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Distribution of Modern Salt-marsh Foraminifera from the Eastern Mississippi Sound, U.S.A.
Abstract
This study documented surface distributions of live and dead foraminiferal assemblages in the low-gradient tidal marshes of the barrier island and estuarine complex of the eastern Mississippi Sound (Grand Bay, Pascagoula River, Fowl River, Dauphin Island). A total of 71,833 specimens representing 38 species were identified from a gradient of different elevation zones across the study area. We identified five live assemblages and nine biofacies for the dead assemblages from estuarine, low marsh, middle marsh, high marsh, and upland transition environments. Although dissolution of calcareous tests was observed in the dead assemblages, characteristic species and abundance patterns dependent on elevation in the intertidal zone were similar between living assemblages and dead biofacies. The assemblages from the eastern Mississippi Sound estuaries were dominated by Ammonia tepida, Cribroelphidium poeyanum, C. excavatum, and Paratrochammina simplissima. The low marshes were dominated by Ammotium salsum, Ammobaculites exiguus, and Miliammina fusca. The dominant species in the middle marshes was Arenoparrella mexicana. The most abundant species in the high marshes was Entzia macrescens. The upland–marsh transition zones were dominated by Trochamminita irregularis and Pseudothurammina limnetis. Canonical correspondence analysis was applied to assess the relationship between a priori defined biofacies and measured environmental data (elevation, grain size, organic matter, and salinity) to test the hypothesis that distribution of foraminiferal assemblages is driven by elevation and hence flooding frequency. Salinity was the second most important explanatory variable of dead assemblages. Riverine freshwater from the Pascagoula River markedly influenced the live and dead assemblages in the Pascagoula River marsh, which was represented by low diversity and densities and dominance by Ammoastuta inepta. The relationship between the measured environmental variables and assemblage distributions can be used in future Mississippi Sound paleo-environmental studies.
... m/m) than Site 1 (−0.01 m/m). No samples were collected in the high marsh or upland for this study which focused on depositional trends within 50 m of the estuarine shoreline unlike Haller et al. (2019) and sea-level studies (Edwards and Wright 2015). ...
... Dry sediment was split into equal parts with a microsplitter, spread over a gridded picking tray, and entire splits were picked from 125 to 500 µm fraction under a binocular dissecting microscope until at least 200 specimens were acquired. Identifications were made by making comparisons with published literature (Edwards and Wright 2015;Haller et al. 2019) and through consultation and specimen identification comparisons. ...
... The results of these multivariate analyses were compared with previous studies that examined foraminiferal assemblages from multiple marsh (Haller et al. 2019) and estuarine environments (Phleger 1954;Lamb 1972;Osterman and Smith 2012; within the coastal zone of Mississippi and Alabama (USA), including Grand Bay (i.e., Haller et al. 2019;. Haller et al. (2019) categorized the northern Gulf of Mexico biofacies into (1) estuary, (2) low salinity, (3) low marsh, (4) middle marsh, (5) high marsh, and (6) upland transition, identifying dominant (> 5% abundance) and characteristic species, as classified by a biofacies fidelity, constancy, and occurrence (BFCO) analysis, for each biofacies (Table 1). ...
Marsh environments, characterized by their flora and fauna, change laterally in response to shoreline erosion, water levels and inundation, and anthropogenic activities. The Grand Bay coastal system (USA) has undergone multiple large-scale geomorphic and hydrologic changes resulting in altered sediment supply, depositional patterns, and degraded barrier islands, leaving wetland salt marshes vulnerable to increased wave activity. Two shore-perpendicular transect sites, one along a low-activity shoreline and the other in a high activity area of the same bay-marsh complex, were sampled to investigate how the marshes within 50 m of the modern shoreline have responded to different levels of increased wave activity over the past century. Surface sediments graded finer and more organic with increased distance from the shoreline while cores generally exhibited a coarsening upwards grain-size trend; all cores contained multiple large sedimentological shifts. ²¹⁰ Pb-based mass accumulation rates over the last two decades were greater than the long-term (centurial) average at each site with the fastest accumulation rates of 7.81 ± 1.58 and 7.79 ± 1.63 kg/m ² /year at the sites nearest the shoreline. A shoreline change analysis of three time-slices (1848–2017, 1957–2017, 2016–2017) shows increased erosion at both sites since 1848 with modern rates of −0.95 and −0.88 m/year. Downcore sedimentology, mass accumulation rates, and shoreline change rates paired with foraminiferal biofacies and identification of local estuarine indicator species, Paratrochammina simplissima , aided in identifying paleo marsh types, their relative proximity to the shoreline, and sediment provenance. The high-energy marsh site transitioned from middle marsh to low marsh in the 1960s, and the low-energy marsh site transitioned later, at the end of the twentieth and early twenty-first century, due to its more protected location. Marsh type transition corresponds chronologically with the coarsening upwards grain-size trend observed and the degradation of Grand Batture Island; since its submergence, signatures of multiple storm event have been preserved downcore.
... Sediment was wet sieved over 63, 125 and 850 μm sieves to remove mud and large organics and ovendried for 2 day at 60 • C. Foraminifera were dry picked from the 125-850 μm fraction (Schönfeld et al., 2012); samples were split with a microsplitter and entire splits were picked until ≥200 specimens were counted. Specimens were identified using previously published literature (Brönnimann, 1979;Loeblich and Tappan, 1988;Edwards et al., 2004;Edwards and Wright, 2015;Haller et al., 2019). Counts of Ammotium salsum (a subjective junior synonym now accepted as Ammotium morenoi; Brönnimann et al., 1992) and Ammobaculites exiguus were combined into a single group (Ammotium cf. A. salsum) due to the large number of broken specimens, similarities in texture, and for comparison with Osterman and Smith (2012) and Haller et al. (2019). ...
... Specimens were identified using previously published literature (Brönnimann, 1979;Loeblich and Tappan, 1988;Edwards et al., 2004;Edwards and Wright, 2015;Haller et al., 2019). Counts of Ammotium salsum (a subjective junior synonym now accepted as Ammotium morenoi; Brönnimann et al., 1992) and Ammobaculites exiguus were combined into a single group (Ammotium cf. A. salsum) due to the large number of broken specimens, similarities in texture, and for comparison with Osterman and Smith (2012) and Haller et al. (2019). Broken specimens were counted only if the umbilicus was preserved; fragmented chambers were not counted. ...
... The decrease of M. fusca, a brackish-estuarine and low-marsh taxa, may be the result of reduced terrestrial influence (e.g., type of OM preserved in sediment) and increased marine influence (e.g., salinity) compared with the 1950s. Haller et al. (2019) recorded an abundance of live calcareous specimens and high total abundances of calcareous species (e.g., Am. tepida, Am. parkinsoniana, H. germanica, and Cribroelphidium excavatum (synonymous with E. excavatum used in this study)) in surficial sediments from GB estuary. The calcareous species observed in Haller et al. (2019) and in this study at sites 238, 239, and 240 are common in the GoM and MsS (Phleger, 1954). ...
