8:30 DISTRIBUTION AND ABUNDANCE OF MARINE MAMMALS IN THE EASTERN GULF OF MEXICO

Theia C. DeLong*, Keith D. Mullin, and Donald G. Redalje, University of Southern Mississippi, Stennis Space Center, MS 39529

The first summer Marine Mammal Survey of the Eastern Gulf of Mexico was conducted on August 16­September 9, 1994, by the National Marine Fisheries Service (NMFS) Southeast Fisheries Science Center to meet its responsibilities under the Marine Mammal Protection Act and the Endangered Species Act. The NOAA Ship Oregon II utilized line transect methods to collect data to study the diversity, distribution and abundance of marine mammals in the Gulf of Mexico. A sawtooth cruise track between the 20 m contour and 8 km past the 2000 m contour, covering a total of 2884 transect km, was surveyed. Environmental data was also collected from a continuous flow thermosalinograph and conductivity-temperature-depth (CTD) and expendable bathythermograph (XBT) stations. Observations produced sightings of 299 herds composed of 4370 total individual animals. At least 13 species were identified. Tursiops truncatus (Bottlenose Dolphin) and Stenella frontalis (Atlantic Spotted Dolphin) accounted for 75% of all marine mammal sightings, and were sighted in depths ranging from 20 m to 700 m. Stenella attenuata (Pantropical Spotted Dolphin) was the next most frequently sighted species, and was observed in depths from 600 m to 3640 m. Sighting data were analyzed using the DISTANCE Sampling program to estimate the density and size of animal clusters (herds), and the density and number of animals in the surveyed area.

8:45 BIOCHEMICAL COMPOSITION AND REGENERATION OF THE EVISCERATION PRODUCT OF SEA CUCUMBERS ISOSTICHOPUS SPP. (ECHINODERMATA: HOLOTHUROIDEA)

Michele P. Copello* and Patricia M. Biesiot, University of Southern Mississippi, Hattiesburg, MS 39406-5018

Evisceration (expulsion of portions of the viscera as a defensive mechanism) followed by regeneration is a characteristic phenomenon in sea cucumbers. Evisceration was experimentally induced in Isostichopus spp. by injecting 0.45 m KCL into the body cavity; non-injected specimens served as controls. Biochemical composition (protein, lipid, carbohydrate, ash) was determined for the evisceration products. One of the control specimens spontaneously eviscerated partway during the recovery period; this evisceration product was also analyzed. On a dry weight basis, the evisceration product of chemically-induced sea cucumbers was 36% protein, 14% lipid, 6% carbohydrate and 45% ash whereas the spontaneously eviscerated material was 26% protein, 18% lipid, 4% carbohydrate and 52% ash. The time course for regeneration in the laboratory was monitored by weighing the control and experimental sea cucumbers periodically for three months. It was not possible to document regeneration in this study because erratic expulsion of cloacal fluid confounded the wet weight data. Furthermore, both control and experimental sea cucumbers lost weight over the course of the study, due either to inadequate diet in the lab or to natural cessation of feeding ("hibernation") during the winter months.

9:00 FEEDING EFFICIENCY OF JUVENILE BLUE CRABS ON TWO MICROGRAZER GASTROPODS WITHIN ESTUARINE GRASSBED HABITAT

Janet Cote*, Todd Randall, and Chet Rakocinski, University of Southern Mississippi, Gulf Coast Research Laboratory, Ocean Springs, MS 39566-7000

Juvenile blue crabs, Callinectes sapidus and Callinectes similis, are common residents of estuarine grassbeds in the southeastern United States. Two species of micrograzer gastropods, Diastoma varium and Astyris lunata, cooccur within the grassbed community and D. varium constitute a major diet component for young blue crabs. It is conceivable that crab predation mediates the coexistence of these gastropod species. Interspecific differences in shell strength, or shell "crushability" of gastropod shells, may provide the mechanism by which juvenile crabs of various sizes select and successfully ingest gastropod prey. In the laboratory, juvenile crabs (carapace widths between 10 and 60 mm) were presented with varying sizes of gastropods. Ingestion success and handling time (i.e., the duration between first contact with the prey and the complete consumption of that food item) were recorded. These observations illustrated that D. varium was handled more efficiently than A. lunata. Comparisons showed a much lower percent ingestion of A. lunata as the prey/crab size ratio increased. Preliminary feeding choice experiments conducted within artificial grassbeds under laboratory conditions showed significantly greater hourly consumption rates of D. varium than of A. lunata as relative prey size increased. Preliminary results suggest that juvenile blue crabs are more effective predators of D. varium, and thus will select D. varium over A. lunata when both prey species are available.

9:15 EARLY DIAGENESIS OF CARBONATE SEDIMENTS IN THE DRY TORTUGAS AND MARQUESAS KEYS, FLORIDA, USA

Alan M. Shiller*, Charlotte A. Brunner, Yoko Furukawa, Tracey Hebert, and Jinchun Yuan, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

Interstitial waters from box and gravity cores were collected to aid in understanding the early diagenesis of Holocene sediments collected near the Dry Tortugas and Marquesas Keys (Florida). These carbonate sediments are composed dominantly of aragonite (Halimeda) needles and are not cemented. Microelectrode and box core work indicated that oxygen was rapidly consumed in the upper few mm and dissolved Mn reached a maximum by 3 cm. However, organic carbon was low (~0.4% at the surface) and hence only minimal sulfate reduction was observed even at 200 cm. Extensive bioturbation and irrigation also appear to be important in keeping the sediments poised above sulfate reduction. Indeed, in some cases concurrent changes in dissolved Mn, Mo, U, and PO₄ are likely related to burrow activity. Small changes in Sr, TCO₂, and Alk indicate the small degree of carbonate dissolution/precipitation. It is likely that the short depth to basement (~3 m), low organic carbon content, and extensive deep bioturbation all combine to keep the sediment column suboxic and prevent extensive cementation. Measurements of F indicate a significant F uptake into the sediments in the upper 10 cm.
 
 

9:30 MODELING AND SIMULATION RESULTS OF OPTIMAL PATHS INFLUENCED BY OCEANOGRAPHIC CURRENTS IN LITTORAL ENVIRONMENTS

Portia J. Harris, Naval Research Laboratory, Stennis Space Center, MS 39529-5004

Modeling and Simulation in littoral environments is a challenge because of the extreme spatial and temporal variability. Visualizations that show optimal paths and other environmental features require high resolution bathymetry, topography, and oceanographic data acquisitions. Interpolation schemes may be used to generate high resolution data, however, uniform precision must be implemented in all data to deter data degradation and resulting anomalies. Oceanographic current, speed, and direction with depth, position, and time components can aid and abet littoral transit for personnel and platforms. Knowledge of maximum and minimum currents helps personnel/platforms conserve energy/fuel respectively in some transit operations. This presentation discusses modeling and simulation results of optimal paths influenced by oceanographic currents in littoral environments.

