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Little Rock Lake (LIRO) is a aquatic site in the American Legion State Forest in Vilas County in north-central Wisconsin. It is hosted by the Wisconsin Department of Natural Resources. LIRO is a 0.16 km² (40 acre) mesotrophic lake with an elevation of 501 m (1640 ft.). The surrounding region is a matrix of hardwood, coniferous, and mixed forests and lakes and streams. LIRO is located within NEON's Great Lakes Domain (D05), which includes northern Ohio, Michigan, northern Wisconsin, and parts of Indiana and Illinois. D05 also includes three terrestrial sites and one additional aquatic site. [1] [8]

The climate of northern Wisconsin is characterized by bitterly cold winters and generally cool summers with brief times of excessive heat. Precipitation varies from year to year, with the majority of precipitation usually falling during the warmer part of the year. Snowfall also varies from year to year, however, the very northern portion of the state can see heavy snowfall due to lake effect events along the southern shore of Lake Superior. From late fall to early spring, most streams and lakes freeze over in northern Wisconsin. In the winter months, snow covers the landscape. In spring, when the snow begins to melt, frequent flooding occurs. The mean average temperature at the site is about 4.4°°ä (40°F). On average, the site receives 796 mm (31.3 in.) of precipitation a year. [5] [9]

The topography of the lake and surrounding land were formed by glacial processes 10,000 to 25,000 years ago. The leftover glacial deposits are mainly comprised of sand and gravel. The geology of the site is defined as migmatic gneiss and amphibolite. [3] [8] [12]

The bed sediments of Little Rock Lake are comprised of 70% sand, 10% gravel, 15% rock and 5% muck. [1]

Little Rock Lake (LIRO) is a seepage lake with a watershed size of about 0.9 km2 (220 acres) and no inflow or outflow streams. The lake consists of two main basins that are separated by a narrow water passage. The water moves southeast to northwest in the ground-water system the lake is situated within. Almost all of the lake’s water comes from rainfall and snowmelt. Precipitation, evaporation and groundwater flow affect the lake’s water levels, area and volume year-to-year. There is a known thermocline of the lake that varies during the seasons, approximately 8 m (26 ft.) deep on rough average. During the summer months, the bottom of the lake becomes anoxic. From late fall to early spring, LIRO may be ice covered. [1] [3] [8] [9]

The riparian canopy surrounding Little Rock Lake is dominated by primarily hardwood and mixed forests and some coniferous forests. Trees found in these habitats are the speckled alder (Alnus incana rugosa), white pine, and white and black spruce trees. [1]

Common fish caught and sampled by NEON technicians at the Little Rock Lake site are the central mudminnow (Umbra limi), rock bass (Ambloplites rupestris), yellow perch (Perca flavescens), and largemouth bass (Micropterus salmoides).

In the 1500s, the Anishinaabe began to explore and settle on the southern shores of Lake Superior, near Little Rock Lake (LIRO). In the 1600s, the Ojibwe tribe formed and found their sustenance fishing in the summer, harvesting wild rice in the fall, hunting and ice fishing in the winter, and tapping maple syrup and spearfishing in the spring. Birch bark was the Ojibwe's main building material to construct shelter. In the mid-1600s, many of the Ojibwe were driven off their land, but reservations remain in the region. The American Legion State Forest, which includes LIRO, was established in 1925 to protect the headwaters of the Wisconsin, Flambeau and Manitowish rivers. In more recent history, LIRO was the site of research efforts to collect and analyze data on water and air pollution. In 1983, the two water basins of LIRO were separated by an impermeable barrier to create a divide so one water body could be the experimental site and one could be the control. For six years, one basin was gradually acidified with sulfuric acid and the other basin went untreated. For over thirty years, research has been conducted and water quality, biological, geological and chemical cycles have been closely monitored at LIRO. Studies found increased water clarity, increased algal growth, slower fish growth rates, unsuccessful reproduction in largemouth bass and mercury contamination in fish. Legislation put in place in the late 80s reduced the threat of acid rain, but climate change and greenhouse gases released from coal-burning power plants in the area remain a threat to lakes in northwestern Wisconsin. [2] [7] [10] [11]

The Wisconsin Department of Natural Resources (DNR) manages the American Legion State Forest, which encompasses Little Rock Lake (LIRO). The Wisconsin DNR manages, conserves and restores their state's water resources to maintain a healthy ecosystem and to benefit its residents. While maintaining Wisconsin's natural resources, the DNR also provides recreational activities for visitors. Fishing is a popular activity for guests at Little Rock Lake. Scientists and students from around the world also conduct research at LIRO due to its shape, location, and history. [2] [4]

The Aquatic Instrument System (AOS) at Little Rock Lake (LIRO) was completed in November 2017. The LIRO site already had two access points to the lake that were utilized. The Northern boat ramp was recommended for NEON infrastructure and maintenance access, where minor maintenance was needed for access. Understory vegetation needed to be removed as well for clearance of the Aquatic Meteorological station. Observations at the site noted that the inlet and outlet infrastructures should be placed closer to shore because there is firmer substrate and in-canopy openings where the solar panels will receive sun exposure. It was proposed that the eastern access to the lake be utilized for installation and seasonal removal of the buoy. The groundwater observation wells network at LIRO consists of eight wells installed using a rotary rig. The wells were to be installed in varying positions among the hills surrounding the lake. The required drill depths for the wells were 7-15 m (23 - 50 ft.) below the ground surface. One issue noted before drilling began was the presence of glacial erratics, which may have posed an issue during drilling due to their size. Electric power at the site is provided by Wisconsin Public Services (WPS) in Green Bay, Wisconsin. There was already a previous power line buried off Rt. 51 that NEON was able to tie into to bring power to the eastern (~300 m) or northern basin (~600 m). [1]