Marine infrastructure supports abundant, diverse fish assemblages at the expense of beta diversity

Abstract

Anthropogenic structures are increasingly common in natural environments and present novel habitats for resident organisms. Marine breakwalls are similar to natural reefs in that they also provide habitat for diverse assemblages of mobile animals. However, it is unclear if fish assemblages on these artificial structures differ from those on neighbouring natural reefs in ecologically important ways. In this study, we compared fish assemblages at breakwalls and natural reefs in three different regions along 530 km of the East Australian coast. We found that fish assemblages associated with breakwalls were more diverse than those associated with natural reefs in two of the three regions studied. The functional niches being filled were similar at both habitats, with the exception of a higher abundance of piscivores at some breakwalls. However, β diversity tended low on the homogenous breakwalls compared to more heterogeneous natural reefs and was significantly lower at one region. The habitat heterogeneity model suggests that structural alterations to the layout of infrastructure could contribute to improving their ecological effects, potentially increasing β diversity.