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.     

Longitudinal development of macroinvertebrate communities below oligotrophic lake outlets

Benthic macroinvertebrates were collected at several sites downstream of three oligotrophic lake outfalls in July 1986. Total numbers, biomass, and species richness increased rapidly immediately downstream from the outlets and then either stabilized or continued to increase downstream in parallel with benthic organic matter standing crops. Filter feeder densities showed an initial buildup and then decline downstream from the outlets. Variability in longitudinal patterns of other functional feeding groups among lake outlets was related to differences in food quantity and quality, and microhabitat. An additional set of samples was collected at Pettit Lake outlet in August 1986. Species richness and total density peaked sooner under baseflow conditions in August than under spring runoff conditions in June. Distributions of all functional feeding groups, except filter feeders, also differed between the two periods, reflecting differences in the physical environment. We conclude that reduced lentic inputs of particulate organic matter seston and improved habitat suitability downstream are responsible for the progressive development of macroinvertebrate communities in oligotrophic lake outlets. These data imply the importance of the habitat templet in the structuring of benthic communities.     

Winter habitat-use pattern of elk, mule deer, and mosse in southwestern Wyoming

Habitat-use patterns of mule deer, elk, and moose were determined on two winter range near Kemmerer, Wyoming. Mule deer used areas with the least snow depth and dominated by sagebrush. Elk were located more often than expected on wind-swept hills but used sagebrush communities more frequently as snow depths increased. Moose were generally found associated with broad, riparian zones. All three species occasionally used the same area but differed in their use of specific vegetation types and topography.     

Biotic and abiotic factors related to redband trout occurrence and abundance in desert and montane streams

Redband trout Oncorhynchus mykiss gairdneri in the Columbia River Basin of western North America occupy desert and montane streams with variable habitat conditions. In general, desert streams are lower in gradient and elevation, contain less large substrate and more silt substrate, are less shaded by overhead vegetation, and have higher summer water temperature than montane streams. Consequently, we assessed whether the relationships between biotic and abiotic factors and the occurrence and abundance of redband trout in southwestern Idaho differed between desert and montane streams (<25 m mean width). Increased occurrence of redband trout in desert streams was most strongly related to increased stream shading and decreased amounts of silt substrate, followed by increased amounts of cobble/boulder substrate and absence of piscivorous fish (i.e., smallmouth bass Micropterus dolomieui and northern pikeminnow Ptychocheilus oregonensis ). In montane streams, increased occurrence of redband trout was most strongly related to decreased site elevation and increases in cobble/boulder substrate, followed by decreases in stream gradient and width. Furthermore, occurrence of redband trout decreased in desert streams at mean summer (June–August) water temperature (Temp smr ) >16 °C, whereas for montane streams, occurrence increased at Temp smr >9 °C. Redband trout density in desert streams was most strongly related to higher stream order (i.e., headwater streams), increased stream shading, and increased amounts of cobble/boulder substrate. In montane streams, redband trout density was not well explained by any stream conditions, but stream shading had the strongest positive relationship with density. Redband trout density was negatively related to Temp smr in desert streams, but the relationship was weak for montane streams. That environmental conditions related to the occurrence and abundance of redband trout differ between desert and montane streams is important for fisheries managers who manage these disparate populations occurring in such close proximity to each other.     

Macrobenthic communities in water bodies and streams of Svalbard,Norway

Diversity of macrobenthic communities was studied from water bodies and streams of Spitsbergen, Svalbard archipelago, Norway. In total 162 quantitative samples from different regions of Spitsbergen were analysed in relation to environmental variables. Macrobenthic communities were found on all kinds of substrates (except for the periglacial zone), representing a wide range of biological communities: solid-bottom, soft-bottom, macrophytes and small brook associated. However, taxonomical structure is very simplified, with particular dominance of the Chironomidae family. Chironomid larvae dominated highly in diversity, abundance and biomass. Overall macrobenthic communities were characteristic, with remarkable dominance of one species and general omnipresent taxonomical scarcity (average 2.8 species per sample). In total we found 30 taxa. We distinguished 16 types of macrobenthis communities, with characteristic dominance of different taxa: chironomids (11 types), oligochaete Enchytraeidae family (3), caddisfly Apatania zonella (1) and gammarid amphipod Gammarus setosus (1). Regarding environmental variables, temperature and pH had the most significant influence on the abundance of macrobenthic organisms. It is hypothesized that the structural convergence of different types of communities is their common response to extreme high Arctic living conditions. On the other hand, different chironomids may dominate in the same habitats and water bodies. This gives the effect of lower average similarity of communities and high β-diversity.     

