Foundation species, or ecosystem engineers, are organisms that physically modify the environment in ways that benefit other species and enhance diversity. For instance, reef-building corals and canopy-forming kelps form structurally complex habitats that support highly diverse communities of marine organisms. Urban stressors that are particularly detrimental to some foundation species (including corals and kelps) are:
- High sedimentation rates
- High nutrient loads
- Extensive cover by algal turfs (competitors)