Aquatic macrophytes of Lake Rotopounamu, a montane volcanic lake in New Zealand

Abstract

Abstract Lake Rotopounamu (710 m a.s.l.) is located in red beech/kamahi forest in Tongariro National Park in the central North Island of New Zealand. The maximum depth of the lake is 7.9 m, and it has neutral pH (7.1), soft water, and a predominantly silty substrate. It probably alternates between warm thereintictic and polymictic. No exotic, aquatic macrophytes are present. Beds of sedges (including Baumea rubiginosa (Spreng.) Boeck.) are patchy on the southern shores. Submerged communities have 2 zones: at 0.1–2.5 m deep a low growing, inshore community of Myriophyllum pedunculatum Hook.f., Lilaeopsis lacustris Hill, and Glossostigma elatinoides Benth. and at 2.5–7.9 m deep a characean algal community of Nitella pseudoflabellata (Nordst.) Bailey and N. leptostachys var. Leonhardii (R.D.W.) R.D.W. Three species of aquatic liverwort are also recorded. The absence of a tall macrophyte zone, found in many other New Zealand lakes, is discussed.