Effects of sewage pollution on growth and oxidative balance in the freshwater clam Diplodon chilensis

SABATINI, S., ROCCHETTA, I., LUQUET, C. , GUIDO, M., RÍOS DE MOLINA, M

Montevideo, Uruguay

Congreso; VIII Congreso SETAC LA; 2007

SETAC LA

We studied the effects of the sewage discharge in the Lake Lacar, Patagonia, Argentina on the freshwater clam Diplodon chilensis. We sampled clams and water from a polluted site near the city of San Martin de los Andes (SMA), and from a control site. Coliform bacteria were counted and clams were measured and weighed. In homogenates of digestive glands we measured total and reduced glutathione, antioxidant enzymes activities, and lipid and protein oxidation. The mean numbers of total coliform bacteria were 17 MPN / 100 ml (control), and > 24000 MPN / 100 ml (SMA). SMA clams were larger than controls. The digestive gland mass to shell length ratio (DGM/SL) was 0.23 ± 0.003 in SMA and 0.13 ± 0.001 in the controls (p < 0.0001, n = 30). No changes were observed in total lipid and protein contents, neither in superoxide dismutase (SOD) activity. Total and reduced glutathione (GSH) and also Glutathione S-transferase (GST) activity were significantly higher in SMA, while oxidized glutathione (GSSG) was similar in both groups. Lipid peroxidation, reflected by Malondialdehyde (MDA), was increased at SMA, indicating oxidative damage. However, there was no difference in protein oxidation. Living in an area highly populated with coliform bacteria (sewage discharge of SMA), exposes these clams to the effects of bacterial lipopolysaccharides (LPS), which are know to produce oxidative stress.  SMA clams seem to rely on increased GSH levels and GST activity to restore the oxidative balance.