In palynology and other laboratory-based disciplines, methodological literature often lags the development and adoption of new practices. Here we highlight the lack of literature on the application of heavy liquid density separation for pollen preparations, a technique that has become common practice in recent years. In a study of Holocene-age sediments from Lake Pupuke, northern New Zealand, we found that the density of the heavy liquid used to separate pollen from the minerogenic fraction, within the range of reported practice, affected pollen counts. When a relatively low density was used (2.0 g/cm 3 ), buoyant pollen grains such as Prumnopitys taxifolia and Dacrydium cupressinum were overrepresented, whereas small, compact pollen grains such as Libocedrus and Metrosideros were underrepresented. This result raises wider concerns, as heavy liquid densities reported in the literature range from 1.88 to 2.40 g/cm 3 . We draw attention to this problem and recommend steps that palynologists can take to ensure that their enumerated pollen assemblages are representative and do not lead to spurious interpretations.

中文翻译：

---

花粉制备中的密度分离：你能走多低？

在孢粉学和其他基于实验室的学科中，方法论文献往往滞后于新实践的发展和采用。在这里，我们强调缺乏将重液密度分离应用于花粉制剂的文献，这种技术近年来已成为普遍做法。在对新西兰北部普普克湖的全新世沉积物的研究中，我们发现，在报告的实践范围内，用于将花粉与矿物成分分离的重质液体的密度会影响花粉计数。当使用相对较低的密度 (2.0 g/cm 3 ) 时，漂浮的花粉粒如 Prumnopitys taxfolia 和 Dacrydium cupressinum 的比例过高，而小而紧凑的花粉粒如 Libocedrus 和 Metrosideros 的比例不足。这一结果引起了更广泛的关注，因为文献中报道的重液体密度范围为 1.88 至 2.40 g/cm 3 。我们提请注意这个问题，并推荐孢粉学家可以采取的步骤，以确保他们列举的花粉组合具有代表性并且不会导致虚假的解释。