Composition and temporal changes in macroinvertebrate communities of intermittent streams in Hawke's Bay, New Zealand

Abstract

Macroinvertebrate communities in three stony‐bottomed intermittent headwater streams in central Hawke's Bay, New Zealand, were sampled once per month (on average) for 11 months from autumn 2005 to summer 2006, and compared with communities in three perennial streams and three intermittent streams with perennial headwaters. Among the intermittent headwater sites, 95 taxa were found, with Oligochaeta, Copepoda, Chironomidae, and Ostracoda occurring in greatest abundance. Eight mayfly, 6 stonefly and 16 caddisfly species were found. Macroinvertebrate abundance at intermittent headwater sites was equal to nearby perennial sites, but taxon richness per sample was lower. Community composition changed progressively during the autumn‐to‐spring flow period (March‐November 2005) at one intermittent headwater site, but at the other two sites a directional change was not evident, probably because stream flow stopped briefly several times during the flow period. Most of the taxa collected in riffles during the flow period were also in disconnected pools after flow stopped in summer (January 2006), but some taxa were absent and the disconnected pools contained several additional species. The disconnected pools in January had higher macroinvertebrate density and richness than connected pools during the flow period. At intermittent sites with perennial headwaters, taxon richness and EFT (Ephemeroptera, Plecoptera, and Trichoptera) richness were intermediate between intermittent headwater sites and perennial streams. Two weeks after flow began, the intermittent sites with perennial headwaters showed much higher EPT abundance and richness than the intermittent headwater sites, but after 8 weeks the proportional difference was less.