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This study investigates the extreme longevity, gro This study investigates the extreme longevity, growth rates, and ecological significance of two proteinaceous deep-sea coral species, Gerardia sp. and Leiopathes sp., found in deep waters around Hawai’i and other global locations. Using radiocarbon dating and stable isotope analyses, the research reveals that these corals exhibit remarkably slow growth and lifespans extending thousands of years, far surpassing previous estimates. These findings have profound implications for deep-sea coral ecology, conservation, and fisheries management.
Key Insights
Deep-sea corals Gerardia sp. and Leiopathes sp. grow exceptionally slowly, with radial growth rates ranging from 4 to 85 µm per year.
Individual colonies can live for hundreds to several thousand years, with the oldest Gerardia specimen aged at 2,742 years and the oldest Leiopathes specimen at 4,265 years, making Leiopathes the oldest known skeletal accreting marine organism.
The corals feed primarily on freshly exported particulate organic matter (POM) from surface waters, as indicated by stable carbon (δ13C) and nitrogen (δ15N) isotope data.
Radiocarbon analyses confirm the skeletal carbon originates from modern surface-water carbon sources, indicating minimal incorporation of old, “14C-free” carbon into the skeleton.
These slow growth rates and extreme longevities imply that deep-sea coral habitats are vulnerable to damage and slow to recover, challenging assumptions about their renewability.
Deep-sea coral communities are critical habitat hotspots for various fish and invertebrates, contributing to deep-sea biodiversity and ecosystem complexity.
Human impacts such as commercial harvesting for jewelry, deep-water fishing, and bottom trawling pose significant threats to these fragile ecosystems.
The study emphasizes the need for international, ecosystem-based conservation strategies and suggests current fisheries management frameworks may underestimate the vulnerability of these corals.
Background and Context
Deep-sea corals colonize hard substrates on seamounts and continental margins at depths of 300 to 3,000 meters worldwide. These corals form complex habitats that support high biodiversity and serve as important ecological refuges and feeding grounds for various marine species, including commercially valuable fish and endangered marine mammals like the Hawaiian monk seal.
Prior estimates of deep-sea coral longevity were inconsistent, ranging from decades (based on amino acid racemization and growth-band counts) to over a thousand years (based on radiocarbon dating). This study clarifies these discrepancies by:
Applying high-resolution radiocarbon dating to both living and subfossil coral specimens.
Using stable isotope analysis to identify coral carbon sources and trophic levels.
Comparing radiocarbon signatures in coral tissues and skeletons with surface-water carbon histories.
Methods Overview
Samples of Gerardia and Leiopathes were collected from several deep-sea coral beds around Hawai’i (Makapuu, Lanikai, Keahole Point, and Cross Seamount) using the NOAA/Hawaiian Undersea Research Laboratory’s Pisces submersibles.
Coral skeletons were sectioned radially, and microtome slicing was used to obtain thin layers (~100 µm) for precise radiocarbon analysis.
Radiocarbon (14C) ages were calibrated to calendar years using established reservoir age corrections.
Stable isotope analyses (δ13C and δ15N) were conducted on dried polyp tissues to determine trophic level and carbon sources.
Growth rates were calculated from radiocarbon profiles and bomb-pulse 14C signatures (the increase in atmospheric 14C from nuclear testing in the 1950s-60s).
Detailed Findings
Growth Rates and Longevity
Species Radial Growth Rate (µm/year) Maximum Individual Longevity (years)
Gerardia sp. Average 36 ± 20 (range 11-85) Up to 2,742
Leiopathes sp. Approximately 5 Up to 4,265
Gerardia growth rates vary widely but average around 36 µm/year.
Leiopathes grows more slowly (~5 µm/year) but lives longer.
Some Leiopathes specimens show faster initial growth (~13 µm/year) that slows with age.
Carbon Sources and Trophic Ecology
δ13C values for living polyp tissues of both species average around –19.3‰ (Gerardia) and –19.7‰ (Leiopathes), consistent with marine particulate organic carbon.
δ15N values are enriched relative to surface POM, averaging 8.3‰ (Gerardia) and 9.3‰ (Leiopathes), indicating they are low-order consumers, feeding primarily on freshly exported surface-derived POM.
Proteinaceous skeleton δ13C is slightly enriched (~3‰) compared to tissues, likely due to lipid exclusion in skeletal formation.
Radiocarbon profiles of coral skeletons closely match surface-water 14C histories, including bomb-pulse signals, confirming rapid transport of surface carbon to depth and minimal incorporation of old sedimentary carbon.