Grand Bay estuary in coastal Mississippi and Alabama (USA) has undergone significant geomorphic changes over the last few centuries as a result of anthropogenic (bridge, road, and hardened shoreline construction) and climatic (extreme storm events) processes, which reduce freshwater input, sediment supply, and degrade barrier islands. To investigate how geomorphic changes may have altered the Grand Bay estuary, sediment push cores were collected for foraminiferal, sedimentological (organic matter content, grain-size distribution), and radiochemical (²¹⁰Pb,¹³⁷Cs, and ⁷Be) analyses. Clay normalized geochronologies were determined with a constant rate of supply model. Based on downcore age-depth relationships, select intervals were analyzed for foraminifera in order to assess alterations in the microfossil assemblage in Grand Bay estuary over the 20th Century. All estuarine samples were low diversity (species richness: 1–10; Fisher's alpha diversity: 0.14–1.75); two species, Ammotium salsum and Paratrochammina simplissima, dominated all downcore assemblages. Paratrochammina simplissima increased in abundance up-core from a minor subsidiary species (median = 4.7% at 19–20 cm) to dominant or co-dominant with A. salsum over the 20th and early 21st Centuries in six cores, comprising up to 60.7% of a single sample. The emerging dominance of P. simplissima since ~1950 along with the reduction of brackish-estuarine taxa and introduction of calcareous species signifies increased salinity and less marsh organic matter preserved in the sediments. While seasonal dissolution limits our ability to chronologically constrain the introduction of calcareous species, P. simplissima, a species not referenced in taxonomic data from the northern Gulf of Mexico until 2012, is well constrained, following its first occurrence in the 1930s.
... Based on a survey of literature on recent Ammonia (Schnitker, 1974;Jorissen, 1988;Langer et al., 1989;Walton and Sloan, 1990;Debenay et al., 1998;Stouff et al., 1999;Hayward et al., 2004;Carboni et al., 2009;Takata et al., 2009;Dupuy et al., 2010;Haller et al., 2019;Hayward et al., 2019, among others), we subdivide the ecopenotypes morphospace as follows. ...
... Massive presence of Ammonia forma tepida indicates stressed environments with clay inputs, low-oxygen and nutrient-rich bottoms. It has been reported in transitional marine environments at shallow depth (10 m to 25 m) such as estuaries (Haller et al., 2019), but also in paralic environments such as suboxic mudflats (Thibault de Chanvalon et al., 2015), marginal marshes and brackish lagoons (Walton and Sloan, 1990;Debenay et al., 1998Debenay et al., , 2000Debenay and Guillou, 2002;Takata et al., 2009;Dupuy et al., 2010;Melis and Covelli, 2013), and even in inland brackish lakes (Wennrich et al., 2007). Its distribution also includes inland saline-water bodies (Walton and Sloan, 1990;Almogi-Labin et al., 1992) lying very far from the sea (Wennrich et al., 2007). ...
The Miocene transgression in central and southern Apennines is commonly represented by a sharp contact between shallow-water open-marine bioclastic limestones and the underlying Cretaceous or Eocene bedrock. Only in a few areas, very proximal marine or paralic deposits, witnessing the first stage of the transgression, have been preserved. These deposits contain rich foraminiferal assemblages commonly dominated by specimens of the genus Ammonia. The paleontological and paleoenvironmental analysis revealed that the Miocene Ammonia shared the same habitat and ecological requirements of living representatives from recent shoreline environments. Small Ammonia forma ‘tepida’ have been found in Miocene marginal paralic organic-rich bottoms with restricted water circulation and possibly under natural metal pollution. Big Ammonia forma ‘beccarii’ characterize Miocene nearshore marine bottoms with vegetated areas under fresh water inputs. The endoskeletal lamellar folding called tooth-plate, which characterizes recent representatives, is observed in fossil specimens of both tepida and beccarii morphogroups, testifying that there were no major changes in the shell architecture of Ammonia since the early Miocene.
... In the innermost sampling points of the present study, we noted the presence of species typical from both tropical [30,63,87] and temperate [88][89][90][91] transitional environments. The species were A. parkinsoniana, C. excavatum, and A. tepida, and they are considered resilient to salinity changes. ...
This study investigates the composition and spatial distribution of benthic foraminiferal assemblages in the estuaries of the Mamanguape and Paraíba rivers in Northeast Brazil. Samples were collected from different sectors along both estuaries and analyzed for foraminiferal density, diversity, and species composition in relation to abiotic factors like salinity, temperature, pH, and sediment grain size. Results show that calcareous foraminifera dominate both estuaries, likely influenced by stable pH and salinity gradients. Additionally, the sediment composition of both estuaries varies from typical tropical estuarine patterns, with the presence of coarse and medium sands suggesting significant environmental dynamics. Statistical analyses confirm that foraminiferal assemblages reflect spatial environmental variations within and between the estuaries, underscoring the potential of foraminifera as bioindicators in coastal ecosystem assessments.
... The nominative species of FA1 C. poeyanum is a common member of marginal marine assemblages (Brewster-Wingard and Ishman, 1999;Ishman, 2000;Cheng et al., 2012;Ellis et al., 2018;Haller et al., 2019) that are negatively correlated with phytodetritus (Brasier, 1975). The presence of other elphidid foraminifera, in the older parts of the core where FA1 dominates, indicates euryhaline salinities (Murray, 1991), suggesting periods of temporarily reduced salinity, possibly related to increased rainfall. ...
This paper is a paleo-ecological study of foraminifera assemblages in the Marquesas Keys, Florida. Please direct questions or requests to tfrankov@fiu.edu
... Calcareous taxa can be dissolved in cores by decreases in pH associated with the decay of organic material in salt marsh peats (e.g. Goldstein and Watkins, 1999;Haller et al., 2019). Because the full relationship between taxa which are still present at the base of the tidal flat (open-ended taxa) and elevation cannot be elucidated properly in the surface data, an attempt was made to refine the transfer function by removing all calcareous (Ammonia spp., Elphidiinae spp., H. depressula, Quinqueloculina sp.) and open-ended (Ammonia spp., Elphidiinae spp., H. depressula, M. fusca, A. exiguus, Reophax sp.) species from the dataset. ...
