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Ephemeroptera: Heptageniidae of Gunnison County, Colorado

Epeorus longimanus
Slate Brown Dun, Dark Gordon Quill, Spotted Epeorus

(Eaton) 1885

Updated 20 Feb 2024
TSN 100637

Locations Collected

Beaver Creek, East Elk Creek, Gunnison River, Red Creek, Steuben Creek, Soap Creek and West Elk Creek (Argyle and Edmunds, 1962). Also East River, Avery Creek and Coal Creek.

Good Links

On this website:
Introduction to Epeorus

Notice the gills meet at the midline, similar to Rhithrogena





Other Websites:
Photos, Map, Museum specimens, DNA - Barcodinglife.org


References

Allan,JD 1975a. The distributional ecology and diversity of benthic insects in Cement Creek, Colorado. Ecology 56:1040-1053. PDF

Allan,JD 1981 Determinants of diet of brook trout (Salvelinus fontinalis) in a mountain stream. Canadian Journal of Fisheries and Aquatic Sciences 38, 184-192. PDF

Allan,JD 1982 The effects of reduction in trout density on the invertebrate community of a mountain stream. Ecology, 63(5), pp.1444-1455. PDF

Allan,JD 1984 The size composition of invertebrate drift in a Rocky Mountain stream. Oikos, pp.68-76.

Allan,JD 1987 Macroinvertebrate drift in a Rocky Mountain stream. Hydrobiologia 144, 261-268.
     The author studied Cement Creek in Gunnison County during the spring, summer and fall of 1975-1978. He found that drift densities (number of animals per 100 m³) was 10 times higher at night. 24 hour totals approached 2000 animals/100m³ in mid-summer down to 500 animals/m³ in the fall. Quote from the abstract: "Ephemeroptera, especially Baetis, dominated the drift." He found that benthic density (number of animals/m² from streambed samples) was the best predictor of 24hr drift rate for Epeorus longimanus. Adding discharge to the calculation (a stepwise regression) did not improve estimates of E. longimanus in the drift.

Allan,JD and Feifarek,BP 1988 Prey preference in stoneflies: a comparative analysis of prey vulnerability. Oecologia, 76(4), pp.496-503.

Alexander,AC; Culp,JM; Liber,K and Cessna,AJ 2007 Effects of insecticide exposure on feeding inhibition in mayflies and oligochaetes. Environmental Toxicology and Chemistry: An International Journal, 26(8), pp.1726-1732. PDF
     Abstract: "The present study examined the effects of pulse exposures of the insecticide imidacloprid on the mayfly, Epeorus longimanus Eaton (Family Heptageniidae), and on an aquatic oligochaete, Lumbriculus variegatus Müller (Family Lumbriculidae). Pulse exposures of imidacloprid are particularly relevant for examination, because this insecticide is relatively soluble (510 mg/L) and is most likely to be at effect concentrations during runoff events. Experiments examined the recovery of organisms after a 24-h pulse exposure to imidacloprid over an environmentally realistic range of concentrations (0, 0.1, 0.5, 1, 5, and 10 μg/L). Effects on feeding were measured by quantifying the algal biomass consumed by mayflies or foodstuffs egested by oligochaetes. Imidacloprid was highly toxic, with low 24-h median lethal concentrations (LC50s) in early mayfly instars (24-h LC50, 2.1 ± 0.8 μg/L) and larger, later mayfly instars (24-h LC50, 2.1 ± 0.5 μg/L; 96-h LC50, 0.65 ± 0.15 μg/L). Short (24-h) pulses of imidacloprid in excess of 1 μg/L caused feeding inhibition, whereas recovery (4 d) varied, depending on the number of days after contaminant exposure. In contrast to mayflies, oligochaetes were relatively insensitive to imidacloprid during the short (24-h) pulse; however, immobility of oligochaetes was observed during a 4-d, continuous-exposure experiment, with 96-h median effective concentrations of 6.2 ± 1.4 μg/L. Overall, imidacloprid reduced the survivorship, feeding, and egestion of mayflies and oligochaetes at concentrations greater than 0.5 but less than 10 μg/L. Inhibited feeding and egestion indicate physiological and behavioral responses to this insecticide."

