Metabolome of Cadmium Stressed Gracilaria caudata (Rhodophyta)

This is the authors' abstract. We don't add key points for this paper.

We report here the effects of cadmium on the metabolome of the macroalga Gracilaria caudata. The IC50 of 3 mg/L (12 µM) was obtained after 48 hrs exposure and induced lower photosynthesis efficiency. Threshold concentrations determined by the Brazilian Environmental Council (CONAMA) in marine waters (0.04 mg/L) and effluent discharge (0.2 mg/L) were also tested, and the latter changed photosynthetic efficiency similarly to IC50. A total of 43 metabolites were identified, including monosaccharides, carboxylic acids, and amino acids. By an unsupervised PCA, we identified significative alterations in the metabolome by the IC50. An OPLS-DA analysis showed that Cd2+ exposure caused the variation of 20 metabolites, mainly glyoxylate-related, ascorbate, floridoside and proline. Five metabolic pathways altered by Cd2+ showed an accumulation of amino acids, carbon metabolism intermediates and antioxidant responses to Cd2+. We recommend a review of the toxicity parameters and methods that guide environmental policies on cadmium levels in Brazilian marine waters.