Report: TR 2011/25
Author: KJ Collier, MP Hamer, MW Davenport
Macroinvertebrates were monitored over 2006-07 using artificial multiplate samplers at six sites on the Waikato River (Huka Falls, Ohakuri, Narrows, Horotiu, Ngaruawahia and Rangiriri), repeating a survey conducted in 1980-82.
The data provide:
In 2006-07, the macroinvertebrate community colonising substrates at these sites was dominated by mollusca (primarily the snail Potamopyrgus antipodarum) in the upper river (Huka and Ohakuri sites) and by crustacea (primarily the amphipod Paracalliope fluviatilis) in the lower river. The use of wood versus perspex substrates did not significantly influence the composition or diversity of macroinvertebrate communities but did affect the abundance of some taxa, indicating that comparisons of composition and diversity can be made between substrate types.
Diversity of the macroinvertebrate community in 2006-07 tended to increase with distance downstream, reaching a peak at the Ngaruawahia site before declining at the Rangiriri site. These longitudinal changes likely reflect downstream patterns in water quality, shore-zone habitat diversity and flow variability within the river.
Downstream patterns of diversity detected in 2006-07 corresponded to those reported by Davenport (1982), and were similar for taxonomic richness although more taxa were collected overall in 2006-07. There appeared to have been a change in macroinvertebrate community composition (excluding oligochaete worms) from the 1980-82 study, with a shift in dominance from chironomid larvae to snails in the upper river in 2006-07, and a shift from dominance of snails to crustaceans in the lower river.
|3.1.1||Deployment and retrieval||2|
|3.2.1||Deployment and retrieval||2|
|4.1.1||Site and seasonal differences||5|
|4.1.2||Sampler effects and study comparisons||8|
|4.2.1||Site and seasonal differences||10|
|4.2.2||Sampler effects and study comparison||11|
|5.1||Spatial and temporal patterns in 2006-07||17|
|5.2||Sampler effects and study comparison||17|
|Appendix 1 - Water temperatures recorded at five sites||23|
|Appendix 2 - Flow records for 5 Waikato River locations||24|