Lakes that are large (>10 acres), deep (> 18 feet), soft or very soft (alkalinity < 50 ppm and < 30 ppm), and seepage have no inlet and outlet, and the main water source is from precipitation or runoff.
The submergent community of this lake type is characterized by a group of slow-growing, mostly rosette-forming aquatic plants called isoetids. Because these plants cannot utilize bicarbonate as a source of carbon, they have substantial root systems that allow them to assimilate inorganic carbon from the sediment. Typical species include water lobelia (Lobelia dortmanna), quillworts (Isoetes spp.), and dwarf water-milfoil (Myriophyllum tenellum). However, their short stature makes them vulnerable to shading, and as a community they are extremely sensitive to nutrient pollution that favors faster-growing submerged and/or floating-leaf species. In deeper water, stoneworts (Nitella spp.), a genus of macroalgae, can be found with high abundance. The floating-leaved community consists largely of water-shield (Brasenia schreberi), but also includes floating lilies (Nymphaea odorata and Nuphar variegata). Associated fish species include bluegill, pumpkinseed, largemouth bass, and yellow perch, rock bass in soft (as opposed to very soft) waters, and cisco in very deep, soft waters.
