Distribution and Dispersal of Aquatic Invertebrates in the Waitomo Stream

Abstract

A survey of the distribution and dispersal of aquatic macro invertebrates was carried out in the Waitomo caves catchment, located South of Hamilton, New Zealand. Eight sites were selected along the Waitomo stream. The sites represented a longitudinal gradient that flowed from the native forested, headwaters to pasture, then into native forest remnants, before flowing into pasture and onto the glowworm caves at the bottom of the catchment. It was found that both the benthic and drift fauna underwent a change in community composition along the length of the catchment. Initially, the diversity decreased and invertebrate abundance increased as the stream flowed from forest to pasture. There was also a change in community composition from 'sensitive' taxa e.g. Plecoptera and Archichauliodes diversus to more 'enrichment' tolerant eg chironomids and Austrosimulium sp. However the biota of the stream was 'restored' upon the stream flowing into a forest remnant, the Aranui reserve. There was also a seasonal reduction in drift of invertebrates from the Waitomo stream over winter. Additionally significant differences were found for many drift taxa between forest and pasture sites. Suggestions as to future research topics and recommendation for restoration of the catchment streams and biota were made.