Vertical land movement variability around the coasts of New Zealand has introduced a great deal of uncertainty to projections of future sea-level rise around major coastal cities. To gain an understanding of how this movement has occurred and changed over time, as well as the other factors driving sea-level change around major cities, four new sea-level reconstructions are presented. These records are from salt marshes in Greater Wellington (Pāuatahanui), Dunedin (Aramoana) and Auckland (Catalina Bay and Rangiototo Island. At Pāuatahanui, relative sea-level rise has risen by 1.50 ± 0.59 mm/yr since 1855, with either a gradual or abrupt deceleration during the twentieth century, followed by a rapid acceleration from ~2000-present to >3 mm/yr, which is not observed at the Wellington tide gauge. This change indicated that modern ~1.7 mm/yr land subsidence rates recorded by global positioning systems from adjacent to Pāuatahanui salt marsh over the last 20 years is a recent feature, the onset of which is recorded in the salt marsh record. Had this not been the case, the rate of relative sea-level rise reconstructed at Pāuatahanui would have been much greater. At Aramoana, which lies at the mouth of Otago Harbour, relative sea level has risen by 2.18 ± 0.83 mm/yr since 1881, showing excellent agreement with the Dunedin tide gauge, with a specific ~60-year recurring trend of accelerations and decelerations replicated at both the salt marsh and the tide gauge. This trend is not observed at other southern South Island foraminiferal sea-level reconstructions, and appears to be due to the influence of Southern Annular Mode (SAM) variability, on the basis of comparisons between the rate of relative sea-level rise and SAM trends. The close agreement between the tide gauge (subsiding by only ~0.69 mm/yr) and the salt marsh (whose sea-level record indicates only very marginally more subsidence) suggests that the high degree of subsidence measured in the city centre is localised to the city, and the result of the compression of soft underlying sediments by large man-made structures. The Pāuatahanui and Aramoana sea-level reconstructions yield valuable insights into the processes that have driven relative sea-level change around Greater Wellington and Dunedin, which will assist in understanding how sea-level rise will affect these sites in the future. One key finding has been the revelation of spatial variability in land movement even on what was considered to be the local scale, to the extent that neither Aramoana truly reflects the scale of sea-level rise at the coast of Dunedin city, nor does Pāuatahanui at the coast of Wellington city. The two sea-level reconstructions from Auckland appear to be less reliable than those from elsewhere, but yield valuable insights into the influence of local processes including freshwater runoff triggered by catchment disturbance, species infaunality, and dissolution on foraminiferal sea-level reconstructions.
... Some multichambered rotaliids and textulariids are reported to penetrate brackish habitats where the salinity drops to very low levels (Boltovskoy & Wright, 1976;Hayward et al., 2006;Haller et al., 2019). However, apart from these marginal incursions, all truly non-marine foraminifers living in freshwater and damp terrestrial habitats are single-chambered monothalamids. ...
Foraminifera are a primarily marine taxon widespread in all oceanic habitats, from shallow, brackish-water settings to deep-seafloor and pelagic realms. Their diversity is remarkable with several thousand species described and a fossil record tracing back to the Cambrian. While foraminifera represent one of the best-studied groups of marine meiofauna, much less is known about their non-marine relatives. The first freshwater foraminifera were described in the 19th century by European and North American protozoologists, but interest in them lapsed during much of the 20th century and was not rekindled until the advent of molecular systematics provided a fresh impetus to their study. Several new species, genera, and families have been described recently based on morphological and molecular data derived from cultured specimens. In parallel, environmental genomic studies revealed that foraminifera are highly diverse and ubiquitous in freshwater and soil environments. Molecular phylogenetic analyses places non-marine foraminifera in a few clades among the large array of single-chambered (monothalamous) lineages, suggesting that several independent colonization events of freshwater and terrestrial habitats occurred. Non-marine foraminifera are turning from obscure curiosities to being recognized as an important part of soil and freshwater microbial communities, a major component of these complex environments.
... The time interval between these two episodes witnessed a period of silting, with the transition from a low salt marsh to a high salt marsh in recent centuries (Fig. 6). During the intermediate stage with little mining and industrial activity, the foraminiferal record of this period is very similar to that observed in undisturbed salt marshes (Jones 2014, Soualili 2018, Haller et al. 2019. No evidence of Roman mining pollution (~2.1-1.5 cal kyr BP) has been found in this core, as in other cores of this estuary (e.g. ...
This paper investigates the paleoenvironmental evolution of a core extracted in the middle sector of the Tinto River estuary, SW Spain, one of the most polluted areas in the world due to mining over thousands of years (>4 kyr BP) and recent industrial discharges. This evolution includes alluvial sands (>6.4 cal kyr BP), bioclastic sands and silts deposited in subtidal and intertidal channels during and after the Holocene transgression maximum (6.4-4.3 cal kyr BP), the sedimentation of clayey-sandy silts in low and high marshes during the last 2.4 kyr BP and a final anthropic filling. Three sharp peaks of pollution have been detected, representing a) a natural origin during the Holocene transgression; b) the impact of the first mining activities (~4.5 cal kyr BP); and c) the effect of industrial discharge and a new period of mining activity throughout the 19th and 20th centuries. Foraminifera, ostracods and molluscs disappeared during these last two peaks.
... Benthic foraminifera are among the main environmental markers in coastal areas. The distribution of these microorganisms is conditioned by diverse physical-chemical parameters of the waters (salinity, dissolved oxygen, pH), as well as by the characteristics of the substrate where they live (granulometry, geochemistry) [1][2][3]. Its abundance and diversity can be altered by changes in the dynamics of the environment, erosion of the bottom or anthropic contamination, among other factors [4,5]. ...
Three zones are differentiated in the marine sector of the Guadalquivir estuary (SW Spain), according to a multidisciplinary analysis (water, sediment, foraminifera). Both salinities and pH increase from the innermost areas (zone 1: Ammonia tepida) to the mouth (zone 3: Ammonia beccarii), with an intermediate zone 2 (Ammonia beccarii-Triloculina trigonula). Both density and diversity are low to very low, except near the transition between zones 2 and 3. Planktonic foraminifera decrease sea Ward from zone 1 to zone 3.
The studied section of the Habai region, Kachchh, India, contains foraminiferal assemblages with 86 species, of which the family Vaginulinidae is dominant. Twenty-seven species are reported from the Indian subcontinent for the first time. Benthic foraminiferal morphogroups, the Fisher index, and multivariate analysis of the Middle to Late Jurassic assemblages reveal their responses to palaeoecological fluctuations in the area. To determine the palaeoenvironmental relevance of the morphogroup relationships, seven sub-morphogroups are recognised based on their lifestyles and feeding strategies. The elongated uniserial, flattened, and biconvex planispiral forms are dominant and show a high percentage of subgroups with a deduced epifaunal to deep infaunal habitat. The Fisher index and statistical approaches including clustering, PCA, PCoA, and CA reveal four benthic foraminiferal assemblages representing five palaeoecological units. During the Bathonian Age, Lenticulina subalata assemblages suggest a stable environment during a transgressive phase. This was followed by an environment characterised by dysoxic conditions, which led to the vanishing of foraminifera and other fauna, resulting in a barren zone. Epistomina ghoshi and Ammobaculites hagni assemblages in the subsequent depositional settings of the Middle Callovian Age record transgressive and progressively deeper outer shelf conditions, with high food flux and adequate oxygen levels, respectively. The deposition shifted again to a regressive environment during the Late Callovian to Oxfordian Age, as this unit is devoid of foraminifera as well as of megafauna, which may be related to the palaeoenvironmental changes and probably indicating unsuitability for life. Overall, the palaeoenvironmental conditions of the studied area exhibit a periodic pattern between the middle and outer shelf zones related to changes in sea level.
