Extreme longevity in proteinaceous deep-sea corals

Abstract

Deep-sea corals are found on hard substrates on seamounts and continental margins worldwide at depths of 300 to approximately 3,000 m. Deep-sea coral communities are hotspots of deep ocean biomass and biodiversity, providing critical habitat for fish and invertebrates. Newly applied radiocarbon age dates from the deep water proteinaceous corals Gerardia sp. and Leiopathes sp. show that radial growth rates are as low as 4 to 35 mum year(-1) and that individual colony longevities are on the order of thousands of years. The longest-lived Gerardia sp. and Leiopathes sp. specimens were 2,742 years and 4,265 years, respectively. The management and conservation of deep-sea coral communities is challenged by their commercial harvest for the jewelry trade and damage caused by deep-water fishing practices. In light of their unusual longevity, a better understanding of deep-sea coral ecology and their interrelationships with associated benthic communities is needed to inform coherent international conservation strategies for these important deep-sea habitat-forming species.

Fig. 1.

Carbon and nitrogen isotopic composition of outermost living polyp tissue (solid symbols) of Gerardia (10 specimens) from the Lanikai DSC bed (closed circles), Cross Seamount (closed diamonds), and Leiopathes (2 specimens) from the Lanikai and Makapuu DSC beds (open squares). Error bars reflect the SD of 3 repeat analyses. The average δ¹³C (http://hahana.soest.hawaii.edu/hot/hot-dogs/) (9, 10) and δ¹⁵N (11) of Hawai'ian POM (closed square) at 150 m at Station ALOHA is also shown. δ¹³C error bars reflect the SD of monthly cruise measurements from March 2000 to December 2007, and the δ¹⁵N error bars reflect the SD of annual particulate export flux from 1991 to 2000 (11).

Fig. 2.

Gerardia sp. ¹⁴C results. (A) Radiocarbon values of samples collected by microtome over the outermost 3 mm from a radial cross-section transect (solid symbols) and tissue (stars) from a pruned branch of a living Gerardia sp. The Gerardia¹⁴C profile is indistinguishable from surface-water Δ¹⁴C history derived from a Porites coral (drilled in 1990) from the west side of the Big Island, HI (inset), and a discrete water sample collected at NEHLA, Keahole Point (Kona HI) in 2005. Center age is 315 calendar years (585 ± 30 ¹⁴C years). Error bars are 1 SD. (B) Radial growth rate (μm year⁻¹) determined on 17 individuals. The average radial growth rate is 36 ± 20 μm year⁻¹ (1 SD, n = 17).

Fig. 3.

Leiopathes ¹⁴C results. Radiocarbon values of samples collected by microtome over the outermost 0.9 mm of a radial cross-section (solid symbols) and tissue (stars) from the stalk of a living Leiopathes. Two outer-most flakes (solid symbols) and tissue (stars) are indistinguishable from the expected surface-water Δ¹⁴C based on the extrapolation of the Porites coral Δ¹⁴C record (inset, citation). The center age is 4,200 ± 70 calendar years B.P. (4,105 ± 40 ¹⁴C years). Error bars are 1 SD.

Fig. 4.

Life spans of Gerardia sp. and Leiopathes during the Holocene. Longevity estimates (age-range) as a function of calendar age (Cal year B.P.) for Gerardia sp. (gray) and Leiopathes (black). The average life span of the Gerardia sp. specimens is 970 years and ranges from ≈300 years to ≈2,700 years. Overlapping specimens in the same manner as tree ring studies will allow continuous records going back ≈5,000 years.

Fig. 5.

Radiocarbon radial transect of specimen BC-RD97–05 (5) showing a faster radial growth rate of 13 μm year⁻¹ over the initial 400 years (inner-most 5.1 mm) compared to the much slower growth rate of 4 μm year⁻¹ over the last 1,960 years (outer most 7.7 mm). The age of the center of the basal attachment structure of specimen (Lan04-Leio1), some ≈15 cm below the cross-sectional disk on the stalk is 4,265 ± 44 years (4,150 ± 35 ¹⁴C years), within the error of the age established for the center of the stalk discussed in the main text (4,200 ± 70 years).[Reproduced with permission from ref. (Copyright 2006, Inter-Research Science).]