Louisiana border some six miles inland from the Gulf of Mexico. It

has an area of 70 square miles divided equally between the two states. The Sabine and Neches Rivers empty into Sabine Lake, delivering an annual silt load of 7 million tons.

Although the lake is shallow, both horizontal and vertical salinity gradients are present. The vertical gradient is well developed in that portion of the lake nearest the Gulf. The horizontal gradient, with highest salinities in that portion of the lake nearest the Gulf, elicits two distinct patterns through the year. During periods of high river discharge, a salinity gradient is established with low salinities at the upper end of the lake and a gradual increase toward the lower end of the lake. During these times, the entire upper portions of the lake can be completely fresh with very low salinities (1-2 ppt) in the lower portion. The second salinity pattern occurs when river discharge is low. At this time, high salinity waters enter the upper portion of the lake from the Sabine-Neches ship channel. At these times the upper and lower portions of the lake have higher salinities, while the center of the lake is less saline. Water temperatures closely follow air temperatures.

Figure 14.

indicates interpolated average salinities and bathymetric contours.

Biologically speaking, Sabine Lake is apparently not a rich nor highly productive body of water. No reference dealing with vegetation were found but Gillespie (1971) found samples from Sabine Pass and two Louisiana stations to be deficient of zooplankton as

Figure 14. Bathymetry and interpolated average salinity contours of Sabine Lake. (From Fisher et. al., Unpublished draft,

12

Beaumont-Port Arthur Sheet, Environmental Geologic Atlas of the Texas Coastal Zone)

Isohaline line n mber indicates average salinity in ppt.

bathymetric contours in feet

compared to other areas in Louisiana both in quantity and number of species present. The most abundant forms are apparently the

ctenophores Beroe ovata and Mnemiopsis mccradyi.

Besides the ctenophores, the copepod Acartia tonsa is typically the dominant zooplankter. Other common zooplankters include the copepods Labidocera, Centropages, Corycaeus, and Eurytemora, decapod larvae, arrow worms, tunicates, and fish larvae and eggs. Zooplankton biomass is highest in April and September and lowest in June-JulyAugust and December-January.

The benthic invertebrates of Sabine Lake are apparently not well known. Our literature notes only two infaunal members, the

commercial oyster, Crassostrea virginica, present but not abundant in the lower portion of the lake, and the clam Rangia cuneata, abundant throughout. Other benthic fauna include the commercially important shrimps and blue crabs. The white shrimp Penaeus setiferus is the most abundant shrimp in the lake, however most are below the legal minimum size and commercial harvest is small. The brown shrimp P. aztecus is present in smaller numbers and is commercially insignificant. Other shrimp occasionally found include the seabob and freshwater shrimp. Sabine Lake supports a modest commercial fishery for the blue crab Callinectes sapidus. These commercial operations are concentrated in the southern part of the lake.

Information on nektonic fauna of Sabine Lake is limited to a paper

by Stevens (1960c) which lists fish by species and relative abundance