Spawning ecology of finespotted Snake River cutthroat trout in spring streams of the Salt River valley, Wyoming

We studied spawning ecology of cutthroat trout ( Oncorhynchus clarki ) in streams that originate as springs along the Salt River, a Snake River tributary in western Wyoming. We assessed (1) relative numbers of upstream-migrant and resident adults present during the spawning period in spring streams, (2) influence of habitat modification on use of spring streams for spawning, and (3) habitat features used for spawning in spring streams. Four spring streams were studied, 2 with substantial modification to enhance trout habitat and 2 with little or no modification. Modifications consisted primarily of constructing alternating pools and gravel-cobble riffles. Only a small portion of adult fish in spring streams during the spawning period had migrated upstream from the Salt River between March and the middle of June. Larger numbers of adult fish and more redds were observed in the 2 modified streams compared with the 2 streams with little or no modification. Most spawning occurred on constructed riffles with small gravel and over a narrow range of depths and velocities. Cutthroat trout, rainbow trout ( Oncorhynchus mykiss ), and their hybrids were observed in 1 stream with habitat modifications, indicating that measures to halt invasion by rainbow trout, as well as habitat improvement, are needed to preserve this native trout within the Salt River valley.     

Macroinvertebrate richness is lower in high-elevation lakes vs nearby streams: evidence from Grand Teton National Park,Wyoming

Mountain ecosystems will be strongly impacted by climate change, yet little is known of extant biodiversity in high-elevation lakes, particularly in North America. In this study, we sampled the littoral zone of six alpine and subalpine lakes in Grand Teton National Park (GRTE), Wyoming, to characterise invertebrate diversity and environmental variation in these climate change-threatened ecosystems. Overall, we collected 19 aquatic invertebrate taxa, and found that each lake harboured a unique assemblage of invertebrates despite close geographic proximity in some instances (e.g. less than 5 km). The results of this study complement previous efforts focused on macroinvertebrate diversity of streams in the Teton Range, highlighting much lower diversity in montane lakes vs nearby streams. Taken together, the two studies establish an important baseline understanding of mountain freshwater biodiversity in GRTE. With rapidly changing hydrologic inputs to mountain lakes driven primarily by the recession of alpine glaciers, these results may help target aquatic invertebrates to monitor as climate change affects the region. Moreover, these data clarify habitat factors, both biotic and abiotic, that influence high-elevation lake assemblages of the Teton Range.     

Effect of excluding shredders on leaf litter decomposition in two streams

The effect of excluding shredders on leaf processing rates was studied in a Rocky Mountain stream in Utah and a cold desert stream in Washington. Experimentally excluding shredders significantly decreased the processing rate in both streams. Processing rates (k) were higher in the desert stream, and it is postulated that this is related to increased microbial activity due to the higher water temperatures.     

Relation of fish communities to environmental conditions in urban streams of the Wasatch Front, Utah

Twenty-eight sites along the Wasatch Front, north central Utah, representing the range of urban land use intensity for wadeable streams of the area, were sampled in September 2000. Fish communities were assessed by single-pass electrofishing, and physical habitat and water-quality characteristics were measured. On average, nonnative species comprised 54% of species richness and 53% of relative abundance, although only Salmo trutta and Pimephales promelas were very abundant at any 1 site. Salmo trutta and Catostomus platyrhynchus , a native species, were the most widely distributed and abundant species captured. Analysis of fish communities using nonmetric multidimensional scaling (NMDS) revealed a community gradient from sites dominated by Salmo trutta and Cottus species ( C. bairdi , C. beldingi ) to sites dominated by Catostomus platyrhynchus . Sites dominated by C. platyrhynchus were smaller in size and had less habitat cover, smaller average substrate size, higher concentrations of dissolved constituents, and higher water temperature than sites dominated by S. trutta . Sites dominated by C. platyrhynchus were located in more intensely urbanized watersheds at lower elevations. Stream size and associated instream habitat availability appear to limit S. trutta distribution and abundance, while native species appear more tolerant of decreased water quality and increased water temperatures in more urbanized streams. Most of the study sites are affected by development of water infrastructure for human water use (e.g., dams and diversions), and this infrastructure may play a role in dispersal of species.     

Reproductive characteristics of two kokanee stocks in tributaries to Flaming Gorge Reservoir, Utah and Wyoming

The charaeteristics of kokanee ( Oncorhynchus nerka ) spawning stocks in the Green River and Sheep Creek (tributaries to Flaming Gorge Reservoir) are described as observed in fall 1985 and spring 1986; the time of spawning; length, age, and sex structure of the stocks; fecundity and egg retention; density of eggs in redds; and the timing of downstream drift of emerging fry. The time of spawning, length-frequency distributions of spawning fish, and egg density in redds differed between the two stocks, but other differences were not observed.     

Mite parasitism of mosquitoes in central Wyoming

Parasitic larval mites including Thyasides sphagnorum were collected from mosquitoes captured in New Jersey light traps over a period of 6 yr and from landings during 1 collecting season in Natrona County, Wyoming. Overall mite prevalence on mosquitoes was 0.42% and abundance was 0.76%. Prevalence on Aedes dorsalis was significantly greater than on other host species. Comparison of light trap data and landing data suggests that parasitized mosquitoes may seek blood meals more frequently than non-parasitized mosquitoes.     

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.     

