Growth rate and age determination of bamboo corals from the northeastern Pacific Ocean using refined 210Pb dating

Abstract

Bamboo corals from Davidson Seamount and from the Gulf of Alaska were aged using a refined 210 Pb dating technique. The goal was to determine growth rates and age for several bamboo corals with higher precision. Radiometric results for 2 Davidson Seamount corals (Keratoisis sp.) converged on a radial growth rate of ~0.055 mm yr -1 . One colony was aged at 98 9 yr, with an average axial growth rate of ~0.7 cm yr -1 . The age of a large colony was >145 yr with an estimated axial growth rate of 0.14 to 0.28 cm yr -1 . Inconsistent rates may indicate nonlinear axial growth. A Keratoisis sp. specimen from the Gulf of Alaska was aged at 116 29 yr from a radial growth rate of ~0.056 mm yr -1 , which led to an average axial growth rate of ~1.0 cm yr -1 . An Isidella tentaculum colony was aged at 53 10 yr and grew most rapidly with a radial growth rate of ~0.10 mm yr -1 and an average axial growth rate of ~1.4 cm yr -1 ; however, the 210 Pb decay pattern may have provided evidence for either a hiatus in radial growth or environmental changes in 210 Pb. Our findings of slow growth and long life compared favorably with other bamboo coral studies and provided age estimates with greater precision. The high longevity of bamboo coral is an indication that recovery from disturbance or removal may take decades to a century. These age data provide a basis for a defensible position on the protection of bamboo coral and essential information for describing other life history characteristics.