Enough is Enough, or More is More? Testing the Influence of Foraminiferal Count Size on Reconstructions of Paleo-Marsh Elevation

2020 ◽  
Vol 50 (3) ◽  
pp. 266-278
Author(s):  
Andrew C. Kemp ◽  
Alexander J. Wright ◽  
Niamh Cahill
Keyword(s):  
Salt Marsh ◽  
Transfer Function ◽  
Sea Level ◽  
Transfer Functions ◽  
Regional Scale ◽  
Weighted Averaging ◽  
Additional Time ◽  
Modest Improvement ◽  
Large Numbers ◽  
Decadal Scale

ABSTRACT 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 assemblages 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 generated PME reconstructions at count sizes of 10–700. Reconstructed 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 modern foraminifera indicates that cross-validated transfer function 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.

The relative utility of foraminifera and diatoms for reconstructing late Holocene sea-level change in North Carolina, USA

2009 ◽  
Vol 71 (1) ◽  
pp. 9-21 ◽  
Author(s):  
Andrew C. Kemp ◽  
Benjamin P. Horton ◽  
D. Reide Corbett ◽  
Stephen J. Culver ◽  
Robin J. Edwards ◽  
...  
Keyword(s):  
North Carolina ◽  
Sea Level ◽  
Salt Marshes ◽  
Transfer Functions ◽  
Tide Gauge ◽  
Regional Scale ◽  
Strong Relationship ◽  
Tide Gauge Records ◽  
Specific Distribution ◽  
Relative Utility

AbstractForaminifera and diatoms preserved in salt-marsh sediments have been used to produce high-resolution records of Holocene relative sea-level (RSL) change. To determine which of these microfossil groups is most appropriate for this purpose we investigated their relative utility from salt marshes in North Carolina, USA. Regional-scale transfer functions were developed using foraminifera, diatoms and a combination of both (multi-proxy) from three salt marshes (Oregon Inlet, Currituck Barrier Island and Pea Island). We evaluated each approach on the basis of transfer-function performance. Foraminifera, diatoms and multi-proxy-based transfer functions all demonstrated a strong relationship between observed and predicted elevations (r2jack > 0.74 and RMSEP < 0.05 m), suggesting that they have equal utility. Application of the transfer functions to a fossil core from Salvo to reconstruct former sea levels enabled us to consider relative utility in light of ‘paleo-performance’. Fossil foraminifera had strong modern analogues, whilst diatoms had poor modern analogues making them unreliable. This result reflects the high diversity and site-specific distribution of modern diatoms. Consequently, we used foraminifera to reconstruct RSL change for the period since ∼ AD 1800 using a 210Pb- and 14C-based chronology, and we were able to reconcile this with tide-gauge records.

scholarly journals Developing detailed records of relative sea-level change using a foraminiferal transfer function: an example from North Norfolk, UK

2006 ◽  
Vol 364 (1841) ◽  
pp. 973-991 ◽  
Author(s):  
Robin J Edwards ◽  
B.P Horton
Keyword(s):  
Transfer Function ◽  
Sea Level ◽  
Transfer Functions ◽  
Sediment Cores ◽  
Sea Level Change ◽  
Relative Sea Level ◽  
Level Change ◽  
The North ◽  
Level Information ◽  
Coastal Deposits

This paper provides a brief overview of the transfer function approach to sea-level reconstruction. Using the example of two overlapping sediment cores from the North Norfolk coast, UK, the advantages and limitations of the transfer function methodology are examined. While the selected cores are taken from different sites, and display contrasting patterns of sedimentation, the foraminiferal transfer function distils comparable records of relative sea-level change from both sequences. These reconstructions are consistent with existing sea-level index points from the region but produce a more detailed record of relative sea-level change. Transfer functions can extract sea-level information from a wider range of sedimentary sub-environments. This increases the amount of data that can be collected from coastal deposits and improves record resolution. The replicability of the transfer function methodology, coupled with the sequential nature of the data it produces, assists in the compilation and analysis of sea-level records from different sites. This technique has the potential to bridge the gap between short-term (instrumental) and long-term (geological or geophysical) records of sea-level change.

scholarly journals A Bayesian hierarchical model for reconstructing relative sea level: from raw data to rates of change

