One of the main factors affecting the distribution and abundance of Dreissena is suitable substrate for attachment (Zhadin 1946, Mordukhai-Boltovskoi 1960, Lyakhnovich et al. 1994, Karatayev et al. 1998). In most lakes, rock and sometimes sand can be the most suitable substrates for zebra mussel attachment. However, in shallow parts of large lakes and reservoirs, even on suitable substrates, particularly sands, zebra mussels can be limited by water motion (Lyakhnovich et al. 1994, MacIsaac 1996).
Sediments with shell fragments, silty sand, and submerged portions of macrophytes are also suitable substrates for Dreissena (reviewed in Karatayev et al. 1998). Zebra mussels can be extremely abundant on submerged macrophytes. The longevity of macrophyte stems or fronds is usually shorter than the life span of zebra mussels. When macrophyte stems die back, Dreissena fall to the bottom and usually die, especially when the lake bottom under the macrophytes is covered by mud with little oxygenation. Therefore, zebra mussels on macrophytes are usually much younger than those on other substrates.
The poorest substrate for zebra mussels is silt (Zhadin 1946, Draulans and Wouters 1988, Lyakhnovich et al. 1994, Karatayev and Burlakova 1995a). However, Dreissena can live on silty sediments containing plant fragments, wood, shells, and stones. Zebra mussels use the hard fragments for initial attachment and subsequently attach to each other, forming druses (Mordukhai-Boltovskoi 1960, Lyakhnovich et al. 1994).
Similar results have been found in North America. Although Dreissena has been reported to colonize areas dominated by silt in the Laurentian Great Lakes (Hunter and Bailey 1992, Dermott and Munawar 1993), Hunter and Bailey (1992) found that Dreissena colonized soft substrates in Lake St. Clair by lateral extension of druses which originated from attachment to small pieces of hard substrate, usually live unionids, unionid shells, or clusters of zebra mussels.
The invasion of the zebra mussel has affected the habitats of soft sand or silty communities in the following ways:
Berkman et al. (1998) provide further information on zebra mussel colonization of soft sediment.