Elphidium Clavatum Research Articles

The ontogeny, palaeoecology and palaeogeographical inference of the ostracod Roundstonia globulifera

The discovery of an abundant monospecific population of Roundstonia globulifera (Brady) 1868 from an early Flandrian (9000–8500 B.P.) Dublin Bay mud horizon at ‐ 18 m Ordnance Datum has resulted in an ontogenetic analysis of the ostracod. Data on size, shape and morphological development through eight growth‐stages are presented. It occurs with a monospecific population of the foraminifer Elphidium clavatum subclavatum Gudina, the ecology of which is known. From this, and sedimentological data, it is inferred that the assemblages lived in shallow, muddy estuarine channels. Information from other parts of the Irish Sea provides evidence of the course of the Flandrian transgression. It is proposed that early in Boreal times, water masses invading from the north and south, were separated by a barrier south of Dublin until 8500 B.P.

Distribution of Foraminiferida South of Sherbrooke, Nova Scotia

Bottom sediment samples (depths to 25m) from St. Mary's River, Gegogan, Wine Bay, Indian and Holland's Harbours, Nova Scotia, identified for the Foraminifera by Habbishaw in 1970, were factor-vector analyzed. Based on 'total' populations 4 benthonic foraminiferal assemblages, not strictly biocenoses, are recognized. Assemblage 1, dominated by Miliammina fusca, has a mean diversity of 4.75, a mean depth of 1.85 m, a mean pH (substrate) of 6.7, and the substrate is coarse-grained. This assemblage is found in the Upper Estuarine (intertidal) Zone in St. Mary's River, south of Sherbrooke. Assemblage 2, dominated by Eggerella advena, has a mean diversity of 12.5, a mean depth of 7 m, a mean pH (substrate) of 8.16, and the substrate is very fine-grained. It is found in the Lower Estuarine Zone in the lower reaches of St. Mary's River, Wine Harbour Bay, the western and northern areas of Gegogan Harbour, and the eastern shore south of Port Bickerton. Assemblage 3, dominated by Elphidium clavatum, has a mean diversity of 14.3, a mean depth of 9m, a mean pH (substrate) of 7.2, and the substrate is coarse- to fine-grained sand. It occurs in the Marginal Marine Zone (Scott) or Nearshore Biofacies (Bartlett) in St. Mary's River (3 to 5 km from the mouth) and at the head and near the mouth of Indian Harbour. Assemblage 4 dominated by Cibicides lobatulus, Eggerella advena and Elphidium clavatum, has a mean diversity of 19.9, a mean depth of 12.2m, a mean pH (substrate) of 7.16, and the substrate is medium- to fine-grained sand. It occurs in the Open Ocean-Nearshore Zone (Scott) or the Open Bay Biofacies (Bartlett), inside and outside Holland's Harbour, the southwest and central area of Indian Harbour, at the mouth of St. Mary's River, on the eastern side of Gegogan Harbour, and east of Crook Point.

Environmental factors affecting the standing crop of foraminifera in sublittoral and psammolittoral communities of a Long Island salt marsh

Representative samples from the epiphytic and psammolittoral communities were made during the summer of 1968 in North Sea Harbor, Southampton, Long Island, USA. In the epiphytic communities, the foraminifera were very patchy; 2.6% of the total samples accounted for 56.4% of the total foraminifera collected. The standing crop and species composition of the foraminifera changed throughout the summer. Two seasonal peaks were observed in the epiphytes. In early summer Protelphidium tisburyensis was the dominant form. In late July and August Elphidium incertum was dominant. Taken as a whole over the entire summer, the following species comprised the epiphytic foraminiferan community: Elphidium incertum (46.63%); Protelphidium tisburyensis (25.64%); Ammotium salsum (9.88%); Elphidium clavatum (6.74%); E. translucens (3.47%); Ammonia beccarii (2.83%); Ammobaculites dilatatus (2.08%); Trochammina inflata (1.8%); Elphidium advenum (< 1%); E. galvestonense (< 1%); E. gunteri (< 1%); Quinqueloculina lata (< 1%); Q. seminulum (< 1%) and Trochammina macrescens (< 1%). Although fewer species were found, many more foraminifera live in the benthos than in the epiphytic community. Taken as a whole, over the entire summer, the following species comprised the foraminifera in the psammolittoral community: Trochammina inflata (49.6%); Elphidium incertum (31.8%); Ammotium salsum (10.9%); Quinqueloculina seminulum (4.2%); Elphidium sp. (1.5); Protelphidium tisburyensis (0.9%); Ammonia beccarii (0.7%); Elphidium clavatum (< 0.1%); and E. translucens (< 0.1%). Three species, Ammotium salsum, Elphidium incertum and Trochammina inflata bloomed successively in the psammolittoral community. The distribution of the latter two species was correlated with the vertical and horizontal changes of grain size; Elphidium incertum distribution clustered around a median grain size of 0.1 mm, whereas Trochammina inflata clustered around a median grain size of 0.46 mm. The sediments were sampled both at high and low tide. No evidence was obtained to suggest migration of foraminifera through the sediments as a function of tidal cycle. Horizontal distribution of the foraminifera in the marsh was correlated with the flow patterns of very small rivulets in the study area. With respect to many species of foraminifera, the overlying epiphytic communities are not continuous with the psammolittoral communities below them in the water column. Protelphidium tisburyensis was an early summer dominant epiphyte, but was rare in the psammolittoral communities. Trochammina inflata, on the other hand, was dominant in the coarser, deeper sediments and was rare in the epiphytic community. Elphidium incertum is presumably a generalist species. It formed half the foraminiferan population throughout the water column. Ammotium salsum was also abundant in both communities.

