Sublethal effects of biochar on earthworm digestive enzymes and oxidative stress

JUAN MANUEL RÍOS; JUAN CARLOS SANCHEZ-HERNANDEZ; XIMENA ANDRADE; MAXIMILIANO ATTADEMO

Madrid

Congreso; 11º CONGRESO IBÉRICO Y 8º IBEROAMERICANO DE CONTAMINACIÓN Y TOXICOLOGÍA AMBIENTAL; 2018

CICTA

Biochar is a solid carbonaceous material generated by pyrolysis of biomass, which has demonstrated to provide multiple environmental services. Beside to be an efficient way of carbon storage, biochar promotes soil fertility and plant growth. Moreover, biochar is an excellent physical support to immobilize toxic metals and organic pollutants, as well as contribute to the degradation of organic pollutants by stimulating soil microorganisms. However, adverse side-effects of biochar on soil fauna has received little attention. With the scope of increase the knowledlement on the potential toxicity of biochar on earthworms, two complementary experiments were performed with the anecic earthworm Lumbricus terrestris and biochar elaborated from spent coffee grounds (SCGs). The first trial assessed the avoidance response of earthworms by a standardized behaviour test (avoidance behaviour test, ISO 17512-1:2008) that implied the amendment of soil with 0, 1, 2.5 and 5% biochar (w/w dry mass). Percentage of earthworms that avoided the biochar-amended soils were quantified after 48 h of incubation. A second trial explored the responses of selected biomarkers of oxidative stress and digestive enzymes in L. terrestris after 7 and 30 d of incubation in soils amended with 0, 1 and 5% biochar. The main results were: 1) biochar had a significant impact in the avoidance behaviour of earthworms, the highest dose being the most repellent to earthworms; 2) biochar was not lethal to earthworms under the experimental conditions of our microcosm study; 3) no significant responses were found in the activity of glutathione-dependent enzymes, but a slight increase of the total antioxidant capacity was observed in the earthworms incubated with biochar; 4) there was a general increase of phosphatase, -glucosidase, esterase and lipase activities in both the gastrointestinal tissue and luminal content of earthworms exposed for 30d to biochar-amended soils. These results suggest that SCG-derived biochar was not lethal to L. terrestris, and doses below 5% w/w dry mass could be suitable for soil quality promotion without significant adverse effects on earthworms.