CDOM) absorbs light at UV–visible wavelengths. The CDOM fraction that can emit blue fluorescence when irradiated with UV light is called fluorescent CDOM (FDOM). The production of coloured HMW–DOM by the marine microbial food web can be followed either in vitro or in situ. In the in vitro methods, the time course of the CDOM absorption spectra and the FDOM excitation–emission matrices are monitored for time intervals that depend on the microbial activity of the incubated waters. The in situ methods require the separation of the physical (advection, mixing) from the biogeochemical sources of variability of the spatial and/or temporal distributions of CDOM and FDOM applying a water masses mixing model (W3M). Finally, the HMW–DOM from different marine ecosystems can be isolated by flow–cross ultra filtration and their optical properties determined to trace their origin and biogeochemical transformations. Furthermore, these materials can be re–dissolved, inoculated with natural microbial assemblages, and incubated to study additional transformations. Examples will be presented on the results obtained (i) following the optical properties of DOM in short and long term in vitro experiments; (ii) applying W3Ms to time–series and oceanic sections of CDOM and FDOM, and (iii) comparing the optical properties of ultra filtered DOM from contrasting marine environmentsN

ESICM LIVES 2016: part two : Milan, Italy. 1-5 October 2016.

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