Development of juvenile culture techniques and testing of potential biomarkers of environmental stress in freshwater mussels (Bivalvia: Unionidae)

The freshwater mussel fauna of the Clinch River in Southwest Virginia has declined in recent decades, principally due to habitat degradation from poor land-use patterns and pollutants. A study was undertaken to determine the feasibility of using river water in a flow-through culture system to rear juvenile freshwater mussels. The culture method placed juvenile mussels, confined in small dishes, into oval troughs supplied with untreated river water. Growth rates of juveniles in the culture system using river water were almost double those in laboratory culture systems, provided that juveniles were placed in the oval troughs during June.; Several factors were investigated to assess their effect on the growth and survival of juvenile mussels in culture systems. Substrate size, silt (<120 mum) or sand (120 < x < 600 mum) had no effect (p < 0.05) on the survival and growth of juvenile mussels. Temperature had a strong influence on the growth of juveniles (p < 0.01), with higher temperatures leading to greater growth rates. Flow velocity of the overlying water affected survival rates in the oval troughs supplied with river water and one of the laboratory experiments (p < 0.05). Flow velocities in the range of 5--10 cm/sec produced the best survival rates, as high as 50% in some dishes. Juvenile densities in the range of 100/56 cm2 to 100/144 cm2 did not effect survival or growth.; Physiological parameters were measured for rainbow mussels ( Villosa iris) and Asian clams (Corbicula fluminea), held in cages at 8 locations in the Clinch River basin, to determine their usefulness as biomarkers and the suitability of the habitats. Parameters measured were: glycogen, glucose, cellulolytic enzyme activity, acetylcholinesterase (AChEase) activity, phosphofructokinase (PFK) activity, fructose-1,6-bisphoshpatase (FBPase) activity, and RNA:DNA. None of the potential biomarkers clearly indicated that a given site was unsuitable during each period tested. However, several parameters suggested that depauperate sites were poor during some season(s). The potential biomarkers that correlated best with the mussel populations at sites were cellulolytic enzyme activity and acetylcholinesterase activity.; Seasonal variability was pronounced for many of the biomarkers, rendering their use in field applications dependent on the prior determination of seasonal patterns. The seasonal variations indicated that mussels and clams do experience significant changes in energy dynamics throughout the year. (Abstract shortened by UMI.)...