Effects of overhead canopy on macroinvertebrate production in a Utah stream

Abstract

I. Macroinvertebrate abundance and production were compared between an open and shaded site of a stream in the Wasatch Mountains, Utah. Mean biomass was significantly higher at the open site for midges (Chironomidae), 4.6x; Baetis hicaudatus, 5.7x; Baetis tricaudatus, 2.3x; Drunella coloradensis, 12x and Cinygmula sp., L6x.Abundance of most other macroinvertebrates (except black flies; Simuliidae) was also greater at the open site, but differences were not significant. Black fly biomass was 1.7x greater at the shaded site.2. Seasonal production, estimated by the size-frequency and instantaneous growth rate methods, was greater at the open site than the shaded site for most taxa (except black flies) and reflected differences in standing crops between the sites rather than differences in rate of growth. Excluding black flies, production at the open site was twice as high as at the shaded site.3. The greater abundance and production of most invertebrate taxa at the open site is probably associated with either higher quality food (algae and algal detritus), or a phototactic attraction to sunlit areas.4. Sampling of large cobbles was an efficient method of sampling all taxa except Cinygmula sp. which was more abundant on smaller substrate particles.

Effects of riparian willow trees(Salix fragilis)on macroinvertebrate densities in two small Central Otago, New Zealand, streams

“…This result has been confirmed elsewhere (Hornick et al 1981;Keithan & Lowe 1985;Hill & Harvey 1990). It has been suggested that riparian vegetation can thus indirectly reduce secondary productivity and invertebrate densities (Allen 1951;Hopkins 1976;O'Hop et al 1984;Behmer & Hawkins 1986). We found that concentrations of chlorophyll a, SSOL and FPOM were similar at open and shaded sites, a result similar to that of Feminella et al (1989).…”

“…This effect was observed across nearly all functional feeding groups in pools and riffles of both streams in all seasons. Similar effects of riparian trees on stream invertebrate abundance have been reported elsewhere in New Zealand (Allen 1951;Hopkins 1976;Graynoth 1979;Suren 1992), and overseas (Hughes 1966;Hawkins et al 1982;Behmer & Hawkins 1986). Two major hypotheses have been proposed to account for such results that they are a food chain effect reflecting lower primary production due to shading by trees, and/or an effect of substrate size.…”

“…The filterer Austrosimulium was, however, more abundant at willow sites in Heeney Creek. Members of this genus have been noted to be more abundant in shaded sites by other authors (Towns 1981;Behmer & Hawkins 1986;Fuller et al 1986). It has been suggested that this is a result of more clean attachment sites being available in shaded areas (Chutter 1968;Casey & Ladle 1976).…”

Macroinvertebrate communities along a third-order Iberian stream

“…For example, some authors have noted that open reaches, as it is the case for site 7, support higher invertebrate abundance than canopied ones (e.g. Hopkins 1976, Hawkins et al 1982, Behmer & Hawkins 1986, Maridet et al 1998, which is attributed to higher food quality of periphyton than leaf detritus (Anderson & Cummins 1979). On the other hand, high faunal density at site 9 could be a consequence of the organic sewage from Guriezo which allows high densities of Chironomidae and Oligochaeta (Wiederholm 1984).…”

Prey availability and diet of juvenile brown trout (Salmo trutta) in relation to riparian willows (Salix‐spp.) in three New Zealand streams

“…Although riparian cover reduces stream temperatures and provides fish with overhead shelter from predators, some studies outside New Zealand have reported greater salmonid abundance in unshaded than in shaded streams (Hawkins et al 1983;Bisson & Seddell 1984;Behmer & Hawkins 1986). For cutthroat trout (Oncorhynchus clarki), prey availability and foraging efficiency were greater in unshaded than shaded streams (Wilzbach & Hall 1985), suggesting that cover may be less important than prey availability in determining habitat choice by fish.…”