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Do sample preparation techniques affect the relative abundance of Florisphaera profunda?
Univ Pavia, Dipartimento Sci Terra & Ambiente, Via Ferrata 9, I-27100 Pavia, Italy..
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
Univ Pavia, Dipartimento Sci Terra & Ambiente, Via Ferrata 9, I-27100 Pavia, Italy..
Univ Pavia, Dipartimento Fis, Via Bassi 6, I-27100 Pavia, Italy..
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2016 (English)In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 127, 42-49 p.Article in journal (Refereed) Published
Abstract [en]

We investigated which method among smearing, settling, filtration, and random settling is the most accurate for determining the relative abundance of Florisphaera profunda. This species is included in paleoproductivity indices because it is one of the most important deep-water dwellers. Therefore, an accurate assessment of its relative abundance is key to monitoring variations in thermocline and nutricline depths. The low birefringence and flat polygonal shape of F. profunda may lead to inaccurate estimates of its relative abundance as it is poorly visible under light microscopy (LM), and different sample preparation may affect the number of specimens on each slide. We studied eight samples from the Ocean Drilling Program (ODP) Site 1209B (Shatslcy Rise, NW Pacific) from the last 450 kyr. Each sample was prepared five times using each technique for a total of 160 slides. Through a rigorous analytical and statistical approach, we demonstrated the high reproducibility of each method and showed good agreement among techniques at low percentages of F. profunda. When the percentage of this species increases, the random settling technique differs from the others. Filtration and random settling preparation techniques were calibrated by spiking samples with microbeads. The ratio of microbeads observed in slides prepared using these two methods reflects bias due to loss of particles in the filtration technique. In addition, a hydrodynamic model for a fluttering and tumbling plate - such as F. profunda nannoliths - is proposed here along with calculated sinking velocities. These findings confirmed the efficiency of the long decantation time proposed for the random settling technique. The analysis of replicates, the validation with microbeads and the estimation of settling velocity of nannofossils in the tube convinced us that the higher relative abundance recorded by the random technique is not due to an imprecision of this method but, on the contrary, reflects the fact that it is more effective.

Place, publisher, year, edition, pages
2016. Vol. 127, 42-49 p.
Keyword [en]
Florisphaera profunda, Preparation techniques, Reliability, ANOVA
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-305528DOI: 10.1016/j.marmicro.2016.07.007ISI: 000383943200004OAI: oai:DiVA.org:uu-305528DiVA: diva2:1039004
Swedish Research Council, 2011-4866
Available from: 2016-10-20 Created: 2016-10-19 Last updated: 2016-10-20Bibliographically approved

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Bordiga, Manuela
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