Salt-marsh Foraminifera Research Articles

Elevation and the Distribution of Salt-Marsh Foraminifera, St. Catherines Island, Georgia: A Taphonomic Approach

Elevation and the Distribution of Salt-Marsh Foraminifera, St. Catherines Island, Georgia: A Taphonomic Approach

The use of testate amoebae in studies of sea-level change: a case study from the Taf Estuary, south Wales, UK

Micropalaeontological techniques play an important role in high-resolution studies of sea-level change. Salt-marsh foraminifera are among the most valuable groups of sea-level indicators as their distribution shows a narrow vertical zonation which can be accurately related to former sea level. This paper focuses on testate amoebae (‘thecamoebians’), a closely related group of protozoans which have also been widely reported in salt marshes, but only in low numbers and diversities and only in the size fraction used in foraminiferal analyses (<63 μm). A new preparation technique is described which is based on the analysis of the <63,um fraction using high power light microscopy. This technique is applied to surface sediment samples from a salt marsh in the Taf estuary in south Wales. The results show that small testate amoebae (<63 μm) are much more abundant and diverse in salt-marsh sediments than the larger testate amoebae (>63 μm). Species diversity increases from 2 (>63 prm) to 36 (<63 μm) and the maximum abundance is 65 600 individuals per cm3. The assemblages display a distinct spatial zonation across the marsh surface which appears to be closely related to elevation and to tidal parameters. The surface distribution of the testate amoebae is compared with the distribution of foraminifera and diatoms at the same site. The implications of using <63-μm testate amoebae as a tool for sea-level reconstruction are discussed.

Salt marsh foraminifera from the Great Marshes, Massachusetts: environmental controls

By using sites in the Great Marshes at Barnstable (Massachusetts, USA) this study examines the effects of a set of environmental parameters on the foraminiferal distribution. The studied parameters are: elevation above mean high water; salinity of the porewater; various sediment characteristics; vegetation; and food source. Relations between the environmental parameters and foraminiferal properties (frequencies, densities and diversities) are quantified with correlation coefficients. For the first time Siphotrochammina lobata and Balticammina pseudomacrescens are documented in the New England region. The following species show a significant correlation with one or more of the studied parameters and are designated as key-species: Haplophragmoides manilaensis, Jadammina macrescens, Balticammina pseudomacrescens, Miliammina fusca and Tiphotrocha comprimata . Based on cluster analysis and the presence, absence or dominance of the key-species characteristic associations are distinguished. The distribution of three associations is indicative of specific marsh environments: the marsh fringe, the middle marsh and the marsh edge. These three marsh units are separated by their own salinity regime, flooding and sediment characteristics. The marsh fringe is typified by the H. manilaensis Association and experiences freshwater input (seepage, surface runoff and rainwater) and only slight marine influence, resulting in low salinity values (2.5–20‰). The width of the marsh fringe is variable, dependent on the amount of seepage which in turn is controlled by the permeability of the basement and the peat. The J. macrescens Association characterizes the middle marsh where salinities are controlled by infiltration of sea- and rainwater and by evaporation. Salinity values are higher than 20‰, while temporarily salinity can reach extreme high values during periods without flooding and high evaporation rates (e.g., 44‰). The fully marine M. fusca Association occupies the daily flooded marsh edge where the salinities have the same values as Cape Cod bay water (ca. 28‰). Unlike many other salt marshes the distribution of foraminiferal assemblages in the Great Marshes does not show a vertical zonation with respect to mean high water. This shows that a worldwide applicable model for paleoenvironmental studies in salt marshes based on foraminifera is not feasible. Each salt marsh has its own characteristics. Regional factors such as climate play an important role in the salinity regime, while the local upland characteristics determine if seepage takes place. Thus each marsh has its own foraminiferal fingerprint showing the opportunistic behaviour of the salt marsh agglutinants. A surface study is an indispensable first step in assessing the value of foraminifera as paleo-ecological indicators.

Stratigraphic evolution of the inner continental shelf in response to late Quaternary relative sea-level change, northwestern Gulf of Maine

