Lake Estuary Research Articles

Estuarine Macrobenthos in Calcasieu Lake, Louisiana: Community and Trophic Structure

Macrobenthic assemblages in Calcasieu Lake estuary (Louisiana) were sampled at 11 sites from October 1983 through November 1985. The sites were numerically dominated by subsurface-deposit feeders, consisting mostly of polychaetes. Greater densities of macrofauna were collected at the northern (upper) stations of the lake than were collected in West Cove or the southern stations. Abundances of polychaetes, oligochaetes, and amphipods at the upper lake stations accounted for most of the differences among stations. The numerical dominance by detritivores (97% of the fauna) and lack of strong sediment or salinity gradients across the estuary, resulted in an absence of temporal pattern in trophic structure of the macrofauna.

Sediments of Sabine Lake, the Gulf of Mexico and Adjacent Water Bodies, Texas-Louisiana

ABSTRACT Sabine Lake, a lake estuary, and the adjacent parts of the Gulf of Mexico, a nearshore neritic environment, were cored and clam-shell sampled to determine if certain physical characteristics of their sediments could be used to differentiate between the two sedimentary environments. Megascopically, in the wet state, the sediments of the two environments appear mainly as grayish to blackish, very fine sandy and silty mud or silty and clayey mud. Some very fine sand and fine sand occur in the northern part of Sabine Lake; very fine sand also occurs along the western part of the Gulf of Mexico shoreline. The sediments of the two environments are usually soft with a high water content and contain variable amounts of shell and plant materials. In the dry state, megascopically, the sediments are seen to be sand, silt or clay, or admixtures of these types and exhibit lighter shades of gray or black color. Analysis of laboratory data shows that the dominant sedimentary type in the two environments, based on mean grain size, is silt with the secondary occurrence of very fine sand and fine sand. Poor sorting is usually characteristic of the sediments of both environments. Comparison of all data indicates that the described sedimentary characteristics would make poor criteria in differentiating between the two sedimentary environments.

Minor internal sedimentary structures in the cored sediments of Sabine Lake and adjacent water bodies, Texas-Louisiana

Minor internal sedimentary structures in the uppermost layer of cored sediments are described and distribution of types is mapped for Sabine Lake, a lake estuary in southeastern Texas and southwestern Louisiana. Terminology and criteria of identificatiin are adapted from the study of Gulf of Mexico sediments by D. G. Moore and P. C. Scruton (1957), except that the term 9mixed structures9 has been substituted for 9mottled structures9 to avoid confusion with color. Mixed structures are the dominant type in Sabine Lake; fine homogeneous structures are next most prevalent, occurring along the southwest shore. Coarse and fine homogeneous, regular-layered, and irregular-layered structures occur in small areas. Possible formation processes are discussed.

Occurrence of Rangia cuneata Gray and Crassostrea virginica (Gmelin) in Sabine Lake, Texas-Louisiana

Sabine Lake is a lake estuary in the extreme south eastern corner of Texas. Field data were obtained from the present-day surface and from depths up to 9 ft. below the surface through the use of a coring device. Rangia cuneata Gray is an estuarine genus and occurs in Sabine Lake mainly N. of 29 degrees 509N. It occupies the fresher portion of the lake and could be used as an index for this biotope. Shells generally occur as scattered individuals. Crassostrea virginica (Gmelin) occurs singly or in reefs S. of 29 degrees 509N. This species serves as an index for the more saline portion of the lake. The pattern of core spacing was too widespread to delineate the geometry of occurrence of either form.

Late Quaternary Geology of Sabine Lake and Vicinity, Texas and Louisiana: ABSTRACT

The late Pleistocene and Recent sediments, faunas, and geomorphology were mapped in the vicinity of Sabine Lake, in an area that straddles the Texas-Louisiana state line and extends into the Gulf of Mexico. The former valley of the Neches and Sabine rivers is entrenched into oxidized Pleistocene deposits to a minimum depth of 120 feet at the Gulf of Mexico shoreline. This valley has been filled in by the streams and closed off at its southern end, except for Sabine Pass, by prograding of the Gulf shoreline to form the present lake estuary, Sabine Lake. The erosion and subsequent alluviation were caused by a fall and rise in sea-level due to waxing and waning of continental glaciers late in Quaternary time. Lithology and fauna, especially the Foraminifera, were determined from cores and clam-shell samples taken in the Sabine Lake estuary and Gulf of Mexico nearshore neritic environments. No End_Page 2519------------------------------ lithologic criteria for distinguishing these two environments were evident in the surface sediments or in core samples taken 3 feet and 6 feet below the surface. Foraminiferal biofacies, however, do differentiate clearly the estuarine and the nearshore neritic environments. The species and their percentages in the bottom sediments of Sabine Lake differ from those of the Gulf of Mexico, and from those in the core samples from 3 and 6 feet. The biofacies of the core samples from under the lake are similar to those of the present Gulf, indicating greater circulation of saline waters from the Gulf of Mexico before the south end of Sabine Lake was restricted. End_of_Article - Last_Page 2520------------