The effect of the release of an artificial discharge of water on invertebrate drift in the R. Wye, Wales

Studies were conducted to determine the effects of experimental manipulations of discharge on invertebrate drift in two regulated rivers in northwestern Montana, USA. During these studies the discharge regime in the Flathead River was characterized by frequent flow fluctuations, while in the Kootenai River high discharge was maintained for much longer periods before flow was reduced to minimum discharge. The magnitude of the response of invertebrates to disturbance was different in the two rivers, in part because of the different frequencies of flow changes. Midstream invertebrate drift increased an order of magnitude during increasing discharges in the Flathead River but was not substantially increased during decreasing discharges. When the prior discharge regime had been sustained at high levels in the Kootenai River, invertebrate drift densities as high as 300000/100 m 3 were measured along the shoreline following reductions in discharge, both immediately after flow began to decrease and after dark on the same day. There was also more recolonization of shoreline areas and more stranding of insects following dewatering of nearshore regions when there had been sustained high discharge levels prior to the flow reduction. More insect stranding occurred during a faster rate of decrease in discharge (50000 to 100000 organisms m-2).

Section: Effects Of Flow Changes On Invertebrate Drift In the Flatheamentioning

confidence: 96%

Section: Effects Of Flow Changes On Invertebrate Drift In the Flatheamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of experimental flow regulation on invertebrate drift and stranding in the Flathead and Kootenai Rivers, Montana, USA

Perry

1986

“…Others have found that abundances remain the same (Irvine & Henriques, 1984;Kraft & Mundahl, 1984;Scullion & Sinton, 1983) or increase under fluctuating flow regimes as well-adapted taxa flourish in the absence of less well-adapted competitors and predators (Armitage, 1978;Novotny, 1985). Effects of flow fluctuations may also include higher invertebrate drift rates as changing discharge patterns influence current velocities, food resources and dissolved gases (Brooker & Hemsworth, 1978;Irvine & Henriques, 1984;Kraft & Mundahl, 1984;Minshall & Winger, 1968;Radford & Hartland-Rowe, 1971;Scullion & Sinton, 1983). Although Cummins (1973) established functional guilds for different aquatic invertebrate taxa 16 years ago, functional responses to flow variations have not been extensively investigated.…”

Section: Introductionmentioning

confidence: 99%

Effect of hydropower peaking flow fluctuations on community structure and feeding guilds of invertebrates colonizing artificial substrates in a large impounded river

Troelstrup

Hergenrader

1990

Artificial substrates were used to monitor the invertebrate communities below a power peaking impoundment and a flow re-regulating impoundment on the Missouri River on northeastern Nebraska, USA. Invertebrate communities on shallow samplers subjected to exposure from diel fluctuations in flow averaged 3 taxa per sampler and 91 organisms per square meter. In the absence of diel fluctuations, number of taxa per sampler increased to 12 and mean densities increased to 743 per square meter. Fluctuating discharges had no significant effect on numbers of taxa or densities on continually submerged artificial substrates. However, greater numbers of taxa and total densities were observed on deep (107 cm) versus shallow (30 cm) samplers below both impoundments.Polycentropodidae (Trichoptera), Chironomidae (Diptera) and Oligochaeta were observed to tolerate diel fluctuations and exposure below Fort Randall Dam while Hydropsychidae (Trichoptera) and Heptageniidae (Ephemeroptera) were extremely intolerant.Collector-gatherers and predator-engulfers were the predominant functional groups colonizing samplers below both impoundments. Higher numbers of collector-gatherers, collector-filterers and scrapers were observed from samplers in the absence of diel flow fluctuations.This study corroborates results from a number of other investigations, separated in space and time. Examined collectively, these studies provide the framework for understanding power peaking as a stress to benthic stream communities.

“…Chironomids make up a large part of many drift collections (Hynes, 1975 ;Davies, 1976;Dance & Hynes, 1979;Raddum, 1985;Perry & Perry, 1986). Many reports show that chironomid larvae exhibit little or no die1 variability in drift compared with groups such as the Ephemeroptera (Anderson, 1966;Hynes, 1970;Davies, 1976;Arm&age, 1977;Brooker & Hemsworth, 1978). Reisen & Prins (1972), Kroger (1974) and Chutter (1975) reported slight tendencies for die1 drift of chironomidae larvae, but Clifford (1972) found chironomid larvae drifting in significantly greater densities at night compared to day, although emerging chironomids drifted in significantly greater numbers during the day.…”

Section: Introductionmentioning

confidence: 99%

Diel drift of Chironomidae larvae in a pristine Idaho mountain stream

Tilley

1989

Simultaneous hourly net collections in a meadow and canyon reach of a mountain stream determined die1 and spatial abundances of drifting Chironomidae larvae. Sixty-one taxa were identified to the lowest practical level, 52 in the meadow and 41 in the canyon. Orthocladiinae was the most abundant subfamily with 32 taxa and a 24 h mean density of 294 individuals 100 m-3 (meadow) and 26 taxa and a mean of 648 individuals 100 m-3 (canyon). Chironominae was the second most abundant subfamily. Nonchironomid invertebrates at both sites and total Chironomidae larvae (meadow) were predominantly night-drifting.Parakiefferiella and Psectrocladius were day-drifting (meadow) whereas 8 other chironomid taxa (meadow) and 2 taxa (canyon) were night-drifting. All others were aperiodic or too rare to test periodicity, Stempellinella cf brevis Edwards exhibited catastrophic drift in the canyon only. The different drift patterns between sites is attributed to greater loss of streambed habitat in the canyon compared to the meadow as streamflow decreased. Consequent crowding of chironomid larvae in the canyon caused catastrophic drift or interfered with drift periodicty. This study adds to knowledge of Chironomidae drift and shows influences on drift of hydrologic and geomorphic conditions.