Accumulations of deltaic and littoral sediments on the inner continental shelf of Maine, Gulf of Maine, preserve a record of postglacial sea-level changes and shoreline migrations. The depositional response of coastal environments to a cycle of regression, lowstand, and transgression was examined with seismic-reflection profiles, vibracores, and radiocarbon dates collected from sediments at the mouths of the Kennebec and Penobscot Rivers. Sequence-stratigraphic analysis of these data reveals two distinctly different successions of late Quaternary deposits that represent end members in an evolutionary model for this glaciated coast. Seaward of the Kennebec River, coarse-grained shorelines with foreset beds occur at depths of 20–60 m and outline the lobate margin of the Kennebec River paleodelta, a complex, rock-framed accumulation of glaciomarine and deltaic sediments capped by estuarine and marine deposits. Sand derived from this system today supports large barrier spits and extensive salt marshes. In contrast, the mouth of the Penobscot River is characterized by thick deposits of glaciomarine mud overlain by marine mud of Holocene age, including gas-charged zones that have locally evolved into fields of pockmarks. The distinct lack of sand and gravel seaward of the Penobscot River and its abundance seaward of the Kennebec River probably reflect differences in sediment sources and the physiography of the two watersheds. The contrasting stratigraphic framework of these systems demonstrates the importance of understanding local and regional differences in sediment supply, sea-level change, bedrock structure, and exposure to waves and tides in order to model river-mouth deposition on glaciated coasts. Evolution of shelf deposits was largely controlled by relative sea level, which locally fell from a highstand (+60 to +70 m at 14 ka) contemporary with deglaciation to a lowstand (−55 m at 10.8 ka). The sea-level lowering was accompanied by fluvial incision of older deposits, producing a regressive, basal unconformity. Major rivers deposited abundant sediment over this surface. Sea level then rose at varying rates, extensively reworking formerly emergent parts of the shelf and producing a shoreface ravinement surface in areas exposed to waves. A tidal ravinement surface has developed in sheltered embayments where erosion is due mainly to tidal currents. Incised valleys in both settings preserve transgressive estuarine deposits that contain lagoonal bivalves and salt-marsh foraminifera at depths of 15–30 m. These deposits accumulated ca. 9.2–7.3 ka, locally a period of relatively slow sea-level rise.

Microhabitats of salt marsh foraminifera: St. Catherines Island, Georgia, USA

Salt marsh foraminifera of St. Catherines Island, Georgia occupy a range of epibenthic to deep infaunal (to 30 cm) micro-habitats. Freshly collected specimens of Arenoparrella mexicana from 27 to 30 cm below the marsh surface extruded pseudopodial nets and actively collected foreign material about the aperture. Salt marsh foraminifera may be primarily epibenthic (0–1 cm), epibenthic to intermediate infaunal (0–10 cm), or deep infaunal (0–30 cm). Most of the twelve commonly occurring species in St. Catherines Island marshes are epibenthic to intermediate infaunal. Species distributional patterns differ with regard to: maximum depth of infaunal occurrences, infaunal microhabitat utilization in different marsh zones and environments, and the presence or absence of subsurface population maxima. Selective preservation impacts both calcareous and agglutinated foraminifera. Intense bioturbation primarily by halophytes and decapod crustaceans may contribute to the deep infaunal occurrences of foraminifera in these environments.

Salinity control on the distribution of salt marsh foraminifera (Great Marshes, Massachusetts)

Salinity control on the distribution of salt marsh foraminifera (Great Marshes, Massachusetts)

Taphofacies Implications of Infaunal Foraminiferal Assemblages in a Georgia Salt Marsh, Sapelo Island

The occurrence of living infaunal foraminifera and selective preservation significantly alter the composition of assemblages that accumulate in subsurface marsh sediments of Sapelo Island, Georgia. Rose bengal staining and observations on live foraminifers from surface and subsurface marsh sediments identified live infaunal populations of Arenoparrella mexicana (Komfeld 1931) and Haplophragmoides wilberti Andersen 1953 to a depth of 30cm below the marsh surface. Other foraminifera are predominantly surface-dwellers, although some (e.g., Ammonia beccarii (Linne 1758), Miliamminafusca (Brady 1870) and Trochammina inflata (Montagu 1808)) also have shallow infaunal occurrences. INTRODUCTION Salt marsh foraminifera have been widely reported from many localities along U.S. coastlines and selected marshes worldwide (e.g., Murray 1971; Scott and Medioli 1980a; Scott and Leckie 1990). Most previous studies traditionally have emphasized live and/or assemblages present in surface sediments of the marsh. Distributional patterns observed in surface sediments have been correlated to environmental factors such as elevation (Scott and Medioli 1978, 1980a), salinity (Murray 1971, 1973; Scott and Medioli 1980a), pH (Phleger and Bradshaw 1966; Scott and Medioli 1980b) and geographic region (Phleger 1967, 1970; Scott et al. 1990), and constitute the basis for many paleoenvironmental interpretations. Infaunal foraminifera, however, reportedly occur in a variety of marine environments ranging from salt marshes (Akers 1971; Matera and Lee 1972; Steineck and Bergstein 1979; Goldstein 1988) to the deep sea (Corliss 1985; Gooday 1986; Mackensen and Douglas 1989; Corliss and Emerson 1990; Loubere and Gary 1990). In salt marshes, infaunal occurrences may ultimately change the composition of death assemblages that accumulate in subsurface sediments. Foraminifera with infaunal occurrences may become enriched (i.e., have higher relative abundances) with depth in sediments compared to those species that are primarily epifaunal. This process, in addition to selective preservation, may produce subsurface remnant or death assemblages that differ from their counterparts at the marsh surface. Subsurface death assemblages should therefore be evaluated to enhance the accuracy of paleoenvironmental interpretations. This study documents the occurrence of foraminifera living infaunally in selected high, transitional, and low marsh habitats of Sapelo Island, Georgia, and evaluates their effects on death assemblages that accumulate in subsurface sediments, particularly with regard to distributional patterns, diversity and stratification. PREVIOUS WORK Although distributional patterns of salt marsh foraminifera have been widely studied, foraminifera of the extensive salt marshes of the southeastern U.S. have received little attention (Goldstein and Frey 1986; Goldstein 1988). Similarly, few studies on taphonomy, infaunal occurrences and comparisons between surface and subsurface assemblages have been conducted. In an earlier report on foraminiferal taphonomy in salt marshes, Scott and Medioli (1980b) studied the long-term accumulation of foraminiferal assemblages in surface sediments and concluded that (live + dead) counts of foraminifera in surface sediments better reflect distributional patterns with regard to paleoenvironmental studies than those of their live or dead counterparts alone. The composition of total assemblages diminishes seasonal effects. However, Jonasson and Patterson (1992) reported that selective preservation in subsurface salt marsh sediments reduces the number of biofacies or assemblages that can be recognized compared to those present at the marsh surface. Several previous studies on infaunal salt marsh foraminifera (Akers 1971; Matera and Lee 1972; Steineck and Bergstein 1979; Goldstein 1988) found that representatives of some species live infaunally. Furthermore, live surface and subsurface assemblages may differ in density and species composition (Steineck and Bergstein 1979). Akers (1971) reported rose bengal-stained specimens of several agglutinated species to a depth of 30-35cm in salt marshes near Beaufort, North Carolina. In studies on foraminifera of selected marshes and adjacent habitats of Long Island, New York, Matera and Lee (1972) also reported rose bengal-stained foraminifera in subsurface sediments. Abundances of Trochammina inflata (Montagu 1808), in particular, increased with depth (to about 8cm) below the marsh surface, and stratification of foraminifera over shallow sediment depths was noted. Steineck and Bergstein (1979), applying cluster analysis to data on living (rose bengal-stained) surface and subsurface foraminifera, identified two biotopes: a surface assemblage and an impoverished subsurface assemblage. Total (live + dead) assemblages and taphonomy, however, were not evaluated. ENVIRONMENTAL SETTING Sapelo Island, one of several Pleistocene barrier islands of the central coast of Georgia, lies approximately seven kilometers micropaleontology, vol. 39, no. 1, pp. 53-62, text-figures 1-6, tables, 1-2, 1993 53 This content downloaded from 157.55.39.211 on Mon, 08 Aug 2016 06:24:55 UTC All use subject to http://about.jstor.org/terms S. T Goldstein and E. B. Harben: Taphofacies implications of infaunalforaminiferal assemblages in a Georgia salt marsh, Sapelo Island TABLE 1 Classification of salt marsh habitats and subenvironments HABITAT

