气候变化领域集成服务门户(CCPortal): An assessment of reef coral calcification over the late Cenozoic

CCPortal

DOI	10.1016/j.earscirev.2020.103154
	An assessment of reef coral calcification over the late Cenozoic
	Brachert T.C.; Corrège T.; Reuter M.; Wrozyna C.; Londeix L.; Spreter P.; Perrin C.
发表日期	2020
ISSN	0012-8712
卷号	204
英文摘要	Shallow-water reef-building corals have an extensive geological record and many aspects of their evolution, biodiversity, and biogeography are known in great details. In contrast, the adaptive potential and risk of extinction of coral reefs in response to excessive warming and ocean acidification remains largely undocumented. It is well established that anthropogenic CO2 emissions cause global warming and ocean acidification (lowering of pH), which increasingly impede the biomineralization process in many marine calcareous biota. The “light-enhanced” calcification machinery of the shallow-water reef corals is particularly threatened by this development through the combined effect of a lowering of the supersaturation of seawater with CaCO3 (aragonite) and an expulsion of the symbiotic zooxanthellae (bleaching). The bleaching is of prime importance, because it interrupts the supply of DIC and metabolites required for pH upregulation within the calcification fluid. The degree of calcification in scleractinian reef corals may therefore represent a suitable tracer to assess the state of the ocean carbonate system and the photosynthetic performance of the zooxanthellae during past episodes of natural environmental change. This study presents the first comprehensive set of calcification data from reef corals covering the early Miocene to early Pleistocene interval (20.8 to 1.2 million years, Ma). Various screening procedures ensured that the studied coral skeletons are pristine and suited to yield meaningful stable isotope data (δ18O, δ13C) and calcification records. δ18O and δ13C values document growth environments consistent with current tropical and subtropical settings. To assess fossil calcification rates, we use a reference dataset of recent corals from the Indo-Pacific (Porites) and an independent validation dataset from the Western Atlantic-Caribbean (Orbicella). Almost all fossil corals document very low annual rates of upward growth (extension rate) relative to present, and lower skeletal bulk density than predicted by established modern relationships. To allow for a quantitative assessment of coral calcification performance, we use a new approach that we term the calcification anomaly. It is insensitive to sea-surface temperature and well-suited for comparative assessments of calcification performance between reef sites and over time. Based on this approach, the majority of fossil corals in our dataset displays hypo-calcification, while a few show optimal calcification and none display hyper-calcification. Compared to present-day growth conditions, the fossil calcification data show that (1) skeletogenesis responded in a fully compatible way to known environmental stresses (e.g. turbid water, elevated salinity, eutrophy), and that (2) the calcification performance within the reef window (i.e. oligotrophic clear-water settings) remained below that of modern z-corals. Since fossil coral δ13C values are compatible with those of modern reef corals, we infer that the light-enhanced calcification system of symbiotic scleractinian corals was fully established by the beginning of the Neogene and that lower-than-present calcification performance was the likely response to a chronically low pH and/or low carbonate saturation state of the global ocean. If so, the present-day saturation state appears to be rather an exception than the norm and probably not a suitable starting point for predicting future calcification trends. In addition, using trends from the geological past for predicting future developments does not consider anthropogenic side-effects such as eutrophication and pollution. © 2020 The Authors
英文关键词	calcification rate; geological past; Neogene; ocean acidification; Quaternary; reef coral
语种	英语
scopus关键词	assessment method; calcification; Cenozoic; coral bleaching; coral reef; fossil; geological record; ocean acidification; paleoceanography; paleoclimate; paleoenvironment; Quaternary; shallow water; Atlantic Ocean; Atlantic Ocean (West); Caribbean Sea; Anthozoa; Porites; Scleractinia
来源期刊	EARTH-SCIENCE REVIEWS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/209641
作者单位	Universität Leipzig, Institut für Geophysik und Geologie, Talstrasse 35, Leipzig, 04103, Germany; Université de Bordeaux / UMR 'EPOC' CNRS 5805, Allée Geoffroy St-Hilaire, CS 50023, Pessac cedex, 33615, France; Département Homme et Environnement, Muséum National d'Histoire Naturelle, HNHP UMR7194, Centre Européen de Recherche en Préhistoire, Avenue Léon-Jean Grégory, Tautavel, 66720, France
推荐引用方式 GB/T 7714	Brachert T.C.,Corrège T.,Reuter M.,et al. An assessment of reef coral calcification over the late Cenozoic[J],2020,204.
APA	Brachert T.C..,Corrège T..,Reuter M..,Wrozyna C..,Londeix L..,...&Perrin C..(2020).An assessment of reef coral calcification over the late Cenozoic.EARTH-SCIENCE REVIEWS,204.
MLA	Brachert T.C.,et al."An assessment of reef coral calcification over the late Cenozoic".EARTH-SCIENCE REVIEWS 204(2020).