Effects of temperature and temperature acclimation on survival of zebra mussels (Dreissena polymorpha) and Asian clams (Corbicula fluminea) under extreme hypoxia

Abstract

Following acclimation to 5°, 15° or 25°C for 14 days, samples of 30 Dreissena polymorpha (zebra mussels) and Corbicula fluminea (Asian clams) were held in either aerated (control) or extremely hypoxic N2 gassed water (PO2 < 3% of full air saturation). Mortality was negligible in all aerated controls. Mean hypoxia tolerance in D. polymorpha ranged from 3–4 days at 25°C to 38–42 days at 5°C. Hypoxia tolerance time of zebra mussels increased significantly with declining test temperature (P < 0.001) and increasing acclimation temperature (P < 0.001). Larger zebra mussels were more tolerant than smaller individuals. Asian clams were 2–7 times more tolerant of hypoxia than zebra mussels, surviving a mean of 11.8 and 35.1 days at 25°C and 15°C, respectively, and without mortality for 84 days at 5°C, and were not influenced by temperature acclimation. At 25°C, larger specimens of Asian clams were less tolerant of hypoxia than smaller individuals. Both species are amongst the least hypoxia tolerant freshwater bivalve molluscs, reflecting their prevalence in well-oxygenated shallow water habitats. Prolonged exposure to extreme hypoxia may provide an efficacious control strategy, particularly for D. polymorpha