Recruitment preferences of non-native mussels: interaction between marine invasions and land-use changes

Abstract

Preferential patterns of settlement of marine invertebrate larvae may significantly affect the expansion of introduced populations when coupled with anthropogenic changes to available substrates in marine environments. In the near-shore marine environments of the southeastern USA the addition of hard substrates into primarily salt marsh habitats may provide necessary settlement sites for recently introduced marine invertebrates such as the Asian green mussel, Perna viridis, and the South American charru mussel, Mytella charruana. Preliminary studies in Florida suggest that M. charruana adults are predominantly found on man-made substrates, especially docks. The present study investigated whether P. viridis and M. charruana preferentially settle on substrates commonly used in manmade structures such as plexiglass, wood and rock, or on natural substrates like the shells of oyster (Crassostrea virginica), green mussels or charru mussels. Frames containing a mixture of these six substrates were deployed at two locations in Florida and retrieved after 1, 2 and 3 months. Over 1-month deployments, both species preferentially recruited to natural substrates. While this pattern was repeated on substrates in the field for 2 months in M. charruana, there were no differences in P. viridis spat density among any of the substrates in the field for 2 or 3 months. These results suggest that man-made hard substrates will likely not affect expansion of these two species by providing preferred settlement sites. Man-made substrates may still, however, provide better locations for survival.