Below-ground processes control the success of an invasive seaweed

1. Whilst the successful establishment and spread of invasive species can be determined by above ground processes, results are often equivocal. Emergent research, mostly from terrestrial ecosystems, demonstrates that below-ground processes (nutrient cycling, chemical properties) under microbial control can mediate interactions between native and invasive plants. Because microbes can control similar sediment properties in marine ecosystem that influence plant fitness, we argue that below-ground properties should also exert strong control interactions between native and invasive marine macrophytes. 2. We coupled surveys of microbial communities and chemistry of sediments collected from an invasive alga (Caulerpa cylindracea), a native competitor (the seagrass Posidonia oceanica) and unvegetated sediments with a large field experiment, in which we manipulated the presence/absence of the canopies of both species to determine the effects of above- and below-ground processes on the success ...