The underwater optical climate of Lake Texoma was measured at eleven fixed stations from August 1996 to August 1997. Secchi transparency and submarine photometry characterized seasonal and spatial values of secchi depth (SD), vertical attenuation coefficient (η''), and depth of euphotic zone (Zeu). Indices of Zeu:SD and η'' × SD were compared with universally applied values derived from inland and coastal waters. Turbidity explained 76% of the variation (p = 0.0001) of η'' among water quality parameters, including chlorophyll-α. Using a spectroradiometer, spectral signatures of chlorophyll-α and turbidity were located. Stations with low turbidity exhibited a distinct green reflectance peak around 590-610 nanometers, indicating presence of chlorophyll-α. Stations with high turbidity exhibited a reflectance peak shift towards the red spectrum, making it difficult to detect the chlorophyll signature. Derivative analysis of the reflectance signal at 590-610, and 720-780 nanometers allowed discrimination of this chlorophyll signature from those of turbidity (0.66 ≤ r^2 ≤ 0.99).

Twenty-eight species of zooplankton were identified from Lake Texoma. Seasonal density of the overall microcrustacean community and seasonal cycles of individual species were compared with northern populations and any available literature from the Southwest. Cycles of occurrence and abundance were similar to those observed in northern populations but tended to occur earlier in the year due to higher temperatures. Spatial distributions within the reservoir were heavily influenced by nutrient and salt input from the Red River, which resulted in dense populations in the Red River Arm. In addition, during the summer, the microcrustacean community was restricted to the epilimnion due to anoxic conditions in the hypolimnion of the reservoir.

This study was initiated after finding two chromosomal types of Peromyscus maniculatus north and south of the Red River in Texas and Oklahoma. The problem was to explain the chromosomal variations and their implications to the systematics of the grassland subspecies of P. maniculatus in this region.

An analysis and correlation of phytoplankton communities with physicochemical data from 3 sites in Lake Texoma was conducted to supplement time-series data. Water and phytoplankton were sampled monthly, March, 1976-February, 1977. Simple correlations were run between all physicochemical parameters and phytoplankton standing crop from the 3 sites. Multiple linear regression analyses were used to develop equations predictive of phytoplankton standing crop and chloride concentration. Minerals leached from marine sediments in the Red River chennel contribute to formation of a, halocline which seals the anoxic hypolimnion from the reservoir surface in midsummer. Conductivity decreased west to east, 2980-1800. pmhos/cm. Maximum mean annual phytoplankton standing crop in Red River arm was 36 percent greater than midlake. Eutrophication was evident.