DETRITUS ABUNDANCE AND BENTHIC INVERTEBRATE CATCH IN ARTIFICIAL SUBSTRATE SAMPLES FROM MOUNTAIN STREAMS¹

Abstract

Artificial substrates were designed using rock filled polyethylene bags which were perforated with holes. The substrates trapped waterborne sediment and detritus which enhanced microhabitat complexity. Colonization was compared in side‐by‐side tests with multiple plate samplers in mountain streams ranging from second to seventh order. After 41 days the bag samples contained more sediment and detritus and more animals than did multiple plates. Plastic bags exceeded multiple plate samples by a factor of nearly 8 for individuals and 1.5 for taxa expressed as numbers/sampler. Although detritus amounts differed significantly between samplers, catch composition was similar in habitat preference and functional groups. Most taxa were “lotic erosional” or “lotic erosional‐depositional” detritivores. The plastic bags better represented the streambed fauna judged by their greater similarity to dip net samples. Bag samplers had 4.5 × the colonization area of multiple plates, hence would be expected to support more species. Catch/m2 of colonization area was not significantly different between samplers. Functionally the plastic bags act as detritus retention devices, offering a diverse, highly dynamic microhabitat for colonization. Results are interpretable in terms of research on microdistribution of stream benthos and the river continuum model. This study supports the conclusion that stream benthos abundance and diversity are related to the amount of detritus. Maximum diversity and numbers of individuals occurred in samples from third and fourth order streams. Grazers reached peak abundances in the same streams where the continuum model predicts P>R Shredders reached maximum abundances in third and fourth order streams where the riparian canopy was greatest. Predator abundance changed little with stream size. Although bag samples required more sorting time, the samplers are catch effective, inexpensive, and adaptable.

Effects of volcanic ash on the benthic environment of a mountain stream, northern Idaho

“…Slack, Tilley, and Hahn (1982) found invertebrate catch may decrease at high detritus loads; a similar phenomenon may have influenced invertebrate densities in this experiment. Peckarsky and Dodson (1980) and Stauffer and others (1976) noted predators colonizing artificial substrates may strongly influence species structure and may retard colonization by other species.…”

“…Slack, Tilley, and Hahn (1982) noted similar abundances of detritovores on artificial substrates (multiple plates, 89 percent; rockfilled perforated plastic bags, 85 percent) and in dip-net (73 percent) collections from the East Fork Salmon River, Idaho, drainage.…”

Analysis of biological data collected in the Bull Run Watershed, Portland, Oregon, 1978 to 1983

“…Changes In diversity or In benthlc-lnvertebrate-assoclatlon patterns from the background data may be a measure of the extent of management activity or may be due to a combination of natural or climatic change and the activity. Previous studies by Stauffer and others (1976), others (1982), andRabenl andMinshall (1977), have shown that stream benthic communities respond to increased levels of suspended sediment, silt, and organic matter in streams.…”

“…Stauffer and others (1976), in a field study in the Roanoke River, Virginia, found that a gradual silting of artificial substrates with time was accompanied by an increase in numbers of dlpterans and a decrease in numbers of tricopterans (caddis flies), plecopterans (stonefIies), and coleopterans (beetles). Slack and others (1982) related stream benthos abundance and diversity on artificial substrates to the amount of organic detritus in a Salmon River, Idaho study. Rabenl and Minshall (1977) found, in field experiments with artificial substrates In Idaho streams, that a light coating of silt reduced some species' populations, but that the substrate-detritus interaction was also a major influence on insect microdistribution.…”

COMPARISON OF FOUR ARTIFICIAL SUBSTRATES AND THE PONAR GRAB FOR BENTHIC INVERTEBRATE COLLECTION1

“…(2) catches of different types of artificial substrates in simultaneous side-by-side exposures (e.g., Ferreira, 1975;Newlon and Rabe, 1977;Slack, et al, 1982), or (3) degree of replicate variability (e.g., Dickson, et al, 1971;Cover and Harrel, 1978). The first two approaches were emphasized in the present investigation.…”