9:45 PHOTOSYNTHESIS-IRRADIANCE PARAMETERS AND TAXONOMIC STRUCTURE IN RELATIONSHIP TO A COASTAL FILAMENT IN THE NORTHWEST ARABIAN SEA

Rory K. Toon* and Steven E. Lohrenz, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

Variations in primary productivity are a response to interacting physical, chemical and biological processes. The northwest Arabian Sea, subject to seasonally predictable oscillations in the physical environment plus the site of variations within seasons provides an ideal setting for investigating physical-biological coupling. Photosynthesis-irradiance parameters, major light absorbing pigment concentration, and dominant accessory pigment composition were determined for natural phytoplankton assemblages along a surface transect in the Oman coastal region during the intermonsoon period. All measurements included size fractions < 2 µm, 2 - 20 µm, and 20 - 200 µm. P-I parameters included PBmax (maximum rate of photosynthesis per unit chlorophyll), a^B (initial adaptive state), and b^B (photoinhibition). Fluorometric chlorophyll a concentrations estimated population size distributions; HPLC-determined pigment concentrations were diagnostic of phytoplankton taxonomic composition. Chlorophyll a concentrations observed within the filament were ten times higher than outside the filament. Within the filament, 13% of the population was made up of large (20 -200 µm) cells and dominated by equal proportions of peridinin (dinoflagellates) and 19'-butanoloxyfucoxanthin (coccolithophores); seaward, fucoxanthin (diatoms) became dominant and approximately 50% of the total population was large cells. Differences in photosynthesis-irradiance parameters were also observed inside and outside the filament as well as among size classes. This study demonstrates the importance of size-dependent biological responses within a highly dynamic physical environment.
 
 

10:00 Break
 
 

10:15 SEASONAL BIOCHEMICAL COMPOSITION OF THE BLUE CRAB CALLINECTES SAPIDUS: ORGANIC RESERVES OF DEVELOPING EMBRYOS AND ADULTS

Janet R. Jacobs¹*, Patricia M. Biesiot¹, Harriet M. Perry², and Christine Trigg², ¹University of Southern Mississippi, Hattiesburg, MS 39406-5018, and ²Gulf Coast Research Laboratory, Ocean Springs, MS 39566-7000

Blue crab males, ovigerous females, and non-ovigerous females with and without egg remnants (indicative of previous brood and no previous brood, respectively) from the Mississippi Sound were sampled in May and August/September, hereafter termed spring and fall, respectively. Gonad and midgut gland samples were taken from all crabs. Ovigerous females were maintained in tanks and developing embryos sampled every other day until hatching. Biochemical composition (protein, lipid, carbohydrate, ash) was determined for all samples. Although spring embryos were significantly larger than fall embryos, there were no differences in the pattern of organic reserve utilization during development. Lipid and protein concentrations decreased during embryogenesis whereas carbohydrate fluctuated only marginally and ash increased. Ovarian protein and lipid content increased as development of the ovary progressed but the midgut gland lipid and protein concentration/content did not fluctuate relative to the stage of ovarian development. It is likely therefore that females rely on dietary intake for nutrients utilized for oogenesis. Males tended to invest less in reproduction than females as illustrated by the relatively small weight of the testes and by the increase in midgut gland wet weight over the summer that occurred only among males. Seasonal variation in testes composition was observed, possibly related to testes ripeness.
 
 

10:30 POTENTIAL OF THE FIRST DORSAL SPINE FOR ESTIMATING THE AGE OF TRIPLETAIL, LOBOTES SURINAMENSIS, FROM MISSISSIPPI COASTAL WATERS

James S. Franks*, James R. Warren, Dyan P. Wilson, Nikola M. Garber, and Kirsten M. Larsen,

University of Southern Mississippi, Institute of Marine Sciences, Ocean Springs, MS 39566-7000

The tripletail, Lobotes surinamensis, is a migratory, pelagic species that occurs throughout the tropical and subtropical seas of the world. In the western Atlantic Ocean tripletail occur from Massachusetts to Argentina, including Bermuda, and throughout the Gulf of Mexico and the Caribbean Sea. The tripletail is a popular sport fish in the northern Gulf region, particularly off Mississippi, however, life history data required for stock assessment of Gulf tripletail are lacking. In a preliminary investigation of the age of tripletail off Mississippi, the first dorsal spine was excised from a sample of tripletail caught in the Mississippi recreational fishery during 1996-1997 and examined for legibility of growth patterns on transverse sections and for general usefulness in age estimation. Most first dorsal spine sections revealed a succession of alternating opaque and translucent bands. Though not validated as annuli, translucent bands (often comprised of multiple small bands) on first dorsal sections were considered probable indicators of age and were counted for a small sample of specimens. Mean length-at-estimated age data based on translucent band counts in first dorsal spine sections were derived for the sample.

10:45 MARINE EQUIVALENT OF LATEST QUATERNARY GLACIAL LAKE COLUMBIA FLOODS FOUND AT ESCANABA TROUGH, GORDA RIDGE

Charlotte A. Brunner* and Gian Zuffa , University of Southern Mississippi, Stennis Space Center, MS 39529, and Università di Bologna, 40127 Bologna, Italy

The Escanaba Trough at the south end of the Gorda Ridge rift valley is filled by more than 500 m of sediment, indicating unusually fast sedimentation rates on young basement in an oceanic setting. In this work we focus attention on the top 80 m of the sequence of turbidites and hemipelagites recovered at ODP Hole 1037B. The interval is divided into 15 lithologic units composed of 12 thick turbidite beds interlayered by thin hemipelagites. The turbidites have sandy bases rich in neritic and bathyal foraminifers and minerals characteristic of the Columbia River drainage basin. The upper portions of each turbidite grades to silty clay, in which vascular plant debris is the dominant constituent of the sand-size fraction. Some units are capped by thin hemipelagites with abundant planktonic and abyssal benthonic foraminifers. The hemipelagites contain dextral Neogloboquadrina pachyderma, which entered the region about 14,000 yBP. AMS C-14 dates of wood and planktonic foraminifers show that sediments between 1.68 and 63.2 mbsf were deposited at a rate >13 m/1000 y between 11,000 and 15,750 yBP. This rate is comparable to those on the active levees of the Amazon Fan, although the Escanaba Trough is much further from its canyon source. Turbidite deposition took place during the last glacial termination and is correlative with lacustrine flood-beds of glacial Lake Columbia.

11:00 MEASURING COLLOIDAL PROPERTIES OF SIZE-FRACTIONATED RIVERINE SUSPENDED MATTER BY FLOW FIELD-FLOW FRACTIONATION

Kenneth P. Grembowicz* and Alan M. Shiller, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

Colloidal particles (<1 µm) are of particular interest because of their large surface area and transport of environmental contaminants in fluvial systems. Many processes occurring in natural waters are critically dependent on particle size. Such things as adsorption, aggregation, deposition, and resuspension often occur in characteristic size ranges. In order to understand these complex mechanisms, it is important to have the analytical tools necessary for fractionating and sizing such samples. Flow field-flow fractionation (flow FFF) is an elution based separation and measurement technique for particles and macromolecules. Particles are separated in a thin ribbon-like channel on the basis of their diffusion coefficient or hydrodynamic diameter. A stream of carrier solution, which is laminar and has a parabolic velocity profile because of the channel thinness (75-200 5m), transports particles toward the channel outflow and a detector. Flow FFF uses a crossflow of carrier solution perpendicular to the channel flow axis which forces particles toward one side of the channel, termed the accumulation wall. Larger particles move closer to the accumulation wall and are retained in the channel longer due to a lower diffusion coefficient. Thus, retention time is proportional to physical properties, such as diffusion coefficient and size. We are currently involved in the development of environmental flow FFF methodology to examine a variety of fluvial systems.

