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 >60% 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.