Argyle,DW and Edmunds,GF 1962 Mayflies (Ephemeroptera) of the Curecanti Reservoir Basins Gunnison River, Colorado. University of Utah Anthropological Papers 59 8, 178-189.
     Quote from page 185: "This species is often found with E. albertae in riffle areas. It seems, however to be more tolerant of cold water and usually achieves greater elevation in its distribution. In this particular drainage, it was found at only one station above the distribution of E. albertae. In Blue Creek it was found at 8360 ft., while E. albertae reached only 8300 ft. in the same stream."

Balistrieri,LS; Mebane,CA and Schmidt,TS 2020 Time-dependent accumulation of Cd, Co, Cu, Ni, and Zn in mayfly and caddisfly larvae in experimental streams: Metal sensitivity, uptake pathways, and mixture toxicity. Science of the Total Environment, 732. html
     Abstract: "Conceptual and quantitative models were developed to assess time-dependent processes in four sequential experimental stream studies that determined abundances of natural communities of mayfly and caddisfly larvae dosed with single metals (Cd, Co, Cu, Ni, Zn) or multiple metals (Cd + Zn, Co + Cu, Cu + Ni, Cu + Zn, Ni + Zn, Cd + Cu + Zn, Co + Cu + Ni, Cu + Ni + Zn). Metal mixtures contained environmentally relevant metal ratios found in mine drainage. Free metal ion concentrations, accumulation of metals by periphyton, and metal uptake by four families of aquatic insect larvae were either measured (Brachycentridae) or predicted (Ephemerellidae, Heptageniidae, Hydropsychidae) using equilibrium and biodynamic models. Toxicity functions, which included metal accumulations by larvae and metal potencies, were linked to abundances of the insect families. Model results indicated that mayflies accumulated more metal than caddisflies and the relative importance of metal uptake by larvae via dissolved or dietary pathways highly depended on metal uptake rate constants for each insect family and concentrations of metals in food and water. For solution compositions in the experimental streams, accumulations of Cd, Cu, and Zn in larvae occurred primarily through dietary uptake, whereas uptake of dissolved metal was more important for Co and Ni accumulations. Cd, Cu, and Ni were major contributors to toxicity in metal mixtures and for metal ratios examined. Our conceptual approach and quantitative results should aid in designing laboratory experiments and field studies that evaluate metal uptake pathways and metal mixture toxicity to aquatic biota."

Carlisle,Daren M; Clements,William H 2003 Growth and secondary production of aquatic insects along a gradient of Zn contamination in Rocky Mountain streams. Journal North American Benthological Society 22(4), 582-597. Abstract and entire paper

De Jong,GD 2024 Habitat and benthic community correlates of Epeorus longimanus (Ephemeroptera: Heptageniidae) microdistribution in a Colorado, USA, stream riffle. Annals of the Entomological Society of America, 117(1), pp.21-26.
     Abstract: "Little is known about the ecology of early instars of most aquatic insects, particularly their associations with microhabitat (<1 m2) features, such as sediment size distributions, other abiotic parameters, and the overall invertebrate community. This study sought to explore correlations between various biotic and abiotic parameters of a southern Colorado stream and the presence of early instars of Epeorus longimanus (Eaton) (Ephemeroptera: Heptageniidae). A total of 18 samples collected in 2007 and 2013 using a Hess sampler in riffle habitats were used to correlate the size of individuals with biological and abiotic characteristics of the stream, including sediment size, periphyton biomass, entrained organic matter, and the remainder of the benthic invertebrate community, all of which were measured using material from within the sampler. Results from both years showed that early instars of E. longimanus were more likely to be found in areas with smaller sediment sizes, higher live periphyton biomass (but lower overall organic matter), and lower densities of invertebrate predators."

