**4.2 Benthic influences**

The presence of live mussels can increase in sediment organic matter, which has been shown to positively influence abundance and diversity of other benthic invertebrates and phytoplankton (Spooner and Vaughn, 2006). Benthic invertebrate diversity can also be increased by the presence of mussel shells (Allen and Vaughn, 2011). Other benthic organisms use the shell as habitat and flow refuges, and in large numbers, the presence of mussel shells can increase landscape-level species diversity and abundance (Gutierrez et al., 2003). The influence of Unionids on benthic communities is so great that Aldridge et al., (2006) found that the abundance of freshwater mussels successfully predicted invertebrate abundance and richness in seven lowland rivers in the UK. Mussels also act as environmental engineers, bioturbating the sediment as they move both vertically and horizontally (Allen and Vaughn, 2011). This activity can increase the depth of oxygen penetration in the sediment, homogenize sediment particle size (McCall et al., 1995), and affect the flux rates of solutes between the sediment and water column (Matisoff et al., 1985).