The cosmopolitan organic-cemented agglutinated foraminifer Trochamminita irregularis previously identified in Australian salt marshes of the Gippsland Lakes in Victoria and Little Swanport Estuary in Tasmania, has been recognised for the first time in Western Australia in the Hay River connected to Wilson Inlet, in the south-west of the State. The irregular test and chamber shapes may be related to the species mode of living restricted to the upper-marsh or river-margin environments in organic-rich sediment associated with filamentous rhizomes/stolons of marsh vegetation. Morphological variation may also be due to highly variable seasonal to daily environmental changes ranging from tidal variation, salinity changes (within a hyposaline range) and variable river flow. Trochamminita ’s fragmented global distribution could likely be attributed to attachment to migratory waterbirds dispersing it along major flyways such as the East Australasian Flyway where Australia acts as one of the main foraging and breeding ground for these birds. The discovery of the species in the Hay River allows some preliminary investigations of the micro-living habitat of Trochamminita and its potential means of dispersion. Molecular and more in-depth ecological studies on living T. irregularis are required to more fully understand this global and ecologically significant marsh indicator species.
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.
A high degree of uncertainty exists for understanding and predicting coastal estuarine response to changing climate, land-use, and sea-level conditions, leaving geologic records as a best-proxy for constraining potential outcomes. With the majority of the world's population focused in coastal regions, understanding how local systems respond to global, regional, and even local pressures is key in developing mitigation, adaptation, and management plans. The geomorphology of Mobile Bay in southeast Alabama (USA) has evolved considerably (e.g., bayhead delta back-stepping) over the late Holocene in response to global and regional sea-level and climate change. Smaller-scale geomorphic changes (e.g., spit and beach ridge development) have also had a significant influence on the evolution of the estuary. Organic matter characteristics, inorganic sediment geochemistry, benthic microfossils, and pollen in a ~ 3500 cal yr BP sediment sequence recovered in a gravity core (20GC) from Bon Secour Bay, a small sub-bay in the southeast corner of Mobile Bay, record time-varying marine influence. Increases in marine influence during ~3500 to 2300 cal yr BP and 1930 to 1160 cal yr BP are defined as zones with high-density and pre-dominantly calcareous foraminiferal species, abundant sand (>10%) and more marine-like geochemical signatures, which contrast the low-density and pre-dominantly agglutinated foraminiferal and more terrestrially influenced estuarine muds observed in other intervals of the sedimentary record (2300–1930 and 1160–400 cal yr BP) and the the modern bay. Hydrodynamic models constrained by geomorphic boundary conditions for the time ~ 3500 cal yr BP, consistent with the most prominent marine-influenced sediment, provide insight to potential coastal configuration that might have permitted such marine water intrusion into the bay. Of several scenarios evaluated, a breach in Morgan Peninsula produces tidal circulation within the basin supportive of persistent marine incursions in the bay between ~3500 to 2300 cal yr BP. The findings show that slight variations in coastal configuration can have broad-scale effects on bays and estuaries with consequences that may relate to water quality, vertebrate and invertebrate habitat, and coastal vulnerability to episodic events like (extra)tropical storms.
Foraminiferal census data from Chincoteague Bay, Newport Bay, the salt marshes of Assateague Island, adjacent mainland salt marshes, and the inner-shelf, were assessed to determine the current assemblages in Chincoteague Bay, and how the different environments surrounding the bay, and the gradients within the bay, influence the microfossil distribution. Determining the current background distribution and its drivers allows for future comparisons to determine paleoenvironmental conditions, impacts from natural and anthropogenic pollution, and the influence of climate change. Foraminiferal census data were compared to sedimentological characteristics and environmental parameters, exhibiting strong correlations with salinity, sediment organic content, and grain-size. Foraminiferal distributions exhibited a gradient from an assemblage dominated by Elphidium cf. E. excavatum near Chincoteague inlet to an assemblage dominated by Ammonia parkinsoniana and Ammobaculites cf. Ab. exiguus in the more restricted central and northern portions of the bay. The sites closest to the mouth of Trappe Creek in Newport Bay, along the western side of Chincoteague Bay and in the central bay, had a greater relative abundance of dead agglutinated taxa compared with the majority of sites in Chincoteague Bay. Despite the overwhelming dominance of calcareous taxa throughout the bay, dissolution may affect the preservation potential of Cribroelphidium poeyanum and Haynesina germanica in the northern and central portions of Chincoteague Bay, as indicated by seasonal pH data. Similarly , the sandy back-barrier lagoonal sites exhibited relatively low densities, potentially a result of dissolution or mechanical destruction.
Species names for Ammonia and Elphidium have continually changed since these taxa were first described in Texas coastal environments. As a result, classification is problematic and the literature is inconsistent. The purpose of this paper is to evaluate the taxonomic status of species currently assigned to Ammonia and Elphidium. This task has been accomplished through extensive literature review and through comparison of specimens from this study with those in the Cushman Collection at the National Museum of Natural History. Most Elphidium found along the Texas coast are assignable to either Elphidium gunteri or E. excavatum, and the Ammonia present are assignable to Ammonia parkinsoniana and A. tepida. Present geographic, molecular and reproductive evidence shows that the species names A. parkinsoniana and A. tepida, not A. beccarii, should be used to describe these morphotypes of Ammonia wherever they occur, including the Gulf of Mexico, the east coast of North America, the Caribbean and the Pacific.
The study of benthic foraminifera in sediment cores provides the opportunity to recognize environmental changes, including those due to the anthropogenic impact. The integration of these data with chemical-physical parameters provides a comprehensive quality assessment. This research was applied to a sediment core collected in the Augusta bay, where a very large commercial and military harbor and one of the largest petrochemical poles in Europe are present. Inside the petrochemical area also operated, from 1958 to 2003, a chlor-alkali plant with mercury cell technology which caused anthropic contamination of surrounding land and marine areas. The sediment core was collected in front of this plant and characterized for grain size and pollutants directly associated to chlor-alkali activity, such as mercury (Hg), barium (Ba), polychlorobiphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). Composition of foraminiferal assemblages and faunal parameters such as specific diversity, faunal density, abundance of abnormal specimens, and foraminiferal size were investigated as potential indicators of environmental status. Statistical analysis indicated a main common origin for Hg, Ba, and PCBs and the influence of pollutants on species distribution and faunal diversity and density. Exceptionally high Hg concentrations (63-680 mg/kg d.w.) were recorded in the whole core, where the geochronological study attributed the most contaminated levels to the period of maximum activity of the chlor-alkali plant, while a decrease of contamination was recorded after the stop of the activity. Distinct foraminiferal assemblages identified different ecozones along the core, which suggested decreasing anthropogenic impact from the bottom to the top.
Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO 2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madre-pora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geo-chemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents
This study evaluates the geophysical influence of the combined effects of historic sea level rise (SLR) and morphology on tidal hydrodynamics in the Grand Bay estuary, located in the Mississippi Sound. Since 1848, the landscape of the Mississippi Sound has been significantly altered as a result of natural and anthropogenic factors including the migration of the offshore Mississippi-Alabama (MSAL) barrier islands and the construction of navigational channels. As a result, the Grand Bay estuary has undergone extensive erosion resulting in the submergence of its protective barrier island, Grand Batture. A large-domain hydrodynamic model was used to simulate present (circa 2005) and past conditions (circa 1848, 1917, and 1960) with unique sea levels, bathymetry, topography and shorelines representative of each time period. Additionally, a hypothetical scenario was performed in which Grand Batture Island exists under 2005 conditions in order to observe the influence of the island on tidal hydrodynamics within the Grand Bay estuary. Changes in tidal amplitudes from the historic conditions varied. Within the Sound, tidal amplitudes were unaltered due to the open exposed shoreline; however, in semi-enclosed embayments outside of the Sound, tidal amplitudes increased. In addition, harmonic constituent phases were slower historically. The position of the MSAL barrier island inlets influenced tidal currents within the Sound; the westward migration of Petit Bois Island allowed stronger tidal velocities to be centered on the Grand Batture Island. Maximum tidal velocities within the Grand Bay estuary were 5 cm/s faster historically, and reversed from being flood dominant in 1848 to ebb dominant in 2005. If the Grand Batture Island was reconstructed under 2005 conditions, tidal amplitudes and phases would not be altered, indicating that the offshore MSAL barrier islands and SLR have a greater influence on these tidal parameters within the estuary. However, maximum tidal velocities would increase by as much as 5 cm/s (63%) and currents would become more ebb dominant. Results of this study illustrate the hydrodynamic response of the system to SLR and the changing landscape, and provide insight into potential future changes under SLR and barrier island evolution.
