Freeze coring is a commonly used method for the investigation of the bed sediment fauna of rivers. It is considered to produce quantitative numbers of invertebrate abundance in different depth layers. Calculations of abundance use total volume of the freeze core sample as spatial reference. This definition of sample volume is incorrect. In the present, study freeze core samples are shown to consist of two parts: (1) a cylindrical inner core in which the pore water has turned into ice and (2) all parts of sediment, which protrude from this inner core. Invertebrates are fixed only within the inner core since the protruding parts contain no pores and therefore no invertebrate habitat. In samples from gravel rivers, the protruding parts form a considerable bias, which depends on the size of the core and the coarseness of the sediment. In the present study, total volume of individual core segments varied between 97 and 248% of actual sample volume. The inner core can be measured directly to avoid the bias. The procedure is proposed for future studies to produce unbiased, comparable values of invertebrate abundance and consequently reliable data on vertical distribution.

中文翻译：

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用于无偏差计算冷冻岩心样品中无脊椎动物丰度的概念模型

冷冻取心是研究河流河床沉积物动物群的常用方法。它被认为是在不同深度层产生定量数量的无脊椎动物丰度。丰度的计算使用冻结核心样本的总体积作为空间参考。这种样本量的定义是不正确的。目前，研究冻结核心样本由两部分组成：(1) 圆柱形内核，其中孔隙水已变成冰；(2) 沉积物的所有部分，从该内核突出。无脊椎动物仅固定在内核内，因为突出部分没有孔隙，因此没有无脊椎动物栖息地。在砾石河流的样本中，突出部分形成了相当大的偏差，这取决于核心的大小和沉积物的粗度。在本研究中，单个岩心段的总体积在实际样本体积的 97% 到 248% 之间变化。可以直接测量内核以避免偏差。该程序被提议用于未来的研究，以产生无偏见的、可比较的无脊椎动物丰度值，从而产生关于垂直分布的可靠数据。