FORAMINIFERA AND POLLEN FROM A MARINE INTERGLACIAL DEPOSIT IN THE WESTERN NORTH SEA

Summary Marine clay appearing to crop out between the Chalk and a boulder clay resembling the Purple Till of Holderness has been sampled by gravity coring on the flanks of the Inner Silver Pit between 53° 24·8′ to 53° 30·2′ N and 0° 40·8′ to 0° 41·8′ E. Foraminiferal assemblages obtained from five sites are mostly dominated by Elphidium clavatum and indicate middle Pleistocene interglacial conditions; in all forty-five species of foraminifera are recorded. Pollen indicating zones IIIb and IV of the temperate Hoxnian stage is present in the same

FORAMINIFERAL SPECIES DENSITIES AND ENVIRONMENTAL VARIABLES IN AN ESTUARY

A pilot study of foraminiferal species densities in the Choptank River, Maryland, a part of the Chesapeake Bay estuarine system, indicated that the density of Elphidium clavatum decreased progressively upstream, while the densities of Ammobaculites exiguus and Ammonia beccarii varied little. Three stations were selected for more detailed analysis.Each station was sampled monthly for foraminiferal density for 12 months, and temperature, salinity, oxygen, and chlorophyll a, b, and c were measured. A general multiple regression‐analysis of variance model containing parameters for environmental variables, station differences, overall periodic differences, and the interaction of station and periodic differences was statistically compared to several more restricted models, with separate analyses for each species.The set of environmental variables is significant at the 95% level for all three species. None of the variables is significant individually. However, the relatively large values of the regression coefficients for the chlorophylls, especially b, suggest that the amount and kind of available food is important in determining species densities.All three species exhibit periodicity, and for each species the periodicity is different at the three stations. Restricted models containing 15 parameters are sufficient to account for the observed species densities in each case.

Foraminiferal Densities and Environmental Variables: Use of Statistical Models to Examine Estuarine Environment: ABSTRACT

Many environmental variables have been suggested to explain species distributions. However, species distributions generally cannot be evaluated statistically because of inadequate sampling procedures. The purpose of the present study is to outline a method of analysis using statistical models. A pilot study in the Choptank River, Maryland, indicated that Elphidium clavatum density decreases progressively upstream, whereas Ammobaculites exiguus and Ammonia beccarii densities change very little. From this pilot study, three stations were selected for detailed analysis. Four foraminiferal samples were taken monthly at each station for a year. Temperature, salinity, oxygen, and chlorophyll a, b, and c were measured each month at every station. A general multiple regression-analysis of variance model was constructed containing 21 parameters for environmental variables, station differences, overall periodic differences, and interaction of station and periodic differences. This model was compared with several containing fewer parameters. Restricted models containing 15 parameters sufficiently accounted for observed species densities in each example. The set of environmental variables is significant at the 95% level for all species, but none is significant individually. However, relatively large values of regression coefficients for chlorophylls, especially b, suggest that food (amount and kind) is important in determining species densities. Each species exhibits periodicity, and for each, periodicity differs at the three stations. Results indicate that the use of statistical models permits greater understanding of relations between foraminiferal species and environments. Such understanding will be of great value in paleoecology. End_of_Article - Last_Page 710------------

Comparison of Clay from the Continental Shelf off Long Island with the Gardiners Clay

Late in 1955 the Woods Hole Oceanographic Institution received from Moran, Proctor, Mueser, and Rutledge, consulting engineers of New York City, a few samples taken from a boring made at the proposed site of an Air Force Texas Tower (TT-4), located about 60 miles south of Moriches Bay, Long Island. Among these samples was an undisturbed clay sample, suggestive of the Pleistocene Gardiners clay of Long Island. For purposes of comparison, the same company later made available a group of ten core samples collected from a formation thought to be Gardiners clay on western Long Island. Standard mechanical analysis procedures were carried out on certain of these samples prior to their being examined for microfossils. The sample from the TT-4 site was located 70 feet below the ocean bottom under a water depth of 185 feet. The overlying sediments were coarse sand and fine gravel. The moist color of this sample was olive-gray as determined from the Rock Color Chart published by the Geological Society of America in 1951. The sediment is a silty clay with a sand content of about 6 per cent. The sand is mostly quartz with a number of reddish-brown silt-stone particles presumably reworked from an older formation. Occasional Foraminifera are found in this coarser fraction. The more common species are Elphidium clavatum Cushman, E. incertum (Williamson), and Quinqueloculina cf. lata Terquem or seminulum (Linnd). There were also a few reworked fossil species of the genera Gyroidina, Elphidium, and Cassidulina(?). These