Long-term effects of resource limitation on stream invertebrate drift

Abstract

We examined the effects of resource limitation on stream invertebrate drift by reducing inputs of terrestrial detritus to a headwater stream in western North Carolina. In the treatment stream, leaf-litter was excluded for 6 years (September 1993 – August 1999), small woody debris was removed for 2 years (September 1996 – August 1998), and large and small woody debris was removed for 1 year (September 1998 – August 1999). Invertebrate abundance in the drift was significantly lower in the treatment stream during the study, but total biomass of invertebrate drift was similar. Although drift densities were higher in the reference stream, a greater proportion of total benthic invertebrate abundance and biomass drifted out of the treatment stream. The proportion of shredder, gatherer, and predator benthic abundance in the drift was significantly greater in the treatment stream, but scraper proportions were higher in the reference stream and filterer proportions were similar for the two streams. Combined data from both streams indicated that the relationship between drift densities and benthic abundance was positive and significant. Our results demonstrate that bottom-up effects of resource reduction in a detrital-based stream influence invertebrate drift, increasing the proportion of the benthic community emigrating from the detritus-poor stream.

Aquatic and terrestrial invertebrate drift in southern Appalachian Mountain streams: implications for trout food resources

“…Seasonal inputs of terrestrial invertebrates and aquatic larval drift rates generally followed our predictions. High aquatic larval drift rates in spring and early summer is typical of southern temperate streams (Stoneburner & Smock, 1979;O'Hop & Wallace, 1983;Benke et al, 1991) and drift rates have been positively correlated with benthic invertebrate densities (Pearson & Kramer 1972, Benke et al, 1991Sagar & Glova, 1992;Siler, Wallace & Eggert, 2001) and emergence (Waters, 1972). It may be assumed that emerged aquatic adults are a loss of energy from the stream, but this study and others (Mason & Macdonald, 1982;Bridcut, 2000) demonstrate emerged aquatic adults can be an important potential energy source in drift (Table 3).…”

“…The higher aquatic larval drift in spring and early summer may also be a result of resource limitation for benthos as litter inputs from the previous autumn become exhausted. Siler et al (2001) found higher proportions of benthic organisms drifting in a treatment stream with detritus removed. However, reduced litter resources alone probably cannot explain all the increased aquatic larval drift because some important species in the drift (e.g.…”

Causes and consequences of invertebrate drift in running waters: from individuals to populations and trophic fluxes

“…Density dependence may also increase drift entry owing to increased competition for space (Corkum 1978;Hildrew and Townsend 1980;Kohler 1992) or resource limitation (Dimond 1967;Richardson 1991;Fonseca and Hart 1996;Rowe and Richardson 2001;Siler et al 2001). While mostly studied in isolation, these factors interact to influence active drift.…”

“…Consequently, density-dependent thresholds that are demonstrable experimentally are inevitably context-specific and therefore likely to be poorly transferrable between streams or lack consistency in synoptic surveys. Studies that manipulated food resources directly have more consistently identified densitydependent thresholds, generally finding decreased drift entry following increases in resources (Hildebrand 1974;Kohler 1985;Richardson 1991;Siler et al 2001;Hammock and Wetzel 2013). Likewise, experimental increases of herbivore densities leading to depleted periphyton also elevated drift (Hillebrand 2005).…”

Stable isotopes identify dispersal patterns of stonefly populations living along stream corridors

“…In more disturbed areas with fragmented forest canopies, wind may be more important in determining dispersal distances and directions (see Briers et al, 2004). Interestingly, upstream flight and oviposition by fecund females of species with little downstream drift as larvae (Saltveit, Haug & Brittain, 2001;Siler, Wallace & Eggert, 2001) could result in individuals accumulating in the upstream reaches, suggesting that our relatively stable headwater stream populations (Macneale, 2003) may be regulated by density dependent factors (Anholt, 1995;Travis, Murrell & Dytham, 1999;Kerans, Chesson & Stein, 2000;Kopp, Jeschke & Gabriel, 2001;Hildrew et al, 2004; but see Humphries, 2002). We speculate that upstream oviposition is adaptive, because those reaches are predictably of higher quality (e.g.…”