New Zealand Journal of Marine and Freshwater Research abstracts

---

Magnitude of effects of substrate particle size, recent flooding, and catchment development on benthic invertebrates in 88 New Zealand rivers

JOHNM.QUINN CHRISTOPHER W. HICKEY

Water Quality Centre
DSIR Marine and Freshwater
Department of Scientific and Industrial Research
P. O. Box 11115, Hamilton, New Zealand

Abstract Data from runs in 88 rivers throughout New Zealand, and a comparison between areas of contrasting substrate size in the Mohaka River, were used to investigate the influences of physical factors on benthic macroinvertebrates. Substrate size preferences were more clearly demonstrated by the comparison of different substrates in the Mohaka River than between runs in the 88 rivers. Taxonomic richness and densities of most collector-browsers were highest on small cobble-boulder substrates. However, filterers and a facultative shredder showed strong preferences for large cobbles and boulders and an undescribed orthoclad showed a strong preference for sand. Among the 80 stony-bedded rivers, those exposed to maximum flows of < 5X, 5-10X, and 10-20x their median flow during 6 weeks before sampling had similar taxonomic richness, densities, and biomass. In contrast, rivers that had experienced maximum flows of > 20X their median flows had markedly lower median taxonomic richness, density, and biomass than less-flooded rivers. Among the 51 stony, "non-flooded" sites, those with 1-30% of their catchments developed to improved pasture had similar community composition to, but higher total biomass than those with < 1% development. However, sites with > 30% catchment development (median = 70%) differed significantly (F < 0.1) from those with less developed catchments: the former had lower diversity, taxonomic richness, numbers of ephemeropteran, plecopteran, and trichopteran species (EPT), and had lower biomass of species that are sensitive to changes in water quality related to eutrophication; they had higher biomass of species that are associated with an abundance of periphyton. Trout biomass was also c. 3-fold lower than in the rivers with lesser-developed (1-30%) catchments.

Keywords benthic invertebrates; aquatic insects; water quality; surveys; sediments; floods; enrichment; periphyton; land use; agriculture

New Zealand Journal of Marine and Freshwater Research, 1990, Vol. 24:411-427 Crown copyright 1990
Received 30 March 1990; accepted 7 June 1990

PDF file of entire paper: medium quality (2007K); (scanned from paper original: notes about this process)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page