A new preparation method for testate amoebae in minerogenic sediments

Testate amoebae are one of a few moisture-sensitive proxies available to study Holocene palaeohydrology. Although the majority of research has been conducted on ombrotrophic peatlands in the Northern Hemisphere, the application of testate amoebae in minerogenic sediments, such as minerotrophic peatlands and saltmarshes, holds considerable promise but is often impeded by the low concentration of testate amoebae and by time-consuming counting. Here a new preparation protocol to concentrate testate amoebae is proposed; it removes more minerogenic particles and organic matter, but results in negligible damage to testate amoebae. Sodium pyrophosphate (Na₄P₂O₇) is introduced to remove fine particles through deflocculation that, in contrast to the commonly used chemical digestion/deprotonation via an alkaline treatment, is more physically benign to testate amoebae. Furthermore, acetone is introduced as an organic co-solvent to increase the solubility of organic matter in the alkaline treatment. We test the new protocol against standard, water-based methods and find that the addition of sodium pyrophosphate yields the highest concentration and increases the total number of testate amoebae recovered. Statistical analyses (multivariate ANOVA and ordination) suggest that the new method retains the assemblage integrity. We conclude by recommending a protocol combining sodium pyrophosphate, acetone and a mild alkaline treatment, as this combination yields the best slide clarity, reduced counting time and results in negligible damage to testate amoebae.