11:15 SEDIMENT FLOW PROPERTIES FROM MICROFABRIC ANALYSES

Dawn Lavoie* and Kishore Mohanty, Naval Research Laboratory, Stennis Space Center, MS 39529 and University of Houston, Houston, TX 77204

Bulk physical sediment properties, including permeability, are needed for many navy applications. Distribution of pore space is thought to be the main variable controlling the permeability of shallow water carbonates sediments recovered from the upper meter of seafloor from the Dry Tortugas. Our objective is to develop a quantitative relationship between sediment microfabric and sediment flow properties. The undisturbed microfabric of the sediments was examined by scanning electron microscopy. Representative images were scanned and analyzed using Image Tool and Image Tool Plug- Ins. Using erosion-dilation analysis, the 2D imaged pores and pore network were defined and quantified. Assuming the sediments to be isotropic, the third dimension was generated using the statistical characteristics of the 2D image itself. The resultant 3D data was used as input to effective medium theory modeling to predict single phase flow within the sediment. The modeling results, when compared with laboratory-measured permeability from the same samples, were in good agreement in unconsolidated sediment. Results from consolidated sediments were somewhat less satisfactory, possibly because the sediment was slightly anisotropic.

11:30 MESOSCALE MODELING FOR THE GULF COASTAL STATES

Paul J. Croft, R.S. Reddy, P.J. Fitzpatrick, and A.M. Sealy*, Jackson State University, Jackson, MS 39217

In the present study, proparatory mesoscale modeling work is being completed for a study of atmospheric processes in the Gulf Coastal States. The study area selected will include portions of Arkansas, Louisiana, and Tennessee and all of Missisippi and Alabama. Expected diagnostic studies include: convective initiation, tropical cyclones and rainfall, heavy rainfall events, air quality and pollution transport, and sensitivity analysis. Each study will be used as a stepping stone toward real-time operatrional prediction using the fifth-generation NCAR/Penn Stte Mesoscale Model (MM5). The MM5 is the most recent in a series of models used for mesoscale simulations and diagnostics. The model consists of a number of components: TERRAIN, DATAGRID, RAWINS, GRIN, and MM5. Each component, or pre-processor, is edited to accommodate detailed study of any region of interest. As part of this effort, involvement of JSU meteorology majors and the local NWS office in Jackson, MS is essential. Students will assist in model set-up and run while the NWS will provide technical advice and assistance in determining the most appropriate model set-up and guidance products to be generated. An additional benefit will be the availability of MM5 modeling results for use in the classroom and for student projects.

1:30 PRODUCTS OF CHLOROPHYLL DIAGENESIS IN MID-ATLANTIC BIGHT CONTINENTAL SHELF SEDIMENTS

Nianhong Chen* and Steven E. Lohrenz, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

Analysis of chlorophyll degradation products in sediments is important in understanding transformation pathways of organic compounds associated with phytoplankton and has been used in the study of carbon cycling. Chloropigments in sediments from the inner and outer shelf of the Mid-Atlantic Bight (MBA) continental shelf were extracted with acetone, followed by dichloromethane, and finally acidic methanol (10% conc. sulfuric acid in methanol, w/w). Chloropigments in acetone and dichloromethane extracts were further separated with gel permeation chromatography (GPC) to partition into three groups: (1) high molecular weight matter (HMWM), (2) pheopigments and phorbin steryl esters (PSEs), and (3) chlorophyll and pheophorbides. For both inner and outer shelf sediments, the proportion of fluorescence in acidic methanol was small (<2%), suggesting that diagenesis of chlorophyll by way of the incorporation into acid-extractable compounds in these sediments was not important. The proportion of fluorescence associated with dichloromethane-extractable chloropigments in sediments of the outer shelf was higher compared to the inner shelf, indicating that the outer shelf sediments had a higher content of 'aged' degradation products of chlorophyll. GPC separation of acetone and dichloromethane extracts indicated that HMWM was an important pathway of chloropigment diagenesis in both inner and outer shelf sediments, but more important for outer shelf sediments.

1:45 SIZE FRACTIONATED PIGMENT DISTRIBUTION IN THE CHESAPEAKE BAY

Chris Carroll* and Steven E. Lohrenz, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

Coastal oceans can exhibit productivity an order of magnitude higher than open oceans and, therefore, play an important role in biogeochemical cycles of carbon. The Chesapeake Bay is a partially mixed estuary typical of this higher productivity. Measurements of photosynthetic pigments from this area were conducted during the COPE II May 1997 cruise. Methods used for this process were fluorometric, high performance liquid chromatographic, and spectrophotometric techniques. Also, water samples were taken for microscopic analysis as well. Size dependent variations were examined in size fractionated samples to assess pigment distribution with relation to temperature, salinity, and temporal changes. It is important to determine the contribution of different size classes of organisms to overall productivity from an ecological perspective, such as assessing phytoplankton species diversity. Also, size fraction analysis helps characterize optical properties of the water column in support of remote sensing. The chlorophyll and phaeopigment content of water samples were determined by filtration on GF/F filters followed by extraction in 90% acetone in darkness and subsequent fluorometeric analysis. Preliminary results show that the <3 µm size fraction is the dominant size fraction in most of the stations farther off shore, where prochlorophytes and smaller cells are expected to be more abundant, while the larger size fractions were the more significant contributors to the chlorophyll concentrations near shore. The fluorometric analysis generally gave chlorophyll a concentrations from ~1 to ~3 µg/L.

2:00 TRANSMISSION ELECTRON MICROSCOPY OF CLAY SEDIMENTS OF BEAR ISLAND FAN, NORWEGIAN SEA

P.J. Burkett* and Nancy Carnaggio, Naval Research Laboratory, Stennis Space Center, MS 39529

Analyses of a single gravity core from Bear Island Fan, Norwegian Sea, using x-ray diffraction, transmission electron microscopy (TEM), and petrographic thin-sections, reveal the mineralogy and microfabric to be diamicton associated with massive submarine landslides and overlying clay hemipelagic facies. The mineral assemblages of bulk samples from the core consist primarily of phyllosilicates (chlorite, illite, smectite, and kaolinite) with quartz and calcite. Texture of the clay microfabric examined at the micron scale reveals a complex 3D arrangement of clay minerals ranging from microcrystalline to poorly sorted to well-defined clay chains. Thin-sections reveal the occurrence of prolific crystalline quartz comprising glacial flour, which correlates to physical properties results of decrease porosity, water content, and shear strength. Eight downcore subsamples from depths between 20-192 cm below seafloor analyzed using TEM microfabric showed features associated with various facies including hemipelagic sediments and two debris flow events. The strikingly similar mineralogy indicates the same geologic source (Barents Sea shelf sediments) but different environments of deposition varying from the raining of hemipelagic materials to episodic debris flows initiated by glaciation.

