Submerged vegetation of Lakes Te Anau, Manapouri, Monowai, Hauroko, and Poteriteri, Fiordland, New Zealand

Abstract

The submerged vegetation in Lakes Te Anau, Manapouri, Monowai, Hauroko, and Poteriteri from the South Island of New Zealand, was surveyed in 1993 using SCUBA methods to record a range of botanical parameters to the deepest extent of the vegetation. This is the first detailed account of the submerged vegetation in these lakes and the first description for Lake Poteriteri. The vegetation of these lakes is comprised predominantly of native species. Isoetes kirkii dominates the shallow‐water assemblage in all lakes. Hydatella inconspicua, an endemic shallow‐water plant of rare status, is reported for the first time in the South Island, New Zealand. Formerly only reported from a limited number of North Island sand dune lakes, the discovery of these southern disjunct populations of H. inconspicua means that this species should no longer be considered endangered. The tall‐growing native vascular species, Potamogeton cheesemanii, Myriophyllum propinquum, and M. triphyllum were recorded in all five lakes. The most frequent tall vascular species in Lakes Te Anau, Manapouri, and Monowai was the adventive Elodea canadensis, which was not recorded in Lakes Hauroko or Poteriteri. Juncus bulbosus, another, adventive species, was recorded in all lakes except Lake Te Anau. The most abundant group of plants within all five lakes were native charophytes. Chara fibrosa was the species with greatest cover in Lakes Hauroko and Poteriteri, whereas Chara corallina was in the other lakes. Bryophytes were the deepest vegetation recorded and were widespread but not abundant within all the lakes. The bottom depth limits of the vegetation ranged from 7.5 to 19 m, with Lake Hauroko, the clearest lake, having the deepest vegetation.