Full text available: http://www.sciencedirect.com/science/article/pii/S0278434315300212
Substantial spatio-temporal variation in foraminiferal inputs occur over short areal distances at the sediment-water interface
and downcore as a result of patchy distributions and seasonal reproduction; foraminiferal assemblages are in turn diagenetically
overprinted by seasonal, inter-seasonal, and inter-annual changes in pore-water chemistry. Seasonal surface and near-surface
assemblages are typically unrepresentative of deeper assemblages that are more likely to be incorporated into the sedimentary
record. Cluster analysis of “artificially time-averaged” (ATA) assemblages revealed a distinct change in assemblages at ~20
cm depth. Differential preservation of foraminifera in the upper 60 cm, and especially the upper 20 cm, of sediment may produce
an apparent paleoenvironmental change that could potentially be misinterpreted as a rapid fall in sea-level over the last
~100–200 years.
Coastal risk assessment and hazard mitigation require datasets on centennial and millennial temporal scales to capture natural variability and multiple occurrences of the largest, but least frequent, events. Coastal sediments from low-energy depositional environments archive geologic evidence of paleo-earthquakes, tsunamis, and storms. Many of the best reconstructions of these events are derived from changes in microfossil (diatoms, foraminifera, and pollen) assemblages. In this review we explain how microfossils are used to reconstruct records of paleoearthquakes by quantifying the amount of coseismic and interseismic vertical land movements along tectonically active coastlines. Examples from the United States (Alaska and the Pacific Northwest), Japan, and Chile show that microfossil-based transfer functions may provide continuous records of vertical land movement during earthquake deformation cycles. We discuss how microfossil habitat preferences and taphonomic character are used to constrain sediment provenance (e.g., beach, nearshore, or offshore sources) and identify overwash deposits, and how this information can be used to reconstruct the recurrence of tsunamis and storms. Analysis of overwash deposits from Thailand and Malaysia indicates the ability of microfossils to resolve individual waves within tsunami sediments, and an example from the Sendai coastal plain in Japan uses foraminifera to ascribe a beach to nearshore provenance for the 2011 Tohoku tsunami deposit. Finally, we present recent examples from the Gulf of Mexico on the use of foraminifera to estimate the volume and distance of transport of storm overwash from hurricanes.
A comprehensive, but simple-to-use software package for executing a range of standard numerical analysis and operations used in quantitative paleontology has been developed. The program, called PAST (PAleontological STatistics), runs on standard Windows computers and is available free of charge. PAST integrates spreadsheettype data entry with univariate and multivariate statistics, curve fitting, time-series analysis, data plotting, and simple phylogenetic analysis. Many of the functions are specific to paleontology and ecology, and these functions are not found in standard, more extensive, statistical packages. PAST also includes fourteen case studies (data files and exercises) illustrating use of the program for paleontological problems, making it a complete educational package for courses in quantitative methods.
Water column velocity and hydrographic measurements on the inner Alabama
shelf are used to examine the flow field and its forcing dynamics during
the Deepwater Horizon oil spill disaster in the spring and summer of
2010. Comparison between two sites provides insight into the flow
variability and dynamics of a shallow, highly stratified shelf in the
presence of complicating geographic and bathymetric features. Seasonal
currents reveal a convergent flow with strong, highly sheared offshore
flow near a submarine bank just outside of Mobile Bay. At synoptic time
scales, the flow is relatively consistent with typical characteristics
of wind-driven Ekman coastal circulation. Analysis of the depth-averaged
along-shelf momentum balance indicates that both bottom stress and
along-shelf pressure gradient act to counter wind stress. As a
consequence of the along-shelf pressure gradient and thermal wind shear,
flow reversals in the bottom currents can occur during periods of
transitional winds. Despite the relatively short distance between the
two sites (14 km), significant spatial variability is observed. This
spatial variability is argued to be a result of local variations in the
bathymetry and density field as the study region encompasses a submarine
bank near the mouth of a major freshwater source. Given the physical
parameters of the system, along-shelf flow in this region would be
expected to separate from the local isobaths, generating a mean offshore
flow. The local, highly variable density field is expected to be, in
part, responsible for the differences in the vertical variability in the
current profiles.
We studied the foraminiferal distribution in two naturally grown salt marshes from the southern North Sea with respect to the tidal frame, salinity, grain size and pH. The salt marshes are situated on the landward sides of the islands of Sylt (Rantum, Germany) and Fanø (Sønderho, Denmark). In both study areas, foraminifera have a vertical distribution with respect to water level, but also show inter-site variability, which can be related to environmental differences (e.g., in salinity and pH) and different flooding dynamics of the coastal salt marsh (Rantum) and the tidal-creek salt marsh (Sønderho). We developed different transfer functions, based on the widely applied standardized water level index (SWLI) approach and on three flooding parameters (duration of submergence (DoS), mean submergence time (MST), and flooding frequency (FF)), in order to assess their predictive ability for relative sea-level estimates for the southern North Sea coastal region. The water-level data used for these approaches are determined based on local water-level conditions, corrected for tidal distortions using water-level measurements for the Sønderho salt marsh and the Rantum tide gauge. The SWLI approach shows a precision (root mean squared error of prediction (RMSEP) of 0.23 m), which is around 15% of the tidal range. All three flooding approaches show comparable results at around mean tide level to mean high water, while at higher elevations, foraminiferal distribution becomes non-linearly correlated to flooding parameters resulting in lower precision of > 1.0 m. Our results suggest that the SWLI approach performs well and that the flooding approaches offer a suitable addition for assessing relative sea-level estimates in the North Sea region. We enhanced the knowledge on changing precision for tide level reconstructions along the elevational gradient in a storm dominated tidal area where elevation and flooding parameters are non-linear correlated.
