LAUSR

Abstract Photosystem II (PSII) herbicides are widely used and commonly detected in coastal environments and seagrass beds are often exposed to these herbicides. While acute inhibition of seagrass photosynthesis by PSII herbicides has been shown, there are few reports on the potential impacts of herbicide exposures on sexual reproduction and on metabolism. Seagrass Zostera marina L., which were in the process of sexual reproduction, were exposed to elevated atrazine concentrations (1, 3 and 10 μg l−1) for 30 days. Results showed that atrazine significantly inhibited photosynthetic efficiency (ΔF/F’m and Fv/Fm) and significant reduced levels of sugars in shoots. The decreased sugars and C:N ratio implied the long term atrazine exposure (10 μg l−1) decreased energy supply and changed carbon and nitrogen metabolism. Atrazine induced increases in γ-aminobutyric acid (GABA) and 1-aminocyclopropane carboxylic acid (ACC). GABA may be involved in C and N metabolism and in combination with ACC to participate in more complicated signal transduction processes. The effects of atrazine on eelgrass energy reserves and metabolism may lead to inhibition on plant growth. Though no significant decreased sexual reproduction effort was found, there may be potential effect of herbicide on eelgrass shoots, especially rhizome function of energy storage and thus on energy investment in flowering.