Biogenic Amines as Biomarkers for the Assessment of Diesel-Contaminated Water Toxicity

This study evaluated the phytotoxicity of diesel oil (DO) using the green alga Pseudokirchneriella subcapitata and the aquatic plant Lemna minor. Toxic effects were assessed in 7-day Algaltoxkit and Lemna bioassays by measuring growth, chlorophyll fluorescence, and biogenic amine (BA) content. L. minor was less sensitive to DO in terms of growth than the alga. Toxicity thresholds (LOEC, 7 days) showed that DO concentrations above 0.11–0.12% significantly inhibited the growth and productivity of both model organisms. Chlorophyll fluorescence proved to be an early and sensitive indicator of DO toxicity. This study also provides the first characterization of BAs in P. subcapitata, identifying histamine, tyramine, putrescine, cadaverine, agmatine, spermidine, and spermine. Agmatine emerged as a common indicator of DO contamination in both species. Its content decreased in P. subcapitata (EC50 = 0.85%) but increased in L. minor (EC50 = 0.38%) under diesel exposure. The findings herein suggest that BA profiling, especially agmatine, can support early detection of hydrocarbon stress in aquatic organisms.