THE HOLOCENE PALEOLIMNOLOGY OF FAVRE LAKE, RUBY MOUNTAINS, NEVADA, USA

With increasing evidence that high-elevation environments respond strongly to changes in temperature and precipitation, and that they respond differently than better studied sites at lower elevations in the same regions, it is critical that we increase our understanding global and regional climate change will affect aquatic ecosystems in montane regions. Concern about the availability of water across the Great Basin adds merit to the study of subalpine and alpine environments. Paleolimnological records from the Great Basin are rare, and those utilizing siliceous microfossils as a proxy for changes in aquatic ecosystems are almost non-existent.

Favre Lake is a small (7.7 ha), relatively shallow (12 m deep) tarn at an elevation of 2,902 m. Much of the watershed surrounding Favre Lake is covered by a veneer of glacial till, which may obscure evidence of water flowing from the adjacent lakes. The abundance of glacial till in the basin indicates that Favre Lake is only partially underlain by crystalline bedrock.

Diatom assemblages were identified and biogenic silica abundance measurements were taken from a 4.2-m-long sediment core collected from the deepest part of the lake. Small fragilarioid taxa (Pseudostaurosira, Staurosira, and Staurosirella) comprise as much as 80% of the assemblage. The remainder of the assemblage is dominated by benthic taxa. Planktonic species are account for about 10% of the assemblage. Biogenic silica values vary between 20 and 30 wt %. These proxies suggest that the lake was small between 7,700 and 5,500 cal yr BP; for most of the remainder of the record, the lake covered a shallow (~1 m deep) shelf, resulting in the dominance of small fragilarioid diatoms. Planktonic species increase in abundance in the last 200 years, indicating the establishment of modern conditions.

Increased knowledge of the behavior of high elevation aquatic ecosystems will improve our ability to develop and evaluate adaptive management strategies appropriate to freshwater ecosystem potential responses to projected climate change.