Primary productivity controls on opportunistic bivalves during Early Jurassic oceanic deoxygenation
Primary productivity controls on opportunistic bivalves during Early Jurassic oceanic deoxygenation
复制标题
DOI：
10.1130/g34819.1
复制
发表时间：
2013-11-01
期刊：
影响因子：
5.8
通讯作者：
Coe, Angela L.
中科院分区：
文献类型：
--
作者：
Caswell, Bryony A.;Coe, Angela L.
托阿尔纪（早侏罗世）海洋缺氧事件（OAE）期间发生的严重古气候变化的特点是三角洲 C-13 负偏移、风化加剧、海水温度升高、海洋脱氧和大规模灭绝。我们提供了来自英国约克郡 Toarcian OAE 的两种主要表层双壳类物种的丰度和大小数据（n 约为 36,000）。我们将生物数据与环境变化的地球化学指标进行统计关联，并表明我们的结果与当今受缺氧影响的生态系统的变化相当。在Toarcian OAE sensu stricto之前的氧气水平下降期间，Bositra radiata占主导地位，并且当δC-13（org）下降时，壳尺寸增加了一倍，表明与初级生产力有关。小型 Pseudomytiloides dubius 在托阿尔纪 OAE 期间占主导地位，并且丰度变化剧烈，表明它是高度机会主义的。 P. dubius 壳尺寸与 Mo 浓度 [Mo] 密切相关；这表明尺寸和通过[Mo]限制固定N-2的初级生产力之间存在关系。导致壳尺寸较小的第二个因素是氧气含量较低。 Toarcian OAE多样性增加后，P. dubius数量减少，贝壳尺寸增加一倍，表明双壳类种群受资源限制较小，条件更加有利。体型频率分布表明，这两种托阿克物种都具有寿命短、繁殖时间短、招募率高和幼体死亡率高的特点。机会主义的 Mulinia Lateris 是当今 P. dubius 的类似物。这项研究为脱氧对海洋生态系统的长期影响（包括今天观察到的影响）提供了案例研究。
Severe paleoclimatic change during the Toarcian (Early Jurassic) oceanic anoxic event (OAE) was characterized by a negative delta C-13 excursion, increased weathering, higher seawater temperatures, oceanic deoxygenation, and mass extinction. We present abundance and size data (n approximate to 36,000) for the two dominant epifaunal bivalve species from the Toarcian OAE, Yorkshire, UK. We statistically correlate the biotic data with geochemical proxies for environmental change and show that our results are comparable with changes in present-day ecosystems affected by hypoxia. Bositra radiata dominated during declining oxygen levels immediately before the Toarcian OAE sensu stricto, and shell size doubled when delta C-13(org) was decreasing, indicating a connection with primary productivity. Small Pseudomytiloides dubius dominated during the Toarcian OAE and varied sharply in abundance, indicating that it was highly opportunistic. P. dubius shell size is strongly related to Mo concentration, [Mo]; this indicates a relationship between size and N-2-fixing primary productivity via [Mo] limitation. A secondary factor contributing to small shell size was lower oxygen levels. After the Toarcian OAE diversity increased, P. dubius was less abundant and shell size doubled, indicating that bivalve populations were less limited by resources and conditions were more favorable. Size frequency distributions show that both Toarcian species had short life spans, rapid generation times, high recruitment, and high juvenile mortality. The opportunist Mulinia lateralis is a present-day analog for P. dubius. This research provides a case study for the long-term impacts of deoxygenation upon marine ecosystems, including that being observed today.