Little Rock Lake Experiment at North Temperate Lakes LTER: Physical Limnology 1983 - 2000

The Little Rock Acidification Experiment was a joint project involving the USEPA (Duluth
Lab), University of Minnesota-Twin Cities, University of Wisconsin-Superior, University of
Wisconsin-Madison, and the Wisconsin Department of Natural Resources. Little Rock Lake is a
bi-lobed lake in Vilas County, Wisconsin, USA. In 1983 the lake was divided in half by an
impermeable curtain and from 1984-1989 the northern basin of the lake was acidified with
sulfuric acid in three two-year stages. The target pHs for 1984-5, 1986-7, and 1988-9 were
5.7, 5.2, and 4.7, respectively. Starting in 1990 the lake was allowed to recover naturally
with the curtain still in place. Data were collected through 2000. The main objective was to
understand the population, community, and ecosystem responses to whole-lake acidification.
Funding for this project was provided by the USEPA and NSF. Parameters characterizing the
physical limnology of the treatment (north basin, stations 1 and 3) and reference basin
(south basin, station 2 and 4) are usually measured at one station in the deepest part of
each basin (stations 1 and 2) at 0.5 to 1-m depth intervals depending on the parameter.
Parameters measured at depth include water temperature, vertical penetration of
photosynthetically active radiation (PAR), dissolved oxygen, chlorophyll and phaeopigments.
Additional derived parameters include fraction of surface PAR at each depth and percent
oxygen saturation. Auxiliary data include time of day, air temperature, cloud cover, and
wind speed and direction and secchi depth. Sampling Frequency: varies - Number of sites: 4