Dodds,GS 1923 Mayflies from Colorado: descriptions of certain species and notes on others. Transactions of American Entomological Society 69, 93-116. PDF
     Discussed as Iron longimanus.

Eaton,AE 1883-1888 A revisional monograph of recent Ephemeridae or mayflies. Transactions of the Linnean Society of London, Second Series, Zoology 3:1-352, 65 pl.
     Described as Iron longimanus.
Page 245 of Eaton's 1885 description of the mayfly Epeorus longimanus in the genus Iron Page 246 of Eaton's 1885 description of the mayfly Epeorus longimanus in the genus Iron

Edmunds,GF and Allen,RK 1964 The Rocky Mountain species of Epeorus (Iron) Eaton (Ephemeroptera: Heptageniidae. Journal of the Kansas Entomological Society 37 (4) 275-288. PDF

Flecker,AS and Allan,JD 1988 Flight direction in some Rocky Mountain mayflies (Ephemeroptera), with observations of parasitism. Aquatic Insects 10(1):33-42. PDF

Flecker,AS; Allan,JD and McClintock,NL 1988 Male body size and mating sucess in swarms of the mayfly Epeorus longimanus. Holarctic Ecology 11(4), 280-285. PDF
     Abstract: "Epeorus longimanus is a widely distributed mayfly in the western United States that forms relatively large mating swarms. The operational sex ratio of swarms is highly male biased and males are potentially polygynous, suggesting that male-male competition over mates may be intense. We investigated whether body size influenced male mating success in E. longimanus, as evidence of sexual selection. Males collected as mating pairs had significantly greater body lengths compared with males collected randomly from the swarm on each of six sampling dates examined, and had significantly greater head widths than males from random collections on two dates. There was no indication that large males occupied preferred positions within the swarm, and we suspect that the large male advantage may be due to greater success in pursuing females. We found no evidence of size-assortative mating in E. longimanus indicating that males attempt to male with every female encountered, consistent with the brief copulatory period in mayflies and overall low parental investment of males."

Gilpin,BR and Brusven,MA 1970 Food habits and ecology of mayflies of the St. Maries River in Idaho. Melanderia 4:19-40. PDF

Hamilton,H and Clifford,F 1983 The seasonal food habits of mayfly (Ephemeroptera) nymphs from three Alberta, Canada, streams, with special reference to absolute volume and size of particles ingested. Arch. Hydrobiol., Suppl, 65(2/3), 197-234. PDF

Harper,PP and Harper,F 1997. Mayflies (Ephemeroptera) of the Yukon. Pp. 152-167 In: H.V. Danks and J.A. Downes, eds. Insects of the Yukon. Biological Survey of Canada (Terrestrial Arthropods). Ottawa, Ontario, Canada.

