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Sandhill Upland Lake - (synonyms: sand-bottomed lake, silt-bottomed lake, oligotrophic lake, sandhill lake).
Sandhill Upland Lakes are generally characterized as shallow rounded solution depressions occurring in sandy upland communities. They are generally permanent water bodies, although water levels may fluctuate substantially, sometimes becoming completely dry during extreme droughts. They are typically lentic water bodies without significant surface inflows or outflows. Instead, water may be largely derived from lateral ground water seepage through the surrounding well-drained uplands and/or from artesian sources via connections with the underlying limestone aquifer.
Vegetation may be largely restricted to a narrow band along the shore, composed of hydrophytic grasses and herbs or a dense shrub thicket, depending on fire frequency and water fluctuations. Shallow, gradually sloping shorelines may have much broader bands of emergent vegetation with submerged aquatic plants occasionally dominating much of the water column; floating plants sometimes cover much of the surface. Typical plants include panicums, rushes, bladderwort, water lilies, sawgrass, pickerelweed, fragrant waterlily, water shield, St. John's wort, arrowheads, beak rush, yellow-eyed grass, hatpins, meadow-beauty, sundews, and spikerush
The substrate of Sandhill Upland Lakes is primarily composed of sands with organic deposits increasing with water depth. Sandhill Upland Lakes characteristically have clear, circumneutral to slightly acidic, moderately soft water with varying mineral content. They may be ultra-oligotrophic, with extremely low nutrient levels, seldom becoming eutrophic unless artificially fertilized by human-related activities.
Sandhill Upland Lakes are frequently extremely important breeding areas for terrestrial amphibians, including the threatened gopher frog, as well as many unusual or endemic insects. They are also important watering holes for many mammals and birds inhabiting the surrounding xeric communities. Wading birds and ducks may also use these lakes as feeding areas.
Sandhill Upland Lakes are extremely vulnerable to hydrological manipulations. Excessive municipal, industrial, or agricultural withdrawals of ground water could lower regional water tables and, thus, induce successional responses in the lake basin. Groundwater pollution, especially from misapplications of chemicals on the surrounding well-drained uplands, could significantly alter the nutrient balance and produce evastating effects on the fauna and flora. Furthermore, because they frequently have direct or indirect connections with the aquifer, Sandhill Upland Lakes often function as aquifer recharge areas and, thus, should be diligently protected from chemical pollution. Invasion by exotic species is also an important concern in Sandhill Upland Lake communities.