Summer food habits of coyotes in central Wyoming

Summer food habits of coyotes ( Canis latrans ) were investigated on a 3100-km 2 area in central Wyoming, divided into one deer-use area and five non-deer areas. Analysis of 404 scats (fecal samples) revealed an overall average of 63 percent occurrence of native ungulates, 63 percent leporids, 46 percent rodents, 14 percent livestock, and 11 percent birds. Pronghorn ( Antilocapra Americana ) was the ungulate most frequently consumed, occurring in about 87 percent of the scats. Mule deer ( Odocoileus hemionus ) occurred in only 8 percent, and in 5 percent the native ungulate remains were not identifiable beyond order. This large percentage of big game in the diet is apparently unusual, because big game has been of minor importance in most coyote food-habit studies. The high incidence of leporids is consistent with other studies performed in arid intermountain areas. Although cricetines, especially deer mice ( Peromyscus maniculatus ), were trapped consistently in all habitats, months, and trapping areas, they were found in scats at a lower frequency than microtines and sciurids. This suggests a coyote hunting strategy that selected for the latter two groups.     

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.     

The raccoon, Procyon Iotor, in Wyoming

Recent distribution maps show raccoon as occupying only the extreme eastern - northeastern portion of Wyoming. However, there is substantial evidence that raccoon are common throughout Wyoming and currently inhabit all the major and many of the minor drainages throughout Wyoming.     

Benthic community structure in two adjacent streams in Yellowstone National Park five years after the 1988 wildfires

Physical characteristics, benthic macroinvertebrates, and periphyton assemblages in two adjacent headwater streams in Yellowstone National Park were evaluated five years after the 1988 wildfires. The catchment of one stream was burned by wildfire (burned stream) while the other catchment was unburned (unburned stream). Physical measures revealed channel alteration in the burned stream relative to the unburned stream Periphyton biomass was lower in the burned than the unburned stream (29.2 vs. 50.5 g/m 2 AFDM, respectively), further demonstrating the unstable physical conditions of that system. Kendall's coefficient of concordance (an index of similarity) between diatom assemblages was 0.22, indicating distinct assemblage composition between streams. Navicula permitis Hust. was the most abundant diatom in the burned stream while Hannaea arcus (Ehr.) Patr. was dominant in the unburned stream. Macroinvertebrate taxa richness, density, and biomass were all greater in the unburned stream, although Chironomidae was the most abundant taxon in both streams. Results suggest the removal of terrestrial/riparian vegetation by wildfire can directly influence benthic assemblages by altering the inherent disturbance regime of the physical habitat templet.     

Habitat and nesting biology of Mountain Plovers in Wyoming

Although previous research has considered habitat associations and breeding biology of Mountain Plovers in Wyoming at discrete sites, no study has considered these attributes at a statewide scale. We located 55 Mountain Plover nests in 6 counties across Wyoming during 2002 and 2003. Nests occurred in 2 general habitat types: grassland and desert-shrub. Mean estimated hatch date was 26 June ( n = 31) in 2002 and 21 June ( n = 24) in 2003. Mean hatch date was not related to latitude or elevation. Hatch success of nests was inferred in 2003 by the presence of eggshell fragments in the nest scrape. Eggs in 14 of 22 (64%) known-fate nests hatched. All grassland sites and 90% of desert sites were host to ungulate grazers, although prairie dogs were absent at 64% of nest sites. Nest plots had less grass coverage and reduced grass height compared with random plots. More than 50% of nests occurred on elevated plateaus. The Mountain Plover's tendency to nest on arid, elevated plateaus further substantiates claims that the bird is also a disturbed- prairie species.     

Standing crops and dynamics of phytomass and minerals in two salt desert shrub communities

Of two salt desert shrub communities studied in Curlew Valley, Utah, the Atriplex confertifolia- dominated community had 15% greater total midsummer phytomass than the Ceratoides lanata community. The larger Atriplex shrubs contained much more woody tissue for support of photosynthetic tissues than did Ceratoides. Atriplex aboveground phytomass and litter were about twice those of Ceratoides. Ceratoides litter was generally fine and easily decomposable, but Atriplex litter contained about equal proportions of coarse, resistant woody tissues and fine, easily decomposable material. Atriplex root phytomass was 1.3 times that of Ceratoides at the 2–30 cm depth, but at depths below 30 cm, Ceratoides exhibited up to three times greater root phytomass and had 23% more root mass overall. Net aboveground community primary production was estimated to be about one-third greater in the Atriplex than Ceratoides community. Turnover times for readily decomposable aboveground litter were quite similar, but, because Atriplex produced coarser litter, its overall rate was somewhat slower than that of Ceratoides. Analyses of selected minerals in plant parts, litter, and soil revealed that about 90% of the mineral capital is in the soil, mostly within organic matter. Nearly equivalent pools of mineral elements were found in the two communities, except for greater Na in the Atriplex community.     

Status and distribution of California Gull nesting colonies in Wyoming

Historically, two California Gull nesting colonies existed in Wyoming. In 1984 there were six breeding locations consisting of 10 different colonies that included approximately 7,273 nests. The increase in the California Gull nesting population in the state is probably a consequence of man-caused environmental changes that have resulted in the creation of additional breeding habitat and new food sources.