1992 BASICS OF THE BASIN ABSTRACTS

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Anderson, A. C., Tulane University School of Public Health and Tropical Medicine, New Orleans, LA

Recreational Impact of Fecal Loading on Lake Pontchartrain Basin Streams.

There have been several epidemiological studies addressing the health implications of exposure to pathogens in recreational waters. These data, including the study done at Lake Pontchartrain, are reviewed. Based on these studies, EPA recommended new bacteriological criteria for recreational water quality: 126 E. coli / 100 ml. fresh water or 33 enterococci / 100 ml. fresh water. Levels of these indicators and sources of contamination are discussed using the Tangipahoa River as a model for fecal loading of Pontchartrain Basin streams. The impact of fecal contamination on other basin streams is also discussed. The status of adoption of the new criteria organisms as bacteriological standards for recreational water is reviewed. The steps being taken to improve recreational water quality in the Pontchartrain Basin are outlined.

Binet, G., St. Charles Parish, Hahnville, LA, and Ensminger, A. B., Wetlands and Wildlife Management Co., Inc., Belle Chasse, LA

Habitat Degradation of the LaBranche Wetlands and an Approach to its Restoration

Considered the most productive wetlands within the Lake Pontchartrain Basin, the LaBranche Wetlands south of Lake Pontchartrain consists of over 14,000 acres of brackish to fresh marsh and forested swamp. Before natural and man-made processes produced massive degradation and habitat changes of the LaBranche Wetlands, the entire area was a freshwater swamp and marsh complex. Between 1970 and 1980, one-fourth of the LaBranche Wetlands habitat was lost due to saltwater intrusion, natural subsidence, channelization, and shoreline erosion. Major contributing factors to LaBranche's decline has been the dredging of access channels for the construction of I-10, the construction of the Mississippi River Gulf Outlet that periodically brings saltwater into Lake Pontchartrain from the Gulf of Mexico, shoreline retreat of over 15' per year due to Lake Pontchartrain wave action, and of course natural sediment depletion and marsh subsidence.

In 1984, a comprehensive marsh management plan was developed for the 12,460 acres of LaBranche Wetlands owned and managed by the St. Charles Land Syndicate. The area under management is generally bounded by Lake Pontchartrain, the Jefferson/St. Charles Parish line, US Highway 61, and Bayou LaBranche. In February 1987, the Louisiana Department of Natural Resources/Coastal Management Division issued a coastal use permit for the plan, and a Section 404 Permit was received from the US Army Corps of Engineers in May 1988. Since that time, the LaBranche area north of the Illinois Central Railroad (just south of I-10) has been passively managed as a brackish to intermediate marsh, while the wetlands south of the Illinois Central Railroad have been actively managed as a fresh marsh and swamp complex. Structural modifications that plug or regulate water flow through man-made canals has greatly improved LaBranche's habitat for both fisheries and waterfowl production, has halted saltwater intrusion in the area, and has increased the land to water ratio within the entire complex. Steps have also been taken to diversify marsh plants by implementing an annual re-vegetation program aimed at introducing non-native and more salt tolerant plant species to the area.

The LaBranche Wetlands is an excellent example of an environmental public/private partnership. Over $2 million worth of marsh management techniques have been implemented in LaBranche since the inception of the plan, utilizing funds in the form of grants, mitigation, donations, and landowner and Parish participation. The landowner and the Parish realizes the major habitat role LaBranche plays to the Lake Pontchartrain Basin, and has assumed an active role in preserving and enhancing its valuable habitat.

Boebel, R. W., Consultant, New Orleans, LA., and Crawford, Frank C., Crawford & Associates, Inc., New Orleans, LA

The Lake Borgne and Lake Pontchartrain Commercial Seafood Production from 1970 to 1989, Volumes and Variations

Landings data compiled by the National Marine Fisheries Service, U.S. Department of Commerce, show that the volume of seafood harvested and sold commercially from lake Borgne and Lake Pontchartrain significantly increased in the Twenty (20) year span, 1970-1989. The year 1989 is the last year that this federal agency recorded fishery data from theses two (2) state lakes.

Six (6) types of seafood (three (3) fish and three (3) shellfish), comprising more than 99% of the total harvest, show an increase in total poundage and total exvessel value from 2,075,100 pounds and $492,777 for year 1970 to 8,946,150 pounds, and $6,103,237 for year 1989. The species included are Drum (black) sea trout (spotted, white), sheepshead (Atlantic), blue crab (hard, soft, peeler), shrimp (brown,white), and oyster. All species increased over the period studied except oyster. Black drum, sheepshead, and blue crab showed the most dramatic expansions of catch.

Substantial volume variations are present for some species within this time span. Causal factors may include economic changes, shifting demographies, and regulatory forces. The introduction of Mississippi River freshwater and silt into these brackish water lakes probably caused some fluctuations. Other physical changes in the environment were occurring. Nevertheless, in 1989 Lake Borgne and Lake Pontchartrain were not hostile to these members of the biota. Marine life was alive, well, and harvested in large volumes by the commercial fishing industry.

Brown, Murray L., Minerals management Service, New Orleans LA

A Public Domain Software Program for Charting Environmental Attributes in Lake Pontchartrain Basin

Although a number of excellent proprietary geographic information systems (GIS) are in use by environmental resource agencies/groups in southeastern Louisiana, there remains a need for an easy-to-use, well documented, public-domain software program that allows general users to prepare and share basic charts of environmental attributes using simple ASCII files. The SEAPLOT software program, originally written for use by oceanographers around the globe, has been expanded to include the Lake Pontchartrain Basin on its regional selection menu. Although the available coastline file is still rather crude, instructions are provided to allow the user to import higher resolution files, if locally available.

SEAPLOT is a menu-driven, interactive code written in GWBASIC (available on most DOS personal computers). Using a specific data format described in the available manual, the user can create, plot, and combine files that depict locational information. To a lesser degree, certain oceanographic parameters can be represented graphically, because the program is provided as source code, the user can easily extend this aspect of SEAPLOT to include water quality parameters. Locational information that can be plotted includes boundaries, points, polygons, as well as associated labels and titles. SEAPLOT is being used in oceanographic research to plot ocean station locations, the tracks of drifting buoys, water current and wind vectors, survey areas, stranded marine mammal sites, oil spill dimensions, instrument sites, shipwreck locations, and satellite analyses of ocean fronts. A utility routine in SEAPLOT allows the user to add information to existing files using an on-screen cursor. There is also a routine to sort data files according to recommended file-naming conventions.

SEAPLOT Version 1.3 (which includes Lake Pontchartrain), with the draft manual and a sampler of different data files, can be obtained by sending one high-density, formatted, 5 1/4 inch floppy diskette to the author at 1201 Elmwood Park Boulevard, New Orleans, Louisiana 70123-2394, U.S.A.

Burns, J. W., Urban Waste Management and Research Center (UWMRC), M. A. Poirrier, Biological Sciences \ UWMRC and K. Preston, Geography \ UWMRC, University of New Orleans, New Orleans, LA

The Occurrence of Potamogeton Perfoliatus L. (clasping pondweed), a Rare Submerged Aquatic Vascular Plant in Lake Pontchartrain

Submersed plants of both freshwater and marine origin comprise important communities within estuaries, but their ecology in estuarine habitats is poorly understood. Potamogeton perfoliatus L. (Clasping Pondweed) is a submersed aquatic vascular plant which is listed as a sensitive species in the coastal zone of Louisiana and is considered extremely rare. Louisiana collections of P. perfoliatus are limited and restricted to Lake Pontchartrain and its surrounding marshes.

Potamogeton perfoliatus was first recorded for Lake Pontchartrain by Riddell in 1838 near the Tchefuncta River Lighthouse. Clair A. Brown also collected a specimen from the beach at Mandeville in 1945. Although Suttkus, Darnell and Darnell; Perret et al.; Chabreck; Turner, Darnell and Bond conducted studies which noted the submerged vegetation of Lake Pontchartrain in 1953-1954, 1971, 1972 and 1980 respectively, P. perfoliatus was not reported in the lake for the following 28 years. Montz reported P. perfoliatus to be abundant both before and after the 1973 opening of the Bonne Carré Spillway, at Pointe aux Herbes in the southeastern sector of the lake. A 1978 icthyological survey by Thompson and Verret, which noted submerged aquatic vegetation at specific stations located around the perimeter of Lake Pontchartrain, did not list P. perfoliatus as a species encountered. During the summer of 1985, a survey of aquatic vegetation in the lake by Mayer did not find P. perfoliatus. Efforts to relocate P. perfoliatus in 1988 by Lester were unsuccessful during an ecological inventory of the sensitive plants and animals for the coastal zone of Louisiana. Brantley and Platt recorded a 7 m x 17 m submerged bed of P. perfoliatus 1500 m west of Bayou Lacombe in June 1990. Additional smaller beds, which yielded fruiting specimens, were located in the same area in August 1990.

