Suspended solid concentration reduces feeding in freshwater mussels

Area of Science:

• Aquatic Ecology
• Environmental Toxicology
• Bivalve Biology

Background:

• Total suspended solids (TSS) are a common aquatic pollutant impacting filter-feeding organisms.
• Freshwater mussels (unionids) are ecologically important but sensitive to environmental changes.
• Previous research suggests TSS interferes with bivalve feeding processes.

Purpose of the Study:

• To investigate the effect of varying total suspended solids (TSS) concentrations on the clearance rates (CR) of four freshwater mussel species.
• To determine if TSS concentration thresholds exist for reduced feeding efficiency in juvenile and adult mussels.
• To compare species-specific and life-stage-specific sensitivities to TSS.

Main Methods:

• Mussel clearance rates (CR) were measured across a range of TSS concentrations (up to 15mgL⁻¹ for juveniles, 100mgL⁻¹ for adults).
• Experiments were conducted using laboratory-transformed juveniles and adult specimens of Lampsilis fasciola, L. siliquoidea, Ligumia nasuta, and Villosa iris.
• CR were assessed in controlled aquatic environments with aeration or swirling to simulate natural conditions.

Main Results:

• One-week-old juvenile mussels showed increased CR with rising TSS, attributed to developmental feeding strategies.
• Older juveniles (2-4 weeks) and adult mussels exhibited a monotonic decrease in CR as TSS concentration increased.
• A significant CR threshold was observed in adult mussels at TSS concentrations ≥8mgL⁻¹, with L. fasciola showing the largest decline (46%) and V. iris the smallest (21%).

Conclusions:

• Total suspended solids (TSS) demonstrably reduce suspension feeding rates in freshwater unionids across different life stages.
• Juvenile mussels exhibit differing sensitivities to TSS compared to adults, with feeding reduction being five times greater in juveniles.
• Species-specific responses to TSS are influenced by riverine conditions, highlighting the need for targeted TSS management to ensure the survival of freshwater mussels.