MACROINVERTEBRATE DISTRIBUTION IN THE LITTORAL-ZONE OF LAKE COLERIDGE, SOUTH-ISLAND, NEW-ZEALAND - EFFECTS OF HABITAT STABILITY, WIND EXPOSURE, AND MACROPHYTES

The macroinvertebrate community was surveyed at eight littoral zone si tes in Lake Coleridge, New Zealand. Sites covered a range of condition s including exposure to prevailing winds, shore-line topography, and p roximity to river inputs-which are a major source of suspended sedimen t to the lake. The littoral zone contained an abundant and diverse mac roinvertebrate fauna (47 taxa). Three communities were identified: a s hallow-water community inhabiting the wave-break zone, dominated by Tr ichoptera and chironomid larvae; a middle-zone community associated wi th macrophyte beds, with high macroinvertebrate abundance and dominate d by gastropods and oligochaetes; and a community in fine sediments be low the macrophytes dominated by oligochaetes. The depth distribution of these communities was related to substrate, macrophyte abundance, a nd shore-line profile. Superimposed on this pattern were the effects o f hillside slope and exposure to prevailing north-west winds. Greatest abundance was associated with macrophytes on stable shores at 4-7.5 m depth, i.e., below the effective wavebase depth. Sediment deposition had only a localised direct effect close to where river water enters t he lake. Indirect effects were mediated through the effects of suspend ed solids on water clarity, bottom limits, and production of macrophyt es and periphyton. Estimates of the proportion of littoral macroinvert ebrate biomass to whole-lake zooplankton biomass was 10:1 and for prod uction was 1.3:1, indicating the potential importance of the littoral zone to whole-lake production.