Export of fine organic particles from headwater streams: Effects of season, extreme discharges, and invertebrate manipulation

Abstract

Export of fine particulate organic matter (FPOM) was measured from streams draining Catchments 53, 54, and 55 (C53, C54, and C55) at the Coweeta Hydrologic Laboratory for 5 yr, encompassing the driest and wettest years of the past 55-yr record. Macroinvertebrate populations in C54 were reduced for 3 yr by seasonal treatments with insecticide. During pesticide treatment, FPOM concentrations decreased abruptly in C54, remained well below those of reference streams for the 3-yr treatment period, and then increased during the 1st yr of recovery. Macroinvertebrate reduction resulted in an estimated 170-200 kg loss in FPOM export during the 3 yr of treatment and 1 st yr of recovery. Annual export of FPOM was strongly related to annual discharge, but the impact of biotic manipulation on FPOM export in C54 was at least as great as that produced by extreme high and low discharges. FPOM export during sampling intervals was directly related to maximum discharge during the intervals. Treatment of CS4 significantly reduced FPOM export per unit maximum discharge. Seasonal relationships between FPOM export and maximum discharge indicated more export per unit maximum discharge in summer in reference streams and C54 in untreated years. In contrast, during treatment years of C54, export per unit maximum discharge was lowest in summer. FPOM concentrations measured during storms showed increasing concentrations with increasing discharge in all streams, however, much more FPOM was suspended in the reference streams than in C54. Thus, macroinvertebrate reduction altered the magnitude of FPOM export during storms, the seasonal pattern of export, and the annual export of FPOM.

Beyond the urban stream syndrome: organic matter budget for diagnostics and restoration of an impaired urban river

“…FPOM resembled a mixture of terrestrial and autochthonous sources, with autochthonous sources attributed to FPOM released from Utah Lake, and high rates of primary production in the upper Jordan River. This provides evidence of multiple pathways of FPOM generation in addition to CPOM being broken down chemically and physically to FPOM and further into DOC (Cummins 1974;Wallace et al 1991). It also supports the findings of Imberger et al (2014) where FPOM in urban Australian streams had isotope values and C:N ratios similar to that of in-stream primary producers.…”

The influence of flow and season upon leaf-litter breakdown in monsoonal Hong Kong streams

“…Litter breakdown rate can affect the availability and temporal stability of allochthonous resources in the streams, as well as the downstream export of fine particulate organic material (FPOM) which can be consumed by collectors (e.g. Wallace et al, 1991). In this study, litter breakdown was slowed downstream of water extraction points during the wet season.…”

Temporal dynamics of seston: A recurring nighttime peak and seasonal shifts in composition in a stream ecosystem

“…The diel pattern appears to be biologically driven because rising water temperatures, and subsequent increases in organism activity (Wallace et al 1991), resulted in greater nighttime suspension (Fig. 4).…”

“…2a,b). The peaks, in spring and summer, can be explained by stream organism activity, such as feeding and bioturbation, because maximum macroinvertebrate activity and biomass occur during these warm seasons (Wallace et al 1991). Bioturbation likely helps to control seasonal patterns because the organic content of seston decreased during the warm months (Fig.…”