Keywords: stream invertebrates, ecosystem functions, water temperature
Climate change is suggested to affect alpine stream ecosystems and their ecological processes. Macroinverterbrate involvement in leaf litter breakdown may be affected by stream temperature fluctuations. This study was undertaken to determine whether temperature influenced leaf litter breakdown, macroinvertebrate activity and colonization.
Rate of leaf breakdown and macroinvertebrate colonisation were measured during autumn, winter and spring 2013 at 5 sites in the upper Snowy River catchment, NSW spanning an altitude range of 1100-2000m. Plucked and oven-dried leaves of snow gum (Eucalyptus pauciflora) were placed in fine (50µm) and coarse-mesh (5-6mm) nylon bags. These bags were incubated in riffle/run reaches over 5 and 10 weeks.
Data collected in autumn (March – May) indicate that Trichoptera larvae (Helicophidae, Conoesucidae, Hydrobiosiidae and Ecnomidae) appeared to effectively fragment leaf litter in coarse mesh bags, at and below tree-line sites, whilst above tree-line sites microbial leaching appear dominate. Rate of leaf break down in both bag types declined with altitude and increasing water temperature, but markedly in coarse-mesh bags. Macroinvertebrate colonisation on coarse-mesh leaf bags decreased with altitude; Trichoptera were common at and below tree line sites with Helicophidae, Conoesucidae, Hydrobiosiidae and Ecnomidae being dominant.
We will also present results of winter and spring monitoring.