Low Florida coral calcification rates in the Plio-Pleistocene
Low Florida coral calcification rates in the Plio-Pleistocene
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上更新世佛罗里达珊瑚钙化率低
DOI：
10.5194/bg-13-4513-2016
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发表时间：
2015
期刊：
影响因子：
4.9
通讯作者：
J. Lough
中科院分区：
文献类型：
--
作者：
T. Brachert;M. Reuter;S. Krüger;J. Klaus;K. Helmle;J. Lough
抽象的。在地质露头和钻孔岩心从礁框架，骨珊瑚的骨骼通常是沥滤和或多或少完全转化为亮晶方解石，因为高度多孔骨架形成的亚稳文石（碳酸钙）经历快速成岩蚀变。在改变，鬼结构的不同的年度增长带往往允许重建的年度扩展（=增长）率，但重建的钙化率所需的骨骼密度的信息总是丢失。本报告介绍了仅经历轻微成岩作用改变的礁珊瑚化石的体积密度、延伸率和钙化率。这些珊瑚来自佛罗里达台地（美国东南部）的未石化浅水碳酸盐岩，这些碳酸盐岩形成于上新世中期至更新世早期的四个间冰期海平面高峰期，时间分别为3.2、2.9、1.8和1.2 Ma。在保存方面，珊瑚骨骼显示出平滑的生长表面，骨骼内孔隙内有少量的海洋文石水泥。在骨骼结构内，通常存在沿着钙化中心的空隙，这些空隙缺乏次生骨水泥。平均伸展率为0.44 ± 0.19 cm/年（范围为0.16至0.86 cm/年），平均体积密度为0.96 ± 0.36 g cm-3（范围为0.55至1.83 g cm−3），钙化率范围为0.18至0.82 g cm−2 yr−1（平均0.38 ± 0.16 g cm−2 yr−1），相当于现代浅水礁珊瑚的50%。为了了解这些低钙化率背后的可能机制，我们将化石钙化率与来自西大西洋（WA）和印度太平洋的现代虫黄藻珊瑚（Z珊瑚）的钙化率进行了比较，并对海表温度（SST）进行了校准。在化石数据中，我们发现了一个广泛的类似关系与SST的Z珊瑚从WA，即密度增加和扩展速率随着SST的增加而降低，但在上新世更新世的一个显着较大的温度窗口。关于珊瑚生长的环境，来自化石珊瑚的稳定同位素代用数据和古代浅海群落的整体结构与混合良好的开阔海洋环境相一致，类似于今天的佛罗里达珊瑚礁区，但受间歇性上升流的影响。上升流沿着平台可以解释低速率的珊瑚礁钙化和无机胶结，但过于本地化，也占整个热带西澳地区上新世Z珊瑚的低扩展率。全球范围内的低文石饱和度对快速的冰川-间冰期CO2循环的响应也是一个潜在的因素，但上新世-更新世大气pCO 2通常被认为与现在大致相似。热应力与全球高的间冰期SST只有间歇性的上升流影响佛罗里达平台的间歇性缓和似乎是低钙化率的另一个可能的原因。从这些观察，我们建议一些目前的珊瑚礁系统受到威胁，从未来的海洋变暖。
Abstract. In geological outcrops and drill cores from reef frameworks, the skeletons of scleractinian corals are usually leached and more or less completely transformed into sparry calcite because the highly porous skeletons formed of metastable aragonite (CaCO3) undergo rapid diagenetic alteration. Upon alteration, ghost structures of the distinct annual growth bands often allow for reconstructions of annual extension ( = growth) rates, but information on skeletal density needed for reconstructions of calcification rates is invariably lost. This report presents the bulk density, extension rates and calcification rates of fossil reef corals which underwent minor diagenetic alteration only. The corals derive from unlithified shallow water carbonates of the Florida platform (south-eastern USA), which formed during four interglacial sea level highstands dated approximately 3.2, 2.9, 1.8, and 1.2 Ma in the mid-Pliocene to early Pleistocene. With regard to the preservation, the coral skeletons display smooth growth surfaces with minor volumes of marine aragonite cement within intra-skeletal porosity. Within the skeletal structures, voids are commonly present along centres of calcification which lack secondary cements. Mean extension rates were 0.44 ± 0.19 cm yr−1 (range 0.16 to 0.86 cm yr−1), mean bulk density was 0.96 ± 0.36 g cm−3 (range 0.55 to 1.83 g cm−3) and calcification rates ranged from 0.18 to 0.82 g cm−2 yr−1 (mean 0.38 ± 0.16 g cm−2 yr−1), values which are 50 % of modern shallow-water reef corals. To understand the possible mechanisms behind these low calcification rates, we compared the fossil calcification rates with those of modern zooxanthellate corals (z corals) from the Western Atlantic (WA) and Indo-Pacific calibrated against sea surface temperature (SST). In the fossil data, we found a widely analogous relationship with SST in z corals from the WA, i.e. density increases and extension rate decreases with increasing SST, but over a significantly larger temperature window during the Plio-Pleistocene. With regard to the environment of coral growth, stable isotope proxy data from the fossil corals and the overall structure of the ancient shallow marine communities are consistent with a well-mixed, open marine environment similar to the present-day Florida Reef Tract, but variably affected by intermittent upwelling. Upwelling along the platform may explain low rates of reef coral calcification and inorganic cementation, but is too localised to account also for low extension rates of Pliocene z corals throughout the tropical WA region. Low aragonite saturation on a more global scale in response to rapid glacial–interglacial CO2 cyclicity is also a potential factor, but Plio-Pleistocene atmospheric pCO2 is generally believed to have been broadly similar to the present day. Heat stress related to globally high interglacial SST only episodically moderated by intermittent upwelling affecting the Florida platform seems to be another likely reason for low calcification rates. From these observations we suggest some present coral reef systems to be endangered from future ocean warming.
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DOI：
10.1016/j.palaeo.2008.11.015
发表时间：
2009-03
期刊：
Palaeogeography, Palaeoclimatology, Palaeoecology
影响因子：
--
作者：
R. Mertz‐Kraus;T. Brachert;K. Jochum;M. Reuter;B. Stoll
通讯作者：
R. Mertz‐Kraus;T. Brachert;K. Jochum;M. Reuter;B. Stoll
上升流减轻了佛罗里达台地珊瑚礁珊瑚的上更新世热应激（美国）
影响因子：
4.9
作者：
Brachert;Krüger;Reuter;Kirkerowicz
通讯作者：
Kirkerowicz
影响因子：
2.5
作者：
Chollett, Iliana;Mumby, Peter J.;Cortes, Jorge
通讯作者：
Cortes, Jorge
佛罗里达碳酸盐台地的硬化年代学数据记录了 4200 万年间冰期古气候（上新世早期至近代）
影响因子：
3.9
作者：
Brachert;Reuter;Krüger;Lohmann;Petuch
通讯作者：
Petuch
从珊瑚霰石δ18O推断东地中海晚中新世海面盐度变化和古气候条件
影响因子：
3.9
作者：
Mertz-Kraus R;Brachert TC;Reuter M;Galer SJG;Fassoulas C;Iliopoulos
通讯作者：
Iliopoulos