Biomarker responses to sewage pollution in freshwater mussels (Diplodon chilensis) transplanted to a Patagonian river

Abstract

Field and laboratory experiments were combined to evaluate biomarker responses of Diplodon chilensis to sewage pollution. Mussels from an unpolluted area in Lacar lake (S0) were caged at a reference site (S1) and at two sites with increasing sewage pollution (S2, S3) in Pocahullo river (all in Argentina). After 1 month, gill (g) glutathione S-transferase (GST) and catalase (CAT) activities, and lipid peroxidation (TBARS) were found to be significantly elevated in S3, gGST being positively correlated with fecal bacteria (FC) concentration. Digestive gland (dg) enzyme activities were depressed and dgTBARS were increased in all transplanted mussels. After 3 mo, most variables returned to control levels in S1 mussels except for dgCAT and dgTBARS. After seven months, GST and CAT activities of S0 and S3 mussels were evaluated in the laboratory, before and after acute exposure (8 h) to high fecal bacteria concentration ([FC] in S3x 2). gGST increased in both groups, while dgGST responded only in S3 mussels. gCAT and dgCAT activities were similarly increased by acute exposure in both groups. Our results suggest that gGST and gCAT are suitable biomarkers for high FC pollution regardless of previous exposure history. In addition, we show that dgCAT is sensitive to the acute increase in FC load, both in naive and long-term exposed individuals, while dgGST becomes responsive after long-term acclimatization.

Keywords:

• Fecal coliforms
• oxidative stress
• detoxifying defenses
• short and long-term response

Acknowledgments

The authors wish to thank Leandro Castiñeira, Carla Alvarez and Fedra Granata for their kind help and Miguel Selser and Flavia Bieczynski for scuba diving. We acknowledge Dr. Martin Tresguerres and Lic. Alejandra Scotti for revising translation.

Funding

This study was supported by grants from Consejo Nacional de Investigaciones Científicas y TecnológicasPIP 0282 and Agencia Nacional de Promoción Científica y Tecnológica PICT-R 2007- 00214to CML and 1293to IR, with permission number 815 from the National Parks Administration (Argentina). We acknowledge material support from Centro de Ecología Aplicada del Neuquén, Cooperativa de Agua y Saneamiento de San Martín de los Andes and Estación de Biología Acuática, San Martín de los Andes.