Patterns of macroinvertebrate colonization in an intermittent Rocky Mountain stream in Utah

Colonization of macroinvertebrates in a headwater mountain stream was monitored using basket and Surber samplers. Taxa showed differences in colonization ability based both on dispersal ability and feeding strategy. Collector - gatherer feeding groups that could actively enter the water, i.e., Baetis mayflies, were the first organisms to colonize bare or new substrate. The slowest colonizers were heptageniid mayflies that colonized primarily from upstream migration. All organisms examined increased drifting behavior in response to decreases in discharge.         

Seasonal trends and colonization patterns of macroinvertebrate assemblages in two streams with contrasting flow regimes

Patterns of colonization by macroinvertebrates were examined in two streams that differ in flow regime: a snowmelt system and a mesic groundwater system. Experiments were conducted during spring runoff, summer baseflow, and winter baseflow using artificial substrata. Colonization patterns reflected seasonal changes in benthic macroinvertebrate assemblages and life histories in each stream. The density and biomass of benthic organisms were approximately 3X greater in winter than in either spring or summer for both streams. Similarly, colonization was greater in winter than in spring or summer for both streams. In spring, colonization patterns were different between streams, with colonization being imperceptible in the snowmelt stream. Macroinvertebrate abundance fluctuated during the summer colonization experiment at both sites, resulting from a complex interplay among population emergence, recruitment, and/or movement. Assemblages in the snowmelt system primarily comprised mobile or ruderal taxa, such as Beatis tricaudatus and Chironomidae, whereas relatively sessile taxa, such as Glossoma nigrior , were predominant in the mesic groundwater system. Seasonal patterns of colonization differed among stream types primarily because of the profound interplay of flow regime and temperature on benthic community structure and organism life history.     

Soft sediment benthic macroinvertebrate communities of the Green River at the Ouray National Wildlife Refuge, Uintah County, Utah

Benthic macroinvertebrates from four habitat types (river channel, ephemeral side channel, river backwater, and seasonally inundated wetland) were examined from the Green River at the Ouray National Wildlife Refuge, Uintah County, UT, June-August 1991. For major taxa (Nematoda, Oligochaeta, Diptera: Ceratopogonidea, and Chironomidae) were quantified. Chuster analysis of densities showed that habitat types with comparable flow conditions were the most similar. Highest to lowest overall benthic invertebrate densities of the four habitats were as follows: ephemeral side channel, river backwater, seasonally inundated wetland, and river channel. Nematodes were the most abundant taxon in all habitat types and sample dates except the August sample of the river channel and river backwater and the July sample of the seasonally inundated wetland.     

Influence of substrate size, Cladophora , and caddisfly pupal cases on colonization of macroinvertebrates in Sagehen Creek, California

Colonization of stream macroinvertebrates onto artificial substrates was examined in Sagehen Creek, California, during 1993. Substrate size and presence or absence of pupal cases of the caddisfly Anagapetus (Glossosomatidae) were examined as possible influences on macroinvertebrate colonization. Macroinvertebrates were collected from substrates after 60 d of incubation and identified to the lowest feasible taxonomic unit. Dry weight of the filamentous green alga Cladophora also was determined for each substrate. A general linear model indicated a significant positive relationship between both substrate size and presence of pupal cases on richness ( P Anagapetus cases on Micrasema bactro , Epeorus , and Rhyacophila sp. 1, and of substrate size on Hydropsyche occidentalis and Epeorus . Neither cases nor substrate size had a significant effect on Cladophora density ( P > 0.05). There were significant negative correlations between Cladophora density and both Shannon H′ and J′ indices. There were significant positive relationships between Cladophora density with Baetis , Simulium , and Chironomidae density. Combined main effects of substrate size, Anagapetus pupal cases, and Cladophora have dynamic influences on this macroinvertebrate fauna. This study demonstrates the complex interplay of biotic and abiotic factors that determine macroinvertebrate distribution and abundance in this system.     

Observations on woundfin spawning and growth in an outdoor experimental stream

The response of woundfin to different substrates and current speeds was investigated in an outdoor experimental stream. Fish spawned in groups of 15 – 20 over 5 – 10 cm rock substrate in a .06 to .09 m/sec current at a depth of 10 cm. Eggs were adhesive on the undersides of the rocks. Fish spawned under these conditions grew to approximately 55 – 60 mm TL in 5 months.     

