Macroinvertebrates associated with aquatic macrophytes in Lake Alexandria, New Zealand

Abstract

Macroinvertebrates from six macro‐phyte communities and from an intermittently vegetated sublittoral community were collected from Lake Alexandrina during a period of 2.5 years. Each of the six communities was dominated by one native species (Myriophyllum triphyllum, Isoetes alpinus, Chara fibrosa var. acanthopitys or Chara globularis) or by the adventive Elodea canadensis. Thirteen of the 21 macroinvertebrate taxa associated with these communities were herbivores and/or detritivores and these contributed at least 90% to total abundance; the remaining eight were predators. The gastropod Potamopyrgus antipoda‐rum was dominant in all communities; overall, gastropods (four species) contributed between 66 and 90% to total abundance. A few species showed a marked preference for certain communities. Seasonal changes in macroinvertebrate abundance and biomass are discussed and the results compared with those from other New Zealand lakes. Biomass data for all communities and the extent of the oscillations in biomass between years are consistent with the designation of mesotrophic status for Lake Alexandrina.