The sensitivity of cold-water corals to environmental change

The classical way in assessing the sensitivity of a marine species – e.g., the most common framework-forming cold-water coral Lophelia pertusa – to environmental conditions in the ocean is based on the comparison of its spatial distribution in relation to a set of environmental (usually some physico-chemical) conditions. Sometimes, this approach is further supported by some laboratory studies addressing the limits of L. pertusa’s sensitivity to specific parameters. Based on a set of environmental parameters this species is assumed to be sensitive to, the related overlapping suitable ranges can then be used for habitat suitability mapping, i.e. to map areas which appear to be habitable to L. pertusa. The fact that often the identified habitable regions are inhabited only locally by L. pertusa demonstrate our still very limited understanding of its sensitivity to environmental settings. Especially as this sensitivity also might be controlled by a combination of multiple stressors without any single stressor reaching a critical level. Furthermore, as the oceans are still largely unexplored, new discoveries constantly change our understanding of L. pertusa’s sensitivity to individual environmental forcing factors.

In times of changing ocean conditions, the future fate of cold-water coral ecosystems depends on e.g. L. pertusa’s sensitivity to such changes. However, without understanding the present-day distribution of this species in the ocean, any projections on their future fate become difficult. An alternative approach to identify parameters critical for their development is a look into the past when cold-water coral ecosystems reacted to such environmental changes in many sites with their local extinction or a new establishment. Comparing such events in the past with reconstructions of the contemporary environmental setting allows identifying – at least in a qualitative sense – the critical controlling environmental factors triggering either their establishment or their demise. Such an approach can focus our investigations and modelling studies to those environmental parameters with a documented power to drastically effect cold-water coral ecosystems – in the one or the other way.