Research Technical Report

Age and growth of three bamboo coral species from the Northeastern Pacific Ocean

Andrews, A.H., R.P. Stone, C.C. Lundstrom, and A.P. De Vogelaere (December 2008)

Poster Presentation, 4th International Symposium on Deep-Sea Corals, Wellington New Zealand, December 1-5, 2008.

ABSTRACT

Bamboo corals (Family: Isididae, Subfamily: Keratoisidinae) are common deep-water inhabitants of continental slopes and seamounts of the Northeastern Pacific Ocean. They are extremely fragile, relatively large, and have a patchy distribution; three attributes that make them particularly vulnerable to disturbance from fishing gear. The goal of this study was to determine the age and growth of bamboo corals from two regions of the Northeastern Pacific with the intention that recovery times from disturbance could be estimated. Age and growth was determined using lead- 210 dating for colonies collected from Davidson Seamount off California and the Gulf of Alaska. Radiometric results for both of the Davidson Seamount corals (Keratoisis sp. D group) converged on a radial growth rate of approximately 0.055 mm yr-1. For the smaller of the two colonies (~70 cm tall), the age was 98 ± 3 years with an average axial growth rate of approximately 0.7 cm yr-1. A minimum age of 145 years (upper limit of 450 years) was determined for the largest colony; an irregular shape and height precluded use of the full colony to calculate an axial growth rate, but based on one major branch length the axial growth rate was lower than expected and ranged between 0.09 and 0.24 cm yr-1. Differences in the axial growth rates between the two colonies may indicate nonlinear growth with increasing colony height. From the Gulf of Alaska, a Keratoisis sp. (B group) colony (120 cm tall) was aged at 116 ± 13 years with an average axial growth rate of 1.03 cm yr-1 (0.93-1.16 cm yr-1, 2SE). The radial growth rate was similar to the Davidson Seamount Keratoisis sp. (D group) at 0.056 mm yr-1. An Isidella n. sp. colony (72 cm tall) was aged at 53 ± 4 years. Of the corals studied here, this colony grew most rapidly with a radial growth rate of 0.099 mm yr-1 and an average axial growth rate of 1.32 cm yr-1 (1.23- 1.46 cm yr-1, 2SE). Our findings of slow growth rates and high longevity compare favorably to those determined for bamboo corals from other regions of the Pacific Ocean and highlight the need for immediate conservation measures to protect these important members of deep-sea ecosystems.

Suggested Citation

Andrews, A.H., Stone, R.P., Lundstrom, C.C., DeVogelaere, A.P. 2008. Age and growth of three bamboo coral species from the Northeastern Pacific Ocean. Poster Presentation, 4th International Symposium on Deep-Sea Corals, Wellington New Zealand, December 1-5, 2008.