Ecological and Conservation Implications
The extreme longevity and slow growth of these corals imply that population recovery from physical disturbance (e.g., fishing gear, harvesting) takes centuries to millennia.
Deep-sea coral beds function as keystone habitats, enhancing biodiversity and providing essential fish habitat, including for endangered species.
Physical disturbances like bottom trawling, line entanglement, and coral harvesting for jewelry threaten these corals and their associated communities.
Existing fisheries management may overestimate sustainable harvest limits, especially for Gerardia, due to underestimating longevity and growth rates.
The United States Magnuson-Stevens Fishery Conservation and Management Act (MSA) recognizes deep-sea corals as “essential fish habitat,” but enforcement and protection vary.
The study advocates for international, ecosystem-based management approaches that consider both surface ocean changes (e.g., climate change, ocean acidification) and deep-sea impacts.
The longevity data suggest that damage to these corals should not be considered temporary on human timescales, underscoring the need for precautionary management.
Timeline Table: Key Chronological Events (Related to Coral Growth and Study)
Event/Measurement Description
~4,265 years ago (calibrated 14C age) Oldest Leiopathes specimen basal attachment age
~2,742 years ago (calibrated 14C age) Oldest Gerardia specimen age
1957 Reference year for bomb-pulse 14C calibration in radiocarbon dating
2004 Sample collection year from Hawai’ian deep-sea coral beds
2006/2007 Magnuson-Stevens Act reauthorization increasing protection for deep-sea coral habitats
Present (2008-2009) Publication and review of this study
Quantitative Data Summary: Isotopic Composition of Coral Tissues and POM
Parameter Gerardia sp. (n=10) Leiopathes sp. (n=2) Hawaiian POM at 150 m (Station ALOHA)
δ13C (‰) –19.3 ± 0.8 –19.7 ± 0.3 –21 ± 1
δ15N (‰) 8.3 ± 0.3 9.3 ± 0.6 2 to 4 (range)
C:N Ratio 3.3 ± 0.3 5.1 ± 0.1 Not specified
Core Concepts
Radiocarbon dating (14C) enables precise age determination of coral skeletons by comparing measured 14C levels to known atmospheric and oceanic 14C histories.
Bomb-pulse 14C is a distinct marker from nuclear testing that provides a temporal reference point for recent growth.
Stable isotope ratios (δ13C and δ15N) provide insights into trophic ecology and carbon sources.
Radial growth rates measure the increase in coral skeleton thickness per year, reflecting growth speed.
Longevity estimates derive from radiocarbon age calibrations of inner and outer skeletal layers.
Deep-sea coral beds are ecosystem engineers, forming complex habitats critical for marine biodiversity.
Conservation challenges arise due to very slow growth and extreme longevity, combined with anthropogenic threats.
Conclusions
Gerardia and Leiopathes deep-sea corals exhibit unprecedented longevity, with lifespans of up to 2,700 and 4,200 years, respectively.
Their slow radial growth rates and feeding on freshly exported surface POM indicate a close ecological coupling between surface ocean productivity and deep-sea benthic communities.
The longevity and slow recovery rates imply that damage to deep-sea coral beds is effectively irreversible on human timescales, demanding precautionary and stringent management.
These species serve as critical habitat-formers in the deep sea, supporting diverse marine life and contributing to ecosystem complexity.
There is an urgent need for international, ecosystem-based conservation strategies to protect these unique and vulnerable communities from fishing impacts, harvesting, and environmental changes.
Current fisheries management frameworks may inadequately reflect the nonrenewable nature of these coral populations and require revision based on these findings.
Keywords
Deep-sea corals
Gerardia sp.
Leiopathes sp.
Radiocarbon dating
Longevity
Radial growth rate
Stable isotopes (δ13C, δ15N)
Particulate organic matter (POM)
Deep-sea biodiversity
Conservation
Fisheries management
Magnuson-Stevens Act
Bomb-pulse 14C
Proteinaceous skeleton
References to Note (from source)
Radiocarbon dating and longevity studies (Roark et al., 2006; Druffel et al., 1995)
Stable isotope methodology and trophic level assessment (DeNiro & Epstein, 1981; Rau, 1982)
Fisheries and habitat conservation frameworks (Magnuson-Stevens Act, 2006/2007 reauthorization)
Ecological significance of deep-sea corals (Freiwald et al., 2004; Parrish et al., 2002)
This comprehensive analysis underscores the exceptional longevity and ecological importance of proteinaceous deep-sea corals, highlighting the need for improved management and protection policies given their vulnerability and slow recovery potential.
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