Geology topics

Research about Little Rock Lake

Source-linked reports with geographic coverage including Little Rock Lake.

3 recordsLinked to original sources

USGS2011

Bi-phasic trends in mercury concentrations in blood of Wisconsin common loons during 1992-2010

We assessed the ecological risk of mercury (Hg) in aquatic systems by monitoring common loon ( Gavia immer ) population dynamics and blood Hg concentrations. We report temporal trends in blood Hg concentrations based on 334 samples collected from adults recaptured in subsequent years (resampled 2–9 times) and from 421 blood samples of chicks collected at lakes resampled 2–8 times 1992–2010. Temporal trends were identified with generalized additive mixed effects models and mixed effects models to account for the potential lack of independence among observations from the same loon or same lake. Trend analyses indicated that Hg concentrations in the blood of Wisconsin loons declined over the period 1992–2000, and increased during 2002–2010, but not to the level observed in the early 1990s. The best fitting linear mixed effects model included separate trends for the two time periods. The estimated trend in Hg concentration among the adult loon population during 1992–2000 was −2.6% per year, and the estimated trend during 2002–2010 was +1.8% per year; chick blood Hg concentrations decreased −6.5% per year during 1992–2000, but increased 1.8% per year during 2002–2010. This bi-phasic pattern is similar to trends observed for concentrations of methylmercury and SO 4 in lake water of an intensely studied seepage lake (Little Rock Lake, Vilas County) within our study area. A cause-effect relationship between these independent trends is hypothesized.

Wisconsin↗

USGS2007

Distribution and grain-size partitioning of metals in bovfom sediments of an experimentally acidified Wisconsin lake

A study of concentrations and distribution of major and trace elements in surficial bottom sediments of Little Rock Lake in northern Wisconsin included examination of spatial variation and grain-size effects. No significant differences with respect to metal distribution in sediments were observed between the two basins of the lake, despite the experimental acidification of one of the basins from pH 6.1 to 4.6. The concentrations of most elements in the lake sediments were generally similar to soil concentrations in the area and were well below sediment quality criteria. Two exceptions were lead and zinc, whose concentrations in July 1990 exceeded the criteria of 50 μg/g and 100 μg/g, respectively, in both littoral and pelagic sediments. Concentrations of some elements, particularly Cu, Pb, and Zn, increased along transects from nearshore to midlake, following a similar gradient of sedimentary organic carbon. In contrast, Mn, Fe, and alkali/alkaline-earth elements were at maximum concentrations in nearshore sediments. These elements are less likely to partition to organic particles, and their distribution is more dependent on mineralogical composition, grain size, and other factors. Element concentrations varied among different sediment grain-size fractions, although a simple inverse relation to grain size was not observed. Fe, Mn, Pb, and Zn were more concentrated in a grain-size range 20–60 tm than in either the very fine or the coarse fractions, possibly because of the aggregation of smaller particles cemented together by organic and Fe/Mn hydrous-oxide coatings.

Wisconsin↗

USGS1993

Hydrology of Little Rock Lake in Vilas County, north-central Wisconsin

Water budgets were developed for Little Rock Lake for October 1983 through September 1990 as part of a study to evaluate the chemical and biological effects of artificially acidifying one basin of the two-basin lake. The 17.9-hectare seepage lake is situated in 60- to 90-meter-thick, predominantly sand and gravel glacial deposits of Vilas County, north-central Wisconsin. Annual precipitation during the study varied from 647 to 926 mm (millimeters). Average annual precipitation during 1951-80, based on nearby National Weather Service stations, was 825 mm. Annual evaporation from the lake surface ranged from 495 to 648 mm. Total lake-stage fluctuation was 930 mm during the study. Lake volume at the maximum stage was 31 percent greater than at the minimum lake stage. Inflow to the lake was dominated by precipitation, which was about 99 percent of total inflow. Ground-water inflow to the lake was transient, occurring only intermittently during October 1983 through September 1986, and amounted to only about 1 percent of total inflow. No ground water flowed into the lake from October 1986 through September 1990. Evaporation accounted for about two-thirds of total outflow from the lake, and lake water discharging to the underlying aquifer accounted for the remainder. The average hydraulic residence times for the 7-year study period were 3.9, 3.3, and 4 years for the entire lake, the south basin, and the north basin, respectively; corresponding chemical residence times were 10.9, 9.3, and 10 years.

Wisconsin↗