In situ short-term growth rates of a cold-water coral

Abstract

Cold-water corals are known to grow much slower than their tropical counterparts. However, this assumption is mainly based on laboratory measurements exposing specimens to conditions that differ from their natural environments. The cosmopolitan scleractinian Desmophyllum dianthus forms dense banks below 18 m in northern Patagonia, Chile. So as to measure in situ growth rates of this cold-water coral, specimens were collected from two sites, weighed and deployed on holders in their natural headlong orientation at the respective collecting site. Corals exhibited a calcium carbonate (CaCO3) mass increase of 5.44 ± 3.45 (mg (cm2 projected calyx area)–1 day–1) after 2 weeks, equivalent to a mass gain of 0.25 ± 0.18 s.d. % day–1. In comparison, D. dianthus specimens from the same collection sites maintained in an on-site flow-through aquarium system showed lower growth rates that were third of the in situ rates. In situ CaCO3 precipitation of D. dianthus extrapolated for 1 year (kg m2 year–1) displays the same order of magnitude as reported for massive growing tropical scleractinians, e.g. Porites sp.

Calcification is not the Achilles’ heel of cold‐water corals in an acidifying ocean

“…Cold‐water coral reefs are being exposed to reduced aragonite saturation levels, raising great concerns about the future for these spectacular deep‐sea habitats (Tittensor et al ., ; Jackson et al ., ). However, many such corals are known to be resistant to corrosive waters as they can grow below the aragonite saturation horizon and in acidified inshore waters (McCulloch et al ., ; Lunden et al ., ; Thresher et al ., ; Jantzen et al ., ,b). In the present study, three coral species calcified in aquaria at the same rates, regardless p CO 2 treatment.…”

Vertical and horizontal distribution ofDesmophyllum dianthusin Comau Fjord, Chile: a cold-water coral thriving at low pH

“…It can form pseudo-colonies with younger individuals growing on the skeleton of older ones and constitutes the framework-building CWC species in coral banks off New Zealand and Chile (Cairns & Stanley, 1982; Squires, 1965). The linear growth rate of deep-sea specimens has been estimated around 0.5–2 mm yr −1 (Adkins et al, 2004) but might be as fast as 2.2–10 mm yr −1 for Chilean corals (Jantzen et al, 2013b; McCulloch et al, 2005) . This cosmopolitan species has been reported over a wide depth range from 35 to 2460 m (Cairns, 1995).…”

Effects of low pH and feeding on calcification rates of the cold-water coralDesmophyllum dianthus

“…In the HF treatment, the additional input of energy from feeding apparently allowed corals to maintain positive skeletal accretion in aragonite undersaturated conditions. This mitigating effect of HF on the response of CWCs to environmental stressors could partially explain the extraordinarily high densities of D. dianthus found in the highly productive waters of the Chilean Patagonia fjords, despite the low pH and aragonite undersaturation that characterizes these regions, particularly in deep areas (Jantzen et al, 2013a(Jantzen et al, , 2013bFillinger & Richter, 2013). At the more extreme values of pH 7.2, however, corals in our experiment were unable to compensate for the adverse effects of acidification regardless of the feeding regime.…”

“…The basaltic walls of the fjord where corals where collected are bathed with seawater of relatively constant temperatures in the 10-12 C range and salinities of 31-33 psu with a marked and stable low-salinity surface layer, and pH values in the 7.4-8.2 range ( Fig. 1; Försterra et al, 2005;Fillinger & Richter, 2013;Jantzen et al, 2013a).…”