Recent surveys beginning August 1991 to the present have located submerged beds of P. perfoliatus on both the north and south shores of Lake Pontchartrain. South shore beds have been located at Pointe aux Herbes (39 m x 26 m) and at the confluence of Irish Bayou with Lake Pontchartrain on the west side of the Pointe aux Herbes peninsula (50 m x 50 m; 15 m x 12 m; 20 m x 15 m). North shore beds were located between Goose Point and the confluence of Bayou Lacombe with Lake Pontchartrain (15 m x 20 m; 10 m x 15 m), approximately 4.0 km east of Bayou Lacombe near Point Platte (150 m x 120 m) and off the swimming beach at Big Point (several individuals). Attempts to relocate P. perfoliatus at Big Point during December 1991 were unsuccessful. Submersed beds of P. perfoliatus reported by Brantley and Platt were also relocated near Bayou Lacombe.

Factors affecting the distribution of P. perfoliatus in Lake Pontchartrain are not known. Some areas have been repopulated after an absence of 18 years, and growth is occurring in previously unreported sectors of the lake. Its status in Lake Pontchartrain is currently being monitored and examined for factors which affect its distribution.

Calix, A. G.; Seeger, E.; Velado, L.; Rucker, J.; TGS Technology, Inc., U.S. Fish and Wildlife Service, National Wetlands Research Center, Slidell, La, and Handley, L. R., U.S. Fish and Wildlife Service, National Wetlands Research Center, Slidell, LA

Shoreline Changes of Lake Pontchartrain 1955-1990

Lake Pontchartrain plays an important role in the wetland ecosystems of Louisiana. Over the past few decades the lake has been directly affected by the urban development of New Orleans and surrounding areas. Shell dredging, saltwater intrusion, shoreline development, and pollution are some of the factors contributing to the lake's problems. Recently, efforts have been made to restore the lake to an ecologically sound and economically viable habitat for Louisiana. The purpose of this study is to cartographically demonstrate the changes in the shoreline of Lake Pontchartrain using historical maps and recent aerial photography.

Caraher, M. F., W. M. Dahl, and D. H. Easley, University of New Orleans, New Orleans, LA

Comparison of Single-Well and Two-Well Tracer Tests for Acquiring Velocity and Effective Porosity Estimates in the Pine Island Aquifer, New Orleans, LA

The Pine Island aquifer is a barrier spit sequence located primarily in the northern portion of Orleans parish, Louisiana. this aquifer is approximately 25 feet thick in the study area located on the western edge of the University of New Orleans Lakefront campus. Estimated transmissivities are approximately 3700 gal/day ft and storativity estimates are approximately 0.00036. Average linear velocities are approximately 0.2 feet per day. The aquifer consists of a fine-grained sand with shell fragments underlain by finer grained bay sediments and overlain by silt and clay fill pumped from Lake Pontchartrain. This aquifer provides an ideal site for comparison of tracer tests. A small well field, which consists of four fully-penetrating wells, have been installed into the Pine Island Aquifer. Both single-and dual-well tracer tests may be used to determine estimates of average linear velocity and effective porosity. These tests may be complicated by minimal gradient that results in low ground-water velocities, such as occur in the Pine Island Aquifer. Low velocities require extended breakthrough monitoring, which may be expensive if shorter well spacing is impractical.

The intent of this project is to provide an inexpensive, simple, and relatively rapid method of estimating velocity and effective porosity in aquifers commonly found south of Lake Pontchartrain. Our study utilizes the single-well drift and pump-back technique described in Hall et al. 91991) and standard dual-wellpumping tracer tests. The single-well drift and pump-back method allows the estimation of both average linear velocity and effective porosity simultaneously. The dual-well test will be performed as a comparison with the single-well test, using the same portion of the aquifer. The results are then evaluated to determine their reliability and overall utility.  

Conatser, W. E., New Orleans, LA

Petroleum Industry Activity in the Lake Pontchartrain Basin

The petroleum industry has had a commercially successful and environmentally compatible history in the waters of the Lake Pontchartrain Basin for over 53 years. Gulf Oil Co. completed the first well in Lake Pontchartrain on July 17, 1938. Since that time 266 wells have been drilled in the waters of Lake Maurepas, Lake Pontchartrain, Lake St. Catherine and Lake Borgne. These wells have penetrated more than 2,762,000' of strata for an average depth of 10,383' per well. The deepest well to date was drilled to a depth of 25,600' by Placid Oil Co. on their State Lease 5407 in Lake Borgne. The deepest well to date in Lake Pontchartrain is the Union Of California - State Lease 6753 #2 which reached a total depth of 22,904'.

The petroleum industry has completed 86 (32.3%) of the wells drilled as commercial or possibly commercial. The first commercial well was drilled by Atlantic Oil and Refining at Big Point Field near the north shore of Lake Pontchartrain in September of 1946. Since that first completion the wells in the waters of the Lake Pontchartrain Basin have produced 10,017,352 barrels liquid hydrocarbons and 116,204,782 MCF natural gas.

It is not possible to predict the future production of oil and gas from the lakes of the study area but the potential is considered significant. Currently oil and gas is produced from strata ranging in age from Middle Miocene through the Upper Cretaceous. Trap types vary from elongate anticlines, to fault closures, to stratigraphic traps. Prospective areas remain to be drilled in the study area. New exploration techniques and recovery advancements could present possibilities for future petroleum production far exceeding those already produced.

Condrey, Richard, Coastal Fisheries Institute and Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA

Historical Ecology of Lake Pontchartrain-Borgne Basin: 1699-1950

Once Iberville passed the buffalo plains and cypress swamps which were to become New Orleans (because the area had a fine path which led to Bayou St. John and then Lake Pontchartrain), he began looking for the right fork of the Mississippi. Failing to find it (since he was on it and failed to recognize Bayou Lafourche as its left fork), he took a small bayou chocked with huge log jams (Bayou Iberville, now Bayou Manchac) through Lake Pontchartrain-Borgne.

Come on a voyage of discovery as we relook at this system through the writings and illustrations of the early explorers and visitors. From Iberville and Collot, through Audubon, and Lafcadio Hearn and Rebecca Harding Davis, watch the massive ecological changes brought by European settlement. Ponder what the system was as you consider what it might become.

Davis, D. W., Louisiana Geological Survey, P.O. Box G - University Station, Baton Rouge, Louisiana 70893

New Orleans--North America's Premier Below Sea Level City

In the current popular and scientific literature one reads with repeated frequency articles related to the greenhouse effect on sea level rise. As the world turns up its global thermostat, melting the polar ice caps and enlarging the world's seas through thermal expansion, coastal cities will be at risk. With nearly two-thirds of the planet's population and more than 40 of its largest metropolitan centers within the coastal lowlands, even a small upward movement in the earth's seas is significant. A change in temperature of as much as 4o C has been predicted by 2030, that could elevate sea level enough to flood New Orleans and other coastal municipalities. From its inception, New Orleans was isolated from the mainland by cypress/tupelo swamps, marshes, and Lake Pontchartrain. It was an "island city" delineated by water courses. When surveyed in 1720 every block was defined by shallow ditches. From its beginning these small channels established New Orleans' dependence on a drainage network.

Levee construction began as early as 1718. By 1720 all inhabitants were instructed to enclose their land in "palisades" or forfeit their property. Ten years later an embankment 1.6 km long protected the "Vieux Carre." Levees, therefore, are an old and integral part of the urban landscape. New Orleans is part of an environmental setting that requires an extensive levee and pump system to manage the region's excess water.

The "Vieux Carre" is the older section of the "Crescent City" and is built on abandoned or modern natural levees. At 4.5 m above sea level, these features are the region's high ground. They furnished the earliest inhabitants with a relatively dry, firm foundation for residential and commercial construction. Draining the surrounding wetland was a major undertaking. When the water was removed the soils shrank and settled and eventually subsided below sea level. Even so, relatively rapid urbanization required additional space. The only property available were the swamps and marshes that framed the initial natural levee site. What was delineated as "uninhabitable wasteland" was slowly reclaimed as the region's incorporated limits increased.