2:15 FORAMINIFERIDA MEMBRANES, A POSSIBLE THERMAL ALTERATION INDICATOR WHICH CAN BE USED TO INFER PALEOTEMPERATURES OF MARINE SEDIMENTS

Allen H. Reed* and Charlotte A. Brunner, University of Southern Mississippi, Stennis Space Center, MS 39529

The Escanaba Trough in the Gorda Ridge Rift System is a Quaternary basin filled by >500 m of turbidites subjected to heating from underlying young basement basalt. The organic matter contained in these sediments undergoes physical and chemical changes due to thermal alteration. Portions of the organic matter follow an alteration pathway from raw organic matter to wet gas to charcoal, while residues undergo alterations that produce distinctive color changes. Pollen changes color from pale yellow to orange to brown when viewed with plain light microscopy, and the colors correspond to discrete sediment temperature ranges. Sediment samples collected during Ocean Drilling Program Legs 139 and 169 contained pollen and foraminifers with notable color alterations. Pollen color changes were quantified to sediment temperatures. Foraminifer color changes may also be used to quantify paleotemperatures, however a correlation between pollen color alteration and foraminifer color alteration needs to be established. I propose to test foraminifer color changes as a proxy to sediment paleotemperature by (1) correlating foraminifer membrane color to that of pollen from altered sediments of the Escanaba Trough and (2) calibrating foraminifer color changes to temperature in laboratory heating experiments. The new proxy is crucial to oil industry exploration in deep water, where pollen is rare and foraminifers are abundant.

2:30 A NESTED GRID MODEL FOR THE MISSISSIPPI BIGHT

Germana Peggion, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

This study addresses the feasibility of a two-way communication procedure between large-scale basin and high-resolution coastal models. The problem is formulated by assuming that there are two dominant scales: the small, energy-containing features and the large, slowly-varying flow. The algorithms are implemented under the condition that the coarse domain extends over the fine grid, so that the coastal model can be forced at the interface by the large-scale flow and a feedback procedure can be applied to the overlapping basin area. The method is applied to analyze the water mass exchanges between the Mississippi Bight (MB) Shelf and the Gulf of Mexico (GOM), and determining the role of local and remote forcings in the cross-shelf processes. The local mechanisms include wind, tides and density differences between coastal and deep ocean waters. Remote forces refer to the influence of the open ocean circulation on the shallow region. While the local mechanisms usually operate on a regular, cyclic fashion, the remote forcings may involve massive, yet episodic events.

2:45 Divisional Poster Session

BIOACCUMULATION AND ELIMINATION OF ATRAZINE AND CHLORPYRIFOS BY JUNCUS EFFUSUS IN A MESOCOSM EXPERIMENT

Julia S. Lytle, Thomas F. Lytle, and Wesley Lewis*, Gulf Coast Research Laboratory, Ocean Springs, MS 39564

Juncus effusus, growing in 48-500L outdoor mesocosms, was exposed to combinations of atrazine, chlorpyrifos, monosodium methanearsonate (MSMA) and methyl mercury chloride, and leaf shoots sampled periodically for 94 days to determine rate of uptake and elimination of both atrazine and chlorpyrifos. Measured water concentrations on day 1 were 212, 9.2, 36, and 1.2 ppb for atrazine, chlorpyrifos, MSMA and mercury respectively. An additional 18 mesocosms received half-strength doses of all compounds. A repeat dose to half the mesocosms occurred on day 62. Atrazine levels increased through day 16 reaching 1130 ppb (wet wt) and declining after day 32 resulting in 65% loss by day 94. Chlorpyrifos peaked at day 1 at 534 ppb with decline beginning on day 4, until background levels were reached at day 32. No overall significant interactive effects due to mixed toxicant exposure were observed. Atrazine and chlorpyrifos accumulations in the half-strength exposures were half that found in the full-strength exposures and fit a linear model of uptake vs dose level. Following second exposure, plants receiving additional atrazine or chlorpyrifos showed an increase in tissue levels (compared to plants not redosed) that approximated that observed after the first exposure. Chlorpyrifos levels were retained longer after the second exposure while atrazine was lost at a rate similar to the first exposure. Results suggest little difference in uptake ability of J. effusus following a second exposure of either compound.

COMPARISON OF OXYGEN DEPLETION BETWEEN OLDER AND NEWER CATFISH PONDS

Frank H. Thompson* and Michael D. Porter, Mississippi Valley State University, Itta Bena, MS 38941

This project evaluates oxygen depletion trends among catfish ponds and compares water quality among older and newer ponds. Dissolved oxygen was determined using a YSI oxygen meter with samples taken at both ends of the pond. Data was collected every two hours between 1800 and 0800 hours every night. When oxygen dropped to critical levels in the ponds, aerators were turned on to stabilize oxygen levels. The research examines geographical patterns in oxygen depletion among ponds, and compares average oxygen values and aeration time between older and newer ponds.

COMPETITIVE POPULATION GROWTH BETWEEN ALGAE IN THE PRESENCE OF FeSO₄ AND MgSO₄

Kimberly Marshall*, Mario L. Pipkin, and Michael D. Porter, Mississippi Valley State University, Itta Bena, MS 38941

Off-flavor in catfish ponds is often caused by a cyanobacteria (blue-green algae) called Oscillatoria chalybea. Blue-green algae blooms release 2-methylisoborneol (MIB), a compound that is easily absorbed across the gill membrane into the bloodstream. Humans are very sensitive to MIB, which produces a musty flavor. Understanding the interactions between green and blue-green algae could be used to improve water quality in catfish ponds. This research examines reducing the population growth of blue-green algae bloom in catfish ponds through competition by green algae. The experiment focuses on the effects of iron and magnesium on cyanobacteria and green algae populations under culture conditions. Preliminary results indicate cell population growth in green algae and a population decline for cyanobacteria when iron or magnesium are added to the water.

HARDBOTTOMS ON THE INNER CONTINENTAL SHELF OF ALABAMA AND NORTHWEST FLORIDA: INTERPRETATION AND CLASSIFICATION OF SIDE-SCAN SONAR IMAGERY

Peter Fleischer* and William W. Schroeder, Naval Research Laboratory, Stennis Space Center, MS 39529, and University of Alabama, Dauphin Island, AL 36528

Hardbottoms are common on the inner continental shelf (18-40 m), of easternmost Mississippi, Alabama, and northwest Florida. Late Pleistocene to Holocene sea-level rise caused planation of the Pleistocene substrate and resulted in exposure of resistant deposits which today are only partly veneered by a thin, mobile sand sheet. Side-scan sonar mosaics of hardbottoms and their surroundings off Alabama and northwest Florida reveal their morphologic, stratigraphic, and hydrodynamic setting. Confirmed by diver observation and sampling, the mosaics display considerable variety among hardbottoms. This diversity can be understood in terms of the heterogeneity of Pleistocene nearshore and estuarine deposits, and their relative resistance to erosion and transport. A proposed inner-shelf hardbottoms classification places hardbottoms on a continuum based on degree on physical displacement. Autochthonous hardbottoms are those in their original stratigraphic or structural position (outcrops, erosional ledges, exhumed bedding trends). Hardbottoms having a clear vertical component of displacement (talus, rubble fields, shell and shell-hash pavements) are parautochtonous. This type grades into allochthonous lags (gravel and shell hash in sand-wave troughs), which are horizontally-transported and reworked. Because this approach is a function of substrate lithification and deposit modification by the hydrodynamic regime, it is useful for identification and interpretation of inner-shelf hardbottoms in general.

