HP3 Freshwater Bivalve Ecotoxicology
Ballroom G, Level 4
2:10 PM - 5:30 PM, Thursday, 13 November 2003
Chair: Cox, Stephen ,
Co-chair: Van Hassel, John ,
(588) The Influence of Asian Clam (Corbicula fluminea) Die-offs on Sediment Quality: Implications for Native Unionid Mussels.
Cooper, N1, Bidwell, J1, Bruenderman, S2, 1 Oklahoma State University, Stillwater, OK, USA2 Missouri Department of Conservation, Columbia, MO, USA
ABSTRACT- The objective of this study was to evaluate the extent to which water quality impacts from die-offs of the Asian clam (Corbicula fluminea) could pose a risk to infaunal organisms such as juvenile unionid mussels. A series of laboratory experiments were conducted to characterize levels of total and unionized ammonia produced in sediment pore and overlying waters as clam tissues decayed. Test chambers containing a gravel substrate or sediment from the Little Black River, Missouri, were prepared by placing varying numbers of dead clams in the substrate and monitoring ammonia, dissolved oxygen levels and pH for 4 to 10 days. Sediment pore waters consistently had higher ammonia concentrations than overlying water, with levels of ammonia positively correlated with temperature and density of clams involved in the die-off. Unionized ammonia concentrations in pore water ranged from 0.022 to 1.05 mg N-NH3/l across all experiments, with many values similar to or exceeding levels reported to be acutely toxic to some species of unionid. While water flow reduced concentrations of ammonia in overlying water, the effects on porewater was dependant on sediment grain size (larger grain size, greater removal of ammonia). In 10-day tests, the ammonia levels often continued to increase through day 7, indicating that the capacity for juvenile mussels to avoid toxicity through behavioral avoidance may be exceeded. Overall, the results indicate that ammonia production associated with Asian clam die-offs could pose a risk to unionid mussels, particularly during warm, low-flow summer months.
Key words: Corbicula fluminea, Ammonia, Unionid, Pore water