An association between freshwater sponges and the zebra mussel in a southern Lake Michigan harbor

Freshwater sponges (Spongillidae) were evaluated in a southern Lake Michigan harbor to determine whether preferences existed for attachment sites. Sponges were enumerated that were growing epifaunally on zebra mussel shells and directly on the associated iron revetment wall surrounding a portion of the harbor. Adult colonies of sponges were non-randomly distributed and found in close association with zebra mussel shells. The mechanism for this biotic interaction is unknown. However, this is another example of benthic restructuring of native fauna precipitated by the non-indigenous zebra mussel.