SURVIVAL AND GROWTH OF ORIZIAS LATIPES EXPOSED TO TRICHLORETHYLENE AT MULTIPLE LIFE STAGES

David H. Barnes¹*, Charles S. Manning¹, William E. Hawkins¹, William W. Walker², and Robin M. Overstreet¹, ¹Gulf Coast Research Laboratory, Ocean Springs, MS 39564, and ²US Environmental Research Laboratory, Gulfbreeze, FL 39561

The effects of trichloroethylene (TCE) to the growth (as standard length, area, wet weight, and dry weight) and survival of the Japanese medaka (Oryzias latipes) at several life stages were examined in a series of 7 day flow-through exposures. Exposures were initiated with medaka at 4, 7, 10, 13, 16, 28, 42, and approximately 180 days post hatch. Growth of the medaka was more sensitive than survival in evaluations with fish 4 to 13 days old. Medaka 7, 10, and 13 days post hatch established the Lowest Observed Effect Concentration (LOEC) based on growth at 8.8 to 10.1 mg/L for the various life stages. There were no significant effects to the growth of fish greater than 16 day old at study initiation. Fish greater than 16 days post hatch at initiation exhibited only treatment related effects to survival. Standard length, area, and weight of controls from initiation to termination demonstrated the most rapid percent increase at the earlier life stages and growth as an effect is best determined during the first 2 weeks post hatch of the medaka. Effective concentrations could be significantly increased by delaying the measurement of growth to times past 2 weeks of age. Calculated LC50 values for the various life stages ranged from a minimum of 21.4 mg/L for the 16 day old fry to a maximum of 41.5 mg/L calculated for the 4 day old fry. Survival of fish 10 to 42 days old at study initiation was most sensitive as a result of TCE exposure.

HEAVY METALS IN SEDIMENTS AND MARSH PLANTS NEAR WATERFRONT GOLF COURSES AND A MUNICIPAL HARBOR

Michael G. Treadway* and Thomas F. Lytle, Cooperative Intern Program Between Mississippi Gulf Coast Community College--Jackson County Campus Honors Biology Students, Gautier, MS 39553, and Gulf Coast Research Laboratory, Institute of Marine Sciences, University of Southern Mississippi, Ocean Springs, MS 39566-7000

Heavy metals are a component of the contaminants that are introduced to coastal waterways and may accumulate in coastal sediments and impact the organisms that reside there. Two possible sources of heavy metal contamination are waterfront golf courses and municipal harbors. Two golf courses near Ocean Springs, Mississippi and the harbor serving that community were selected for a study to determine the level of heavy metals in sediments and the associated marsh plants. Sites were chosen near the golf courses that received large amounts of runoff and the site in the harbor was selected to be near a region where the city formerly discharged treated sewage effluent. The plants that were collected included the dominant marsh plants, Juncus roemerianus and Spartina alterniflora, as well as several less abundant plant species. Plants and sediments were analyzed for the metals, Hg, Ag, Co, Cu, Cd, Zn, Fe, Pb, and Mn by atomic absorption spectrophotometry. Plants were also collected from a clean sediment site and the results of the contaminated sites were compared. A further objective of this study was to see how efficiently marsh plants may remove metals from sediments which may be useful in pollution cleanup.

FATE OF CHLORPYRIFOS AND FLUORENE IN SEDIMENT PORE WATER ASSOCIATED WITH ESTUARINE PLANTS

Carlissa Moore* and Julia S. Lytle, Cooperative Intern Program Between Mississippi Gulf Coast Community College--Jackson County Campus Honors Biology Students, Gautier, MS 39553, and Gulf Coast Research Laboratory, Institute of Marine Sciences, University of Southern Mississippi, Ocean Springs, MS 39566-7000

Estuarine sediments are natural sinks for toxic compounds and pose a risk to this ecosystem. Toxic sediments are a global environmental concern, and remediation of these sediments is an important and economic management issue. The role plants play in remediating sediments is not completely understood, yet it is recognized that plants can take up certain toxins as well as metabolize them. The fate of toxins in sediments may also be affected by the plant exudates which provide nutrients to a diverse microbial community and enhances toxin solubility. To assess what role the plant/sediment rhizosphere plays in degrading toxins, sediment surrounding roots of four marine plant species were collected from both polluted and nonpolluted areas. Pore water was extracted from each sediment and spiked with chlorphyrifos and fluorene, a pesticide and a polynuclear aromatic hydrocarbon, respectively. Triplicate aliquots of spiked pore water from each sediment were placed into test tubes with 12 g of a standard homogenized marine sediment, thoroughly agitated and incubated at 30°C. Loss of chlorpyrifos and fluorene from the pore water was assessed on days 7, 14, and 21. Degradation rates in pore water from each plant rhizosphere, both polluted and nonpolluted, were compared.

CONTINUING EROSION IN SOUTHEASTERN COASTAL MISSISSIPPI - POINT AUX CHENES BAY, WEST GRAND BAY, MIDDLE BAY, GRANDE BATTURE ISLANDS: 1995-1997

Warren T. O'Sullivan* and G. Alan Criss, Cooperative Intern Program Between Mississippi Gulf Coast Community College--Jackson County Campus Honors Biology Students, Gautier, MS 39553, and Gulf Coast Research Laboratory, Institute of Marine Sciences, University of Southern Mississippi, Ocean Springs, MS 39566-7000

This study is part of a continuing effort to document erosion in southeastern coastal Mississippi. Shoreline change measurements were made at twenty station locations around Point aux Chenes Bay, West Grand Bay, and Middle Bay including remnants of the Grande Batture Islands. Linear shoreline change measurements were made in October 1997 based on reference markers placed in October 1995. New markers were placed inland of the old reference markers at each station for the purpose of future surveys. Probable scenarios for the progression of erosion are described. Historical data from previous surveys conducted in February 1990, July 1992, and October 1995 are discussed. Significant erosion continues to occur unabated throughout most of the area, which is part of the Grand Bay National Wildlife Refuge, with an attendant loss of an important part of Mississippi's diminishing marsh environment.

