Introduction

Figure 1. Location map showing the sampling sites in Mobile Bay. Grabs were collected at these sites for up to three seasons. Box cores were collected in August 2010 only at sites 2, 4, 5, 7, 8, 12, and 20. See table 1 for information. [larger version]

A study was undertaken in order to understand recent environmental change in Mobile Bay, Alabama. For this study a series of surface sediment and box core samples was collected (fig. 1). The surface benthic foraminiferal data provide the modern baseline conditions of the bay and can be used as a reference for changing paleoenvironmental parameters recorded in the box cores. The 14 sampling locations were chosen in the bay to cover the wide diversity of fluvial and marine-influenced environments on both sides of the shipping channel (fig. 1, table 1 [56-KB Excel file]).

Data Collection and Processing

In order to best remove the spatial and temporal variability of the living foraminifera assemblages, multiple samples were collected at each station throughout the year. Surface sediments were collected with a van Veen grab sampler in September 2009 (11 stations), May 2010 (13 stations), and August 2010 (12 stations) (table 1 [56-KB Excel file]). Eleven to 35 cubic centimeters (cm³) of the topmost surface sediment were collected with a spatula and immediately placed in two graduated centrifuge tubes (A and B) with a solution of Ethanol and Rose Bengal. The sample tubes were shaken several times over the next 24 hours to ensure equal staining of protoplasm.

The stained samples were transferred to the U.S. Geological Survey foraminiferal lab in St. Petersburg, Fla., and were processed within 6 weeks of collection. The volume of the sediment was recorded using the volume gradation of the tube. The stained wet sediment was washed over a 63-micron (µm) sieve. In some cases, an additional washing was necessary following the procedure for the box core samples described below. After washing, the >63-µm fraction was oven dried at ≤60 degrees Celsius, and then dry sieved at 125 µm.

In most cases the entire >125-µm fraction was spread across a 45-square, hole-punched tray, one or more times, and each stained specimen was dropped through a hole in the punched tray onto a stationary 60-square micropaleontological slide placed in a cardboard cutout for later counting and identification (appendix 1). Each sample (up to six at each station) was picked and counted individually, but eventually the data were combined to provide a complete representation of the living foraminiferal community (table 2 [55-KB Excel file]).

The dead (non-stained) surface foraminifers were also picked, identified, and counted in a manner similar to the stained samples (appendix 1, table 3 [51-KB Excel file]). Because the dead assemblages were more abundant, these samples were split using a micro-splitter to obtain approximately 300 specimens.

During the August 2010 research cruise aboard the U.S. Geological Survey RV Gilbert, box cores were also collected from eight stations using a modified Wildco-type box corer. After placing the box corer on deck, a 6 inch (in.) plastic core liner was inserted into the box core. The sediment cores were refrigerated after collection and the sediment cores were extruded and sampled at 1-centimeter (cm) intervals within 48 hours after collection. The box core samples were refrigerated and transported to the U.S. Geological Survey foraminiferal lab in St. Petersburg, Fla. The samples remained refrigerated until lab processing.

To process the core samples, 20 cm³ of each sample were measured with a syringe. When a sample contained less then 20 cm³, the entire sample was used. Each sample was placed in a beaker with 10 percent calgon solution and agitated on a shaker plate for up to 1 hour before being washed over a 63-µm sieve. The sieves were cleaned with a sonicator and visually inspected between washes. The >63-µm fraction was oven dried at ≤60°C, then dry sieved at 125 µm. In some cases the addition of a hydrogen peroxide solution and a second wash was needed when the first wash did not fully clean the foraminifera. The >125-µm size fraction was picked for foraminiferal specimens in the same process described for the surface samples using the hole-punch tray. A micro-splitter was used in most cases to obtain approximately 300 specimens. The foraminifers were then counted and identified (appendix 1, tables 4-10 [90-KB Excel file]). All faunal slides will be curated at the Natural History Museum, Smithsonian Institution, at the conclusion of the study.