Hoover,TM 2001 Hydraulic habitat preferences of the torrential mayfly Epeorus longimanus (Ephemeroptera: Heptageniidae): the ecological importance of near-bed flows (Doctoral dissertation, University of Northern British Columbia). 253 pages. doi:https://doi.org/10.24124/2001/bpgub223
     Abstract: "The larval stage of the mayfly Epeorus longimanus (Ephemeroptera: Heptageniidae) is an inhabitant of torrential stream habitats. It possesses several adaptations to high velocity environments, including a flattened body shape, a tilted head shield, and a "sucker-like" arrangement of abdominal gills. In order to relate the behavioural and morphological adaptations of E. longimanus to its habitat requirements, the distribution of this mayfly and a suite of environmental parameters were measured at a range of spatial scales (i.e. watershed, within-stream, and within-stone scales).
     Benthic macroinvertebrates were collected at 39 stream sampling sites throughout the lower portion of the Torpy River watershed in eastern British Columbia, in order to (1) identify the particular habitat preferences of larval Epeorus, and (2) examine the community structure of benthic macroinvertebrates in a northern watershed . Several environmental variables (e.g. discharge, stream surface slope, substrate size, pH, conductivity, riparian vegetation, etc.) were measured and related to patterns of faunal abundance using canonical correspondence analysis (CCA); this ordination technique divided the collected invertebrate taxa into four functional assemblages, each with well-defined habitat requirements and trophic relationships. The results of the CCA showed that Epeorus larvae prefer high discharge streams with coarse substrata. To further examine the habitat requirements of this genus, benthic samples and several descriptors of the flow environment of the stream environment (e.g. mean velocity, near-bed velocity, depth, substrate size, Froude number, etc.) were obtained at 50 regularly located sampling sites in two adjacent, high-discharge streams with coarse bed material. Observed patterns of abundance of Epeorus were significantly and negatively related to velocity, depth, channel Reynolds number, and relative roughness.
     The near-bed hydraulic environment of shallow torrential streams was characterised by measuring velocity profiles, near-bed (U0.002m) and mean (U0.5D) velocities, and shear stresses (τw) over the surface of five experimentally deployed and three naturally occurring stones in a high-discharge stream in the Torpy River watershed. The velocity profiles measured above the stones regularly deviated from the "classic" log-normal shape . The profiles were often "wedge-shaped"; velocities were greatest a few millimetres above the bed, and decreased logarithmically below and above this height. Wall shear stresses and near-bed velocities generally increased from the front to the rear of each stone.
     The daytime and night-time distributions of E. longimanus were recorded and related to shear stress, periphyton biomass, and substrate characteristics (e.g. stone roughness, topography). During the daytime, larvae preferred areas of the stone surface with high shear stress ; during the night-time , larvae preferred areas of the stone surface with higher elevation and attached boundary layer flows. Periphyton density was significantly related to stone surface roughness and stone surface topography. A stone reversal experiment suggested that hydrodynamic factors , rather than food (periphyton) availability, proximally influence the microdistribution of E. longimanus larvae; however, the precise nature of the forces to which they respond remains unknown. E. longimanus larvae were also found to exhibit a strong diurnal migration, generally migrating to the upper surface of streambed stones at night, and retreating to the underside of the stones during the day.
     This study represents one of the first detailed examination of the relationship between the distribution of microscale hydrodynamic parameters, (e .g. shear stress, near-bed velocity) and benthic organisms at organism-defined spati al scales. The results demonstrate that flu id dynamics are the proximate factor that determines the microdistribution of benthic organisms in torrential stream environments. Additional research is required to investigate the ecological importance of these small-scale hydrodynamic parameters. In order to understand the behaviour and ecology of benthic stream organisms, models of flow in natural stream channels must be expanded to include patterns of flow at small, organism-defined scales immediately adjacent to the bed."


Kiffney,PM and Clements,WH 1994 Effects of heavy metals on a macroinvertebrate assemblage from a Rocky Mountain stream in experimental microcosms. Journal of the North American Benthological Society 13(4) 511-523.
     Abstract: "Natural assemblages of stream benthic macroinvertebrates were collected using artificial substrates from a Rocky Mountain stream and exposed for 10 d to a mixture of heavy metals (Cd, Cu, and Zn) in stream microcosms. Metal levels were 0, 1х, 5х, and 10х where х = 1.1, 12, and 110 μg/L Cd, Cu, and Zn, respectively. The 1х treatment was similar to chronic criteria values recommended by the US Environmental Protection Agency (EPA) for each metal and total metal levels measured in water at the Arkansas River, Colorado, a US EPA superfund site. Most ephemeropterans and plecopterans were sensitive to metals; however, some taxa within these groups were metal tolerant. Densities of Baetis tricaudatus (Ephemeroptera:Baetidae), Epeorus longimanus and Rhithrogena hageni (Ephemeroptera:Heptageniidae), and Drunella grandis and D. doddsi (Ephemeroptera:Ephemerellidae) were reduced in the 1х treatment. The response of D. grandis to metals was size-dependent with small larvae being more sensitive than large ones (p = 0.02). Chironomids were generally tolerant to metals. These data show that a metal mixture was extremely toxic to stream macroinvertebrates from a Rocky Mountain stream. Our results were similar to field biomonitoring studies at the Arkansas River and Eagle River, Colorado, that examined the effects of metals on stream macroinvertebrate communities. We suggest that multispecies experiments using indigenous stream organisms be combined with field biomonitoring to rigorously define the biological effects of heavy metals on lotic systems. "