Much of the New Orleans' metropolitan complex has subsided to the point where in order to drain properly pumps siphon excess rainfall up into Lake Pontchartrain. Human-induced negative land surfaces are producing, in many instances, below sea-level citizens. Regional governments have learned, nevertheless, to live with this and other environmental dilemmas. Canals, pumps, and large-diameter drainage pipes assist in keeping the neighborhoods relatively dry. With much of the urbanized area less than 3 m above mean sea level, the margin of safety is exceedingly small. This is particularly true for those sections of the levee-protected metropolitan region 2 m to 4 m below sea level. In as much as arable land has always been in short supply, the only practical and realistic solution was to reclaim the "uninhabitable" swamps and marshes. Soils associated with these aquatic habitats are subaqueous in origin and high in organic detritus. When air dried, these histosols lose nearly 85% of their mass. The end result is the surface subsides, because of the loss of volume within the soil column.

The product of reclaiming these marginal tracts is that the New Orleans' metropolitan region is sinking. With a projected rise in sea level of 1.2 mm/yr, coupled with a constant battle with subsidence, the New Orleans metroplex faces a challenging future. In addition, the metropolitan area is at risk from hurricanes. Under the right conditions, a tropical depression moving across Lake Pontchartrain's southeastern quadrant would move considerable water over the lakefront levees into the below-sea-level bowl that distinguishes parts of Jefferson and Orleans parishes. For more than two and a half centuries the "Crescent City" and its satellite communities have been at odds with the elements. Despite these issues, the region has developed, prospered, and flourished within this inhospitable environment, but the future must be considered carefully.

DeLaune, R.D and Pardue, J.H., Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA

Distribution of Heavy Metals in Bayou Trepagnier Bottom Sediment

The depositional pattern of metals was determined in bottom sediment of Bayou Trepagnier (located in the La Branche Wetland bordering Lake Pontchartrain). The majority of flow into the Bayou is from an industrial outfall. Eight cores were taken from Bayou Trepagnier and one core from Mississippi Bayou ( a control site ) along a transect extending to Lake Pontchartrain. Results indicated that Bayou Trepagnier sediment was contaminated with chromium, lead, and zinc. Chromium levels of over 5,000 mg/kg of sediment were measured in sediment profiles. Lead concentrations on the order of several thousand mg/kg were observed in the lower sediment profile taken near the industrial discharge sites.

Zinc concentrations of greater then 1,000 mg/kg of sediment were recorded. Concentrations of metal increased with depth in the profile. Metal concentrations were normalized to Al in the sediments and compared to uncontaminated sites in Louisiana. Bayou Trepagnier sediments were shown to be highly enriched with respect to Cr and Pb when compared with other areas of the state. Sedimentation in recent years (determined from 137Cs dating) was burying or removing metals from the surface environment where bioavailability is greatest.

Delaune, R.D. and Lindau, C.W.,Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA

Stable Nitrogen Isotopes Studies Fingerprint Surface Water Inorganic Nitrogen Sources Entering the Pontchartrain Basin

Estuaries such as Lake Pontchartrain are generally nitrogen limiting. Nitrogen entering the system can influence water quality of the lake. A recent study investigated the use of natural abundance variations in 15N/14N ratios for identification and tracing surface water inorganic N sources entering the Pontchartrain Basin.Surface water samples were collected from selected streams with distance from a point source in the northern Basin and analyzed for NH4+-N, NO3--N and associated 15N/14N (d15N%) concentrations. Ammonium-N from domestic sewage sources entering the Basin was found to have distinct d15N ranges. Domestic sewage discharge was traced for about 30 km downstream from discharge point using 15N/14N ratios. At the sewage point source NH4+-d15N values averaged +43% and increased linearly to +162% with distance from the discharge. Surface water NO3--d15N values generally ranged from +1 to +99% and no significant association was observed between d15N values with distance from the domestic sewage point sources. The discrete NH4+-d15N signatures of domestic sewage compared to downstream surface water. NH4+-d15N values demonstrated that N isotopic ratios can be used as tracers for identifying the sources of nitrogen entering the Pontchartrain Basin. Such sources include the nitrogen in dairy manure entering the Tangipahoa river and septic and sewage being introduced into the Amite and Tickfaw rivers. Expanded studies are currently being initiated to further quantify nitrogen sources entering the basin.

Demans, Charles R. and Garrison, Charles R.

Water Quality Monitoring Activities of the U.S. Geological Survey in the Lake Pontchartrain and Lake Maurepas Basins

The Louisiana District of the U.S. Geological Survey Water Resource Division has been involved in monitoring the water quality of surface- and ground-water resources of the Lake Pontchartrain and Lake Maurepas basins since 1927. Surface-water samples and volumetric flow rate discharge measurements have been made at 210 sites in these two basins. Surface water quality samples have been collected at 102 sites, accounting for 2,187 water samples to date. Bed samples have been collected at 28 of the above sites, accounting for 30 samples. Water and bottom material have been analyzed for suspended sediment, nutrients, bacteria, major ions, trace metals, and pesticides. Currently, there are three active water-quality sites within the two basins. These data were collected as part of cooperative programs with the Department of Transportation and Development, the U.S. Army Corp of Engineers, and the U.S. Geological survey NASQAN program.

Ground water has been sampled at approximately 1,160 sites within the basins, accounting for 3,823 samples. Ground water has been analyzed for primarily major ions and selective nutrients, although synthetic organic compounds, trace metals, and bacteria have been run at selective sites. Ground-water data have been collected as part of cooperative programs with the Department of Transportation and Development, Jefferson Parish Department of Water, and St. John the Baptist Parish Department of Water.

The U.S. Geological Survey also has completed several interpretive studies within the Lake Pontchartrain and Lake Maurepas basins. Studies completed on ongoing include:

- Movement of bacteria in shallow ground water,
- Assessment of trace metals in coastal streams (Pear River, Tickfaw River),
- Hydrology of Fritchie marsh, coastal Louisiana,
- Ground-water resources of southern Tangipahoa Parish, and
- Several other general water-quality studies.

 

Devall, Margaret S. and Parresol, Bernard R. Souther Forest Experiment Station, 701 Loyola Avenue, Rm. T-10210, New Orleans, LA 70113

Assessing the Effectiveness of Several Protective Measures Against Herbivory of Cypress Taxodium Distichum Seedlings

Second growth cypress remains an important source of lumber and is important for its ecological and aesthetic role, and for wetland preservation. Louisiana contains a larger inventory of baldcypress than any other state, but subsidence and hydrological modification are reducing natural regeneration. Planting programs have been instituted, but nutria and swamp rabbits have become serious deterrents to the success of cypress plantings in Louisiana. This study examines the effect of treatments offering possible protection against herbivory by nutria and swamp rabbits, and assesses seedling growth (height and root collar diameter) with various treatments. Treatments include application of tanglefoot, a sticky resin; application of ropel, a rodent repellent; and the use of plastic tree guards. Study sites are a marsh that was formerly a cypress swamp on the U.S. Fish and Wildlife Service's Bayou Sauvage Wildlife Refuge and a marsh on Southeast Louisiana University's Turtle Cove Research Station near Pass Manchac. The Study is in its second year.

 

Dranguet, C. A., Southeastern Louisiana University, Hammond, LA., and
Heleniak, Roman J., Southeastern Louisiana University, Hammond, LA.

Man in the Basin: Habitation and Forest Exploitation in the Pontchartrain Basin

Man's entrance into the Pontchartrain Basin has been marked by a degradation of the cypress swamp that at one time surrounded Lake Pontchartrain. The coming of the railroad to the western shore of the Lake in 1854 opened the area to commercial exploitation. through war, flood, and man's utilization of the Basin's resources, the gradual shrinking of the forest was only inevitable.

The purchase of vast tracts of virgin cypress stands by commercial lumber interests in the 1880's sealed the eventual fate of the forest. A short one hundred years elapsed between the introduction of modern transportation and logging techniques, the establishment of communities, and the final destruction of the swamp habitat.

Duffy, K. C., Dept. Oceanography and Coastal Sciences, LSU, Baton Rouge,
LA., and Baltz, D. M., Coastal Fisheries Institute, LSU, Baton Rouge LA.

The Influence of the Introduced Eurasian Milfoil (Myriophyllum spicatum) and Native Aquatic Vegetation on Fish Nursery Habitat in Lake Pontchartrain

Quantitative samples in monospecific stands of submerged aquatic vegetation (SAV) and bare sands habitats have been collected on a monthly basis from three stations in the northeastern area of the Lake Pontchartrain estuary since July, 1991. the samples of the community associated with the SAV beds are being collected with a Wegener ring (1.2 m ), in a microhabitat approach to describe the population response of fish, invertebrate, and SAV species to environmental variables. These data are being used to evaluate the impact of an introduced SAV species on the community structure of coastal fishes and invertebrates in Lake Pontchartrain and its adjacent waters. Historically, the dominant native SAV species were Vallisneria americana and Ruppia maritima; however, Myriophyllum spicatum became established and abundant in the 1970's. In this study, we have seen dynamic changes in the SAV species composition that may be seasonal or directional and related to recent changes in lake water quality. Presently, 9 fish and 9 invertebrate species have been identified. From the preliminary samples, the mean numbers per sample (range) for fishes and
invertebrates, respectively, are 12.5 (0-39), and 235.7 (11-508). Species of commercial and recreational interest include juvenile spotted seatrout and blue crab, and post-larval penaeid shrimp.