Present effects of past wildfires on the diets of stream fish

We investigated present indirect effects from a decade-old burn on the diets of stream fish. Based on soil instability and burn patterns from a 12–14-year-old wildfire complex, we separated 9 streams into 3 conditions: unburned, burned, and burned/scoured (i.e., experiencing a massive scour event 1 year post-burn). In the streams, we measured light levels and water temperatures, and we estimated fish density and biomass. We removed the digestive tracts from 9–15 rainbow trout ( Oncorhynchus mykiss ) from each stream and used a gravimetric procedure to analyze gut contents. Canopy cover development may dictate the composition of dietary items. Greater amounts of aquatic invertebrates and inorganic material were found in trout from streams with reduced overhead canopy. Further, these streams had lower amounts of terrestrial invertebrates and organic materials in the diets of fish. Although trout abundance was not different among the stream treatments, fire-induced, indirect effects on fish diets were still evident more than a decade after the burn. This suggests that recovery rates for trout assemblages may take longer than predicted and may depend on riparian recovery.     

Present effects of past wildfires on leaf litter breakdown in stream ecosystems

We investigated the present effects from a 10-year-old wildfire on leaf litter breakdown rates in 3 headwater streams in central Idaho. These systems experienced a massive debris flow one year after the fire. Based on soil instability and burn patterns, we identified 3 stream conditions: unburned, burned only, and burned/scoured. We placed leaf bags containing willow leaves ( Salix sp.) in each stream type and removed bags at various time intervals until all bags were collected 100 days after their introduction. Leaf material was dried and weighed, and decay rate coefficients were calculated. Macroinvertebrates colonizing the bags were enumerated and identified, and selected taxa were placed into trophic groups. We found that the unburned stream had the fastest leaf litter breakdown rate, the lowest level of incident light reaching the stream, and the largest amount of benthic organic matter. The burned/scoured stream was nearly opposite in all respects. Numbers of 2 detritivore invertebrate taxa, Serratella tibialis and Zapada oregonensis, were highest in the unburned stream but lowest in the burned/scoured stream. A third taxon, Baetis sp., showed the opposite relationship. Presence of predatory invertebrates did not affect detritivore abundance or leaf decay rate in the bags. Our research suggests that recovery response variables of some stream systems may not have returned to prefire levels even a decade after the initial wildfire. In this study, the recovery of our streams appears to be connected to the return of the riparian zone, though fire-induced debris flows may slow or alter final recovery of the stream system.     

Effects of watershed alteration on the brook trout population of a small Black Hills stream

The impacts of adjacent landscaping activity and livestock presence on the brook trout ( Salvelinus fontinalis ) population of a small Black Hills stream were evaluated. Moderate changes in temperature, turbidity, and fecal coliform numbers did not influence brook trout densities. Stream morphometry, particularly factors affecting stream cover, appeared to have the greatest impact on numbers of trout. Brook trout were poor indicators of moderate changes in water quality, but they were adequate indicators of the physical perturbations within the stream.      

Effects of livestock grazing exlosure on aquatic macroinvertebrates in a montane stream, New Mexico

Aquatic macroinvertebrate populations inhabiting reaches of a stream within areas excluded from livestock grazing for a decade were markedly different from those in grazed areas when density, biomass, biotic condition indices, and mean chi square indices of the two populations were compared. Increased densities and biomasses of more tolerant forms of macroinvertebrates were observed in grazed reaches. Because pretreatment data were not available, differences in macroinvertebrate populations and relative tolerances of taxa in grazed and ungrazed areas could be as easily attributed to linear changes in stream habitat as to removal of domestic livestock. Results of this study have implications for the design of future research on the effects of livestock grazing on stream environments and biota: (1) baseline/pretreatment information is prerequisite, and (2) the study should take a watershed (ecosystem) approach.     

The effects of varied densities on the growth and emigration of adult cutthroat trout and brook trout in fenced stream enclosures

We evaluated the effects of various density treatments on adult fish growth and emigration rates between Bonneville cutthroat trout Oncorhynchus clarki utah and brook trout Salvelinus fontinalis in stream enclosures in Beaver Creek, Idaho. We used 3 density treatments (low, ambient, and high fish densities) to evaluate density-related effects and to ensure a response. Intraspecific ambient-density tests using cutthroat trout only were also performed. Results indicated an absence of cage effects in the stream enclosures and no differences in fish growth between ambient-density stream-enclosure fish and free-range fish. Brook trout outgrew and moved less than cutthroat trout in the stream enclosures, especially as density increased. In all 3 density treatments, brook trout gained more weight than cutthroat trout, with brook trout gaining weight in each density treatment and cutthroat trout losing weight at the highest density. At high densities, cutthroat trout attempted to emigrate more frequently than brook trout in sympatry and allopatry. We observed a negative correlation between growth and emigration for interspecific cutthroat trout, indicating a possible competitive response due to the presence of brook trout. We observed similar responses for weight and emigration in trials of allopatric cutthroat trout, indicating strong intraspecific effects as density increased. While cutthroat trout showed a response to experimental manipulation with brook trout at different densities, there has been long-term coexistence between these species in Beaver Creek. This system presents a unique opportunity to study the mechanisms that lead cutthroat trout to coexist with rather than be replaced by nonnative brook trout.     

