Effects of organic pollutants on oceanic photosynthetic function mediated by Prochlorococcus

Abstract

Prochlorococcus is the smallest and most abundant photosynthetic organism known on Earth and a major contributor of ocenic primary production. This cianobacterium is ubiquist in every ocean from 40°N to 40°S, from surface to 200 m depth in the water column, reaching abundances close to 10 cells/mL worldwide [1]. Its large surface/volume ratio gives it a high efficiency for light and nutrients capture. On the other hand, this characteristics also implicate a higher intake and a faster bioconcentration of pollutants, resulting in an extreme sensitivity to a variety of environmental stressors, from UV radiation to organic pollutants [2]. Therefore, Prochlorococcus constitutes an excellent sentinel organism to evaluate the dependence of the photosynthetic function to environmental variables and anthropogenic impacts in middle latitudinal oceans. Over the past century the global phytoplankton concentration has declined and changes in chlorophyll and primary production have been detected, which has been attributed to the impact of global climate change [3]. Global Change is a set of interlinked vectors, being one of the best studied the climate change. Neverthelees, the only vector whose global impact has not been quantifyed yet is chemical pollution [4]. In this way, the main objective of the present work was to measure the photosynthetic capacity of Prochlorococcus in Atlantic, Indian and Pacific oceans during the Malaspina circumnavigation, and study its relationship with the concentrations of diverse organic pollutants. This study was performed within a framework of more than 300 biological, physical and chemical variables, using both field sample collection and experiments on board with wild communities