During the identification process, it was recognized that calcareous foraminifers in Mobile Bay were being subjected to dissolution. Therefore, after the surface fauna were identified and counted, both the living and dead surface samples were analyzed again to assess the amount of calcareous foraminiferal dissolution in each sample (table 11 [50-KB Excel file] and table 12 [56-KB Excel file]). Some specimens too dissolved to identify were not included in the assemblage count but were included in the counts of dissolution. As a result, the total foraminiferal numbers in the dissolution count may be higher than the foraminiferal numbers in the assemblage count data. The amount of dissolution for the specimens was graded on a three-point scale: no dissolution, mild dissolution, and strong dissolution. Mild dissolution is characterized by the first few chambers of the test affected by decalcification. Strong dissolution is characterized by a star shape that occurs when the outer chambers are completely dissolved, leaving behind the inner organic lining (Le Cadre and others, 2003).

Acknowledgments

The U.S. Geological Survey Coastal and Marine Geology Program provided funding for this research as part of the Northern Gulf of Mexico Ecosystem Change and Hazard Susceptibility Project. We thank Chris Smith, Chris Reich, and Caitlin Reynolds (USGS- St. Petersburg Coastal and Marine Science Center) for help with sample collection and processing. Tim Dellpenna (Texas A&M University at Galveston) graciously allowed the use of the box core. Captain Rich Young (USGS- St. Petersburg Coastal and Marine Science Center) assisted in the box coring cruise.

Reference Cited

Le Cadre, Valerie, Debenay, J.P., Lesourd, Maurice, 2003, Low pH effects on Ammonia beccarii test deformation: implications for using test deformations as a pollution indicator: Journal of Foraminiferal Research v. 33, p. 1-9.

Suggested Citation

Richwine, K.A., and Osterman, L.E., 2012, Benthic foraminiferal census data from Mobile Bay, Alabama—Counts of surface samples and box cores: U.S. Geological Survey Data Series 704, available only online at https://pubs.usgs.gov/ds/704/.

Appendix 1. Mobile Bay foraminifers.

Ammobaculites exiguus Cushman and Bronniman, 1948, Contributions from the Cushman Laboratory for Foraminiferal Research, v. 24, pt. 2, p. 39, pl. 7, figs. 7, 8.

Ammobaculites salsus Cushman and Bronniman, 1948, Contributions from the Cushman Laboratory for Foraminiferal Research v. 24, pt. 2, p. 16, pl. 3, figs. 7-9.

Miliammina fusca (Brady) = Quinqueloculina fusca Brady, 1870, Annals and Magazine of Natural History, ser. 4, v. 6, p. 286, pl. 11, figs. 2, 3.

Other Agglutinated, any other agglutinated species

Paratrochammina simplissima (Cushman and McCulloch) = Trochammina pacifica Cushman 1925, var. simplex Cushman and McCulloch, 1939, Allen Hancock Pacific Expeditions, v. 6, n. 1, p.104, pl. 11, fig.4,

Textularia spp. a variety of species most commonly Textularia parvula Cushman 1922, Bulletin 104. United States Natural History Museum., pt. 3, p. 11, pl. 6, figs. 1, 2.

Ammonia parkinsoniana (d'Orbigny) = Rosalina parkensoniana d'Orbigny, 1939, in Ramone de la Sagra, Histoire physique, politique et naturelle de l'ile de Cuba "Foraminiferes", p. 99, pl. 4, figs. 25-27.

Ammonia tepida (Cushman) = Rotalia beccarri (Linné) var. tepida Cushman, 1926, Publications of the Carnegie Institute, Washington, no. 334, p. 79, pl. 1.

Bolivina spp., rare specimens of this genera

Buccella hanni (Phleger and Parker) = Eponides hanni Phleger and Parker, 1951, Geological Society of America Memoir 46, pt. 2, p. 21, pl. 11, figs. 1a, b, 2a, b.

Bulimina spp., rare specimens of this genera

Buliminella elegantissima (d'Orbigny) = Bulimina elegantissima d'Orbigny, 1839, Voyage dans l'Amerique meridionale, v. 5, pt. 5, "Foraminifers" p. 51, pl. 7, figs. 13,14.

