Speaker

Marlene Wall (GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany)

Abstract

Cold-water corals (CWCs) are often found in deep waters, which makes their physiological assessment in situ challenging. However, in a few locations worldwide, CWCs emerge from the deep and form viable populations in shallow waters, such as in Comau Fjord, Patagonia, Chile. We therefore used the Comau Fjord and the rather ‘extreme’ conditions in shallow waters as our natural laboratory to gain insights into the performance and physiological trade-offs of CWCs. We examined a range of coral traits (growth, energy reserves, fatty acid composition) as well as the microbial community associated with CWCs in the context of the prevailing local environmental conditions. We used the stony coral Desmophyllum dianthus as a model species, which exhibited distinct phenotypes both at depth and along a natural gradient of environmental conditions in shallow waters. The high environmental variability in shallow waters resulted in a suppressed CWC phenotype compared to its counterparts in deeper waters, but provided us with an opportunity to understand the interactions between performance (in terms of growth) and other physiological traits of corals, such as energy content or their microbial associations. All of the coral holobiont traits examined provided important insights into coral functioning and trade-offs and pointed to additional environmental factors that may be responsible for the distinct phenotypes. Deep-water emergence exposes CWCs to local anthropogenic activities such as intensive salmon farming in the regions. This allowed us to explore its potential imprint in the corals microbial associations and to gain a more holistic understanding of CWCs holobiont function.