Method Development for a Short-Term 7-Day Toxicity Test with Unionid Mussels.

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Aquatic Toxicology

Background:

• Standard US EPA freshwater effluent testing uses fish (Pimephales promelas), cladocerans (Ceriodaphnia dubia), and algae (Raphidocelis subcapitata).
• There is a need for additional taxa in effluent testing due to the ecological importance and sensitivity of other aquatic organisms.
• Unionid mussels are proposed as suitable additional test species due to their ecological roles (sediment dwelling, filter feeding) and sensitivity to contaminants.

Purpose of the Study:

• To develop and validate a short-term (7-day) effluent toxicity test method for unionid mussels.
• To evaluate the comparative sensitivity of mussel species against standard test organisms.
• To establish optimal feeding and age parameters for a reliable mussel toxicity test.

Main Methods:

• Comparative sensitivity of two mussel species (Villosa constricta, Lampsilis siliquoidea) and standard species (P. promelas, C. dubia) to mock and field effluents.
• Optimization of feeding rates for different juvenile age groups (1-3 weeks) of L. siliquoidea.
• Validation of the mussel test method using a 7-day reference toxicant (sodium chloride) exposure and an interlaboratory study.

Main Results:

• Mussel species demonstrated equal or greater sensitivity (2-fold) to effluents compared to standard species.
• Optimal feeding rates were determined for juvenile L. siliquoidea, supporting substantial growth (30-52% length increase).
• An interlaboratory study confirmed the precision and reliability of the 7-day L. siliquoidea NaCl test, with acceptable variation (34% CV).

Conclusions:

• Unionid mussels, specifically Lampsilis siliquoidea, are highly sensitive and suitable for short-term effluent toxicity testing.
• The developed 7-day test method for L. siliquoidea is robust, reproducible, and offers valuable data alongside standard EPA test species.
• This research supports the inclusion of mussels in regulatory aquatic toxicity testing protocols.