BRACHYURAN RECRUITMENT DYNAMICS: A COMPARISON OF BLUE CRAB SETTLEMENT INDICES AT FOUR SITES ALONG THE MISSISSIPPI GULF COAST, 1996

Kirsten M. Larsen*, Harriet M. Perry, Christine Trigg, and Marjorie Williams, University of Southern Mississippi, Gulf Coast Research Laboratory, Ocean Springs, MS 39566-7000

The spawning season for the blue crab, Callinectes sapidus, extends from March through November in the northern Gulf of Mexico. After an offshore larval stage, blue crab postlarvae (megalopae) enter the Mississippi Sound and settle in near-shore, shallow water habitats. Megalopal settlement, using stationary collectors attached to a fixed pier, has been monitored daily from May through October (1991 through 1997) at a station in eastern Mississippi Sound (permanent site). While the magnitude of settlement is highly variable, the temporal periodicity of megalopal settlement is similar from year to year. Settlement does not reflect seasonality of spawning. Although ovigerous females are found in March and April, and megalopae have been found in plankton samples in April and May, settlement rarely occurs in the spring. Factors influencing settlement include planktonic availability of megalopae, competency of the megalopae to settle, circulation patterns that may move early larvae (zoeae) away from the study area or inhibit movement of late stage larvae into the estuary, and suboptimal environmental parameters. Occurrence of large numbers of megalopae in spring plankton samples from waters near the barrier island passes suggests the possibility that small-scale, local hydrographic features may preclude or influence settlement at the permanent site. In 1996 settlement was monitored at three additional sites along the coast. The average number of megalopae per collector at each site was compared to average numbers collected at each of the other sites over the duration of the sampling (paired t-test, = 0.05). No significant differences in the average number of megalopae per collector between sites were found with the exception of the western-most site (>1 per day). Settlement at neighboring sites was positively correlated, however, no significant correlation was found between settlement at the permanent site and the two western-most sites. Observed settlement patterns may reflect different circulation regimes in the eastern and western Sound. Temporal periodicity of settlement was in agreement with data from previous years. Minimal settlement occurred in the spring suggesting that factors other than local small-scale circulation features are affecting spring megalopal settlement.

CALLINECTES SAPIDUS: RELATIONSHIP BETWEEN ABUNDANCE OF EARLY CRAB STAGES AND SUBSEQUENT NUMBERS OF LATE STAGE JUVENILES IN MISSISSIPPI COASTAL WATERS

Harriet M. Perry*, James R. Warren, Christine Trigg, and Lisa Engel, University of Southern Mississippi, Gulf Coast Research Laboratory, Ocean Springs, MS 39566-7000

Fishery independent blue crab data have been collected since 1974. Juvenile abundance is monitored monthly with a variety of gear types. Annual variations are evident in both recruitment of small crabs to the juvenile population and in the total number of crabs collected. High catches of small crabs occurred in the 1970s followed by much reduced catches in the early and mid 1980s. Catches began to rise again in the late 1980s. These same general trends were observed in catches of larger juveniles. Catch data (n = 24,690 crabs) were grouped into 10.0 mm carapace width (CW) size groups. The number of crabs in each size interval was calculated for the period of low juvenile abundance (1982 through 1987) and was compared to similar data for the years of higher abundance preceding (1974 through 1981) and following (1988 through 1995) this period. In each group, there was a decrease in numbers of individuals with increasing size. Mortality of early crab stages (3.0 to 29.9 mm CW) is extremely high. As crabs approach 30.0 mm CW, the rate of disappearance begins to level off but continues to gradually decrease. The rate of decrease was not significantly different among the three groups of pooled data, suggesting that they are declining at an equal rate relative to initial abundance of early juveniles in any given time period. Therefore, indices of abundance of early crab stages may predict relative abundance of later-stage juveniles.

3:45 Divisional Business Meeting
 
 

9:00 REMOTE ACCESS TO THE UNDERSEA ENVIRONMENT VIA THE RUTGERS/NURP FACILITY

Vernon Asper¹*, Steven E. Lohrenz¹, and Waldo Wakefield², ¹University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529, and, ²Mid-Atlantic Bight National Undersea Research Center, Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901-8521

The NOAA National Undersea Research Program has funded the construction of a facility at the Rutgers Tuckerton Field Station which will allow users to install equipment on the sea floor and monitor its performance from anywhere in the world. The heart of this system is a "node" or underwater connection hub which is linked to the field station via an electro-optic cable. Standard sensors on the node include a profiling CTD, optical sensors, flow sensors and a video camera. Individual scientists attach specific sensor systems to guest ports on the node, which provides them with power and high-speed communications. All signals are multiplexed and transmitted via an 11 km subsea cable to a Sun server in the field station which de-multiplexes them and makes them available to user-supplied computers via a local serial link. This system has just become operational, with the first data and control signals having been transmitted from our fluoresence sensors. The capability to monitor and control instruments on the sea floor over 1,000 miles away holds tremendous promise for expanding our knowledge of the coastal marine environment.

9:15 DYNAMICS OF OPTICAL PROPERTIES ACROSS A PLUME FRONT

Jennifer R. Bivens¹*, Donald G. Redalje¹, and Alan D. Weidemann², ¹University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529, and ²Naval Research Laboratory, Stennis Space Center, MS 39529

As part of the Naval Research Laboratory funded Chesapeake Bay Plume Experiment, we collected optical data during the May 1997 COPE II cruise from the plume of the Chesapeake Bay over a three week period. There are many questions concerning the biological responses at water mass fronts. Higher biomass on the more dense side of a front is often attributed to the physiology of the organism as well as the physical interactions at the front. Data collected included absorption and attenuation measurements using the Wetlabs ac-9 meter, and fluorescence using a Turner designs fluorometer and the Wetlabs SAFIRE, a multispectral fluorometer. The instruments serially collected flow through data for 15 days, crossing the plume front repeatedly. The data has been analyzed to describe the in situ changes in the optical properties, caused by the various water mass constituents. The preliminary results indicate changes in the optical properties across the plume front. Final results will be applicable to validation of remote sensing reflectance employed in determinations of bio-optical-physically coupled models.

9:30 USE OF SINGLE-PLANE STRUCTURED LIGHT RANGE SENSING TO ACQUIRE 3D DATA FOR USE IN TAXONOMIC, MORPHOMETRIC, AND ANATOMICAL STUDIES

Stuart G. Poss*, and Robert L. Cromwell, University of Southern Mississippi, Gulf Coast Research Laboratory,Ocean Springs, MS 39566-7000, and Purdue University, West Lafayette, IN 47907-1550

Single-plane structured light range-sensing provides abundant, accurate 3D data that can be used in a wide variety of contexts. An inexpensive sensor of simple design has been developed that provides surface data (x,y,z coordinate positions) for typically 75,000 points on a specimen in under 2 minutes. Each surface point is accurately localized to within 0.2-0.08 mm depending upon the lens system and position of the CCD camera. The system runs on a Linux workstation and can be built for under $4,000, including computer. 3D data obtained from the sensor can be used for a variety of purposes. Several applications relating to the use of these data for purposes of biological taxonomy, systematics, and morphology are presented. These involve using the system to generate 3D reconstructions and acquire accurate morphometric measurements of fish bones for comparative studies. The system provides a cost effective means of building virtual collections of objects that can be disseminated among investigators via the Internet. Implications of sensor technology to future of the fields of taxonomy and systematics will be discussed.

