Patch- and reach-scale dynamics of a macrophyte-invertebrate system in a New Zealand lowland stream |
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Authors: | Collier Kevin J Champion Paul D Croker Glenys F |
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Institution: | (1) National Institute of Water and Atmospheric Research Ltd, P.O. Box 11-115, Hamilton, New Zealand |
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Abstract: | Abundant growths of macrophytes are a common feature of streams in open lowland areas of New Zealand during summer, but the
values of these to aquatic biota are poorly understood. We studied the temporal dynamics of, and associations amongst, elements
of a macrophyte-invertebrate system to provide an improved information base for lowland stream management. The biomass of
macrophytes increased significantly over the four quarterly sampling occasions from 43.8 g m-2 in June to 370.8 g m-2 in March; biomass was dominated by Egeria densa on all dates, except in December when Potamogeton crispus was dominant. We
did not detect strong associations between epiphyton biomass and invertebrate abundance in our study, but this may reflect
the fact that we sampled loosely-adhering epiphyton on young, surface-reaching shoots whereas invertebrates were collected
from macrophytes growing through the water column. Density of some invertebrate species per gram dry weight of plant material
varied by macrophyte type, with the chironomids Tanytarsus vespertinus and Naonella forsythi displaying positive correlations
with Egeria and Potamogeton biomass, respectively. The shrimp Paratya curvirostris accounted for 50% of phytophilous invertebrate
biomass, with Chironomidae the only other group to comprise more than 9%. Abundance of total phytophilous invertebrates displayed
a positive linear relationship with macrophyte biomass in a sample (0.1 m2), and a humped relationship with species richness, such that highest numbers of taxa occurred at macrophyte biomass levels
around 400 g dw m-2. Our study suggests that intermediate macrophyte biomass levels are likely to enhance macroinvertebrate biodiversity in sandy-bottomed
lowland streams.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | lowland streams macrophytes Egeria Potamogeton epiphyton phytophilous invertebrates New Zealand |
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