Patterns in the deep sea: On the interaction between cold-water corals and their environment

Our largest ecosystem, covering more than two-thirds of our planet, is hidden from sight beneath the upper 200m of the ocean: the deep sea. Despite the limited food availability, the deep sea is dotted with extensive, highly productive cold-water coral (CWC) reefs that create habitat for many species. Sadly, due to global change, suitable CWC habitat is expected to decrease by more than 50% this century.
Not considered in these predications, however, is that CWCs are ecosystem engineers: they change the environmental conditions to suite their own preferences. The coral skeleton attenuates currents and promotes turbulence which enhances the capture of food particles by the corals. We found that, due to these engineering effects, CWC reefs form regular patterns on the seafloor which possibly allows them to adjust gradually to climate change.
When reef growth and sediment infill are sufficient, CWC reefs can even form mounds of several hundred meters high. We showed that the interaction between these mounds and waterflow increases the vertical food supply towards the reefs, but might also restrict CWCs from ‘moving’ to deeper waters to avoid the adverse effects of global warming.
The internal tides might provide a way out of this predicament. These waves of several hundred meters high in the deep sea are beneficial for CWC reefs and we found a global relation between the depth of internal-tide generation and CWCs. With climate change, internal tides will likely be generated shallower on continental slopes, possibly creating new suitable habitat for CWCs.