2015 ◽  
Vol 11 (5) ◽  
pp. 4851-4893 ◽  
Author(s):  
N. Cahill ◽  
A. C. Kemp ◽  
B. P. Horton ◽  
A. C. Parnell
Keyword(s):  
Transfer Function ◽  
Sea Level ◽  
Hierarchical Model ◽  
Tide Gauge ◽  
Bayesian Hierarchical Model ◽  
Weighted Averaging ◽  
Relative Sea Level ◽  
Holistic Model ◽  
Tidal Elevation ◽  
Bayesian Hierarchical

Abstract. We present a holistic Bayesian hierarchical model for reconstructing the continuous and dynamic evolution of relative sea-level (RSL) change with fully quantified uncertainty. The reconstruction is produced from biological (foraminifera) and geochemical (δ13C) sea-level indicators preserved in dated cores of salt-marsh sediment. Our model is comprised of three modules: (1) A Bayesian transfer function for the calibration of foraminifera into tidal elevation, which is flexible enough to formally accommodate additional proxies (in this case bulk-sediment δ13C values), (2) A chronology developed from an existing Bchron age-depth model, and (3) An existing errors-in-variables integrated Gaussian process (EIV-IGP) model for estimating rates of sea-level change. We illustrate our approach using a case study of Common Era sea-level variability from New Jersey. USA We develop a new Bayesian transfer function (B-TF), with and without the δ13C proxy and compare our results to those from a widely-used weighted-averaging transfer function (WA-TF). The formal incorporation of a second proxy into the B-TF model results in smaller vertical uncertainties and improved accuracy for reconstructed RSL. The vertical uncertainty from the multi-proxy B-TF is ∼ 28 % smaller on average compared to the WA-TF. When evaluated against historic tide-gauge measurements, the multi-proxy B-TF most accurately reconstructs the RSL changes observed in the instrumental record (MSE = 0.003 m2). The holistic model provides a single, unifying framework for reconstructing and analysing sea level through time. This approach is suitable for reconstructing other paleoenvironmental variables using biological proxies.

Reconstructing Holocene sea level using salt-marsh foraminifera and transfer functions: lessons from New Jersey, USA

2013 ◽  
Vol 28 (6) ◽  
pp. 617-629 ◽  
Author(s):  
ANDREW C. KEMP ◽  
RICHARD J. TELFORD ◽  
BENJAMIN P. HORTON ◽  
SHIMON C. ANISFELD ◽  
CHRISTOPHER K. SOMMERFIELD
Keyword(s):  
New Jersey ◽  
Salt Marsh ◽  
Sea Level ◽  
Transfer Functions ◽  
Holocene Sea Level

The application of foraminifera to reconstruct the rate of 20th century sea level rise, Morbihan Golfe, Brittany, France

2011 ◽  
Vol 75 (1) ◽  
pp. 24-35 ◽  
Author(s):  
Veronica Rossi ◽  
Benjamin P. Horton ◽  
D. Reide Corbett ◽  
Eduardo Leorri ◽  
Lucia Perez-Belmonte ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Transfer Function ◽  
Sea Level Rise ◽  
Sea Level ◽  
20Th Century ◽  
Salt Marshes ◽  
Tide Gauge ◽  
Strong Relationship ◽  
Tide Gauge Record ◽  
Foraminiferal Distribution

AbstractForaminiferal assemblages preserved within salt-marsh sediment can provide an accurate and precise means to reconstruct relative sea level due to a strong relationship with elevation, which can be quantified using a transfer function. We collected a set of surface samples from two salt marshes in the Morbihan Golfe, France to determine foraminiferal distribution patterns. Dominant taxa included Jadammina macrescens, Trochammina inflata, Haplophragmoides spp. and Miliammina fusca. We developed a foraminifera-based transfer function using a modern training set of 36 samples and 23 species. The strong relationship between observed and predicted values (r2jack = 0.7) indicated that foraminiferal distribution is primarily controlled by elevation with respect to the tidal frame and precise reconstructions of former sea level are possible (RMSEPjack = 0.07 m). The application of the transfer function to a short salt-marsh core (0.32 m) allowed the reconstruction of former sea levels, which were placed in a chronological framework using short-lived radionuclides (210Pb and 137Cs). The agreement between the foraminifera-based sea level curve and the Brest tide-gauge record confirms the reliability of transfer function estimates and the validity of this methodology to extend sea level reconstructions back into the pre-instrumental period. Both instrumental and microfossil records suggest an acceleration of sea level rise during the 20th century.

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