9:45 SPECTRAL REFLECTANCE RATIOS AND THEIR RELATIONSHIP TO CHLOROPHYLL CONCENTRATIONS OFF CAPE HATTERAS, NC

Vivienne C. Lochhead*, Steven E. Lohrenz, and Donald G. Redalje, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

Validation of satellite ocean color algorithms for estimating phytoplankton chlorophyll concentrations in coastal waters requires in situ comparisons of spectral reflectance and photosynthetic pigment concentrations. Using a Satlantic Profiling Spectroradiometer, profiles of irradiance and radiance at 14 spectral channels (10 nm bandwidth) were obtained off Cape Hatteras, North Carolina during cruises in March and July 1996. Radiance reflectance ratios at 490/555 nm were calculated using Prosoft Version 3.6a provided by the manufacturer. These ratios were consistent with the spectral channels available on the newly launched SEAWiFS ocean-color satellite. Chlorophyll concentrations were measured by filtration of samples on glass fiber filters (Whatman GFF), extraction of pigments into 90% acetone/deionized water for 24 h at -20 C and subsequent assay using a Turner Designs Model 10 fluorometer. Correlations between reflectance ratios and pigment concentrations were significant in March, but not July when surface pigment concentrations were lower relative to other constituents such as dissolved organic matter. Results suggest that ocean color algorithms derived for clear ocean waters may need to be refined for application in coastal waters influenced by dissolved organic matter or suspended particles.

10:00 Break

10:15 THE DISTRIBUTION OF HYDROGEN PEROXIDE IN THE CENTRAL ATLANTIC OCEAN

Jinchun Yuan* and Alan M. Shiller, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS 39529

The concentration of hydrogen peroxide in seawater samples in the central Atlantic Ocean were determined during a transect from Uruguay to Barbados in May and June of 1996. In the surface waters of open ocean, the concentration of hydrogen peroxide increased with latitude from little over 20 nM in the south (33.8S) to more than 70 nM in the north (8.9N). The concentration of hydrogen peroxide in unfiltered and 0.4 mm filtered samples were identical. Depth profiles of hydrogen peroxide exhibit surface maxima of 29 to 165 nM and decreasing concentration with depth. Although higher surface concentrations were found at stations in the Amazon Plume, these stations showed a dramatic decrease in hydrogen peroxide with depth and integrated water column hydrogen peroxide was not significantly higher than at open ocean stations. Other factors affecting hydrogen peroxide concentrations were time of day and rainfall.

10:30 A COUPLED LAYER-LEVEL OCEAN MODEL PROCESS STUDY

A. Louise Perkins* and Lucy F. Smedstad, Naval Research Laboratory, Stennis Space Center, MS 39529

Using the hybrid ocean model developed by Paul Martin, we study the exchange of energy between a nested NRL Layered Ocean Model (NLOM) in the Mediterranean Sea, and a hybrid coordinate level model in the Gulf of Sidra. Our version of NLOM consists of a full basin Mediterranean Sea model containing a refined Ionian Basin model. The Ionian Basin model is then coupled to the hybrid level model in the Gulf of Sidra, where a process study is prosecuted. On weekly time scales, we find that proximity to the slope topography retards flow unrealistically in the model.

10:45 VARIABILITY IN THE INHERENT OPTICAL PROPERTIES IN SPRING AND SUMMER CASE II WATER MASSES OFF CAPE HATTERAS, NORTH CAROLINA

Kenneth V. Matulewski*, Donald G. Redalje, and Steven E. Lohrenz, University of Southern Mississippi, Institute of Marine Sciences, Stennis Space Center, MS, 39529

As part of the Ocean Margins Program sponsored by the Department of Energy, this study examined how inherent optical properties (IOPs), such as absorption, scattering, and attenuation vary on spatial (horizontal and vertical) and temporal (daily and seasonal) scales. We looked at both ranges of variation and gradients over time and space. Data were collected on three cruises which were conducted on the continental shelf off Cape Hatteras, North Carolina in July of 1994, March of 1996, and July of 1996. Total absorption as measured by an ac-9 absorption/attenuation meter was compared to that measured by the quantitative filter pad technique. IOP data was then be compared to temperature versus salinity plots to assess the use of IOPs in determining the existence and location of different water masses. Preliminary results show that the ac-9 measurements of total absorption are comparable to those measured by the quantitative filter pad technique. We also show that there are both onshore-offshore and vertical gradients in IOPs, and that IOPs can be useful in describing different water masses, although the water masses are slightly different than those identified by temperature versus salinity plots.
 
 

11:00 EFFECTS OF ESTUARINE RHIZOSPHERE ON PLANT UPTAKE AND DEGRADATION OF CHLORPYRIFOS IN SEDIMENTS

Julia S. Lytle* and Thomas F. Lytle, University of Southern Mississippi, Institute of Marine Sciences, Ocean Springs, MS 39564

Estuarine sediments are natural sinks for toxic compounds such as pesticides from agricultural fields. Plant effects on pesticide degradation are not completely understood, but previous studies suggest that the plant rhizosphere enhances the rate of degradation of certain toxic compounds and also enhances solubilization of the toxin for plant uptake. A study designed to assess the role of estuarine plants and their rhizosphere on the degradation of chlorpyrifos was carried out in microcosm experiments. A homogenized estuarine sediment was prepared in four blocks of quadruplicate chambers, each of three blocks contained plants of a single species, Scirpus olneyi, Spartina alterniflora, and Sesbania vesicaria. The fourth block contained only sediments. After 6 weeks of growth and establishment of plant rhizosphere, three chambers in each block were dosed with 100 ppb chlorpyrifos. Treated plants were used to determine whether one species is more effective than another in degrading sediment chlorpyrifos, either by increasing total microbial activity due to exudate enrichment or by producing a more selective degrading population due to the unique species exudate. Chlorpyrifos uptake in plant tissue and loss in sediments was measured using immunoassay techniques on days 2, 8, and 32. Greatest decrease of chlorpyrifos occurred in surface sediments associated with S. alterniflora while greatest accumulation of chlorpyrifos was in S. vesicaria tissue.

1:30 MISSISSIPPI GULF COAST STRIPED BASS RESTORATION PROGRAM - HELP!!

Mitch Spicer* and Larry Nicholson, Cooperative Intern Program Between Mississippi Gulf Coast Community College--Jackson County Campus Honors Biology Students, Gautier, MS 39553, and Gulf Coast Research Laboratory, Institute of Marine Sciences, University of Southern Mississippi, Ocean Springs, MS 39566-7000

In 1967, the Anadromous fish department of the Gulf Coast Research Laboratory began the restoration of striped bass in coastal rivers of Mississippi. Each year this ongoing program produces thousands of striped bass which are stocked into the local rivers. After the striped bass are released, the fishing public plays a major role in providing information (fishery dependent data) concerning the growth, location, and general physical condition of the fish they catch. These data are an essential part of the restoration program. Traditionally, less than three percent of the people catching striped bass report their catch. The objective of this study is to create a cohesive history of the program in order to increase public awareness and promote greater participation.