 

Earl, C., Hicks, B., and Hull, F., U.S. Army Corps of Engineers, New Orleans, LA

Jefferson and Orleans Parishes, Louisiana, Urban Flood Control and Water Quality Management Study

The new Orleans District Corps of Engineers is currently conducting a reconnaissance study entitled, Jefferson and Orleans Parishes, Louisiana, Urban Flood Control and Water Quality Management. The purpose of the study is to consider measures to alleviate rainfall flooding in the parishes and to improve the water quality of stormwater discharges into Lake Pontchartrain, Lake Borgne, and the Barataria Estuary.

Our goal for the water quality management plans under consideration is to reestablish the designated use of the receiving waterbody, such as making it swimmable and fishable.

During the reconnaissance phase we rely heavily on existing data. We determined the impacts of stormwater runoff using a preliminary screening procedure recommended by EPA. Based on research of the best available technology, we will estimate the cost and effectiveness of the
various water quality management plans.

The Reconnaissance Report will discuss a wide range of alternatives, such as source controls, in-line treatment, and end-of-pipe treatment.

Ellis, L. E., Biological Sciences / Urban Waste Management and Research Center (UWMRC), UNO; Francis, J. C., Biological Sciences / UWMRC, UNO; and Tracy D. K., Biological Sciences, UNO.

Determination of Fecal and Total Coliform Levels in Lake Pontchartrain by Polymerase Chain Reaction (PCR)

Fecal coliform and total coliform levels were monitored in Lake Pontchartrain over a several month period using oligonucleotide primers for detection of the lacZ and uid DNA sequences by PCR. Good correlation was realized between PCR detection and standard method procedures. Refrigerated storage of water samples prior to PCR detection was evaluated. Bacteria were detectable for 10 days but showed significant declines after 48 hours. High fecal and total coliform levels in Lake Pontchartrain appear to be associated with high turbidity of the water.

 

Emmer, R. E., College of Urbanand Public Affairs, University of New Orleans, New Orleans, LA.

Shrinkage of the Pontchartrain Basin, The Need for a Cooperative Regional Approach

The Pontchartrain basin in shrinking in our perception of its size, the remoteness of the headwaters, the vastness of its waterbodies, the supply of natural resources, and the rapidity of population growth and how soon their presence is felt by neighbors. Tradition segments the basin into four regions: metropolitan New Orleans or the south shore; the river parishes from St. Charles to Iberville Parish; the north shore of St. Tammany, Washington, and Tangipahoa Parishes; and the distant headwaters, the Amite River watershed including East Baton Rouge, Livingston, East Feliciana, and St. Helena parishes. these regions have historically acted independently for several reasons. Culturally, they were distinct, i.e., Anglo-Saxon vs. French vs. The City. Second, the  regions were separated by distance. Trips between regions as late as the 1940s were major excursions because of the absence of all-weather roads and bridges over major waterbodies such as the Rigolets, Pass Manchac, and the many rivers. Third, the economic foundation of each region was different. Finally, popular beliefs and attitudes ranged from Laisse lse bons ton rouler to strict biblical followings.

Communities were scattered clusters of homes and businesses along the Mississippi River; isolated groupings of stores and residences at cross-roads or spaced along the bayous, railroads, and highways. Because these enclaves were small they were insulated from their neighbors and, thus, were little affected by or had little effect on the nearest villages, much less Lakes Maurepas or Pontchartrain. The Pontchartrain minimal if any significant adverse impacts extending beyond the boundaries of the community. Post World War II growth, improved highways, the automobile, and industrial development have changed the basin from overall rural to an emerging suburban/urban
system. Time and space are compressed and with an increasing population problems are magnified. The basin has become one community whether it wants to be or not. I turn, our common problems must be approached in new ways.

The Pontchartrain basin as one community faces many institutional and environmental problems. Federal, state, and local laws and jurisdictions overlap and, in many instances, conflict in mission and authority. In addition, the private landowner is concerned with his/her right to use property in a way that benefits them. Water quality, wetland loss, harvesting of renewable resources, and extraction of minerals are issues that confront decision makers in the basin and can no longer be ignored. Planning offers the vehicle for addressing these issues in a timely and systematic manner. Former Governor of California Edmund G. Brown said, "planning is thinking ahead intelligently ..."
and an idea that has received wide acceptance. In fact, it is methodically avoided by many parishes and municipalities. Such as negative attitude requires modification if the institutional and environmental problems of the basin are to be solved in a timely fashion. The Lake Pontchartrain Basin Foundation through a grant from the Environmental Protection Agency is undertaking a basin planning process that will confront many of the most difficult institutional and environmental problems in the basin. What evolves will be a formal regional cooperative mechanism for formulating positive actions that result in a healthier and safer place to live for the people in the basin.

 

Farabee, M.V., and R.C. Cashner, Department of Biological Sciences, University of New Orleans, New Orleans, LA

Distribution of Fishes and Community Stability in Bayou Lacombe

Bayou Lacombe is a relatively small drainage system tributary to the northeastern section of Lake Pontchartrain. Based on records from fish collections made since 1951, a total of 77 resident and migratory species have been documented for the system. Bayou Lacombe has been the focus of four major ichthyofaunal surveys. The most extensive study was done by Sobczak, in which 10 stations were sampled monthly from August, 1973 to August, 1975, and the most recent survey included monthly samples at five sites from November, 1988 to October, 1989. Numerical
dominants in the upper reaches of Bayou Lacombe include grass pickerel, chubsuckers, black bullhead, bayou topminnow, mosquitofish, dollar sunfish, and warmouth. The middle of the river has greater numbers of cyprinids, blackspotted topminnow, brook silverside, and longear sunfish. The longitudinal pattern of distribution of fishes in Bayou Lacombe is characterized by a rather abrupt change in the fauna between upper, middle, and lower reaches, rather than addition of species.
Morisita's Index (Im) and Percent Similarity Index (PSI) indicate that the greatest dissimilarities between fish assemblages occur between the lowermost stations and those above tidal influence. Stations near the mouth of Bayou Lacombe are characterized by euryhaline forms, such as bay anchovy, Gulf menhaden, inland silverside, sciaenids, and gobies. Community similarities were calculated for five common stations between the 1973-75 and 1988-89 surveys. Relatively low values for Im and PSI may indicate less stability and persistence of fish communities over time than reported for midwestern streams. The most abundant species, the blacktail shiner, collected during the 1973-75 study was not represented in any of the 60 collections made during the 1988-89 survey.

Francis, J. C., Biological Sciences / Urban Waste Management and Research Center (UWMRC), UNO; Wijesundera, V., UWMRC, UNO; Barbe, D. E., Civil Engineering / UWMRC, UNO; Mulino, M. M., Steimle & Assoc., Inc., Metairie, La.; and Poirrier, M. A., Biological Sciences / UWMRC, UNO.

Historic Changes in Secchi Disk Transparency in Lake Pontchartrain

A major environmental concern about Lake Pontchartrain is an assumed long-term decrease in water clarity. Available data on Secchi disk transparency in Lake Pontchartrain from 1953 through 1990 were examined to determine if changes in water clarity had occurred. Linear regression analysis of Secchi disk transparency versus time indicated a statistically significant (5% level) decrease in transparency with time.

The relationship between Secchi disk transparency and two environmental factors, salinity and wind speed, were studied using regression analysis. The analysis revealed a statistically significant, positive relationship between water clarity and salinity, and a statistically significant, negative relationship between water clarity and wind speed. Further analysis indicated that neither average annual salinity nor average annual wind speed had realized a statistically significant change during the period from 1953 through 1990.

Secchi disk transparency data were adjusted for the effects of salinity, wind speed, and both salinity and wind speed. The base for adjustment in each case was the long-term average of the variable for
which adjustment was being made. Regression of Secchi disk transparency versus time, with adjustment for salinity, revealed a statistically significant relationship, indicating that adjusting the
data for the effect of salinity had not removed the long-term decrease in water clarity. However, regression of Secchi disk transparency versus time, with adjustment for wind speed, indicated that there was no longer a statistically significant relationship between Secchi disk transparency and time. Adjusting the data for the effect of wind speed had removed the long-term decrease in water clarity. Also, regression of Secchi disk transparency versus time, with adjustment for both salinity and wind speed, revealed no statistically significant relationship, indicating that adjusting the data for the effects of both salinity and wind speed had removed the long-term decrease in water clarity.

