Secondary production of chironomid communities in insecticide‐treated and untreated headwater streams

Abstract

SUMMARY. 1. Production of chironomid communities of three first order, Appalachian Mountain streams was estimated and the effects of an insecticide-induced disturbance on chironomid production was examined.2. Annual production of non-Tanypodinae chironomids in the streams during the first study year (no treatment) ranged from 1366 to 3636 mg m~2, while production of Tanypodinae chironomids ranged from 48 to 116 mg m~2. Production/biomass ratios ranged between 19 and 23 for non-Tanypodinae and from 6 to 7 for Tanypodinae chironomids.3. Insecticide applications resulted in significantly lower chironomid densities and biomass in the treated stream relative to the pretreatment year and reference stream. Annual production of non-Tanypodinae (703 mg m~2) and Tanypodinae (32 mg m~2) chironomids in the treated stream decreased by 64% and 67%, respectively, compared with the pretreatment year. In contrast, production of non-Tanypodinae (2084 mg m ) increased by 34% and production of Tanypodinae (96 mg m ) by 57% in the reference stream.

Contrasting response of stream detritivores to long-term nutrient enrichment

“…Headwater streams at Coweeta are extremely heterotrophic, and allochthonous inputs of detritus provide Ͼ90% of the energy base for microbial and invertebrate production Hall et al 2000). The streams used in this study have very similar physical and chemical characteristics (i.e., watershed area, slope, elevation, discharge, and temperature) (see Lugthart and Wallace [1992] for more detail) but differ (since July 2000) in their concentrations of dissolved N and P as a result of our experimental nutrient enrichment of C54. Natural concentrations of inorganic N and P in these streams are very low ((NO 3 …”

“…Organic material in the smaller size fraction (from 250 m to 1 mm) was subsampled (1/8 to 1/64 of whole samples) (Waters 1969), and animals were removed from subsamples with a dissecting microscope at ϫ15 magnification. The amounts of leaf litter and FPOM (i.e., food resources) in each sample were also quantified according to Lugthart and Wallace (1992). Although these food resource data are used in calculations presented below, the detailed methodology and time-series results are presented elsewhere (Cross 2004).…”

“…Each month, samples were taken in two distinct stream habitats (i.e., mixed substrate [cobble, pebble, gravel, sand, silt] and bedrock outcrops, following Lugthart and Wallace [1992]). …”

“…(Plecoptera: Peltoperlidae) larvae were chosen as representative K-selected taxa (i.e., slow growth and low reproductive rates). These stoneflies exhibit slow growth rates (e.g., O'Hop et al 1984;Johnson et al 2003), have relatively long larval life spans (ϳ540 d), and account for a significant proportion of the abundance and biomass of the study stream communities (Lugthart and Wallace 1992;Wallace et al 1999; this study). Tallaperla spp.…”

Secondary production as part of bioenergetic theory—contributions from freshwater benthic science

“…Furthermore, in many cases the production response might be different than, say, the biomass response. For example, Bruce Wallace and colleagues (Lugthart et al, 1990;Lugthart and Wallace, 1992;Chung et al, 1993;Whiles and Wallace, 1995) examined effects of the pesticide Table 4 of Benke and Wallace (1997 Benke and Wallace (1997), with permission methoxychlor on species and functional-group production and found this gave a more complete picture of disturbance and recovery than abundance or diversity. But there are several topics that cannot even be addressed with only density or biomass, such as in the quantification of food webs as described above.…”