New Zealand Journal of Marine and Freshwater Research abstracts
New Zealand's National River Water Quality Network: long-term trends in
macroinvertebrate communities
MIKE R. SCARSBROOK
IAN K. G. BOOTHROYD
JOHN M. QUINN
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 11 115
Hamilton, New Zealand
email: m.scarsbrook@niwa.cri.nz
Abstract Aquatic macroinvertebrates were sampled annually at
66 sites of the National Rivers Water Quality Network (NRWQN) from 1989 to
1996. At each site, temporal trends in number of taxa, total abundance,
Macroinvertebrate Community Index (MCI), the quantitative version of MCI
(QMCI), number and percent of Ephemeroptera, Plecoptera, and Trichoptera,
Shannon's Diversity Index (H'), Jaccard's similarity index, and Bray-Curtis
similarity index were analysed using non-parametric Spearman rank correlations.
Sixty-nine significant (
P < 0.10) trends were found out of a total of
594 analyses. There were 27 positive trends (i.e., showing increases in
invertebrate community measures through time) and 42 negative. MCI and
Jaccard's Index exhibited the greatest number of trends (13), and Shannon's
diversity the least (1). A number of sites (8) showed a significant trend of
decreasing taxa richness, particularly pollution-sensitive Ephemeroptera,
Plecoptera, and Trichoptera (EPT). However, MCI values, which are strongly
linked to numbers of EPT taxa, had the highest number of positive trends (12),
with only one site showing a negative trend. Overall the trend in MCI scores
was particularly strong for "baseline" sites, and less so for "impact" sites.
The percentage of baseline sites with MCI scores indicative of clean water
increased from 3% in 1989 to 46% in 1996. At two sites trends in MCI and number
of EPT taxa gave conflicting signals. Regional patterns were apparent, with
trends in MCI in particular being more common in the east and lower half of the
North Island, and the lower half of the South Island than in other areas.
Observed trends in some macroinvertebrate community measures, particularly MCI,
coincided with reported general improvements in water quality.
Keywords macroinvertebrates; community composition; biotic
indices; rivers; water quality; trend assessment
M98050
Received 27 July 1998; accepted 20 August 1999
PDF file of entire paper: medium quality (1348K); (scanned from paper original: notes about this process)
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