Analysis of variance of monthly salinity data from 1953 through 1990 revealed a statistically significant monthly seasonality with the highest values occurring in November and the lowest values occurring in May. Similarly, analysis of variance of monthly wind speed data from 1953 through 1990 revealed a statistically significant monthly seasonality with the highest values occurring in February and the lowest values occurring in August. These seasonal effects are not equally represented in the available data on Secchi disk transparency in Lake Pontchartrain. When the seasonal bias is removed from the data set, it no longer supports the conclusion of a statistically   significant change in Secchi disk transparency from 1953 to 1990.

 

Goyer, R.A., G. J. Lenhard, J. L. Chambers, LA Agricultural Experiment Station, LSU, Baton Rouge, LA, and V. R. Van Sickle, U.S. Fish & Wildlife Service, National Wetlands Research Center, Lafayette, LA

Herbivory in Baldcypress: A Threat to the Pontchartrain Basin

The future of the baldcypress is closely linked to its ability to withstand environmental, biological and man-caused stresses. Currently, all three of these categories of stress are impacting cypress in south
Louisiana and, particularly, threaten trees in and near the Ponchartrain Basin. Studies underway by the authors are evaluating the impact of an herbivore - the fruit tree leafroller (Lepidopter: Tortricidae) - on baldcypress. Further evaluations are being conducted to ascertain the interaction(s) of herbivory with flooding caused by man made and environmental changes (e.g., global warming and associated changes in hydrology). Studies to date have revealed continued expansion of fruit tree leafroller populations into the periphery of the Ponchartrain Basin. In areas having experienced repeated defoliation of cypress, radial growth has shown marked reduction. Additionally, crown deterioration, increased transparency and dieback have occurred along
with scattered tree mortality. The threat to baldcypress results from herbivory coupled with changes in hydrology. Sapling and pole-sized cypress exhibiting high live-crown ratios appear most heavily browsed. Transect evaluations presently underway are aimed at evaluating severity of herbivory in relation to seasonal flooding regimes. Rates of refoliation on both mature and young saplings are compared to further elucidate the ability of cypress to respond to herbivore and flooding stresses.

 

Hardy, J. W., Southern Regional Climate Center, Department of Geography & Anthropology, Louisiana State University, Baton Rouge, La, 70803

Fresh Water Input into Lake Pontchartrain

Fresh water input into Lake Pontchartrain will be determined for a wet year and dry year. The amount of runoff generated by each drainage basin of Lake Pontchartrain will also be examined. Fresh water input into Lake Pontchartrain will be found in part from measured runoff at gaging stations along Highway 190. The Thornthwaite water budget model will be used to estimate the surplus water, hence runoff, for the part of the Pontchartrain drainage basin below the gaging stations. Actual evaporation and the change in soil moisture storage will be subtracted from precipitation to give the surplus for the ungaged uplands. The freshwater input into Lake Pontchartrain from the ungaged swamps, marshes, and lakes will be found by subtracting potential evaporation from precipitation.

 

Hastings, Robert W., Turtle Cove environmental Research Station, Southeastern Louisiana University, Hammond, LA

Surface Drift Movement of Larval Marine Fishes and Other Organisms through Passes of the Upper Lake Pontchartrain Estuary

The fish fauna occurring in the oligohaline upper Lake Pontchartrain estuary consists of about half freshwater species and half marine. Freshwater species are present throughout the year whereas most marine species are seasonal in their occurrence, leaving the upper estuary for the winter. A major occurrence, leaving the upper estuary for the winter. A major influx of such species occurs in the spring as larvae and early juveniles. Surface plankton net sampling has been conducted to monitor patterns of movement for several fish species, such as bay anchovy (Anchoa mitchilli), gulf menhaden (Brevoortia patronus), gulf pipefish (Syngnathus scovelli), naked goby (Gobiosoma bosci), and tidewater silverside (Menidia beryllina), as well as several invertebrates such as blue crab (Callinectes sapidus ). Samples have revealed significant seasonal, diel, and spatial patterns of occurrence for several species common in the estuary. Thus they may exercise significant control over their movements, even though they are small and appear to be poor swimmers. Although open waters of the upper estuary are clearly used as nursery habitats for such species, their use of enclosed marsh canals and bayous may be more limited. Studies are continuing to address such movement (or lace of movement) of small planktonic organisms into enclosed waters, and how diel variation in activity patterns affects their patterns of occurrence in surface plankton samples.

 

Keim, B.D., Southern Regional Climate Center, Department of Geography and Anthropology, Louisiana State University, Baton Rouge, Louisiana 70803.

Storm Frequencies and Storm Runoff into Lake Pontchartrain

The large number of recent heavy rainstorms in southeastern Louisiana has raised concerns about changing frequencies and magnitudes of heavy rainfall in the area. A changing heavy rainfall climatology over the Lake Pontchartrain Basin may have noteworthy impacts. Most storm runoff
from New Orleans is discharged into the lake and is obviously important to the lake's water quality. Furthermore, storm runoff from the rivers draining the Florida Parishes transports agricultural wastes into the lake and influences lake salinity levels. This paper examines the historical storm events in metropolitan New Orleans and the Florida Parishes from the nineteenth century to the present. The seasonality and synoptic situations of storm rainfall will also be examined.

 

Lawler, G. C., Delgado Community College, New Orleans La., and Hartzog, L., Army Corps of Engineers, New Orleans, LA.

Baseline Pollutant Data on Water Column, Sediment, and Bivalve Tissue Samples from the Inner Harbor Navigational Canal, Chef Menteur Pass, and the Rigolets

As part of the environmental impact statement supporting the Army Corps of Engineers' Hurricane Barrier Protection Plan, pollutants in the water column, sediment, and bivalves of the Inner Harbor Navigation Canal (IHNC), Chef Menteur Pass, and The Rigolets were investigated. This investigation was carried out in tow phases. In phase I, methods were developed, the three passes were screened for pollutants, and replicate samples were analyzed to determine the number of samples required to achieve reasonable analytical precision. Phase I culminated with the production of a sampling protocol, which included various sampling options and tables relating numbers of samples to analytical precision. Phase II, which was designed to detect seasonal fluctuations of
pollutants, was aborted with the Hurricane Barrier Protection Plan was abandoned. The first samples were collected for analysis in May of 1980. The data generated from these and subsequent analyses qualify as baseline data for these location and matrices because the analyses were carried out under rigorous conditions of quality assurance and the analytical techniques employed were state-of-the-art. The major analytical effort was directed toward detecting and quantifying EPA
designated priority pollutants. In addition, organic fractions were routinely searched for compounds of probable anthropogenic origin. Water samples were analyzed for asbestos, heavy metals, base-neutral and acid extractable organics, organochlorie pesticides and polychlorinated biphenyls, volatile organics, acrolein and acrylonitrile, total cyanides and total recoverable phenolic. Sediment samples were analyzed for heavy metals, total base-neutral extractable organics, individual
base-neutral extractable organics, organochlorine pesticides and polychlorinated biphenyls, and volatile organics. Bivalve tissue samples from oysters (Crassostrea virginica) and clams (Rangia cuneata) were analyzed for heavy metals, total base-neutral extractable organics, individual base-neutral extractable organics, organochlorine pesticides and polychlorinated biphenyls, and voltile organics. The results of these analyses were compiled in seven data reports submitted to the Army Corps of Engineers in association with the "Nutrient and Toxic Substance Chemistry of Chef Menteur Pass, The Rigolets, and Inner Harbor Navigation Canal, Lake Pontchartrain, Louisiana" program. The results of dissolved inorganic nutrient analyses conducted on the water samples
were included in the data reports.

 

Lopez, John A., Amoco Production Co., New Orleans LA

Potential Significance of Active Faults in Lake Pontchartrain

Examination of conventional seismic data collected in Lake Pontchartrain leads to the compelling conclusion that the eastward extension of the Baton Rouge-Denham Springs faults system is within Lake Pontchartrain and not as previously mapped on the northshore of the lake. The
Pleistocene/Holocene contact previously mapped as faults on the north shore is probably a depositional contact. The faults within the lake are presently active as is the Baton Rouge/Denham Springs fault system. Evidence for recent movement on the faults within the lake is strongly
suggested by offset of the bridges which cross the lake. Offset varies from 2 to 6.5 inches depending on the age of the bridge. Movement on the fault is approximately 1 inch per decade (.25 cm / year). Less detailed mapping suggests the fault system extends into Chandeleur Sound. Thus the Baton Rouge-Denham Springs fault system is a regional basement fault system extending 120 miles from Baton Rouge to Chandeleur Sound. One of the probable effects of this fault system is to trigger small earthquakes, such as the 1987 Irish Bayou earthquake. Other historic earthquakes located 5 to 20 miles south of the fault trace may have also been related to the fault system. Past activity suggests that an earthquake hazard is minimal. Other consequences or significant questions in relation to the active faults are:

1) The current high rate of movement on the faults is probably higher than in the geologic past. So why does movement on the faults appear to have accelerated in the Holocene?

