The Mobile River is the fourth largest river system in the United States and the Mobile River Delta complex is the largest internal delta complex in the United States (Isphording et al., in press). Total drainage area for the Mobile River is approximately 115,513 square kilometers. Discharge rates range from 283 cubic meters per second in dry fall months to 3,115 cubic meters per second during spring floods (Isphording et al., in press).
Within the Mobile River Delta there are three major plant types. These include forested wetlands, marshes, and submersed grassbeds. Percentages are 86.8%, 9.2%, and 3.2% respectively (Stout et al.,1982). The three methods by which the palynomorphs of such plants are transported are wind, water, and insects. Ninety-five percent of all palynomorphs, though, are deposited within one kilometer of the source plant (Traverse, 1988).
The objectives of this proposed study area as follows:
Approximately two percent of the Earth's total sediments are organic matter (Traverse, 1994). Palynomorphs, a major constituent of this organic matter, may be studied as clasts as long as certain parameters are followed.
The Mobile River drains approximately 115,513 square kilometers of the southeastern United States. This drainage basin includes 16,835 square kilometers of northern Mississippi, 14,245 square kilometers of northwest Georgia, 388 square kilometers of Tennessee, and 86 percent of Alabama (Isphording et al., in press). Total annual sediment produced by the Alabama and Tombigbee Rivers is 4.25 billion kilograms per year. 3.7 billion kilograms per year enters the delta as suspended load and 553 million kilograms per year enters as traction load (Isphording et al., in press). In addition to sediment entering the delta by the Alabama and Tombigbee Rivers, 82 million kilograms per year of sediment enter the delta from the adjacent uplands (Isphording et al., in press). The Mobile Bay is the place for final deposition of the majority of the sediment. Approximately 30 percent of the sediment remains in the delta and the remaining 70 percent is deposited in the Mobile Bay (Isphording et al., in press).
The purpose of this study is to provide an actualistic investigation that examines transport and deposition of palynomorphs in a large scale fluvial setting. Few studies have been made palynomorphs in a river system. Alfred Traverse (1961-1962) conducted a similar study on the Trinity River, Texas. This study looked at pollen at the surface and at mid-depth along three sampling stations on the river. Chmura and Liu (1989) performed a large scale investigation as related to river size. This study sampled seven times at a depth of one meter. The purpose herein is to provide a large scale investigation as related to river size and to sample several sites at three depths.
The study area consists of a 56 kilometer long section of the Mobile River Delta. This extends from an area just north of the Alabama River and Tombigbee River intersection to the Battleship Parkway. Twelve sampling sites will be used within the study area and include: the Tombigbee River north of its confluence with the Alabama River; the Alabama River north of its confluence with the Tombigbee River; the Mobile River (north and south); the Tensaw River (north, central, and south); and the Apalachee, Blakely and Spanish Rivers (south).
A total of thirty-six samples will taken during each excursion. At each of the twelve sites samples will be taken at the water surface, at mid-depth, and at the sediment/water interface. Sampling will be performed using two pieces of equipment. For surface and mid-depth water sampling the one liter LaMotte water sampler will be used. To acquire samples at the sediment/water interface a Wilco bottom sampler will be used. To ensure continuity between samples one gallon of sample will be taken at each level. Samples will then be sieved through a ten micron sieve and placed in individual sample bottles. Following this each sample will be processed using standard palynological techniques (Doher,1982). At this point palynomorphs are impregnated with methanol and an alcohol-water separation can be made (Hansen and Gudmundsson, 1979). After this separation the palynomorphs can be mounted to individual glass slides using glycerin jelly. The samples can now be point counted using the Zeiss axioscope.
After point counting of each sample is completed a determination of palynomorphs per gallon can be made using the following formula: E/300=L/x where "E" represents the number of Lycopodium grains counted for every 300 palynomorphs. "L" represents the total number of Lycopodium grains in every tablet used in the alcohol-water separation. "x" represents the total number of palynomorphs present in the given sample.
At this time a comparison can be made of samples from site to site or over a given period of time. Seasonal variations in palynomorph types and concentration of palynomorphs within the overall study area can be made. Also, correlation to higher and lower water levels and discharge rates can be made using data from the Barry's Steam Plant gaging station.
The proposed study offers insight into the transport biases which affect a certain palynological assemblage and correlations between the amount of palynomorphs within the Mobile River Delta and the seasonal release of such palynomorphs. With the use of twelve sampling sites, three water depths, and the extensive length of the study area, transportation of palynomorphs can be assessed. Seasonal variations in palynomorphs can be analyzed using known plant types in the drainage basin and the palynomorph types found within each sample (Stout et al., 1982).
CHMURA, G.L.,and LIU, KAM-BIU, 1990, Pollen in the lower Mississippi River, Review of Paleobotony and Palynology, v.64, pp.253-261.
DOHER, I., 1980, Palynomorph Preperation Procedures Used in the Paleontology and Stratigraphy Laboratories U.S. Geological Survey, Geological Survey Circular 830, 29 p.
HANSEN, J.M., and GUDMUNDSSON, L., 1979, A method for separating acid- insoluble microfossils from organic debris, Micropaleontology, v.25, no.2, pp 113-117.
ISPHORDING, W.C., IMSAND, D.F., and JACKSON, B.R., in press, Fluvial Sediment Characteristics of the Mobile River Delta: Gulf Coast Association of Geological Societies.
STOUT, J.P., LELONG, M.J.,DOWLING, H.M., and POWERS, M.T.,1982, Wetland Habitats of the Alabama Coastal Zone, Alabama Board Technical Report, no. CAB 81-49A, 25 p.
TRAVERSE, A., 1992, Organic Fluvial Sediment: Palynomorphs and "Palynodebris" in the Lower Trinity River, Texas, Ann. Missouri Botanical Gard., v. 79, no. 1, pp110-125.
TRAVERSE, A., 1988, Paleopalynology, Allen and Unwin, Boston, 600 pages.
TRAVERSE, A., 1994, Sedimentation of Organic Particles, Cambridge University Press, Great Britain, 544 pages.
See Felton and Webster for related M.Sc. Theses.