Effects of atrazine and its two major derivatives on the photosynthetic physiology and carbon sequestration potential of a marine diatom

Abstract

As one of the most commonly used and frequently detected herbicides in the coastal seawater, the ecotoxicity of atrazine to phytoplankton has been well demonstrated. However, little attention has been paid to the ecotoxicity of its two major hydrolysates (desisopropylatrazine (DIA) and desethylatrazine (DEA)), which are also widely distributed in natural seawater. Here we present a comprehensive analysis of the photosynthetic physiology and chromophoric dissolved organic matter (CDOM) characteristics of the diatom Phaeodactylum tricornutum Pt-1 (CCMP 2561) under atrazine, DIA and DEA stress, respectively. The results showed that both atrazine and the two derivatives had significant negative effects on the concentration of chlorophyll a, maximum quantum efficiency (Fv/Fm) and relative electron transport rates (rETR) of P. tricornutum Pt-1. Furthermore, the CDOM pattern released by P. tricornutum Pt-1 cells also changed significantly after 7-day exposure. Compared with the control group, the fluorescence intensity (3D-EEM spectra) of protein-like components was obviously lower, while that of the humic acid-like components was higher. The findings of this study indicate that the ecotoxicity of atrazine might have been underestimated in previous investigations: both atrazine and its two major derivatives are not only phototoxic to microalgae but also influence the carbon sequestration potential in the coastal seawater.