2) The coincidence of the regional fault system within Lakes Maurepas, Borgne, and Pontchartrain suggests a genetic relationship. Do prior models for the formation of Lake Pontchartrain need to re-evaluated?

3) At least two significant studies of ground water aquifers in Lake Pontchartrain indicate that some of the faults do seal some of the aquifers. Since the faults are a series of discontinuous faults the hydraulic connection of fresh and saline aquifers is complex and probably intimately related to
faulting in the lake.

4) The high rate of fault movement conflicts with the interpreted top of the Prairie Terrace accepted by most workers. Is the second weathered surface and not the first weathered surface in the lake truly the top of Prairie Terrace?

Some of these questions may be academic and others may have more civic significance, but all of these and others can be addressed with further basic research. Much can be gained by research efforts by greater exchange of data and ideas between professionals which generally operate in different institutional or commercial spheres.

Otvos, E. G., Gulf Coast Research Laboratory, Ocean Springs, MS
39564-7000

Lake Pontchartrain Basin Evolution; Late Pleistocene-Holocene Geological History

The Pleistocene sedimentary cycle that preceded Holocene evolution of the lake system, climaxed 128-122 ka B.P.during the Sangamonian Interglacial. It produced the muddy-sandy, microfossil-rich, marine-to-estuarine Biloxi Formation, c. 13.5 m thick under Fontainebleau State Park and south Hancock County, MS, and overlain by the thin regressive alluvial Prairie unit. The oxidized, seaward-sloping Prairie coastwise surface, cut by approximately E-W-trending faults,
forms the northern border of the Lake. A buried segment of the Gulfport barrier complex, the Gulfwide Sangamonian high shoreline indicator, occurs at nearby Port Bienville, MS. The previously reported presence of another Pleistocene segment beneath the Lake, c. 10 km from the north lake shore, is not yet proven. (Earlier, this 3-5 m thick sand body, appearing as channel-filling beneath the muddy lake deposits in the Causeway foundation-drillholes, has been described as the "Miltons
Island Beach Trend", Saucier's assumed earlier Holocene lake shoreline.) Stream channels became deeply incised in the general area and clusters of wind-blown dunes formed along river floodplains in the Florida Parishes during subsequent marine lowstands of the Wisconsinan glacial interval. By c. 4.5 ka B.P., Holocene transgression filled most of the "Pontchartrain Embayment" with higher salinity but still brackish waters. Westward-directed littoral drift from Pearl River delta shores 5.0-3.7 ka constructed a chain of sandy underwater shoals, probably also including small barrier islands in front of the embayment. These barrier sand bodies are 6-12 m thick. Occasionally, they extend near, even slightly above the land surface (Pine and Oak "Islands" in New Orleans East).

Sediment and microfossil data marked steady eastward growth of the Mississippi delta toward the shoals. A delta spur separated Lake Maurepas from Pontchartrain. By 4.0 ka, the Morrison Rd. Pit area (at Frenchmans Wharf Apartments, on Interstate Highway 10, New Orleans East), was covered by subdelta clays and sandy muds (Otvos, 1978). Recently obtained radiocarbon dates (Dr. F. Stapor, Jr.) indicate that shore processes continued 4 km to the east at Bullard Rd. until c. 3.5 ka. As late as 3100-2900 yr B. P. barriers of the separate South Hancock-Sauvage trend were active shore zones in easternmost Orleans Parish.

Intensive regional delta growth (St. Bernard and other subdeltas in present Orleans-St. Bernard Parishes) subsequently buried the two barrier trends under the extensive marshlands. Pontchartrain's waters freshened as a wide belt of delta land gradually cut off the bay from the Gulf. Lake beaches and numerous Indian midden mounds date from this period. Cessation of delta growth and continuing subsidence soon increased shore erosion. Improved connection with the Gulf, most recently through the man-made Gulf Outlet Channel, slightly increased salinities. Intensive commercial clam shell-dredging in recent decades (Otvos and Sikora, 1990) liquefied central lake sediments and profoundly impacted bottom biota, including the Rangia bivalve fauna. Lake tidal gage data indicate minor subsidence probably along faults. Tectonic and eustatic changes, sediment compaction and marsh degradation -related to natural and man-induced causes- will remain critical factors in future basin development.

 

Perret, William S., L. Brandt Savoie, John F. Burdon and Karl A. Mapes, Louisiana Department of Wildlife and Fisheries.

The Fisheries of the Pontchartrain Basin

The Lake Pontchartrain Lacustrine Basin is bordered by 8 parishes and drains 8 additional parishes of Southeast Louisiana and numerous counties of southwest Mississippi. Preliminary data indicate that in 1990, -*-% (-*- pounds) of Louisiana's commercial fishery landings were within the basin. Historical records indicate that the Basin has contributed significantly to the states fishery production. Landings include species caught from freshwaters to adjacent continental shelf waters of the Gulf of Mexico.

In 1990 a significant number od commercial and recreational fishermen resided within the Basin. Freshwater recreational fishermen from the Basin accounted for 22% (108,107) while saltwater anglers accounted for 42% (88,331) of the states licensed resident population. Commercial licenses sold within the Basin accounted for 31% (32,612) of the state's total.

Utilization of the Basin's fishery resources by recreational and commercial groups have continued to increase during the last three decades but overall fishery production has not kept pace. While
landings may have increased in some cases, the addition of more user's has resulted in a decreased catch per effort.

The Basin's fishery has been significantly impacted by wetland and estuarine habitat loss or modification due to such activities as leveeing, reclamation, subsidence, sea level rise, erosion, toxins and eutrophication. Salinity modifications often accompany habitat modifications and may significantly impact the distribution of fishery species. Point and non-point source discharges of pollutants have impacted the quality of the harvest waters of many species, especially the American oyster. Introduction of species or pathogens not endemic to the Basin may also pose a threat to the fisheries.

Its diverse habitats and resources portray a region that is providing adequate fishery production, despite its problems. However, it evident that there are many significant economic and social changes occurring with more on the horizon. Sustaining or enhancing the fishery resources of the Basin has no single solution. conservation, implementing comprehensive wetland management plans, implementing comprehensive inventories of habitat types, and strengthening the environmental consciousness of all who live, work and play in the Basin will help.

*Landing data is forthcoming for NMFS.

Powers, S.P., Poirrier, M.A., and Yund, P.O., Department of Biological Sciences and the Urban Waste Management and Research Center, University of New Orleans, New Orleans, Louisiana 70148.

The Effects of New Orleans Urban Runoff on the Benthic Community of Southern Lake Pontchartrain

Between the summer of 1991 and the winter of 1992 we conducted a study of the benthic community of southern Lake Pontchartrain to assess the impact of New Orleans urban runoff on Lake Pontchartrain. A sampling grid, which extended North from the shoreline eight kilometers and 5 kilometers East to West, was established in southern Lake Pontchartrain adjacent to three outfall canals in Jefferson Parish (Parish line, Duncan, and Elmwood canals). Two macrofauna and two meiofauna samples were taken from sets of sites within the sampling grid between June 1991 and February 1992. Differences in species diversity, abundance, dominance, and trophic structure among sites were analyzed to assess the effect of the outfall canals on the benthic community.

Results from our study indicate that there is a pronounced effect on the communities immediately adjacent to the outfall canals (0m-400m(?)). These sites were characterized by low species diversity
values, reduced numbers of mollusks (particularly juveniles), and increased abundance of nematodes, oligochaetes, and capitellid polychaetes on all sampling dates. A transient effect was also seen in the meiofauna community following a period of high rainfall. This short term effect extended much further than the chronic effect (2.40 km) and was probably a result of the large input of freshwater into the lake. We also compared the effects of three different canals, which differed in
discharge capacity and levels of toxins, on the associated benthic communities. A comparison with previous benthos surveys allowed us to evaluate the effect of sewage diversion into the Mississippi River, initiated in 1989.

