Life Sciences Commons^™

Recent Trends In Water Clarity Of Lake Pontchartrain, J.C. Francis, M.A. Poirrier

Gulf and Caribbean Research

An analysis of Secchi disk transparency observations from 3 sites on the Lake Pontchartrain Causeway indicates that water clarity has increased at the north shore and mid-lake sites, but has not changed at the south shore site. Louisiana Department of Environmental Quality data from 1986 through 1995 were used in the analysis. Further analysis indicates that the increased transparency was not caused by changes in salinity or wind speed. The best explanation for the observed increase is the cessation of shell dredging in 1990.

Behavioral Ecology Of Two Teal Species (Blue-Winged Teal, Anas Discors, And Green-Winged Teal, Anas Crecca) Overwintering In Marshes Of Coastal Louisiana, Usa, Gary R. Gaston, Jeanne C. Nasci

Gulf and Caribbean Research

Feeding and other dominant activities of Blue-winged Teal (BWT, Anas discors) and Green-winged Teal (GWT, Anas crecca) were compared from October 1987 to March 1988 in southwestern Louisiana, USA. Three observation towers were constructed near similar intermediate marsh habitats in areas where BWT and GWT concentrated for feeding. These observation towers allowed activities of the two species to be compared throughout the nonbreeding season. Although BWT and GWT often fed together, time spent in various activities differed. Feeding was the most frequent activity of both BWT(64.5%) and GWT (55.3%), but BWT spent more time feeding (P < 0.01) and alert (P < 0.05), but spent less (P < 0.01) time resting than GWT. Within each species there were differences in activity budgets among daily time blocks and among months, but few differences among the three habitats studied. Temperature and light intensity were correlated with resting (+), feeding (-), locomotion (-), and preening (+). Daily and monthly activity budgets of BWT and GWT were similar, as were ingested foods, suggesting that these two species used the study areas primarily for foraging, and left the areas for other activities. Predation and diminished resources during late winter may have affected activities of BWT and GWT as well.

Historic Trends In The Secchi Disk Transparency Of Lake Pontchartrain, J.C. Francis, M.A. Poirrier, D.E. Barbe, V. Wijesundera, M.M. Mulino

Gulf and Caribbean Research

A major environmental concern about Lake Pontchartrain is an assumed long-term increase in turbidity based on Secchi disk transparency observations. Regression of the available data on Secchi disk transparency versus time (1953 through 1990) reveals a statistically significant decrease in transparency of about 40%. However, the data set is biased in that it does not adequately represent the seasonal effects of salinity and wind speed. Two analytical procedures were undertaken to determine the extent to which the apparent long-term decrease in transparency was dependent on the seasonal bias. One procedure involved seasonal adjustment of the data for the effects of …

Long-Term Study Of Benthic Communities On The Continental Shelf Off Cameron, Louisiana: A Review Of Brine Effects And Hypoxia, Gary R. Gaston, Kenneth A. Edds

Gulf and Caribbean Research

A long-term data set compiled from our studies and a variety of investigations was analyzed to determine the effects of nine years of discharged brine (concentrated salt water) on benthic organisms surrounding a brine diffuser off Cameron, Louisiana (USA). These investigations began three months before brine discharge was initiated in 1981. A preliminary summary by Giammona and Darnell (1990) relied on just three years of discharge data and gave misleading reports of brine impacts.

Brine effects over the nine years of study were minimal, in part because the fine sediments of the study area were numerically dominated by opportunistic species. …

A Preliminary Checklist Of Epiphytic And Benthic Marine Diatoms Of Louisiana, Robert S. Maples

Gulf and Caribbean Research

A checklist of diatoms collected from the various habitats in coastal salt marshes, estuaries, and nearshore Gulf waters of Louisiana has been compiled for the first time. The checklist includes 193 taxa (species and their varieties) in 38 genera. The largest number of taxa are species of Navicula and Nitzschia with 46 and 36, respectively. Future studies of the varied habitats along the Louisiana coast should result in many new additions to this preliminary checklist.

