Production of chromophoric dissolved organic matter by marine phytoplankton

9 pages, 3 figures, 3 tables

Incubation experiments with axenic cultures of four common phytoplankton species of the genera Chaetoceros, Skeletonema, Prorocentrum, and Micromonas were performed to test for the production of fluorescent dissolved organic matter (FDOM) by marine phytoplankton. Our results prove that the four species exuded both fluorescent protein-like and marine humic–like materials in variable amounts, with more production by the diatoms Chaetoceros sp. and Skeletonema costatum and less by Prorocentrum minimum. Whereas the exudation of protein-like substances by healthy phytoplankton cells has been recognized, the in situ production of marine humic-like substances is still a matter of debate. Using axenic cultures, we demonstrate unequivocally that phytoplankton can directly contribute to the autochthonous production of colored humic-like substances in the ocean. Extrapolation of these findings to the field indicates that about 20% of the marine humic–like substances produced in the highly productive coastal upwelling system of the Rıa de Vigo could originate from growing phytoplankton. Therefore, the exudation of FDOM by marine phytoplankton should be considered in future studies of the dynamics of colored DOM in marine systems

This study was funded by an I3P-predoctoral fellowship to C.R.-C. from the Consejo Superior de Investigaciones Cientıficas (CSIC) within the project "Organic matter sources, microbial diversity, and coastal marine pelagic ecosystem functioning (respiration and carbon use)" (MODIVUS, CTM2005-04795/MAR). H.S. benefitted from fellowships from the Spanish Ministerio de Educación y Ciencia (SB2006-0060 and JCI-2008-2727) and the Portuguese Fundaçao para a Ciência e a Tecnologıa (FRH/BPD/34041/2006)

Peer reviewed