Annotated inventory of invertebrate populations of an alpine lake and stream chain in Colorado

Benthic macroinvertebrates were collected during the ice-free season (1 July-20 October) over a five-year period from a chain of alpine lakes and intervening streams in the Green Lakes Valley (3,347-3,615 m) in Boulder County, Colorado. A list of taxa was developed for 1981 and 1982, with taxonomic additions for 1983- 1985 and comments on community structure, seasonal and elevational changes in species abundance, and noteworthy occurrences. A total of 111 taxa was collected, of which 84% occurred in streams, 58% being exclusively lotic. Dipterans composed 73-81% of total abundance in streams. The littoral benthic zone of lakes was predominantly trichopterans and dipterans, 44-60% and 24-39%, respectively. Numerically important organisms in various lakes and streams were chironomids, simuliids (particularly Metacnephia ), oligochaetes, and the bivalve Pisidium casertanum . An isolated lake and its outlet stream, with unique characteristics, were the sole locations of Gammarus lacustris (Amphipoda) and Glossiphonia complanata (Hirudinea). Manipulated lowering of a lake along the main drainage exposed abundant and luxuriant colonies of the bryozoan Fredericella sultana . This organism was found on 43% of all rocks sampled, a preponderance heretofore unknown for this, or any, ectoproct in alpine or arctic lakes.     

Short-term effects of wildfire on montane stream ecosystems in the southern Rocky Mountains: one and two years post-burn

The frequency and intensity of wildfire in the western United States has increased over the last century, creating a heterogeneous mosaic of landscapes in various stages of recovery. The 2002 Hayman Fire was one of the largest wildfires in Colorado history and was unprecedented for its speed and intensity, with over 50%–70% of the burn area classified as moderate to high severity where much of the canopy crown was consumed. We evaluated the short-term impact of the Hayman Fire on ecological properties in montane stream ecosystems in the summers of 2003 and 2004, one and two years post-fire. Fire significantly altered surface temperature, dissolved oxygen concentration, and the chemical composition of stream water, including concentrations of nitrate, phosphate, and mineral salts. However, fire did not have significant impacts on stream conductivity, pH, or total concentrations of cations or anions during our study period. Streams in the burn area contained fewer benthic macroinvertebrate taxa compared to unburned streams during the year after fire and contained lower invertebrate densities and biomass compared to reference streams 2 years post-fire. Average C:N ratio of the benthic macroinvertebrate community was significantly and negatively related to stream nitrate concentration, possibly due to a shift in community composition or invertebrate nitrogen acquisition in fire-affected streams.     

Density and biomass of redband trout relative to stream shading and temperature in southwestern Idaho

Density and biomass of redband trout ( Oncorhynchus mykiss gairdneri ) relative to stream temperature were examined in headwater reaches of Big Jacks and Little Jacks Creeks in southwestern Idaho. Stream shading was greater (mean of 80% versus 46%) and solar insolation was lower (mean of 7.9 versus 15.1 mJ · m -2 · day -1 ) in Little Jacks Creek ( P P ≤ 0.07) but increased more rapidly and to higher levels (24° - 26° C) in Big Jacks Creek. Daily maximum water temperatures (23 km downstream of headwater springs) during July 1996 were lower in Little Jacks Creek (ranged from 18° to 22° C) than in Big Jacks Creek (20.2° to 26° C, P P -2 and 25.0 g · m -2 ) compared to Big Jacks Creek (0.3 fish · m -2 and 8.9 g · m -2 , P = 0.01). Trout density was negatively correlated with increases in water temperature ( P = 0.03) and solar insolation ( P = 0.09) in both streams. Trout biomass increased with stream shading and was negatively correlated with solar insolation ( P < 0.1). Warmer water temperatures in Big Jacks Creek were likely due to historical summerlong livestock grazing, which drastically reduced riparian shading.     

