Lahontan Reservoir Research Articles

Improved Microcosm Design for Performing Reservoir Water Quality Investigations

Microcosms suspended in lakes and reservoirs have been effective for performing in situ water quality studies; these systems have also been proposed for the determination of rate constants for dynamic water quality models. A number of different microcosm designs have been used. The most common design consists of a polyethylene cylinder with external supports to which the plastic is glued. The primary problem with previous microcosm designs is their structural instability resulting in destruction during rough water conditions. The purpose of this paper is to report a strong and easily-assembled microcosm system. The microcosm design used 0.0152-cm (6-mil) clear polyethylene plastic heat sealed into a cylinder 0.776 m in diameter. The plastic cylinder was supported from inside by aluminum rings 0.0381-m wide, 0.0025-m thick, and 0.76-m in diameter. The rings were coated with spray plastic to negate leaching of aluminum and possible toxicity during experiments. The bands, which supported the microcosms at 1-m intervals, were held in place from the outside of the plastic cylinder by a second band similar to a large hose clamp. The microcosms performed well under extreme conditions, including winds to 110 km/hr, during water quality investigations at Lahontan Reservoir, Nevada.

Stable Carbon and Nitrogen Isotope Tracers of Trophic Dynamics in Natural Populations and Fisheries of the Lahontan Lake System, Nevada

The influence of combined inorganic N on the growth of N2-fixing blue-green algae (Aphanizomenon flos-aquae) in Lahontan Reservoir was detected with N isotopic compositions (δ15N = + 1.2 to + 7.0) that were enriched in 15N. In Pyramid Lake, however, the δ15N of the entire food web was influenced by a contribution of isotopically light N released from N2-fixing blue-green algae (Nodularia spumigena). Carbon isotope ratios (δ13C) of these unpalatable, blue-green algae from both lakes were different enough from the zooplankton and higher animals to preclude a direct trophic link. An enrichment in 13C with trophic level in the food chain was measured in both lakes. Carbon isotope ratio measurements clearly illustrated the isotopic similarity between hatchery-raised Lahontan cutthroat trout (Salmo clarki henshawi) and cui-ui (Chasmistes cujus) and the artificial diet, but differed from the δ13C of their wild counterparts consuming natural foods. There is a consistent isotope fractionation between the δ13C of scales and the δ13C of muscle from fish that is species specific. This finding demonstrates that fish scales, as well as muscle, can be used to determine diet.

Species Composition and Seasonal Succession of the Zooplankton Community of Eutrophic Lahontan Reservoir, Nevada

Species Composition and Seasonal Succession of the Zooplankton Community of Eutrophic Lahontan Reservoir, Nevada

Total mercury in fishes and selected biota in Lahontan Reservoir, Nevada: 1981.

Total mercury in fishes and selected biota in Lahontan Reservoir, Nevada: 1981.