Technical Note: On methodologies for determining the size-normalised weight of planktic foraminifera
Technical Note: On methodologies for determining the size-normalised weight of planktic foraminifera
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DOI：
10.5194/bg-7-2193-2010
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发表时间：
2010-01-01
期刊：
影响因子：
4.9
通讯作者：
Wilson, P. A.
中科院分区：
文献类型：
--
作者：
Beer, C. J.;Schiebel, R.;Wilson, P. A.
浮游有孔虫的大小标准化重量（SNW），测试壁厚度和密度的措施，是一个潜在的海洋碳化学古代用品。随着越来越多的注意力被给予开发这个代理，重要的是，方法之间的研究是可比的。在这里，我们比较了SNW数据产生的两种不同的方法来解释测试尺寸的变化，即（i）窄（50 μ m范围）筛分法和（ii）单独测量的测试尺寸的方法。使用标本从200-250 μ m筛馏分范围内收集的多个样本从北大西洋，我们发现，筛分并没有约束尺寸足够好地隔离的变化驱动的重量测试壁厚和密度的变化，从那些驱动的大小。我们估计，作为本研究的一部分产生的SNW数据与约+/-11%的不确定性或误差条相关。与窄筛分法相关的误差可以通过减小筛窗的尺寸、使用较大的测试和增加所使用的测试数量来减少。然而，在无法进行大量大型测试的情况下，与这种筛选方法相关的大量错误仍然是不可避免的。在这种情况下，单独测量的测试尺寸方法提供了一种更好的方法来估计SNW，因为正如我们的结果所示，这种方法将测试壁厚和密度变化驱动的重量变化与尺寸驱动的重量变化隔离开来。
The size-normalised weight (SNW) of planktic foraminifera, a measure of test wall thickness and density, is potentially a valuable palaeo-proxy for marine carbon chemistry. As increasing attention is given to developing this proxy it is important that methods are comparable between studies. Here, we compare SNW data generated using two different methods to account for variability in test size, namely (i) the narrow (50 mu m range) sieve fraction method and (ii) the individually measured test size method. Using specimens from the 200-250 mu m sieve fraction range collected in multinet samples from the North Atlantic, we find that sieving does not constrain size sufficiently well to isolate changes in weight driven by variations in test wall thickness and density from those driven by size. We estimate that the SNW data produced as part of this study are associated with an uncertainty, or error bar, of about +/- 11%. Errors associated with the narrow sieve fraction method may be reduced by decreasing the size of the sieve window, by using larger tests and by increasing the number tests employed. In situations where numerous large tests are unavailable, however, substantial errors associated with this sieve method remain unavoidable. In such circumstances the individually measured test size method provides a better means for estimating SNW because, as our results show, this method isolates changes in weight driven by variations in test wall thickness and density from those driven by size.