Effects Of Saltwater Intrusion From The Inner Harbor Navigation Canal On The Benthos Of Lake Pontchartrain, Louisiana, Jane A. Junot, Michael A. Poirrier, Thomas M. Soniat

Gulf and Caribbean Research

A study of the benthos of southern Lake Pontchartrain, Louisiana, was conducted from July 1976 to July 1978. Seven offshore stations and three stations in the New Orleans Marina complex were sampled seasonally. Offshore stations formed a transect from the Lake Pontchartrain Causeway to the Inner Harbor Navigation Canal (I.H.N.C.). A west to east gradient of increasing salinity and salinity stratification was evident.

Faunal differences among stations were assessed using indices of diversity, biological dominance, pollution, and station homogeneity. The fauna of the marina stations had a low species diversity and was dominated by annelids, indicative of a stressed environment. …

Community Structure Of Diatoms Epiphytic On Pneumatophores Of The Black Mangrove, Avicennia Germinans, In A Louisiana Salt Marsh, Robert S. Maples

Gulf and Caribbean Research

The taxonomy, diversity, and similarity of diatom assemblages epiphytic on pneumatophores of black mangrove, Avicennia germinans (L.) L., in southeastern Louisiana were investigated. A total of 109 taxa representing 27 genera were identified in samples from five sites. The most abundant taxa were Nitzschia brittonii Hagelstein, Nitz. frustulum (Kutz.) Grun., Navicula diserta Hust., Denticula subtilis Grun., and Amphora tenuissima Hust. Comparisons with previous studies indicate that the diatom flora epiphytic on A. germinans in this study is much more characteristic of temperate salt marshes than of subtropical mangrove communities.

Trends In Ex-Vessel Value And Size Composition Of Reported May - August Catches Of Brown Shrimp And White Shrimp From The Texas, Louisiana, Mississippi, And Alabama Coasts, 1960-1978, Charles Wax Caillouet, Dennis Brian Koi

Gulf and Caribbean Research

Exponential models were used to characterize (1) ex-vessel value (in dollars) per shrimp by size category (count; i.e., number of shrimp per pound, heads off); (2) size composition (expressed as cumulative weight of the catch in pounds, heads off, by size category); and (3) ex-vessel value composition (expressed as cumulative ex-vessel value, in dollars, of the catch by size category) for reported May-August catches (inshore and offshore combined) of brown shrimp (Penaeus aztecus) and white shrimp (P. setiferus) from the Texas, Louisiana, Mississippi, and Alabama coasts (statistical areas 10-21) from 1960 to 1978. Exponents of the …

Effects Of 1973 Floodwaters On Plankton Populations In Louisiana And Mississippi, Suzanne R. Hawes, Harriet M. Perry

Gulf and Caribbean Research

Studies to assess the impact of floodwater diversion on plankton populations in coastal waters of Mississippi and Louisiana were conducted from 23 April 1973 through 13 July 1973. Fixed stations in Lake Pontchartrain, Lake Borgne and western Mississippi Sound were sampled once in April, twice in May and June, and once in July. Stations in Terrebonne Parish, Louisiana were visited once in May, June and July.

Data are presented on changes in the species composition of zooplankton subsequent to the opening of the Bonnet Card and Morganza floodways. The hydrographic conditions at the time of sampling are discussed.

A Study Of Syngnathus Scovelli In Fresh Waters Of Louisiana And Salt Waters Of Mississippi, Edward Caldwell Whatley

Gulf and Caribbean Research

A breeding population of Syngnathus scovelli was discovered in 1960 in Lake St. John near Ferriday, Louisiana, which is over 300 river miles from the Gulf of Mexico by the shortest possible route. Although S. scovelli has been known to be euryhaline, this constitutes the first record of a breeding population in fresh water.

This study encompassed the period from July 1960 through February 1966. During this time S. scovelli were maintained for varying periods of time in fresh water aquaria. The longest period of time any one specimen lived in captivity was from 29 September 1960 until 16 November …

A Seasonal Ecological Study Of Foraminifera From Timbalier Bay, Louisiana, Robert P. Waldron

Gulf and Caribbean Research

This study concerns the ecological habits of living Foraminifera from a shallow Louisiana coastal bay during a period of ten months. It is a part of an extensive study undertaken by the Coastal Studies Institute of Louisiana State University to determine the effect of chemical and physical properties of water upon marine life in a large, open bay over an extended period of time. Samples were collected monthly from established locations for the chemical, biological and foraminiferal determinations. Results of the chemical and biological studies will be published by the respective investigators in subsequent papers.

The period of time covered …