Nitrate-Induced Toxicity and Potential Attenuation of Behavioural and Stress Biomarkers in Tubifex tubifex

摘要

Nitrogen is one of the major components of all biological systems. In the aquatic ecosystem, it is available in the inorganic forms of ammonia, nitrite, and nitrate. Climate change due to global warming and anthropogenic misconduct increases the amount of nitrogen in rivers and other aquatic ecosystems. That revolve nitrate pollution is a serious global concern. The benthic macroinvertebrates, which are necessary for maintaining the structure and functioning of the aquatic ecosystem, are the primary victims of this pollution. The determination of nitrate toxicity on the benthic oligochaete worm Tubifex tubifex is primarily detailed in this article along with enzymatic, toxicokinetic and statistical evidences. The acute toxicity of nitrate for 96 h of exposure on the worm is reported to be 664.38 mg/l. The nitrate-treated worms during acute exposure displayed certain behavioural abnormalities such as erratic movements, wrinkling tendency, profuse mucus secretion, and lower clumping tendency. The effect of sublethal concentration (10 and 20 of 96 h LC50) of nitrate on differential expression of oxidative stress enzymes was also investigated over a period of 14 days exposure. The nitrate exposed worms showed an increased level of MDA that signifies lipid deterioration. The integrated biomarker response (IBR) assessment revealed that the combined effect of stress biomarkers increased gradually with increasing exposure time and nitrate concentration. The maximum integrated biomarker response was observed at 14(th) day of T2 concentration (20 of 96 h LC50 value) of nitrate. Species sensitivity distributions (SSD) illustrated the toxic impact of nitrate on T. tubifex in the aquatic ecosystem with respect to other aquatic invertebrate species. The toxicokinetic-toxicodynamic studies through GUTS modelling applied to predict the LC50 value for a longer period of nitrate exposure on the worm are reported to be 403.6 mg/l. It is concluded that nitrate exposure detrimentally affects the survival rate and alter oxidative stress biomarkers in T. tubifex. Evaluation of nitrate toxicity in T. tubifex will be useful to determine the acceptable concentration of nitrate for aquatic organisms. GRAPHICS .