1:45 THE APPLICATION OF MITOCHONDRIAL DNA CONTROL REGION IN STUDIES OF POPULATION STRUCTURE OF GREY MULLET IN NORTH AMERICA

Nikola M. Garber*, Walter D. Grater, and Kenneth C. Stuck, Institute of Marine Sciences, Gulf Coast Research Laboratory, Ocean Springs, MS 39566-7000

In animal eukaryotic cells, a small amount of DNA is found outside the nucleus within the mitochondria. This mitochondrial DNA (mtDNA) evolves independently and at a faster overall rate than nuclear DNA. Specific genes and non-coding regions within the mtDNA also evolve at different rates and can therefore be used in phylogenetic, systematic, and population level genetic studies. The non-coding control region is the most rapidly evolving segment in mtDNA and been used to distinguish populations of marine fish. Grey mullet, Mugil cephalus, has a worldwide distribution and is common in coastal waters of the continental United States and Hawaii. Because of declining numbers, a program has been implemented in Hawaii to enhance natural mullet populations through release of cultured stocks. Similar enhancement efforts have been proposed in Mississippi. Therefore, studies have been initiated to determine the population structure of grey mullet in North America and Hawaii using direct sequence analysis of the mtDNA control region. Polymerase chain reaction (PCR) and universal primers to conserved regions of the mtDNA which flank the control region were used to produce a 2000 bp fragment. The fragment was partially sequenced, and internal primers were designed to amplify the hypervariable portion of the control region. The procedures developed in the initial phase of this study will be used to conduct future genetic studies with mullet.

2:00 MOLECULAR METHOD FOR IDENTIFICATION OF TWO MULLET SPECIES FROM NORTHERN GULF OF MEXICO

Kelli D. Marshall*, Lidia M. Stuck, and Kenneth C. Stuck, Cooperative Intern Program Between Mississippi Gulf Coast Community College--Jackson County Campus Honors Biology Students, Gautier, MS 39553, and Gulf Coast Research Laboratory, Institute of Marine Sciences, University of Southern Mississippi, Ocean Springs, MS 39566-7000

Morphological identification of two local species of mullet, Mugil cephalus and Mugil curema, is often unreliable, in particular when specimens are larvae or juvenile stages. A variety of molecular techniques have been utilized for phylogenetic analysis of fish and to distinguish and identify morphologically similar species regardless of the stage of development. We applied the molecular technique known as Restriction Fragment Length Polymorphism (RFLP) to detect differences in DNA sequence between the two species of mullet. Samples of gill tissue from both species of fish were collected, followed by extraction of total DNA. A fragment of fish mitochondrial DNA was then amplified by polymerase chain reaction (PCR) using appropriate primers. The sequence of the amplified fragment is known from previous research and available through the EMBL data bank. The sequence was scanned using the "Primer Detective" computer program to determine restriction sites. Based on that information, restriction enzymes were selected. The amplified DNA fragment was then digested with the selected set of restriction enzymes and electrophoresed on an agarose gel to visualize results. The two species of mullet were identified based on the unique fragment pattern obtained.

2:15 WATER QUALITY IN SAINT LOUIS BAY, MISSISSIPPI: A BENTHIC APPROACH

Elizabeth I. Phelps* and Donald G. Redalje, University of Southern Mississippi, Stennis Space Center, MS 39529

The greater availability of nutrients to phytoplankton populations in coastal waters cause these waters to be more productive than open ocean waters. The Bay of Saint Louis is such an area. These nutrients can be introduced through both point (rivers and bayous) and non-point (the surrounding watershed, and septic tank leakage) sources. This increase in production, and thus phytoplankton biomass will cause an increase in the quantity of organic matter being supplied to the sediments surface, which will in turn affect the inhabitants of the benthos. To study this relationship, nine stations have been set up throughout Saint Louis Bay. Twice monthly, water samples are taken for chlorophyll a, total organic carbon and nitrogen, and nutrients (dissolved forms of nitrogen, phosphorous, and silicon). In addition, profiles of salinity, temperature, dissolved oxygen, turbidity, and pH are obtained using a YSI 6000 multi-parameter water quality monitor. Grab samples are taken monthly for macrobenthic biomass, and sediment characteristics (grain size, water content and inorganic and organic forms of carbon and nitrogen). Preliminary results indicate that there is spatial variability in sediment characteristics which influence the macrobenthic species inhabiting the area. In addition, it is apparent that the quantity and quality of organic matter falling to the benthos is influencing the macrobenthic inhabitants.

2:30 STOCK ASSESSMENT OF SPOTTED SEATROUT (CYNOCSION NEBULOSUS) IN MISSISSIPPI COASTAL WATERS

James R. Warren, University of Southern Mississippi, Institute of Marine Science, Ocean Springs, MS 39564

Spotted seatrout are probably the most highly sought sport fish in Mississippi's coastal waters. This population also supports a relatively small commercial harvest, currently operating under a 40,000 pounds per year quota. A perceived reduction of inshore stocks has caused concern about the abundance of the population and whether the stock can sustain itself under the current level of utilization. Fishery independent sampling from 1992-96 and fishery dependent data from the recreational and commercial catch from 1984-1996 have been used to assess the population parameters of age structure, length-at-age estimates and length-weight relationships. Age structures were used to estimate fishing mortalities using catch curve and virtual population analyses. A spawning stock biomass and spawning potential ratio (SPR) were estimated from these data. Current estimates of SPR are approximately 19% which is generally considered slightly below the lower threshold for many species. Because fish as young as one year of age were found to contribute to the spawn suggests that this population can sustain itself at the current level of exploitation even though the population is at a relative low SPR.

2:45 USE OF MARSH VEGETATION IN PHYTOREMEDIATION OF MERCURY CONTAMINATED SEDIMENTS

Thomas F. Lytle* and Julia S. Lytle, University of Southern Mississippi, Institute of Marine Sciences, Ocean Springs, MS 39566

Efforts at finding suitable plant candidates for remediation of contaminated soils have failed to use plants of use in clean-up of brackish coastal sediments. A homogenized estuarine sediment was placed in four blocks of quadruplicate chambers, one block contained no plants and each of the other three blocks contained plants of a single estuarine species, Scirpus olneyi, Spartina alterniflora, and Sesbania vesicaria. Methyl mercury in aqueous medium was percolated through the sediment elevating the top 1 cm to 0.4-1.0 ppm total Hg, about twice the background level in Southeastern U.S. sediments. At day 7, leaves achieved maximum Hg concentrations with 0.6 ppm (dry wt.) in S. vesicaria being higher than other plants. By day 31 all plants had depleted sediments of Hg to a greater degree than occurred in non-plant sediments but S. vesicaria had reduced Hg levels twice as effectively as other species. A comparison of difference in total acid soluble thiol levels and the antioxidant, glutathione, in tissues (presumed to be phytochelatins) indicated no significant production of these sequestering compounds in response to Hg. Other antioxidants, vitamin C and peroxidase enzymes also showed little difference in treated and control plants suggesting that at this level of Hg treatment, these plants could easily tolerate the oxidative stress of Hg, and the plants, particularly S. vesicaria, show promise for phytoremediation of Hg contaminated sediments.