The input of foraminiferal infaunal populations to sub-fossil assemblages along an elevational gradient in a salt marsh: application to sea-level studies in the mid-Atlantic coast of North America

Abstract

The suitability of marsh sites for sea-level studies was examined based on a field study along a transect from high to low marsh. Living foraminifera at Bombay Hook (Delaware, USA) are considered to be shallow infaunal (i.e., uppermost 10 cm). Peak concentrations were found at 1-10 cm in the high marsh, 1-5 cm in the intermediate marsh, and 3-5 cm in the low marsh. However, sporadic deep infaunal inputs in the low marsh could significantly contribute to the sub-fossil assemblage. In the upper 10 cm buried (death ? sub-fossil) and living assemblages showed a strong correlation, and the seasonal pattern of the buried assemblage paralleled the living one, suggesting that the buried assemblage reflected the most recent reproductive inputs. The cumulative standing crop of each dominant species was used to estimate their contribution to the buried assemblage in order to assess if the community is vertically homogeneous and, therefore, if the infaunal production causes differential sub-surface enrichment. The results showed that a ''shallow'' (0-5 cm) infaunal contribution is able to explain much of the sub-fossil assemblage beneath the surface in the high and intermediate marsh plots. However, in the low marsh plot, the deep infaunal contribution was greatest and significantly affected the sub-fossil assemblage. Therefore, modern analogues for sea-level studies in mid-Atlantic North American marshes should include the uppermost 5 cm. The interval proposed for the high and intermediate marsh is thin enough that epifaunal species are not underrepresented and encompasses only *8 years (based on burial rates) providing a high temporal resolution.

Comparison of Rose Bengal and Celltracker Green Staining for Identification of Live Salt-Marsh Foraminifera

“…Live specimens were more abundant at shallow depths, and their abundance decreased with increasing depth. This distribution appears to indicate that the optimum depth for live T. salsa is the top 10 cm of sediment, which is similar to the distribution of many other foraminiferal species throughout the world that normally inhabit this depth range (Goldstein and others, 1995;Ozarko and others, 1997;Hippensteel and others, 2000;Leorri and Martin, 2009).…”

“…Biological staining techniques are used to label live individuals and appropriately include or exclude them from analyses (e.g., Patterson and others, 2000;Edwards and others, 2004; Barbosa and others, 2005). In addition, some studies need to identify an appropriate cm-sampling depth that best represents the proportion of live and dead individuals within a given modern assemblage for later comparison with fossil assemblages (e.g., Goldstein and Harben, 1993;Leorri and Martin, 2009). Bernhard (2000) reviewed a wide variety of possible techniques for identifying live versus dead foraminifera.…”

Distributions of salt-marsh foraminifera along the coast of SW California, USA: Implications for sea-level reconstructions

“…Most paleoenvironmental studies of intertidal marshes use the foraminiferal assemblages in surface sediment (upper 1 to 2 cm) as a modern counterpart assuming that they are characterized primarily by epifaunal production (e.g., Scott and Medioli, 1980;Gehrels, 1994;de Rijk, 1995;Horton, 1999;Patterson et al, 2004;Woodroffe et al, 2005;Kemp et al, 2009a) or shallow infaunal (Buzas et al, 1993). However, several studies have shown that intertidal foraminifera can live infaunally as deep as several decimeters in some marsh settings (e.g., Goldstein et al, 1995;Ozarko et al, 1997;Goldstein and Watkins, 1998;Saffert and Thomas, 1998;Goldstein and Watkins, 1999;Patterson et al, 1999;Hippensteel et al, 2002;Culver and Horton, 2005;Duchemin et al, 2005;Tobin et al, 2005;Berkeley et al, 2007;Leorri and Martin, 2009;Milker et al, 2015a). In such cases sampling the uppermost surface sediment (0-1 cm) would produce poor modern analogues (Duchemin et al, 2005).…”

Influence of Patchiness on Modern Salt-Marsh Foraminifera Used in Sea-Level Studies (North Carolina, Usa)

“…Furthermore, it has implicit assumptions about the nature of foraminiferal populations including infaunal habitation (e.g. Goldstein and Harben, 1993;Ozarko and others, 1997;Goldstein and Watkins, 1998;Patterson and others, 1999;Horton and Murray, 2006;Leorri and Martin, 2009), seasonal and inter-annual variability (e.g. Buzas and others, 2002;Hippensteel and others, 2002;Horton and Murray, 2006;Berkeley and others, 2008;Martin and others, 2009) and small-scale (meter) spatial patterns, termed patchiness (Buzas, 1968;Swallow, 2000;Morvan and others, 2006).…”