Papers and Reports

Algae growing in the surface water of Las Vegas Bay, an arm of Lake Mead, may receive nutrients contained in the stream entering through Las Vegas Wash. The stream water is more dense than the lake water due to dissolved salts. Existing hydrodynamic theory predicts that the stream should form a submerged layer isolating the nutrients from the surface. The theory was tested by introducing dye into the stream during two 14-day experiments; salinity, temperature, and dye concentration were monitored in the inner portion of the bay. Significant dye concentrations were found in the surface waters during both experiments, and two modes of internal waves with amplitudes up to 6 m were observed. The wave motion provided the main mechanism for transport to the surface in the first experiment; in the second an additional mechanism was the creation and destruction of temporary thermoclines due to meteorological variation. An approximate nutrient balance shows that in each case about 10% of the entering nutrients were available to the surface water within the 14-day period of the experiments.