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

Abstract

Salt-marsh foraminifera are frequently used around the world as proxies in paleoenvironmental studies of sea-level change. Quantitative reconstructions of sealevel change use transfer functions which are based on the vertical zonation of saltmarsh foraminifera with respect to the tidal frame. This paper explores for the first time the environmental factors that control the foraminiferal assemblages in Southern California marshes using modern surface samples (1 cm thick) from two marshes Seal Beach and Tijuana Estuary. The dead foraminiferal assemblages demonstrate distinct zonation across the salt-marsh surfaces which is primarily related to elevation. Other variables less important than elevation such as O2, temperature, salinity and pH additionally control the distribution pattern of these assemblages. The tidal flat and low marshes are characterized by high abundances of Miliammina fusca and calcareous species. The middle marsh is dominated by Jadammina macrescens and Trochammina inflata, while the high marsh zone is dominated by Trochamminita irregularis, Miliammina petila, J. macrescens and T. inflata. Regression modelling was used for the development of a sea-level transfer function based on a combined training set of surface samples from the two study sites. The performance of the Weighted Average-Partial Least Squares (WA-PLS) transfer function suggests a robust relationship between the observed and estimated elevations (r 2 Jack = 0.72), and is capable of predicting former sea levels to a precision of ±0.09 m. Our results can be used for future paleoenvironmental reconstructions along the Southern California coast, an area that has experienced changes in sea level in the past and will be affected by future sea-level rise coupled with climate and anthropogenic changes, resulting in wide impacts on the natural coastal habitats in this region.

Development of a Training Set of Contemporary Salt-Marsh Foraminifera for Late Holocene Sea- Level Reconstructions in southeastern Australia

“…Multivariate analyses demonstrate that elevation (as a proxy for duration and frequency of tidal inundation, or hydroperiod) has an influence on foraminiferal distribution, and supports findings reported across the literature (e.g. Avnaim-Katav et al 2017;Barnett, Garneau & Bernatchez, 2016;Edwards,Wright & van de Plassche, 2004;Gehrels, 2000;, Milker et al 2015a). The ratio of the first constrained DCCA eigenvalue (λ1) to the second unconstrained eigenvalue (λ2) indicates the importance of an environmental variable as a determinant of species distribution (e.g.…”

Advances in the observation and understanding of changes in sea level and tides

“…There are many technical aspects involved in analysis of sediment cores before useful data can be obtained (e.g., how to handle problems of sediment compaction), although considerable experience in best practice has been acquired over many years. 114 and stratigraphic marker techniques (e.g., 137 Cs, pollen, charcoal, Pb isotopes, and metal concentrations). For example, the 137 Cs method can be used to detect the time in the mid-1960s when nuclear bomb testing was at its peak.…”

“…114 and stratigraphic marker techniques (e.g., 137 Cs, pollen, charcoal, Pb isotopes, and metal concentrations). For example, the 137 Cs method can be used to detect the time in the mid-1960s when nuclear bomb testing was at its peak. In some regions (e.g., the southwest Pacific and the Atlantic coast of North America), pollen in the cores can provide time markers by indicating changes in vegetation following settlement by Europeans during the 18th and 19th centuries.…”

“…131 An advantage of the salt marsh technique, additional to its temporal coverage, is that it can be applied to parts of the world without any historical tide gauge information, notably in the southern hemisphere, thereby extending the geographical coverage of our knowledge of sea level change. Aside from the North American studies mentioned above, examples include measurements as far apart as New Zealand and Australia, [132][133][134] Greenland, 135 Iceland, 136 SW California 137 (although this paper does not include an actual sea level reconstruction), Norway, 138 NW England and Scotland, 139,140 northern Spain, 141 and Croatia. 142 And for many other examples, see the review of Ref.…”

How can past sea level be evaluated from traces of anthropogenic layers in ancient saltpans?

“…These organisms which partly produce calcareous skeletal remains, depend on various ecological conditions such as substrate type, dissolved oxygen concentration, food availability and salinity [ 17 – 22 ]. In shallow aquatic environments, these parameters are often closely related to water depth and sea level [ 23 , 24 ]. Foraminifera and ostracods demonstrate great sensitivity to environmental change that might be expressed by variations in the assemblage composition and distribution patterns, for example, by disappearance or appearance of species and/or replacement by other taxa; shifts in abundances and diversity; and abnormalities in test features [ 18 , 20 – 22 , 25 , 26 ].…”