 

Preston, K.P., Geography/Urban Waste Management and Research Center (UWMRC), Poirrier, M.A. and Burns, J.W. Biological Sciences/UWMRC, University of New Orleans, New Orleans, LA

Community Structure and Distribution of Submerged Aquatic Vegetation in Lake Pontchartrain, LA

Submerged aquatic vegetation (SAV) generally occurs along the shallow, less exposed shoreline areas in the Lake Pontchartrain Basin and provides a number of important ecological functions. Submerged grassbeds help stabilize sediments, reduce shoreline erosion, assimilate pollutants, and release oxygen. Moreover, they provide a protected habitat for larval and juvenile stages of many estuarine organisms and a food source for waterfowl, fish, invertebrates, and other aquatic species. Over the past 40 years several studies have noted a decrease in grassbed coverage and a decrease in depth of grassbed growth. Areal coverage of SAV in Lake Pontchartrain has decreased by 50% between 1973 and 1983. While previous studies provide general qualitative information about the status of grassbeds in Lake Pontchartrain, they provide little quantitative information concerning community structure and diversity and seasonal variation in growth and distribution. Moreover, they fail to take into account the patchy nature of grassbed distribution when estimating areal coverage thus likely overestimating the actual coverage of SAV beds in Lake Pontchartrain.

In this study species composition, community structure, and diversity relations were determined for five grassbed sites in Lake Pontchartrain. Foliar cover of all SAV species was measured along five
randomly placed transects in each site during the summer of 1991. The measurements were repeated during the winter of 1992 along a random subset of transects at each site. The seasonal variation in SAV distribution and the degree of deciduousness among the dominant species could thus be ascertained. Foliar cover for each species was stratified by depth interval and substrate type along each transect in order to identify the influence of these physical variables on SAV growth. In
addition, the degree of patchiness within grassbeds was used to modify estimates of grassbed coverage in Lake Pontchartrain.

 

Rheams, Anne B. Louisiana Department of Environmental Quality, Baton Rouge, LA

Lake Pontchartrain Basin: Urban Nonpoint Source Pollution Problems and Solutions

Recent water quality monitoring studies in urban areas have shown that the highest pollutant loadings and concentrations usually occur during rainfall events in the first 0-1 inch of rain, commonly referred to as the "first flush." In urbanizing an area, impervious surface-area such as streets, parking lots, and rooftops is increased. These smooth, impenetrable surfaces allow little or no detention or infiltration of stormwater. As precipitation falls on urban areas, it picks up contaminants from the air, littered and dirtied streets and sidewalks; petroleum residues from automobiles, exhaust products, heavy metals and tar residuals from the roads; chemicals applied for fertilization, weed and insect control; and, sediments from construction sites. The dumping of chemicals such as used motor oil and antifreeze into storm sewers is another source of urban nonpoint source (NPS) pollution.

Lake Pontchartrain is severly impacted by urban runoff and has been targeted as a priority watershed within the Department of Environmental Quality's (DEQ) Urban NPS Program. According to the state's 1990 Water Quality Inventory (305(b) Report) and the 1991 NPS Assessment Report, Lake Pontchartrain ranks second in the state in total water quality management subsegments impaired and/or threatened by urban runoff. This information is based on evaluative data from the DEQ regional offices and specific water quality monitoring stations in the basin.

In addition to the need for physical, corrective measures such as best management practices (BMPs) to prevent and reduce urban NPS pollution, source control through public education regarding NPS problems and solutions is critical to urban NPS pollutant abatement. DEQ's urban NPS public education and involvement strategy includes the dissemination of educational materials such as brochures, posters, fact sheets, and bumper stickers. DEQ's Storm Drain Stenciling Program has been initiated in both Jefferson and Orleans Parishes in an effort to alert basin residents of the connection between storm drains and the water quality of the lake. The purpose of the stencil program's message is to serve as a deterrent to people who dump pollutants such as used motor oil down storm sewers, not knowing that the sewers drain directly into the lake instead of a wastewater treatment facility. Other educational and technical assistance activities include an urban NPS video, a model ordinance report, establishment of WATERWATCH groups, and a lawn care demonstration project.

DEQ's Urban NPS Program includes a task for the implementation of urban BMPs and the evaluation of their effectiveness in improving water quality. DEQ is accepting proposals for BMP projects in priority watersheds such as Lake Pontchartrain.

While the Urban NPS Program's strategy for implementation is non-regulatory, many of the problems related to pollution from urban runoff will be addressed through EPA's stormwater regulations. Both Orleans and Jefferson Parishes, bordering the south shore of the lake, are in the process of applying for stormwater permits.

Rohli, R.V., Southern Regional Climate Center, Department of Geography & Anthropology, Louisiana State University, Baton Rouge, LA

Deviations Between Modeled and Measured Runoff in the Lake Pontchartrain Basin

A Thornthwaite monthly water-budget model is used to estimate monthly surface runoff into the Lake Pontchartrain Basin from the Comite, Amite, Tickfaw, Natalbany, Tangipahoa, and Tchefuncte Rivers for the last fifty years. The modeled outputs for each drainage basin are compared to measured monthly runoff data obtained from the U.S. Geological Survey for the same time periods. Statistical tests are implemented to identify those basins where seasonal and annual ratios of modeled to measured runoff differ significantly from each other. Hypotheses about the differences are developed, and model adjustments are recommended for better estimation of runoff from ungaged areas of the Pontchartrain Basin.

 

Sabaté, R.W., The San'Doil Co., New Orleans; Dewailly, E.L., Lumitox Gulf, New Orleans; Stiffey, A.V., University of New Orleans

Algal Bioluminescence in Toxicity Testing

Environmental quality commonly is determined by bioassays, which measure the response (primarily death rate) of living organisms to the presence of toxins. Subject organisms range from indigenous populations to selected species with demonstrated standard responses, predominantly minnows and shrimp. Cumbersome culture facilities and laboratory techniques, which translate to time and expense, together with the desire for on-site testing, has led to experimentation with monocellular
species. These offer the added statistical advantage of larger numbers (thousands or hundreds vs tens) of individuals in a sample aliquot.

Lumitox (R) is a new, compact, fast (hours vs days) patented bioassay that uses the marine bioluminescent dinoflagellate alga Pyrocystis lunula. When agitated, P. lunula generates a brilliant flash of light. In the presence of varying concentrations of toxins, this light - as measured by a patented photometer - is quenched in a predictable manner. The procedure is very sensitive to small changes in toxic concentrations both at high and low levels, is repeatable with low variation, and is effective in turbid or colored media.

The U.S. Navy inventor of Lumitox (R) has demonstrated its testing efficacy with many substances, including pesticides, defoliants, marine antifouling paint, waterbottom samples, and oil-well drilling fluids, the latter confirmed by Louisiana State University. In conjunction with University of New Orleans, Lumitox (R) will engage in environmental testing and develop a portable testing unit.

 

Smith, Sue K., Louisiana State University, Baton Rouge, LA

North-Shore Sources of Suspended Sediment in the Surface Runoff to Lake Pontchartrain

The Lake Pontchartrain Basin in southeast Louisiana comprises Lakes Pontchartrain and Maurepas, along with the surrounding land area. The major north-shore streams that contribute fresh water into the basin are the Amite, Tickfaw, Tangipahoa, and Tchefuncte river systems, along with their tributaries. These streams head in southern Mississippi and flow southward across a series of down-stepping terraces through a region that is used mostly for agriculture and forestry. Hydrologic
data are available for approximately 50 years for these streams. The data show some variations in stage, discharge, and water quality. Suspended sediment data show distinct differences between the seasons of the year and between the different rivers. During this time period, some of the streams have also shown some changes in their planform dimensions. The nature of these variations and changes are discussed, and some possible explanations are offered.

 

Thiyagarajah, A., and Ledet, M. J., college of Pharmacy, Xavier University of Louisiana, 7325 Palmetto Street, New Orleans, LA

Histopathological Assessment of Two Species of Fish from the Bayou Trepagnier

Bayou Trepagnier is located in the Lake Pontchartrain Basin, in St. Charles Parish of Louisiana. Bayou Trepagnier receives treated wastewater and storm water from an oil refinery and manufacturing complex. According to the Water Pollution Control Division of the Louisiana Department of Environmental quality reports, benzene, toluene, ethylbenzene, dichlorobenzene and chloroform were detected in fish and crabs collected from the lower stations on Bayou Trepagnier. Benzene is classified by USEPA as a known human carcinogen. The purpose of this preliminary study is to assess the fish health histologically. We selected mollies (Poecilia latipinna) and sheepshead minnows (Cyprinodon yariegatus) as test organisms because these species are very sensitive to carcinogens. Fish were caught by beach seine twice in November, 1991. Fish were examined grossly, and then processed for histological assessment. Preliminary observations indicate that the majority of the lesions are present in the cartilage, muscle, liver, and pancreas. Liver lesions range from fatty change to precancerous lesions. The preneoplastic lesions include basophilic cell foci, vacuolated cell foci, clear cell foci, and spongiosis hepatis. Other lesions include, fatty change in the exocrine pancreas, fat necrosis, vasculitis, protozoan and metazoan parasites in various tissues, and inflammatory lesions. These lesions will be described and discussed.