In the present study we investigate the ecology and distribution of living benthic foraminifera to test the effect of hyper tidal exposure and their suitability as sea level indicators. Within a salt marsh area along the Canche Estuary (northern France), four transects were sampled to see the effects of maximal tidal constraints (shore transects) and minimal tidal constraints (alongshore transects). Multivariate analyses have been performed to determine the correlations between biotic (foraminiferal absolute abundances) and abiotic factors (elevation, grain-size, TOC and total sulphur). For each of the principal benthic foraminiferal species the tolerance to subaerial exposure have been estimated as well. Two distinctive foraminiferal zones have been identified along the vertical tidal gradient: a zone I in the higher part of the salt marsh dominated by agglutinated and porcelaneous taxa, and a zone II in the lower one dominated by hyaline specimens. Hyper tidal exposure constraints the foraminiferal vertical zonation in accordance with the tidal frame. However it does not constitute a threshold parameter able by itself to explain all the faunal variations in the Canche Estuary. For sea level indicators, foraminifera should be considered relative to tidal subaerial exposure rather than to absolute altitude.
We investigated the utility of foraminifera, testate amoebae and bulk-sediment δ¹³C measurements for reconstructing Holocene relative sea level from sequences of salt-marsh sediment in Newfoundland, Canada. Modern, surface sediment was collected along transects from low to supra-tidal elevations in eastern (at Placentia) and western (at Hynes Brook and Big River) Newfoundland. Consistent with previous work, low-diversity assemblages of foraminifera display an almost binary division into a higher salt-marsh assemblage dominated by Jadammina macrescens and Balticammina pseudomacrescens and a lower salt-marsh assemblage comprised of Miliammina fusca. This pattern and composition resembles those identified at other high latitude sites with cool climates and confirms that foraminifera are sea-level indicators. The lowest occurrence of testate amoebae was at approximately mean higher high water. The composition of high salt-marsh testate amoebae assemblages (Centropyxis cassis type, Trinema spp., Tracheleuglypha dentata type, and Euglypha spp.) in Newfoundland was similar to elsewhere in the North Atlantic, but preservation bias favors removal of species with idiosomic tests over those with xenosomic tests. The mixed high salt-marsh plant community in Newfoundland results in bulk surface-sediment δ¹³C values that are typical of C3 plants, making them indistinguishable from freshwater sediment. Therefore we propose that the utility of this proxy for reconstructing RSL in eastern North America is restricted to the coastline between Chesapeake Bay and southern Nova Scotia. Using a simple, multi-proxy approach to establish that samples in three radiocarbon-dated sediment cores formed between the lowest occurrence of testate amoebae and the highest occurrence of foraminifera, we generated three example late Holocene sea-level index points at Hynes Brook.
Salt-marsh foraminifera serve as proxy sea-level indicators due to a quantifiable relationship with elevation in the contemporary environment. In this paper, we document the distribution of salt-marsh foraminifera from two microtidal sites, Jadrtovac and Blace, along the Adriatic coast of Croatia and assess their suitability as proxies for elevation in transfer-function-based reconstructions of sea level, which is not yet established for the Mediterranean region. The assemblages are dominated by typical salt-marsh agglutinated taxa, Jadammina macrescens and Trochammina inflata, and the calcareous taxa Ammonia spp. and Quinqueloculina spp. Quantitative analyses revealed that the assemblages are divided into three faunal zones, which are elevation dependent, and that the assemblage dominated by J. macrescens and T. inflata extends to higher elevations in the intertidal frame. The training set was used to develop a tidal-level transfer function using linear regression due to the short environmental gradients observed. The model predicts sea level with a precision of ± 0.08 m. This study highlights the strong potential of salt-marsh foraminifera in reconstructing RSL trends for the Mediterranean region, where studies of past sea-level have previously been restricted to other indicators.
Stratigraphic, sedimentologic (including CT 3D X-ray tomography scans), foraminiferal, and radiocarbon
analyses show that at least six of seven abrupt peat-to-mud contacts in cores from a tidal marsh at Talbot
Creek (South Slough, Coos Bay), record sudden subsidence (relative sea-level rise) during great megathrust
earthquakes at the Cascadia subduction zone. Data for one contact are insufficient to infer whether
or not it records a great earthquakedit may also have formed through local, non-seismic, hydrographic
processes. To estimate the amount of subsidence marked by each contact, we expanded a previous
regional modern foraminiferal dataset to 174 samples from six Oregon estuaries. Using a transfer
function derived from the new dataset, estimates of coseismic subsidence across the six earthquake
contacts vary from 0.31 m to 0.75 m. Comparison of subsidence estimates for three contacts in adjacent
cores shows within-site differences of �0.10 m, about half the ±0.22 m error, although some estimates
may be minimums due to uncertain ecological preferences for Balticammina pseudomacrescens in
brackish environments and almost monospecific assemblages of Miliammina fusca on tidal flats. We also
account for the influence of taphonomic processes, such as infiltration of mud with mixed foraminiferal
assemblages into peat, on subsidence estimates. Comparisons of our subsidence estimates with values
for correlative contacts at other Oregon sites suggest that some of our estimates are minimums and that
Cascadia's megathrust earthquake ruptures have been heterogeneous over the past 3500 years.
Foraminifera populations have been analyzed from 550 bottom samples, 65 submarine cores, and 27 serial plankton tows from the northwestern Gulf of Mexico. Twenty-five complete hydrographic stations and 473 bathythermograms give data on the temperature and salinity conditions. Field and laboratory methods are described.
Six benthonic Foraminifera depth facies are recognized, with boundaries at the following approximate depths: 80–120 m., 180–220 m., 500–750 m., 1000–1300 m., and 1800–2000 m. Subfacies are recognized in some traverses, especially in depths shallower than 100 m. Determination of facies and subfacies is based largely on overlap ranges of species. Temperature range is suggested as a key factor affecting facies distribution. The most marked facies boundary is at 80–120 m., the depth of the top of the main thermocline. Above this depth oceanographic conditions are strikingly different from those at greater depths.
Living specimens of 78 benthonic species have been collected. There is good correlation between abundance of living specimens and empty tests for each species. Average production of living benthonic Foraminifera is approximately 10 times as great above 100 m. as at greater depths. Production rates and population census give a possible method for determining relative rates of sedimentation.
Planktonic Foraminifera in abundance are characteristic of offshore water masses. Living planktonic specimens are found at all depths of water sampled down to 1400 m., the deepest plankton tow taken. At most stations there is a larger population of planktonic specimens in the upper 50 m. than at other depths; at a few stations there is a larger population at greater depths.
Most of the submarine cores contain a fauna below the surface which is characteristic of areas having lower surface-water temperatures than the present Gulf of Mexico. This lower fauna is interpreted as late glacial in age. Faunas in a few cores suggest rise of sea level since late glacial time.
In this 2006 volume John Murray investigates the ecological processes that control the distribution, abundance and species diversity of benthic foraminifera in environments ranging from marsh to the deepest ocean. To interpret the fossil record it is necessary to have an understanding of the ecology of modern foraminifera and the processes operating after death leading to burial and fossilisation. This book presents the ecological background required to explain how fossil forms are used in dating rocks and reconstructing past environmental features including changes of sea level. It demonstrates how living foraminifera can be used to monitor modern-day environmental change. Ecology and Applications of Benthic Foraminifera presents a comprehensive and global coverage of the subject using all the available literature. It is supported by a website hosting a large database of additional ecological information (www.cambridge.org/0521828392) and will form an important reference for academic researchers and graduate students in Earth and Environmental Sciences. © Cambridge University Press, 2009 and John Murray 2006. All rights reserved.
