REPORT Age and growth of the cold-water scleractinian Solenosmilia variabilis and its reef on SW Pacific seamounts S. J. Fallon • R. E. Thresher • J. Adkins Received: 8 May 2013 / Accepted: 21 October 2013 / Published online: 16 November 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Little is known about growth rates of deep- water reef-forming corals or the rates at which these reefs accumulate. Such information is critical for determining the resilience of the reefs to anthropogenic impacts such as trawling and climate change. We radiocarbon date live- caught and sub-fossil samples of the bioherm-forming coral Solenosmilia variabilis collected from precisely known depths and locations by means of a remotely operated vehicle on seamounts south of Tasmania, Australia. The growth rate of colonies live-caught between 958 and 1,454 m, which spans most of the depth range of the spe- cies locally, ranged from 0.84 to 1.25 mm linear extension yr -1 and tended to be higher in the deeper-caught material. Analysis of skeletal microstructure suggests annual depo- sition of growth increments near the growing tips, but not closer to the base, as the skeleton is extended and thick- ened. Dating of sub-fossil material indicates S. variabilis has been present on Tasmanian seamounts for at least the last 47,000 yrs and a reef accumulation rate of 0.27 mm yr -1 . Keywords Accumulation rate Á Annuli Á Demography Á Deep sea Á Growth rate Á Scleractinia Introduction Although scleractinian corals occur commonly and at high diversity at depths below 50 m (Cairns 2007), little is known about their ecology and demography as compared to their much better studied, more conspicuous and more easily accessed shallow-water relatives (Freiwald and Roberts 2005). Recent surveys document extensive cold- water reefs on seamount and other rocky substrates glob- ally, many of which have been or are likely to be subject to the impacts of deep-water fishing (Pitcher et al. 2007; Roberts et al. 2009). Age and growth studies carried out on a few of the deep-water taxa suggest that many are slow- growing and long-lived, usually in excess of a century (Risk et al. 2002; Andrews et al. 2002; Adkins et al. 2004; Roark et al. 2005; Sherwood and Edinger 2009), which has raised concerns about the resilience of deep-sea coral communities to adverse anthropogenic impacts (Koslow et al. 2001; Althaus et al. 2009). The bioherm-forming colonial coral, S. variabilis, is widely distributed on seamounts globally (Davies and Guinotte 2011). In the SW Pacific, it is the dominant reef- forming species that builds extensive reefal structure at a depth band of roughly 1,000–1,300 m on seamounts off New Zealand and Australia (Koslow et al. 2001; Thresher et al. in press). These reefs are relatively high in species richness, suggesting that they are important habitat for seamount biota. They are also fragile and easily damaged by near-bottom trawling (Althaus et al. 2009) and may be particularly susceptible to adverse effects of climate change in general and ocean acidification in particular (Guinotte et al. 2006). To an extent, this apparent vulner- ability depends on the growth rate of the coral and its ability to regenerate after damage and to grow into and colonize new habitat. To begin to quantify this resiliency, Communicated by Geology Editor Prof. Bernhard Riegl S. J. Fallon Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia R. E. Thresher (&) CSIRO Climate Adaptation Flagship, GPO Box 1538, Hobart, TAS 7001, Australia e-mail: Ron.Thresher@csiro.au J. Adkins California Institute of Technology, Pasadena, CA, USA 123 Coral Reefs (2014) 33:31–38 DOI 10.1007/s00338-013-1097-y