 

Thompson, Bruce A., Coastal Fisheries Institute, Louisiana State University, Baton Rouge, Louisiana 70803-7503

A Review of Fish Studies on Lake Pontchartrain

Many questions have been asked over the years about the fish assemblages of Lake Pontchartrain. The members of this 130 species assemblage play important roles in both the ecology and economics of the region. Over the past 40 years there have been four major, multi-gear, year-long
studies of the fishes of Lake Pontchartrain; two in the 50's, and two in the 70's. The last fish survey was done during 1978, 14 years ago! The relative abundance of many common fish species in the lake has changed little between 1953 and 1978 and no change in the community proportion of marine, estuarine or freshwater fishes was found. The lake serves a major function as nursery and feeding grounds for large numbers of juvenile fishes. Certain environmental changes may be impacting the lake's ability to continue to function as a major nursery. The salinity regime of the lake, controlled primarily by riverflow, seems to control which fish species will be dominant. Overall, the fish assemblage appears to have a "healthy" indication of seasonal change and a lack of
overdominance as found in more disturbed estuarine systems.

 

Thomson, A., University of New Orleans, New Orleans, La., and LeBlanc, R.J., Sr., Rufe LeBlanc School of Clastic Sediments, Houston, TX

Geological History of Lake Pontchartrain

The Lake Pontchartrain Basin of southeastern Louisiana lies between the Late Pleistocene Prairie Terrace to the north and the Late Holocene Mississippi Deltaic Plain Complex to the south, a distance of about 28 miles. The western margin of the Basin is near the present Mississippi River southeast of Baton Rouge, and the eastern margin of the Basin is near the western end of the Mississippi Sound. Thus, the width of the Basin is about 90 miles.

Lake Pontchartrain is the largest lake within the Basin. It has an areal extent of about 700 square miles and lies to the east of Lake Maurepas and the west of Lake Borgne. The areal extent of these three lakes comprises more than half of the Basin.

Considerable research on the geology of the Pontchartrain Basin was conducted over a period of over 40 yrs (1935-1977) by several Louisiana State University Geology professors and their graduate students and former students, with funds provided by the Corps of Engineers and
several oil companies. None of this research has produced any evidence that the area encompassed by Lake Pontchartrain was once an extensive deltaic plain.

Research results indicate the origin of the Pontchartrain Basin was different from the origin of Lake Pontchartrain within the Basin. Sub-regional tectonic processes (faulting and subsidence) were mainly responsible for the development of the Basin. In contrast, Lake Pontchartrain originated as a result of sedimentation processes. After the last rise in sea level reached its present stand about 5000 years ago an arm or embayment of the Gulf of Mexico extended inland as far north as the latitude of Mandeville, La. Later the western portion of the embayment was isolated from the Gulf by arms of the Cocodrie and St. Bernard Deltas of the Mississippi River, producing Lakes Maurepas and Pontchartrain. Thus, in spite of subsidence and some down-faulting within the embayment, the Mississippi River overwhelmed the region with sediments, and Lake Pontchartrain remains isolated from the Gulf, with the exception of the narrow Rigolets outlet into Lake Borgne. After the St. Bernard Delta was abandoned, the trunk course of the present Mississippi River contributed little sediment to the lake.

In conclusion, it is highly probable that faulting within the Pontchartrain Basin (south of the Pleistocene Terrace) has played a minor role in the origin and development of the lake, but there is
overwhelming evidence that Lake Pontchartrain was created as a result of Mississippi River diversion and sedimentation.

 

Turbeville, J.H.Jr., Conoco Inc., New Orleans, LA

The Geology and Geohydrology of an Area Representative of Near Surface Aquifer Systems on the Mississippi River Flood Plain in South Louisiana

The Mississippi River Flood Plain is approximately 100 miles wide, extending from Lake Pontchartrain to Lafayette, and traversing the entire state of Louisiana from north to south. The near surface aquifer system created on the floodplain coincides with both the most heavily industrialized and environmentally sensitive areas in the state. This includes the great majority of Lake Pontchartrain and wetland areas.

The study area is located outside of Luling, Louisiana, between the cities of New Orleans and Baton Rouge. It is 1/2 mile south of the Mississippi River and 10 miles southwest of Lake Pontchartrain. Located on an industrial park, the area encompasses two separate sources of known dichloroethane contamination (a dense non-aqueous phase liquid or DNAPL), the Ethylene Maleic Anhydrite (EMA) and Deep Well Pond sites. There were 23 wells used in the study that penetrate four stratigraphic layers. Layers I and III are considered to be aquitards, layers II and IV are aquifer sands. The aquifer system interval ranges from 2' to 40' measured from ground surface.

Stratigraphic correlations of the aquifer system were completed by constructing a series of cross-sections (10) across the area. A total of 7 geologic maps were then generated on the base, top and thickness of each aquifer unit. A hydraulic gradient map was constructed, and coupled with hydraulic conductivities (from slug tests), average linear velocities of groundwater were calculated.

The penetrated stratigraphy is from Holocene to Recent in age and consists of 4 units. Layers I and III are organic rich clays deposited as part of the natural levee system. Layers II and IV are silt to
coarse grained sands in fining upward sequences deposited as overbank or swale fill that vary in proximity and source direction from the Mississippi (or paleo Mississippi) River. Maximum vertical relief is created on the flood plain from the natural levee systems, which vertically accrete until the river overruns the levee and eventually abandons the channel.

Both layers II and IV are partially confined aquifers that are moderately heterogeneous with respect to hydraulic conductivity. Hydraulic conductivity values are relatively low and range from .1 to 3
ft/day, increasing to the south and in the basal portions of layers II and IV. Groundwater flow direction averages southwest, with a hydraulic gradient averaging .0036. The Mississippi River is thought to be a head boundary that fluctuates with the rivers stage.

Groundwater velocity is relatively slow with a calculated range from .001 ft/day to .04 ft/day, increasing to the south of the study area. This is considerably slower than what is observed in areas of known contamination in the EMA and Deep Well Pond areas. Contaminant dispersion (spreading out) appears to be a significant factor based upon contaminant plume delineation from soil vapor analysis relative to known source area.

There is potential for DNAPL contamination to follow the structural base of layers II and IV, thereby retarding or accelerating migration velocity, depending on its directional relationship to groundwater flow. Sharp basal contacts created from fining up sequences in both layers enhance this effect.

 

Vega, A. J., Southern Regional Climate Center, Department of Geography & Anthropology, Louisiana State University, Baton Rouge, LA, 70803

Long-term Climatic Variability of Modeled and Measured Runoff within the Lake Pontchartrain Basin

This study examines long term climatic variability of modeled and measured runoff within the Lake Pontchartrain Basin. Runoff estimates will be determined using a Thornthwaite water-budget model for the Comite, Amite, Tickfaw, Natalbany, Tangipahoa and Tchefuncte Rivers. Time series analysis will be employed to determine yearly, seasonal and monthly climatic trends in association with individual water years (October to September). Long-term trends will be accessed for each of
the drainage basins and collectively to determine patterns of climate variability (i.e. wet or dry months, seasons, years). This analysis will determine associations between the frequency of extreme temporal precipitation events and global circulation variability.

 

Wee, James L., Booth, Dennis J. and Bossier, Michael A., Department of Biological Sciences, Loyola University, New Orleans, Louisiana

Synurophycean Algae from the Lake Pontchartrain region: A Preliminary Survey from the Southern Atlantic Coastal Plain of North America

Forty-three taxa of Synurophyceae were identified by means of transmission electron microscopy from 10 samples collected in southeastern Louisiana, USA, on the southern portion of the Atlantic
Coastal Plain Province of North America. Mallomonas prora and Synura australiensis are reported for the first time from North America. Samples were collected during a one month time period when water temperatures ranged from 15.5-24.5 C. Sample pH values ranged from 4.42-7.21. Notable scale morphology variation was described for some taxa. The flora included three warm water taxa but was dominated by temperate and cosmopolitan taxa. Comparisons with related studies from New World, subtropical regions in Florida, USA, and Argentina, were made, and significant North American range expansions were noted. The large number of aquatic habitats, 7-8 consecutive months at temperatures (6-20 C) best suited for development of synurophyte populations, and proximity to major bird migrations routes are postulated as explanations for the large number of reported species.

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