Cold water corals exhibit CaCO3 precipitation comparable to their tropical counterparts – but only in situ

Cold water corals (CWC) are commonly known as slow growing organisms compared to their tropical congeners. This may be attributed to the low temperature they thrive in or to their lack of autotrophic symbionts. However, recent sighting of deep-sea corals, e.g. Lophelia pertusa growing on oil rigs, exhibit high growth rates. The measured growth rate naturally varies on the measure that is applied, for instance length extension versus CaCO3 precipitation. Skeletal characteristics may be different between species, for example some corals like Desmophyllum dianthus grow dense skeletons with pronounced growth in girth. Additionally few growth rates of CWC have been measured in situ and therefore true growth performance may be underestimated. Commonly growth is indirectly measured via dating techniques, estimated or determined in vivo in the laboratory. Corals isolated from their natural habitat and consequently under very different conditions may not show realistic metabolic responses. Here we show results of a study on short-term growth of Desmophyllum dianthus in situ and in an on-site flow through system. Aquaria corals exhibited growth rates of only one third compared to specimens in the field. Accordingly CWC growth may be underestimated in their growth potential when only studied in the laboratory.