In paleontological investigations the number of individuals of a particular species, n i , is often expressed as a proportion of the total number of individuals, ∑ i=1 S n i = n, for all, S, species. This proportion, p = n i /n expressed in percent, is referred to by various authors as percent species, relative abundance, percentage abundance, species frequency, fractional abundance, and so on. Naturally, researchers are interested in the confidence limits that can be placed on these estimates, and in the number of individuals required to obtain them. The binomial distribution was used by Dryden (1931), Dennison and Hay (1967), Wright and Hay (1971), and Patterson and Fishbein (1989) for this purpose.
Most paleoenvironmental assessments of fossil salt-marsh foraminiferal faunas are based on modern analogue samples from the surface 1–2 cm. Usually no account is taken of the faunal modifications that result from the 60–90% of the fauna that live at greater infaunal depths or from the patchy loss of
agglutinated tests that mostly occurs in the oxic and taphonomically active zone (TAZ, upper 10–15 cm). Here we provide examples of the highly variable foraminiferal test distribution in New Zealand salt marsh cores and surface transects. Using these, we suggest two simple adjustments that could be made to quantitative estimates of paleoelevation derived from fossil salt marsh faunas based on modern surface
analogues: 1) Determine a minimum dead specimen density (8 per cm3 in this study) below which all fossil faunas are considered to have suffered significant taphonomic loss (in the TAZ) and their paleoelevation estimates are deemed suspect and may be applied tentatively to core depths ~15+ cm above. 2) Move the core depths of all acceptable paleoelevation estimates upwards by the mean infaunal depth of the dominant species (2.5–8 cm in this study). We applied these adjustments to two late Holocene cores located 5 m apart in salt marsh in tidal Big Lagoon, Marlborough, New Zealand. Fifty percent (18) of the fossil faunas have unacceptably low specimen densities (<8 per cm3). A 15 cm thick fine pebbly sand bed contains a mix of calcareous tests derived from subtidally offshore and from intertidally within the adjacent sheltered lagoon, and agglutinated tests of salt marsh taxa inferred to be displaced and/or infaunally in-situ. These faunas provide strong evidence for sand deposition on top of the high salt marsh by the outgoing surge of a tsunami. The upper 7 and 13 cm of the sand lacks calcareous tests, which are inferred to have been dissolved by acidic pore waters following colonisation by salt marsh vegetation. Our taphonomically- and infaunally adjusted paleoelevation estimates, generated by modern
analogue technique using a training set of 1017 modern New Zealand faunas, provide near-identical elevational histories for both cores. Both core sequences (70 and 85 cm thick) were deposited within a 50 cm-wide elevational envelope in middle- and high-tidal salt marsh. Both record an inferred 0.5 m co-seismic subsidence event coincident with emplacement of the tsunami sand (~840 cal yrs BP) and a second smaller, ~0.3 m, presumably co-seismic, subsidence event coincident with a sharp peat-mud contact in one core (~500 cal yrs BP).
Populations of living Foraminifera were studied from six areas of marine marsh in Galveston Bay. The general marsh foraminiferal assemblage is an Ammotium salsum‐Miliammina fusca one, with common Ammonia beccarii , Arenoparrella mexicana , and Trochammina inflata , and also containing Ammoastuta inepta , Elphidium spp., Tiphotrocha comprimata , and Trochammina macrescens in somewhat smaller frequencies.
The following marsh environments have distinctive assemblages of Foraminifera: 1) channel or bay bordering a marsh, 2) fringing Spartina zone, 3) Salicornia berm, 4) inner Spartina zone, 5) inner Salicornia zone, 6) lagoon barrier marsh, 7) “more saline” marsh, and 8) “less saline” marsh. Living populations are very small to very large, living‐total population rates are large and deposition rates are high.
Extreme range of environmental conditions limits the variety of marsh Foraminifera. Knowledge of the environment is inadequate to explain distributions within the marsh.
A nearshore sediment transport model is developed and presented for the southwest Alabama and Mississippi barrier island coast along the northern Gulf of Mexico, USA. A cellular-type nearshore transport system, supplied by differential sediment sources, characterizes the present day study area, in contrast with previously formulated hypotheses of a net unidirectional, integrated nearshore transport system supplied by a single sediment source. Computer simulations of net longshore sediment transport between Dauphin Island, Alabama, and West Ship Island, Mississippi predict six distinct transport cells characterized by net westward longshore sediment transport. Along eastern Dauphin Island, net longshore transport is eastward toward Mobile Pass. Granulometric trends and changes in the composition of foreshore (step), beach (mid-tide level) and foredune sediments support transport predictions and suggest the possibility of onshore sediment transport along the western flank of the study area. Step and mid-tide sediment grading (coarsening downdrift) is evident along Dauphin Island, and shows a strong relationship with predicted breaker wave height. West of Dauphin Island, sediment samples are characterized by higher concentrations of calcium carbonate (shell) by weight, and heavy minerals, coinciding with a decrease in the inner shelf slope. Field observations and historic shoreline trends are in agreement with longshore sediment transport predictions. For example, chronic shoreline retreat along Dauphin Island, coincides with an increase in net longshore sediment transport, and the highest erosion rate is localized at the net longshore sediment transport reversal (nodal point). Contemporary drift cells appear to experience minimal net sediment exchange because of net longshore transport values approaching zero at most cell termini and ongoing maintenance dredging at the inlets, implying that they function as sediment sinks. Alternative sources of sediment appear to be internal on these barriers.
Examination of 10 carefully compiled large data sets reveals that the species-occurrence frequency distribution of each fits the log series distribution well and therefore sample size effects can be predicted. Results show that as many as 25% of the species will not be found a second time even if both samples are of the same size. If the two samples are of unequal size, then the larger sample may have as many as 70% unique species and the smaller sample no unique species. The implications of these values are important to studies of species richness, origination, and extinction patterns, and biogeographic phenomena. I provide graphs showing the predicted sample size effects for a range of data set size, species richness, and relative data size. For data sets that do not fit the log series distribution well, I provide example calculations and equations which are usable without a large computer. If these graphs or equations are not used, then I suggest that species which occur infrequently be eliminated from consideration. -from Author
Distinct assemblages of benthic foraminifera live at different heights above mean tide level. Analysis of modern foraminifera contained within surface sediments permits quantification of species – height relationships which can be remarkably precise (centimetre to decimetre). Armed with this knowledge, it is possible to infer the height at which a sediment sample accumulated from the foraminifera it contains. Fossil assemblages recovered from core material can be used to infer palaeomarsh-surface elevation and produce reconstructions of relative sea-level change. We review the strengths and limitations of intertidal foraminifera as sea level indicators, and the methods used to collect, process and analyse them.
