HR: 0800h
AN: B31D-0618    [Abstracts]
TI: The Impact of Seawater Saturation State on Early Skeletal Development in Larval Corals: Insights into Scleractinian Biomineralization
AU: * Cohen, A L
EM: acohen@whoi.edu
AF: Woods Hole Oceanographic Institution, 266 Woods Hole Road Department of Geology and Geophysics, Woods Hole, MA 02543, United States
AU: McCorkle, D C
EM: dmcCorkle@whoi.edu
AF: Woods Hole Oceanographic Institution, 266 Woods Hole Road Department of Geology and Geophysics, Woods Hole, MA 02543, United States
AU: de Putron, S
EM: Samantha.dePutron@bios.edu
AF: Bermuda Institute of Ocean Sciences, Ferry Reach, St Georges, GE 01, Bermuda
AB: Understanding the response of coral calcification to changes in seawater saturation state (ocean acidification) could provide important insights into the fundamental processes of scleractinian biomineralization. In particular, larval calcification, which involves initiation of skeletogenesis by a previously non-calcifying planktonic planula, offers a unique opportunity to examine the role and limitations of biological control over an essentially physicochemical process. Larvae of the brooding Atlantic coral Favia fragum were settled in unmodified seawater onto clay tiles within 12h of spawning, and placed into non-through flow 30 L aquaria prior to initiation of calcification. Seawater chemistry was pre-adjusted via HCl addition and continuous bubbling with laboratory air, yielding four aragonite saturation states: Omega(aragonite) = 3.71 (unmodified), 2.4, 1.04, and 0.22. The aquaria were held at 25 °C on a 12h/12h light/dark cycle, and sets of tiles harvested at 1, 5 and 8 days post-spawning. Accretion of aragonite (confirmed by Raman spectroscopy) in all treatments indicates that the settled larvae were able to elevate the saturation state of aquarium seawater sequestered within their calcifying space. However, external aqueous carbonate chemistry had a striking effect on larval mortality, on the nature and timing of basal plate formation, on skeletal growth rates (based on the length and cross-sectional area of septa), and on the structure and organization of aragonite crystals within the septa (imaged using SEM). Larval survival rates at the two lower saturation states was only 40% of that in the control and Omega = 2.35 treatments, and skeletal growth decreased by 30 % (relative to the control) in seawater with saturation state comparable to that predicted for the mid-latitude surface ocean by 2100 AD. SEM imaging of the larval skeletons revealed significant differences in the morphology of aragonite crystals accreted under different conditions. In stark contrast to the fine, closed, densely packed spherulitic bundles accreted in the control system, larvae in the lower Omega treatments produced a disorganized conglomerate of large, highly faceted crystals, consistent with slow growth under low saturation state conditions. Our results suggest that the coral calcification response to changes in seawater saturation state is linked to a physiological limitation on the organism's ability to elevate the saturation state of seawater within the calcifying space. Further, our data indicate that ocean acidification due to fossil fuel CO2 emissions will likely have a strong negative effect on the recruitment and early skeletal development of larval corals over the next several decades.
DE: 0419 Biomineralization
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 3600 MINERALOGY AND PETROLOGY
DE: 4220 Coral reef systems (4916)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting