Enough is enough, or more is more? Testing the influence of foraminiferal count size on reconstructions of paleo-marsh elevation

Andrew C. Kemp*, Alexander J. Wright, Niamh Cahill

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Salt-marsh foraminifera are sea-level proxies used to quantitatively reconstruct Holocene paleo-marsh elevations (PME) and subsequently relative sea level (RSL). The reliability of these reconstructions is partly dependent upon counting enough foraminifera to accurately characterize assemblages, while counting fewer tests allows more samples to be processed. We test the influence of count size on PME reconstructions by repeatedly subsampling foraminiferal as-semblages preserved in a core of salt-marsh peat (from Newfoundland, Canada) with unusually large counts (up to 1595). Application of a single, weighted-averaging transfer function developed from a regional-scale modern training set to these ecologically-plausible simulated assemblages gener-ated PME reconstructions at count sizes of 10-700. Recon-structed PMEs stabilize at counts sizes greater than ~50 and counts exceeding ~250 tests show little return for the additional time invested. The absence of some rare taxa in low counts is unlikely to markedly influence results from weighted-averaging transfer functions. Subsampling of mod-ern foraminifera indicates that cross-validated transfer func-tion performance shows only modest improvement when more than ~40 foraminifera are counted. Studies seeking to understand multi-meter and millennial scale RSL trends should count more than ~50 tests. The precision sought by studies aiming to resolve decimeter- and decadal-scale RSL variability is best achieved with counts greater than ~75. In most studies seeking to reconstruct PME, effort is more productively allocated by counting relatively fewer foraminifera in more core samples than in counting large numbers of individuals. Target count sizes of 100-300 in existing studies are likely conservative and robust. Given the low diversity of salt-marsh foraminiferal assemblages, our results are likely applicable throughout and beyond northeastern North America.

Original languageEnglish
Pages (from-to)266-278
Number of pages13
JournalJournal of Foraminiferal Research
Issue number3
Early online date1 Jul 2020
Publication statusPublished - Jul 2020


This work is a contribution to IGCP project 639 "Sea-level change from minutes to millennia" and PALSEA 3 (a PAGES / INQUA working group) and was supported by NSF awards OCE-1458921 and OCE-2002431. Foraminiferal data from Big River were collected as part of a series of projects including "Ocean-climate variability and sea level in the North Atlantic region since AD 0" funded by the Dutch National Research Program on Global air pollution and Climate Change, "Coastal Records" funded by Vrije Universiteit Amsterdam, and "Simulations, observations & palaeoclimatic data: climate variability over the last 500 years" funded by the European Union. We thank Marty Buzas, Steve Culver, Robin Edwards, Simon Engelhart, Andrea Hawkes, and Alan Nelson for their valuable input on an early version of this manuscript and an anonymous reviewer for their comments.

FundersFunder number
Dutch National Research Program on Global air pollution and Climate Change
National Science FoundationOCE-1458921, OCE-2002431, 2002431
European Commission
Vrije Universiteit Amsterdam


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