Preservation Potential of Salt Marsh Foraminifera from the Fraser River Delta, British Columbia

Preservation Potential of Salt Marsh Foraminifera from the Fraser River Delta, British Columbia

On the significance of test form in benthic salt-marsh Foraminifera : Price, M. V., 1980. J. foram. Res., 10(2): 129–135

On the significance of test form in benthic salt-marsh Foraminifera : Price, M. V., 1980. J. foram. Res., 10(2): 129–135

Competition for food and other niche-related studies of three species of salt-marsh foraminifera

The niches of 3 species of salt-marsh foraminifera, Allogromia laticollaris, Rosalina leei, and Spiroloculina hyalina were assessed in the laboratory. The 3 species reproduce within the following ranges: temperature (10° to 33°C), salinity (12 to 45‰) and pH (5 to 10). Competition for food among the 3 species was evaluated. S. hyalina did not compete with other species. Intraspecific competition (crowding) appears to be an important factor limiting the reproduction of A. laticollaris. Crowding seems to have little effect on the other 2 species. The feeding of foraminifera is affected by the quality and quantity of food organisms. The feeding rate of the species tested is directly related to concentration within a range of 102 to 106 cells fed. S. hyalina is a bacterial feeder. A. laticollaris is a rare species which may become locally abundant when dominant species are missing. S. hyalina is also a rare species, which can bloom where the density of bacteria is relatively high and in the absence of competing species. R. leei is a stable, conspicuous species, whose moderate numbers are relatively unaffected by physical stress and competition. Some new laboratory data on Ammonia beccarii were obtained so that this species could be compared with the other studied. Differences in niches are graphically presented.

Trophic Dynamics and Niches of Salt Marsh Foraminifera

Energetic considerations of the growth of three species of littoral benthic foraminifera, Allogromia laticollaris, Rosalina leei , and Spiroloculina hyalina , have been made on laboratory-grown populations. Under optimum laboratory conditions A. laticollaris has the greatest intrinsic rate of increase (r = 2.533 org/day); S. hyalina (r = 1.472 org/day), and R. leei (r = 0.272 org/day) being less fecund. The respiration rates of the three species were similar (0.5–4.5 μ1/mg body wt/hr) within the temperature range (15–35 C) tested. The species studied are selective feeders. Only 4-5 of 28 species of algae tested were consumed in significant quantities (40-150 × 108 g/foram/day). Although great numbers of bacteria were eaten, their biomass was negligible when compared to the algae. The ecological growth efficiency (Ee) of the three species tested is highest in fresh cultures (5-20%) and declines rapidly. Evidence suggests that the species studied are well adapted for the rapid changes in the microbial community structure which take place throughout the summer, and that community stability and high rate of productivity are achieved through diversity.