Longitudinal changes in biota along four New Zealand streams: Declines and improvements in stream health related to land use

  • Niyogi D
  • Koren M
  • Arbuckle C
 et al. 
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Abstract

We studied four streams in southern New Zealand in 2002 to document
downstream changes in water quality, habitat, and stream biota in
relation to land use. Two streams were in catchments that had increasing
intensity of agricultural development downstream from relatively
pristine headwaters. A third stream had the most intense land use in the
headwaters and a riparian corridor of regeneratinga native forest along
its middle reaches. A fourth stream had low intensity pasturing in its
lower reaches, but also downstream increases in sedimentation from
natural and historic mining sources. Four to six sites were sampled
along each stream. Pastoral land cover in catchments was positively
related to nutrient concentrations and fine sediment cover in the
streams. At the most agricultural sites, dissolved inorganic nitrogen
reached concentrations of 2 mg/litre, and fine sediment covered 33% of
the stream bottom. Several biotic indices for invertebrates, including
the Macroinvertebrate Community Index (MCI), were lower at the
agricultural sites, which had MCI scores around 100. The indices were
negatively related to fine sediment cover. The site with the intact
riparian zone had declines in sedimentation downstream, which were
paralleled by increases in invertebrate richness and biotic indices. Our
findings support the notion that the restoration of riparian zones can
improve stream habitat and invertebrate health.

Author-supplied keywords

  • Land cover
  • Macroinvertebrates
  • Riparian
  • Sedimentation
  • Stream health
  • Streams

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Authors

  • Dev K. Niyogi

  • Mark Koren

  • Chris J. Arbuckle

  • Colin R. Townsend

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