Temporal Changes in the Macroinvertebrate Fauna of Two Glacial Lakes, Cootapatamba and Albina, Snowy Mountains, New South Wales

Abstract

Before 2003, unique assemblages of aquatic invertebrates in Lake Cootapatamba and Lake Albina lived in a fishless environment. A sequence of events in 2003 following a large-scale bushfire in the area allowed the native Mountain Galaxias Galaxias olidus to enter Lake Cootapatamba. This study determines the extent of any temporal changes in the invertebrate assemblages of each lake and whether the introduction of fish into Lake Cootapatamba affected these assemblages. The littoral and benthic fauna of both lakes were found to have changed since the earliest studies of these lakes in 1997/1998 and 1976, respectively. In particular, there has been a large decrease in the abundance of the isopod Metaphreatoicus australis and planarians, and the gastropod Glacidorbis hedleyi and amphipod Neoniphargus sp. have apparently disappeared. The effect is greatest in the benthos and in Lake Cootapatamba, so while fish seemed to have affected some invertebrates in some habitats, other factors may be acting. Sometime since 1976, the exotic worm Lumbriculus variegatus arrived into Lake Albina. Shifts in the representation of other taxa, such as ephemeropterans, plecopterans, tricopterans, dipterans and coleopterans, are thought to reflect natural year-to-year fluctuations but more data are needed.