Buliminella morgani Anderson, 1961, LA Geol. Bull., no. 35, pt. II, p. 87, pl. 19, fig. 10.

Cibicides spp. rare specimens of this genera

Elphidium excavatum (Terquem) = Polystomella excavata Terquem, 1876, Societé Dunquerquoise, Memoires, v. 19 (1874-75), p. 429, pl. 2, figs. a-d.

Elphidium mexicanum = Elphidium incertum (Williamson) var. mexicanum Kornfeld, 1931, Contributions from the Department of Geology., Stanford Univ., vol. 1, no. 3, p. 89, pl. 16, figs. 1, 2.

Elphidium poeyanum (d'Orbigny) = Polystomella poeyana d'Orbigny, 1839, in Ramone de la Sagra, Histoire physique, politique et naturelle de l'ile de Cuba "Foraminiferes", p. 55, pl. 6, figs. 25, 26.

Epistominella exigua (Brady), Parker, 1954, Harvard Museum of Comparative Zoology Bulletin, v. 111, no. 10, p. 533, pl. 10, figs. 22, 23.

Fursenkoina spp., rare specimens of this genera

Gavelinopsis translucens (Phleger and Parker) = "Rotalia" transluscens Phlegar and Parker 1951, Geological Society of America Memoir. 46, pt. 2, p. 24, pl. 12, figs. 11a, b, 12a, b.

Glandulina laevigata (d'Orbigny) = Nodosaria laevigata d' Orbigny 1826, Annales des Sciences Naturelles. ser. 1, v. 7, p. 252, pl. 10, figs. 1-3.

Hanzawaia concentrica (Cushman) = Truncatulina concentrica Cushman, 1918, United States Geological Surey Bulletin. 676, p. 64, pl. 21, fig. 3.

Haynesina germanica (Ehrenburg) = Nonionina germanica, Ehrenburg, 1840, Koenigliche Preuss Akademie Der Wissenschaften, v. 11, p. 23, pl. 1, figs. 1a-g.

Miliolinella subrotunda (Montague) = Vermiculum subrotundum Montague 1803. Note: Type species concept was revised with the establishment of neotype for M. subrotunda in 1974.

Other Calcareous any other calcareous species

Other Milliolids includes any other Quinqueloculina spp., Triloculina spp., etc.

Pseudononion atlanticum (Cushman) = Nonionella atlantica Cushman, 1947, Contributions from the Cushman Foundation for Foraminferal Research, v. 23, pt. 4, p. 11, pl. 5, figs. 21-23.

Quinqueloculina compta Cushman, 1947, Contributions from the Cushman Foundation for Froraminiferal Research, v. 23, pt. 4, p. 87, pl. 19, fig. 2.

Quinqueloclina laevigata d'Orbigny 1826, Annales des Sciences Naturelles, v. 7, p. 143, pl. 3, fig 31-33.

Quinqueloclina lamarckiana d'Orbigny, Phleger and Parker, 1951, Geological Society of America Memoir, 46, pt. II, p. 7, pl. 4, figs. 1a, b; 2a, b.

Reussella spinulosa (Reuss) = Verneuilina spinulosa Reuss, 1850, Denkschriften Kaiser. Akademie Der Wissenschaften Math. - Natur. Classe. v. 1, p. 374.

Rosalina concinna (Brady) = Discorbina concinna Brady, 1884, Rept. Voy. Challenger, Zool., v. 9, p. 646, pl. 90, fig. 7, 8.

Rosalina floridensis (Cushman) = Discorbis bertheloti var. floridensis Cushman, 1930, Journal of Paleontology, v. 40, no. 4, p. 364, pl. 33, figs. 13 a-c.

Trifarina bella (Phleger and Parker) = Angulogerina bella Phleger and Parker, 1951, Geological Society of America Memoir, 46, pt. II, p. 12, pl. 6, figs. 7, 8.