New Zealand Journal of Marine and Freshwater Research abstracts
Invertebrate community dynamics in soft-bottomed streams of northern
New Zealand: a spatio-temporal hierarchy
Kevin J. Collier
National Institute of Water and Atmospheric
Research Limited
P.O. Box 11 115
Hamilton, New Zealand
email: k.collier@niwa.co.nz
Abstract Environmental and macroinvertebrate data collected
across a range of spatial and temporal scales are synthesised to investigate
factors influencing invertebrate community structure and composition in soft-bottomed
streams (≥50% of streambed substrata in sand-silt) of northern New Zealand.
A total of 75 macroinvertebrate taxa was recorded from sand-silt substrata
at 13 Waikato sites (54 taxa) and 8 Northland sites (53 taxa) where faunas
were dominated by Ephemeroptera, Trichoptera, Chironomidae, and Mollusca.
Differences in upstream geology, climate, land cover, and hydrology, potentially
coupled with biogeographic factors, appeared to contribute to a regional
separation in invertebrate community structure (taxa presence-absence). In
the Waikato, site-specific conditions had a stronger influence on community
structure and composition than substratum (sand-silt, macrophyte or wood).
However, within sites, substratum type had strong effects on macroinvertebrate
communities that persisted through time. On macrophytes, faunal composition
varied considerably over time and among sampling patches, reflecting phenological
shifts in the species and biomass of plants present, successional changes
in invertebrate taxa, and micro-scale variations in water velocity. Macrophytes
can provide important sites for energy transfer, although pathways leading
to invertebrate nutrition appeared site-specific and temporally variable.
Collectively, these data point to a spatio-temporal hierarchy of factors
that influence invertebrate community structure and composition in soft-bottomed
streams. The major differences compared with stony streams occur at the micro-
to meso-scales, with greater significance of non-benthic substrata (wood
and macrophytes) as invertebrate habitat and sites of energy transfer in
soft-bottomed streams, and the temporally variable influence of changing
macrophyte biomass on local hydraulic conditions and water quality. To help
reduce the effects of high spatial and temporal variability and obtain a
representative picture of reach-scale conditions for stream health assessment
purposes, long-term invertebrate monitoring of soft-bottomed streams should
incorporate all velocity and substrata conditions, and aim to collect samples
at a consistent stage of the macrophyte phenological cycle.
Keywords sand-silt; macrophyte; wood; lowland; inorganic
substrata; artificial substrata; monitoring; biodiversity
M03020; Online publication date 15 March 2004; Received 2 May 2003; accepted
10 October 2003
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38:
1-18
0028-8330/04/3801-0001 © The Royal Society of New Zealand 2004
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