Composition and abundance of periphyton and aquatic insects in Sierra Nevada, California, stream

The species composition of periphyton and benthic insect communities and abundances of common taxa (&;gt;0.1&;#37; of individuals) were examined during snow-free months in Convict Creek, a permanent snowmelt- and spring-fed stream in the Sierra Nevada of California. The communities were highly diverse. The most abundant taxa in the periphyton were diatoms ( Achnanthes minutissima, Cocconeis placentula lineata, Cymbella microcephala, C. sinuata, Fragilaria construens, F. crotonensis , Navicula spp., Synedra acus , and S. rumpens ), except in late spring and summer when several seasonal blue-green algae ( Chamaesiphon incrustans, Lyngbya spp. and Oscillatoria spp.) are at their maximum densities. Most common periphyton taxa vary systematically in abundance with season, but relative abundances of taxa also appear to be influenced by streambed scouring and by concentrations of ambient nutrients. Data on population densities and length frequencies of larval and nymphal stages of common benthic insects and occurrences of pupal and adult stages were examined to determine life history patterns. Taxa hatching in winter and spring and abundant as immatures in late spring include ephemeropterans ( Epeorus longimanus, Drunella flavilinea , and Caudatella heterocaudata ), plecopterans ( Calineuria californica, Doroneuria baumanni, and Pteronarcys princeps ) and dipterans ( Cryptolabis sp.). Common taxa hatching in late spring or summer are the plecopteran Malenka ( californica? ) and the trichopterans Arctopsyche grandis and Rhyacophila acropedes . Several bivoltine and multivoltine ephemeropterans ( Baetis devinctus and B. tricaudatus ) and dipterans ( Simulium spp. and Chironomidae) have summer cohorts. Taxa hatching in late summer or autumn and most abundant in autumn include ephemeropterans ( Baetis spp., Ephemerella infrequens, Epeorus dulciana, Ironodes lepidus , and Paraleptophlebia pallipes ), trichopterans ( Hydropsyche oslari, Lepidostoma spp., Glossosoma califica, Micrasema sp., Brachycentrus americanus, Neophylax sp., and Rhyacophila vaccua ) and dipterans ( Antocha monticola, Pericoma sp., and Chironomidae). Major recurring events that may influence life history patterns and structure of the benthic insect community are (1) near-freezing, nighttime winter water temperatures and occasional anchor ice, (2) a prolonged period of high discharge in late spring and early summer (3) a brief summer, and (4) a prolonged period of moderate stream discharge in autumn when the substratum is stable and food is abundant.     

Benthic insect fauna of a clean-water stream on Utah's Colorado Plateau, USA

Extensive collecting using a variety of methods was conducted in 1994 and 1995 in association with Pleasant Creek in south central Utah, USA, in an effort to inventory the aquatic insects. Collecting efforts yielded 133 insect taxa from 12 sample sites in 8 study areas from near the headwaters of Pleasant Creek and downstream to where it flows out of Capitol Reef National Park. Applying Protocol III methodology of Plafkin et al. (1989), we determined species assemblages of benthic insects and calculated selected ecological indices based on monthly collections from March through August 1994. Richness, equitability index, and mean diversity index values at all sample sites approached, or were greater than, the generally accepted values for clean-water streams in the mountains of the western United States.     

Aquatic invertebrate fauna of a northern prairie stream: range extensions and water quality characteristics

The benthic macroinvertebrate fauna of southern Saskatchewan, Canada, has received little attention relative to other regions of western North America. Therefore, little is known of the related aquatic ecosystem health and biogeography of regional aquatic insects. Here we present the results of an aquatic macroinvertebrate survey for the Pipestone Creek watershed in southeastern Saskatchewan. We qualitatively sampled aquatic macroinvertebrates in 5 sites on 4 dates through spring, summer, and fall 2006. Sampling produced 294 taxa of macroinvertebrates including 25 provincial range extensions to the southeast corner of the province. Presence/absence data of taxa grouped the sites into lentic and lotic sites. However, the relative proportions of the taxa varied greatly among sites, with no 2 sites having a community similarity greater than 50%. Functional feeding group analyses separated the sites into collector-dominated and scraper/grazer-dominated sites. However, the taxonomic make-up of the feeding groups varied among sites and also among dates. A modified Hilsenhoff Biotic Index of the site communities indicated that all were influenced by organic pollution. Results of this study suggest that although the watershed is enormously diverse, its biological communities are likely influenced by organic pollution. Further, range expansions of species found here, such as the stonefly Perlesta placida , have implications for invasion pathways and post-glaciation species islands in a prairie landscape.     

Invertebrate communities,sediment parameters and food availability of intertidal soft-sediment ecosystems on the north coast of British Columbia,Canada

ABSTRACT

The Skeena River estuary supports commercial and culturally important salmon fisheries. However, considerable development has occurred in the area, and more has been proposed. If anthropogenic development degrades this critical habitat, the Skeena salmon run, that every year contributes $110 million to local economies, may be negatively impacted. Benthic invertebrates are common indicator species, as they often respond to disturbances before commercial species, warning of potential impacts. Unfortunately, invertebrates in the Skeena estuary have not been extensively studied, and we lack the detailed understanding of their community structure and dynamics for them to serve as indicator species in this region. Therefore, present conditions of the Skeena estuary are established here (invertebrate community, sediment conditions and food availability), in order to provide the data required both to anticipate changes associated with potential anthropogenic disturbances and to detect changes in this system if development occurs.     

Influence of soil and site characteristics on Palouse prairie plant communties

The structure of grassland communities can vary widely in response to heterogeneous habitat variables. In this study we document plant communities, soil types, and site characteristics for 12 Palouse prairie remnants in southeastern Washington and northern Idaho. We used general linear models to test the predictive value of 6 biophysical variables (slope, aspect, distance from edge, edge type, vegetation structure, and soil type) on 3 plant community metrics: species richness, Simpson’s diversity index, and the dominance of exotic species. From full models including all variables, we used Akaike’s information criterion (AIC) to select the best model for each metric. Aspect and vegetation structure were significant predictors of species richness ( R 2 = 0.08) and diversity ( R 2 = 0.09), while aspect, soil type, distance from edge, and edge type (type of adjacent matrix habitat) influenced the dominance of exotic species ( R 2 = 0.28). Additional soil sampling determined that the depth to a restrictive layer also had significant impacts on the dominance of exotic species ( R 2 = 0.31). This study confirms that biophysical characteristics influence Palouse prairie plant communities and may help set research and conservation priorities for isolated and uninventoried remnants.     

Action of the saproxylic scarab larva Cetonia aurataeformis (Coleoptera: Scarabaeoidea: Cetoniidae) on woody substrates

The saproxylic beetle Cetonia aurataeformis Curti (Scarabaeoidea: Cetoniidae) is a common Iberian species, whose larvae develop in tree cavities feeding on wood and litter. The aim of this paper is to analyse how the larvae of this cetonid modify the woody substrate by feeding and what the ecological implications on their microhabitat could be. Thermal analysis and infrared spectroscopy have been used to study the changes suffered by different substrates, litter and wood of Betula alba and Quercus pyrenaica, after digestion by the larvae. Results show that larvae of C. aurataeformis are able to digest polysaccharides and lignin producing a residue richer in nutrients than the original substrate and with an organic structure that contains a fraction of lignin that is easier to decompose. The main conclusion is that the action of cetonid larvae on woody substrates could facilitate their use by other saproxylic organisms in natural ecosystems.     

Influence of fire and juniper encroachment on birds in high-elevation sagebrush steppe

We examined relationships between high-elevation sagebrush ( Artemisia spp.) steppe habitats altered by prescribed fire and western juniper ( Juniperus occidentalis ) encroachment on breeding distributions of Brewer's Sparrows ( Spizella breweri ), Vesper Sparrows ( Pooecetes gramineus ), Green-tailed Towhees ( Pipilo chlorurus ), and Sage Thrashers ( Oreoscoptes montanus ) on Steens Mountain in southeastern Oregon. In 2000 we conducted fixed-radius point count surveys at 172 sites encompassing burned and unburned sagebrush habitat and a range of juniper densities. For each bird species we developed habitat models using local variables measured in the field and landscape variables derived from remotely sensed data. Akaike's Information Criterion (AIC c ) was used to select the best-approximating model from a suite of a priori candidate models. Brewer's Sparrows, Sage Thrashers, and Green-tailed Towhees were positively related to increasing local sagebrush cover or percent sagebrush in the landscape, whereas Vesper Sparrows were negatively associated with sagebrush cover and positively related to increases in sagebrush fragmentation at local and landscape scales. Including a measure of juniper encroachment substantially improved models for all species in the analysis. Green-tailed Towhees showed a curvilinear response to the amount of juniper in the landscape. All other species showed a strong negative relationship with juniper. Our results indicate that, although changes in sagebrush habitat associated with fire had a negative influence on sagebrush birds, juniper encroachment due to fire suppression also impacted this high-elevation sagebrush bird community.