Lehmkuhl,DM 1968 Observations on the life histories of four species of Epeorus in western Oregon (Ephemeroptera: Heptageniidae). Pan-Pacific Entomologist 44(2):129-137. PDF

McCafferty,WP; Durfee,RS and Kondratieff,BC 1993 Colorado mayflies (Ephemeroptera): an annotated inventory. Southwestern Naturalist 38 (3) 252-274. PDF
     Quote from page 261: "Edmunds and Allen (1964) noted this was the most widespread of the western species of Iron and that it evidently is not found cohabitating with I. albertae." They report Gunnison County Museum specimens from the Crystal River, East River and Gunnison River.

McCafferty,WP and Provonsha, AV The Mayflies of North AmericaSpecies List (Version 8Feb2011)
     Here is the geographic range and synonyms:
Epeorus longimanus (Eaton), 1885 [CAN:FN,NW;USA:FN,NW,SW]
    * Iron longimanus Eaton, 1885 (orig.)
    * Iron proprius Traver, 1935 (syn.)

Mebane,CA; Schmidt,TS; Miller,JL and Balistrieri,LS 2020 Bioaccumulation and toxicity of cadmium, copper, nickel, and zinc and their mixtures to aquatic insect communities. Environmental toxicology and chemistry, 39(4) 812-833. PDF

Peckarsky,BL 1983 Biotic interactions or abiotic limitations? A model of lotic community structure. In: Dynamics of Lotic Ecosystems. Eds: Fontaine III,Thomas D; Bartell,Steven M Ann Arbor Science, Ann Arbor, Michigan, 303-323.

Peckarsky,BL 1996 Alternative predator avoidance syndromes of stream-dwelling mayfly larvae. Ecology, 77(6), pp.1888-1905. PDF
     Abstract: "Experiments were conducted to compare the patterns, mechanisms, and costs of predator avoidance behavior among larvae of five species of mayflies that co-occur with the predatory stoneflies, Megarcys signata and Kogotus modestus in western Colorado streams. Mayfly drift dispersal behavior, use of high vs. low food (periphyton or detritus) patches, microhabitat use, positioning, and activity periodicity were observed in the presence and absence of predators in circular flow-through chambers using natural stream water. Also, distances from predators at which prey initiated escape responses were compared among prey and predator species. Costs of predator avoidance behavior were assessed by measuring short-term (24 h) feeding rates of mayflies in the presence or absence of predatory stoneflies whose mouthparts were immobilized (glued) to prevent feeding. The intensity and associated costs of predator avoidance behavior of mayfly species were consistent with their relative rates of predation by stoneflies. Megarcys consumes overwintering generation Baetis bicaudatus > Epeorus longimanus > Cinygmula = Ephemerella; Kogotus consumes summer generation Baetis > Epeorus deceptivus = Cinygmula; Megarcys eats more mayflies than Kogotus. While Megarcys induced drift by Baetis, Epeorus, and Cinygmula, this disruptive predator avoidance behavior only reduced food intake by Baetis and Epeorus. The morphologically defended mayfly species, Ephemerella, neither showed escape behavior from Megarcys, nor any cost of its antipredatory posturing behavior. Only Baetis responded by drifting from Kogotus. No mayfly species shifted microhabitats or spent less time on high-food patches in the presence of foraging stoneflies. However, predators enhanced the nocturnal periodicity of Baetis drift, which was negligible in the absence of stoneflies as long as food was abundant. Lack of food also caused some microhabitat and periodicity shifts and increased the magnitude of both day and night drift of Baetis. Thus, Baetis took more risks of predation by visual, drift-feeding fish not only in the presence of predatory stoneflies, but also when food was low or they were hungry. All other mayflies were generally nocturnal in their use of rock surfaces, as long as food was abundant. Finally, the distances at which different mayfly species initiated acute escape responses were also consistent with relative rates of predation. This study demonstrates alternative predator avoidance syndromes by mayfly species ranging from an initial investment in constitutive morphological defenses (e.g., Ephemerella) to induced, energetically costly predator avoidance behaviors (e.g., Baetis). Although the costs of Ephemerella's constitutive defense are unknown, experiments show that prey dispersal is the mechanism underlying fecundity costs of induced responses by Baetis to predators, rather than microhabitat shifts to less favorable resources or temporal changes in foraging activity. A conceptual model suggests that contrasting resource acquisition modes may account for the evolution and maintenance of alternative predator avoidance syndromes along a continuum from Baetis (high mobility) to heptageniids (intermediate mobility) to Ephemerella (low mobility). Prey dispersal (swimming) to avoid capture results in reduction of otherwise high fecundity by Baetis, which trades off morphological defense for enhanced ability to acquire resources. Thus, improved foraging efficiency is the selection pressure maintaining the highly mobile life style in Baetis, which increases resource acquisition and fecundity, offsetting the high mortality costs associated with this behavior."

Peckarsky,BL; Encalada,AC and McIntosh,AR 2011 Why do vulnerable mayflies thrive in trout streams?. American Entomologist, 57(3), pp.152-164. PDF

Poff,NL and Ward,JV 1991 Drift responses of benthic invertebrates to experimental streamflow variation in a hydrologically stable stream. Canadian Journal of Fisheries and Aquatic Sciences, 48(10): 1926-1936.
     Abstract: Field experiments were conducted in the regulated upper Colorado River to assess drift responses of lotic macroinvertebrates to streamflow manipulations. In each of three seasons, drift was collected in one control and two experimental riffles. On the first day, no flow manipulations occurred. Six hours before sunset on the second day, streamflow was simultaneously reduced and elevated in two experimental riffles with instream diversion structures. Following flow elevation, both mean daily drift density and drift rate generally increased for 13 taxa across all seasons. Flow reductions generally induced elevated drift densities for most taxa, but drift rates declined for some taxa. Patterns of diel drift periodicity were less frequently modified by flow manipulations. Taxa with typical nocturnal peaks in drift activity (Baetis spp., Epeorus longimanus, Triznaka signata) generally maintained this pattern despite some increases in diurnal drift. For a few taxa, modification of diel drift patterns occurred, either as nocturnal decreases following reduced flow (Paraleptophlebia heteronea, Ephemerella infrequens) or as diurnal drift increases in response to either elevated flow (Lepidostoma ormea, Chironomidae larvae) or reduced flow (Simuliidae). With some exceptions, observed drift responses could be used to suggest active versus passive processes of drift entry.

Rader,RB and Ward,JV 1987 Resource utilization, overlap and temporal dynamics in a guild of mountain stream insects. Freshwater Biology, 18(3), pp.521-528. PDF
     Abstract: "1. Resource utilization was quantified for six mayfly (Ephemeroptera) and one caddis (Trichoptera) species comprising a lotic scraper/collector-gatherer guild across three niche dimensions (temporal, trophic and spatial). Based on trophic differences and inferred microspatial utilization, the members of this guild separated into two groups: (1) cryptic detritivores and (2) exposed algivores.
2. Each species demonstrated a slow seasonal univoltine life cycle except for Epeorus longimanus (Eaton) and Baetis bicaudatus (Dodds) which were fast seasonal univoltine and multivoltine, respectively.
3. Temporal sequencing of periods of peak resource utilization were not demonstrated by the members of this guild. A null analysis indicated that periods of peak resource utilization were aggregated."


