Shallow moving structures promote marine invader dominance.
Increases in urban development have resulted in severe habitat modification in many estuaries throughout the world. Many estuaries are now dominated by artificial structures, which might have many effects on native species. The provision of these additional hard surfaces provides added free space for sessile marine invertebrates (e.g., mussels, barnacles, lace corals, etc.) and recent research suggests invasive species may be better able to exploit these artificial structures (particularly pontoons) than are native species. The impacts of these invasive invertebrates on native species are generally unknown, but some can smother and out-compete natives.
This study examined the recruitment of marine invertebrates to small settlement panels attached to fixed or moving experimental structures at depths of 0.5 m or 2 m. The panels were left in the water for three months before being collected and all species growing on them were identified and counted.
Invasive species as a group were most abundant on shallow, moving plates (essentially floating surfaces), and were more abundant than native invertebrates on all treatments. Some individual invasive species, however, did respond differently to movement and depth. For example an invasive marine worm occupied more space on fixed than moving structures. It is likely that many invasive species are adapted to living on floating surfaces in high water-flow environments because they have been transported around the globe on the hulls of ships. Thus, the continuing addition of shallow, moving structures such as pontoons to our estuaries is likely to enhance the dominance of invasive species in these environments. Ongoing research is investigating the potential impacts these species might have on native invertebrates living on rocky reefs.