Sewage sludge toxicity assessment using earthworm Eisenia fetida: can biochemical and histopathological analysis provide fast and accurate insight?

Sewage sludge (SS) is a complex organic by-product of wastewater treatment plants. Deposition of large amounts of SS can increase the risk of soil contamination. Therefore, there is an increasing need for fast and accurate assessment of SS toxic potential. Toxic effects of SS were tested on earthworm Eisenia fetida tissue, at the subcellular and biochemical level. Earthworms were exposed to depot sludge (DS) concentration ratio of 30 or 70 %, to undiluted and to 100 and 10 times diluted active sludge (AS). The exposure to DS lasted for 24/48 h (acute exposure), 96 h (semi-acute exposure) and 7/14/28 days (sub-chronic exposure) and 48 h for AS. Toxic effects were tested by the measurements of multixenobiotic resistance mechanism (MXR) activity and lipid peroxidation levels, as well as the observation of morphological alterations and behavioural changes. Biochemical markers confirmed the presence of MXR inhibitors in the tested AS and DS and highlighted the presence of SS-induced oxidative stress. The MXR inhibition and thiobarbituric acid reactive substance (TBARS) concentration in the whole earthworm's body were higher after the exposition to lower concentration of the DS. Furthermore, histopathological changes revealed damage to earthworm body wall tissue layers as well as to the epithelial and chloragogen cells in the typhlosole region. These changes were proportional to SS concentration in tested soils and to exposure duration. Obtained results may contribute to the understanding of SS-induced toxic effects on terrestrial invertebrates exposed through soil contact and to identify defence mechanisms of earthworms.

Blood chemistry and histological properties of wild and cultured sea bass (Dicentrarchus labrax) in the North Adriatic Sea.

Histological and biochemical procedures were employed to study liver histomorphology and plasma levels of aspartate aminotransferases (AST), alanine aminotransferase (ALT), triglyceride (TRIG), cholesterol (CHOL), glucose (GLU) and total protein (TP) in cultured (CSB) and wild sea bass (WSB) (Dicentrarchus labrax) from the northern part of the Adriatic Sea. Histopathological changes in liver included varying degrees of infiltration and lipid degeneration of hepatocytes in examined cultured fish. No significant differences between median AST values of CSB (44 IU) and WSB (45 IU) were observed. Values of ALT were <5 IU in both groups. TRIG, CHOL, GLU and TP levels were higher in CSB (2.08 mmol/L, 3.67 mmol/L, 10.66 mmol/L and 49 g/L, respectively) than in WSB (0.67 mmol/L, 2.74 mmol/L, 3.68 mmol/L and 36 g/L, respectively). The study showed differences between plasma biochemical parameters and liver histomorphology of CSB and WSB. This can be explained as a consequence of different diets (artificial in contrast to natural foods), which influence energy metabolism.