Original paper

Influence of unionid mussels (Mollusca: Unionidae) on sediment stability: an artifi cial stream study

Zimmerman, Gregory F.; de Szalay, Ferenc A.


Few studies have tested how unionid mussels affect benthic substrates in streams. We tested effects of burrowing by live mussels on sediment stability in an artifi cial stream facility. We added 25 live mucket (Actinonaias ligamentina) and 25 live kidneyshell (Ptychobranchus fasciolaris) mussels in 0.5 m2 cells (100 mussels/m2) and used adjacent cells without mussels as a control. Sediment cohesion (sediment shear strength and compression) was measured before and every 1-2 weeks after mussels were added to the cells. Sediment erosion was measured on Weeks 1 and 4 during high flow events created by increasing flow rates to 15 cm/s for 2.75 h. Streambed sediments were destabilized when mussels were burrowing, but sediments were stabilized when mussels were sessile. Unionid mussels decreased shear strength in Week 1 as they repositioned themselves in the cells. However by Week 4, shear strength was 24 % higher and compression was 31 % higher in cells with embedded mussels than in control treatments. Mussel presence had no detectable effect on amount or grain size of sediments that were eroded during high flow events. These results suggest that physical characteristics of the streambed can be altered by high density mussel beds, which may impact benthic biotic communities.


actinonaiasbenthicbiostabilizersecosystem engineerserosioninvertebratesptychobranchus