Abstract
Deep-sea corals have emerged as potential proxies of changing paleoceanographic properties. The utility of deep-sea corals for the purpose of interpreting paleoclimatic reconstructions is still in the discovery phase. However, long life spans, a relatively stable habitat, and unique growth geometry provide support to the growing body of research that has identified deep-sea corals as indicators of past climate and ocean properties.  Two colonies of Acanella were collected from the permanent thermocline at depths between 414 and 437 m in the Makapuu Coral Bed, Oahu, HI in 1997 by submersible. Here I present results from a pilot study of the deep-sea coral Acanella to evaluate its use as a paleoceanographic archive. Commonly referred to as “bamboo coral” due to their alternating segments of calcite and gorgonin, Acanella was radiocarbon dated using samples from the protinaceous gorgonin knuckles. Scanning electron microscope (SEM) images, stable isotope data  (δ18O and δ13C), and a radiocarbon study of this azooxanthellate, ahermatypic coral were used to conclude that the vicinity where Acanella was growing in Makapuu Coral Bed most likely experienced significant shifts in thermocline depth over the course of the coral’s lifespan. Samples were taken from the innermost and outermost growth bands of two Acanella thick sections (one from each colony studied here). These samples were corrected for a reservoir effect of 450 years and yielded an age of 270 +/- 35 years old for colony one and 22 +/- 35 for colony two. Colony one of Acanella may have recorded shifts in the thermocline near Hawaii as indicated by a 6º warming of ocean temperatures over 50 years. This warming trend was not observed in colony two, indicating that more information on growth geometry and deep-sea coral biology is needed in order to safely confirm that Acanella is consistently archiving paleoceanographic properties of the microhabitat in which the corals grow.

Hourigan Lantier, Geraldine, 2006. Evaluating the deep-sea coral Acanella from Hawaii as a paleoceanographic archive.
Unpublished MSc. thesis, State University of New York at Albany.   95 pp., + vii
University at Albany Science Library call number:  SCIENCE Oversize (*) QC 869 Z899 2006 L36

MS thesis  pdf (10.9 MB)