Environmental conditions on different populations of the freshwater bivalve Diplodon chilensis (Hyriidae)

IARA ROCCHETTA

Bremerhaven

Conferencia; Alfred Wegener Institute Meeting; 2012

Alfred Wegener Institute

The effect of environmental conditions, mainly organic matter input from different origin, were analyzed in three populations of Diplodon chilensis (Hiridae, Bivalvia) from North Patagonia (Lacar lake, Argentina), in order to determine how natural and anthropogenic organic matter provided by the forest or urban discharges may influence their growth, density morphometric and metabolic parameters. These populations are exposed to different levels of natural organic matter, due different annual precipitation rates (Yuco and Nonthué sites), or to increased organic matter associated to urban discharges (San Martín de los Andes Bay, SMA site). In Nonthué, a dense neighboring forest provides higher quantities of vegetal detritus compared to Yuco, while in SMA sewage discharges supplement the natural organic matter (OM) input. Our results show that size distribution and the growth rate are affected by increased OM, independently of its natural or anthropogenic origin. The modal shell length interval for both SMA and Nonthué was two-fold higher than compared to Yuco, in agreement to the growth rate increase, but only SMA bivalves show lower maximum age and density. No individuals under 7 years old have been found in this population. Additionally, we have detected an increase in lipid peroxidation levels and defense/detoxify enzyme glutathione-S-transferase (GST) activity in SMA bivalves and changes in the lipid and fatty acid composition, respect to the other two populations. The differences in OM quality plus the evident eutrophic process taking place in SMA during last decade are reflected in their population and stress parameters. The absence of young individuals in this site suggests that juvenile mussels are unable to survive under these conditions and/or recruitment to the population is impaired.