We studied 18 sampling stations along a transect to investigate the similarity between live (rose Bengal stained) foraminiferal populations and dead assemblages, their small-scale spatial variations and the distribution of infaunal foraminifera in a salt marsh (Toms Creek marsh) at the upper end of the South Slough arm of the Coos Bay estuary, Oregon, USA. We aimed to test to what extent taphonomic processes, small-scale variability and infaunal distribution influence the accuracy of sea-level reconstructions based on intertidal foraminifera. Cluster analyses have shown that dead assemblages occur in distinct zones with respect to elevation, a prerequisite for using foraminifera as sea-level indicators. Our nonparametric multivariate analysis of variance showed that small-scale spatial variability has only a small influence on live (rose Bengal stained) populations and dead assemblages. The dissimilarity was higher, however, between live (rose Bengal stained) populations in the middle marsh. We observed early diagenetic dissolution of calcareous tests in the dead assemblages. If comparable post-depositional processes and similar minor spatial variability also characterize fossil assemblages, then dead assemblage are the best modern analogues for paleoenvironmental reconstructions. The Toms Creek tidal flat and low marsh vascular plant zones are dominated by Miliammina fusca, the middle marsh is dominated by Balticammina pseudomacrescens and Trochammina inflata, and the high marsh and upland-marsh transition zone are dominated by Trochamminita irregularis. Analysis of infaunal foraminifera showed that most living specimens are found in the surface sediments and the majority of live (rose Bengal stained) infaunal specimens are restricted to the upper 10 cm, but living individuals are found to depths of 50 cm. The dominant infaunal specimens are similar to those in the corresponding surface samples and no species have been found living solely infaunally. The total numbers of infaunal foraminifera are small compared to the total numbers of dead specimens in the surface samples. This suggests that surface samples adequately represent the modern intertidal environment in Toms Creek.
The coastal zone of the southern Delmarva Peninsula exhibits a wide variety of barrier island system subenvironments. This study investigated, a) whether 20 a priori subenvironments could be distinguished from each other on the basis of total (living plus dead) foraminiferal assemblages, and b) the potential utility of modern foraminiferal assemblages as paleoenvironmental indicators in barrier island systems. Sixty-eight foraminiferal species were recorded from 57 surface sediment samples. The values of species diversity (H(S)) and equitability (E) exhibit a striking contrast between the marshes and other areas. The marshes had higher values of species diversity and equitability than the tidal flats and the channels-inlets-shore face. Stepwise regression analyses indicate correlation of the seven most frequently occurring species in total assemblages (>30% of the total stations) with combinations of one to three environmental variables at the 95% level. Species diversity data and taxonomic composition data analysed by canonical variate analysis indicate that not 20, but four major environments can be readily and reliably distinguished, namely, brackish marsh / channel, lagoonal tidal flats, lagoonal marshes / washover fans, and channels / inlets / shoreface. Combined sedimentologic and microfaunal data can provide greater environmental discrimination. Although these modern foraminiferal distribution pat-terns are useful as a model for paleoenvironmental interpretations of Quaternary coastal deposits, the model should be applied with great caution because the nature of fossil assemblages in short cores taken in outer fringe marsh and tidal flat environments indicates that taphonomic loss of foraminiferal tests is both considerable and variable.
Foraminifera and arcellaceans ("thecamoebians") were examined from 73 surface samples collected to represent four vegetation zones (I-IV) that have been defined in the Mississippi Delta Plain. Previous studies of benthonic foraminifera had not differentiated these environments. Saline marshes (I) are characterized by a vertical zonation typical of most marshes, with a variety of estuarine species in the low marsh and trochamminids in the upper marsh. Brackish marshes (II) are dominated by a completely different set of species, all agglutinated, but the vertical zonation is weak, probably because of the low vertical gradient. Emergent freshwater or intermediate marshes (III) are dominated by arcellaceans but there are significant numbers of foraminifera, indicating episodic marine incursions. The freshwater floating marsh zone (IV) has only arcellaceans. A previous study of arcellaceans living in the lacustrine environment below the floating marsh reveals a different arcellacean fauna than that observed above it. These data suggest that marsh foraminifera have potential application as sea-level indicators in the delta region arid that fossil remains of these protozoans can be used to differentiate coastal vegetation zones in the fossil record.
We present an expanded training set of salt-marsh foraminifera for reconstructing Holocene relative sea-level change from 12 sites in New Jersey that represent varied physiographic environments. Seven groups of foraminifera are recognized, including four high- or transitional-marsh assemblages and a low-salinity assemblage. A weighted-averaging transfer function trained on this dataset was applied to a dated core from Barnegat Bay to reconstruct sea level with uncertainties of ± 14% of tidal range. We evaluate the transfer function using seven tests. (1) Leave-one-site-out cross validation suggests that training sets of salt-marsh foraminifera are robust to spatial autocorrelation caused by sampling along transects. (2) Segment-wise analysis shows that the transfer function performs best at densely sampled elevations and overall estimates of model performance are over optimistic. (3) Dissimilarity and (4) non-metric multi-dimensional scaling evaluated the analogy between modern and core samples. The closest modern analogues for core samples were drawn from six sites demonstrating the necessity of a multi-site training set. (5) Goodness-of-fit statistics assessed the validity of reconstructions. (6) The transfer function failed a test of significance because of the unusual properties of some cores selected for sea-level reconstruction. (7) Agreement between reconstructed sea level and tide-gauge measurements demonstrates the transfer function's utility. Copyright © 2013 John Wiley & Sons, Ltd.
Foraminiferal assemblages have been collected from ten intertidal study areas situated on the east, south and west coasts of the UK. The assemblages display a vertical zonation which indicates that the distribution of foraminifera in these intertidal environments is usually the direct function of altitude with the duration and frequency of intertidal exposure the most important factors. Multivariate analyses separate foraminiferal assemblages into two faunal zones: a high-and middle marsh zone consisting of differing abundances of Jadammina macrescens, Trochammina inflata and Miliammina fusca; and a low-marsh and tidal flat zone dominated by calcareous foraminiferal species, notably Elphidium williamsoni, Haynesina germanica and Quinqueloculina spp. These faunal zones are similar to those in other mid-latitude, cool temperate intertidal environments although there are spatial and temporal variations between areas. The altitudinal ranges of the faunal zones are employed to identify the vertical relationship of the local environment in which the assemblage accumulated to a reference tide level. © 1999 Elsevier Science B.V. All rights reserved.
Sedimentological and micropaleontological analysis of fifteen 3-m gouge-auger cores revealed a lack of spatio-lateral continuity for paleohurricane deposits from the back-barrier marshes of Folly Island, South Carolina. The offshore-indicative calcareous microfossil content of some storm deposits was taphonomically altered or destroyed, and in many cases cores taken 10 m apart provided significantly different storm records. In several low-marsh cores, where bioturbation is more intense, storm deposits were completely unrecognizable using foraminifer or sedimentological analyses. In nearly all cores the sedimentary record of storm deposits was more extensive than the record produced using foraminifers, and, as a result, the sedimentary proxy produced shorter hurricane return periods. While offshore-indicative foraminifers in the salt marshes behind Folly Island are good indicators of their original source and mode of deposition (storm current transport from the shelf by overwash, storm inlet, or via Lighthouse Inlet), their susceptibility to destruction from bioturbation and dissolution suggests that they provide a less accurate or less complete record of storm frequency than previously thought.
A modified ignition loss method is described for determining organic and carbonate carbon in calcareous sedimentary materials using equipment found in most laboratories. The method has been found to equal or excel the accuracy and precision of other methods tested and has the advantage of being considerably faster if large numbers of samples are to be analyzed.