Rader,RB and Ward,JV 1988 Influence of regulation on environmental conditions and the macroinvertebrate community in the upper Colorado River. Regulated Rivers: Research and Management 2:597-618.
     Heptagenid mayflies were eliminated at the regulated site directly below the dams, but E. longimanus reappeared at the recovery site downstream.

Radford,DS and Hartland-Rowe,R 1971 The life cycles of some stream insects (Ephemeroptera, Plecoptera) in Alberta. The Canadian Entomologist, 103(4) 609-617.
     Names have changed since 1971:
1971 Name 2020 Name
Nemoura besametsa Prostoia besametsa
Epeorus deceptivus Epeorus deceptivus
Epeorus longimanus Epeorus longimanus
Ephemerella coloradensis Drunella coloradensis
Arcynopteryx aurea Perlinodes aurea
Nemoura cinctipes Zapada cinctipes
Nemoura columbiana Zapada columbiana
Nemoura oregonensis Zapada oregonensis
Cinygmula ramaleyi Cinygmula ramaleyi
Ephemerella doddsi Drunella doddsi
Rhithrogena doddsi Rhithrogena hageni
Abstract: " The life histories of Nemoura besametsa, Epeorus deceptivus, Epeorus longimanus, and Ephemerella coloradensis are described as "fast seasonal" types and Arcynopteryx aurea, Nemoura cinctipes, Nemoura columbiana, Nemoura oregonensis, Cinygmula ramaleyi, Ephemerella doddsi, and Rhithrogena doddsi as "slow seasonal" types according to Hynes´ (1961) classification. All of the species are univoltine with the exception of N. cinctipes which may be bivoltine. There seems to be a correlation between life cycles and food availability. A means of ecological separation in the four Nemoura species is elucidated. Stream temperature was found to influence growth rates."


The United States Geological Survey (USGS) National Water Quality Assessment Data Warehouse (NAWQA) shows this species is present in Gunnison County. Data as of 1Sep2005

Wellnitz,T 2014 Can current velocity mediate trophic cascades in a mountain stream?. Freshwater Biology, 59(11) 2245-2255. PDF

Wellnitz,T and Poff,LN 2006 Herbivory, current velocity and algal regrowth: how does periphyton grow when the grazers have gone?. Freshwater Biology, 51(11) 2114-2123. PDF
     Abstract: " 1. An experiment conducted in streamside channels was used to document the regrowth of grazed periphyton. Our objective was to determine the relative importance of current velocity, grazing duration, and grazer type in shaping the trajectory of algal and periphytic regrowth.
2. The grazing mayflies Baetis bicaudatus and Epeorus longimanus were used alone and in combination to create three grazing treatments at slow, medium and fast current (2-5, 15-20 and 30-40 cm s-1, respectively). Duration treatments consisted of 2, 4, 6, 8, 10 days of grazing. Chlorophyll a and ash-free dry mass (AFDM) accumulation on grazed tiles was measured (as periphytic AFDM and chlorophyll a, respectively) at 2, 4, 6, 8 and 10 days following the removal of grazers.
3. Chlorophyll a and AFDM was best predicted by interactions between current velocity, grazing duration and regrowth time.
4. The two grazer species did not differ in their effect on Chlorophyll a and AFDM during the period of periphytic regrowth that followed grazing.
5. Longer grazing duration reduced periphytic biomass, but also accelerated algal regrowth, and this growth enhancement was more pronounced at slower current velocities.
6. Data from this study suggest that herbivory can have important historical effects on periphytic accrual. "


Brown,WS 2004 Mayflies (Ephemeroptera) of Gunnison County, Colorado, USA
www.gunnisoninsects.org

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