Biological changes along the continuum of an agricultural stream: influence of a small terrestrial preserve and use of adult caddisflies in biomonitoring

Abstract

We monitored benthic macroinvertebrates and adult caddisflies along an agricultural stream continuum upstream, within, and downstream of a small forested preserve. The habitat upstream of all sites was 460% disturbed by agricultural activities. The percentage of riparian disturbance was markedly lower adjacent to the sites inside the preserve than those outside. Water physicochemical factors did not exhibit clear changes among sites, except for nitrate concentration, which was highest upstream of the preserve. Biological diversity of adult caddisflies was significantly higher within the preserve. Biological diversity of benthic invertebrates exhibited similar results except for non-significance between the upstream and preserve sites. Pollution tolerance and percentage of filtering collector metrics were unchanged among sites for both assemblages. The percentage of adult caddisflies in the shredder functional group increased significantly within the preserve but remained small relative to that of pollution-tolerant filtering collectors. The small terrestrial preserve promoted a three-fold increase in species diversity, even without corresponding changes in water quality or trophic structure. Such an increase, however, may not be as detectable with traditional benthic biomonitoring techniques due to the difficulties of sampling benthic microhabitats representatively and identifying specimens to the species level.

Abrupt biological discontinuity in a small Michigan (USA) stream due to historical riparian canopy loss

“…Such concentrations accumulate naturally in larger rivers or anthropogenically in disturbed streams (Allan 2004). Michigan streams disturbed by agriculture have levels two to three times that of Fairbanks Creek (Castillo et al 2000;Houghton et al 2011a). Our low specific conductance values, as well as the lack of difference in both variables between study sites, suggested no important differences in natural or anthropogenic sediment input throughout the continuum of the stream.…”

“…In the case of adult caddisflies, the lack of response from the scraper functional group has been noted in previous studies (Houghton 2006(Houghton , 2007. While scraper taxonomic richness may be proportional within the Trichoptera (e.g., Wiggins 1996), scraper specimens are not abundant in blacklight samples relative to filtering collectors or shredders, or in benthic samples compared to scraper taxa of other orders (Houghton 2011a). Thus, the metric may not be abundant enough to be informative of stream conditions when using Trichoptera exclusively.…”

“…Recent studies of agricultural watersheds, however, have noted positive correlations between the amount of intact riparian vegetation and the biological diversity in the adjacent streams (Rios and Bailey 2006;Urban et al 2006). More specifically, Houghton et al (2011a) found that sites in a southern Michigan agricultural stream protected by riparian canopy had three times the number of adult caddisfly species as sites without canopy, even though physicochemistry remained unchanged and typical of agricultural streams.…”

Influence of a forest preserve on aquatic macroinvertebrates, habitat quality, and water quality in an urban stream

“…Contrarily, diversity and density of benthic communities recovered to levels in control streams without corresponding improvements in water quality. Houghton et al (2011) monitored benthic macroinvertebrates and adult caddisflies along an agricultural stream upstream, within, and downstream of a small forested preserve in Michigan. They found that the diversity of adult caddisflies was significantly higher within the preserve, with a three-fold increase in species diversity despite no clear improvements in water quality.…”

Nocturnal flight periodicity of the caddisflies (Insecta: Trichoptera) in a large Michigan river

“…Due to the importance of caddisflies in aquatic ecosystems (Mackay and Wiggins 1979) and their utility in biological water quality monitoring (Barbour et al 1999;Dohet 2002;Houghton 2007;Houghton et al 2011a), it is imperative that field samples accurately represent caddisfly populations (Figure 1). Studies of adult caddisflies usually rely on ultraviolet light traps to obtain such samples.…”