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Mountain Streams (mountain + stream)
Selected AbstractsMODELING METALS TRANSPORT AND SEDIMENT/WATER INTERACTIONS IN A MINING IMPACTED MOUNTAIN STREAM,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004Brian S. Caruso ABSTRACT: The U.S. Environmental Protection Agency (USEPA) Water Quality Analysis Simulation Program (WASP5) was used to model the transport and sediment/water interactions of metals under low flow, steady state conditions in Tenmile Creek, a mountain stream supplying drinking water to the City of Helena, Montana, impacted by numerous abandoned hard rock mines. The model was calibrated for base flow using data collected by USEPA and validated using data from the U.S. Geological Survey (USGS) for higher flows. It was used to assess metals loadings and losses, exceedances of Montana State water quality standards, metals interactions in stream water and bed sediment, uncertainty in fate and transport processes and model parameters, and effectiveness of remedial alternatives that include leaving contaminated sediment in the stream. Results indicated that during base flow, adits and point sources contribute significant metals loadings to the stream, but that shallow ground water and bed sediment also contribute metals in some key locations. Losses from the water column occur in some areas, primarily due to adsorption and precipitation onto bed sediments. Some uncertainty exists in the metal partition coefficients associated with sediment, significance of precipitation reactions, and in the specific locations of unidentified sources and losses of metals. Standards exceedances are widespread throughout the stream, but the model showed that remediation of point sources and mine waste near water courses can help improve water quality. Model results also indicate, however, that alteration of the water supply scheme and increasing base flow will probably be required to meet all water quality standards. [source] Leaf Decomposition in a Mountain Stream in the Sultanate of OmanINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2009Maha Al-Riyami Abstract Decomposition of Juglans regia leaves was studied in fine and coarse mesh bags in a permanent mountain stream in Oman. A rapid initial mass loss, attributed to leaching, was followed by a more gradual decline. Daily exponential decay rates (k) calculated over 32 days were 0.011 (fine mesh litter bags) and 0.014 (coarse mesh litter bags). The difference between bag types was not significant, suggesting limited impact of leaf-shredding invertebrates. Ergosterol levels on leaves from fine mesh bags peaked at 0.3 mg g,1 AFDM after 16 days of stream exposure. During the experimental period, which followed the annual leaf fall, the concentration of aquatic hyphomycete conidia in the stream varied between 82 and 1362 l,1. Based on the morphology of conidia found in the water column or released from leaves, we identified 14 species of aquatic hyphomycetes. Tetracladium apiense was the most common taxon (62.2% of conidia in water column during the field experiment). Three other Tetracladium species contributed another 8%. Plating out leaf particles yielded common epiphytic taxa such as Alternaria sp., Aureobasidium pullulans and Phoma sp. The measured metrics of leaf decay in this desert stream fall within the range of values observed in temperate and tropical streams, with clear evidence for an early leaching phase, and no evidence of a strong impact of leaf shredders. The community of aquatic hyphomycetes appears impoverished. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The influence of predatory fish on mayfly drift: extrapolating from experiments to natureFRESHWATER BIOLOGY, Issue 8 2002ANGUS R. MCINTOSH 1.,A knowledge of how individual behaviour affects populations in nature is needed to understand many ecologically important processes, such as the dispersal of larval insects in streams. The influence of chemical cues from drift-feeding fish on the drift dispersal of mayflies has been documented in small experimental channels (i.e. < 3 m), but their influence on dispersal in natural systems (e.g. 30 m stream reaches) is unclear. 2.,Using surveys in 10 Rocky Mountain streams in Western Colorado we examined whether the effects of predatory brook trout (Salvelinus fontinalis) on mayfly drift, that were apparent in stream-side channels, could also be detected in natural streams. 3.,In channel experiments, the drift of Baetis bicaudatus (Baetidae) was more responsive to variation in the concentration of chemical cues from brook trout than that of another mayfly, Epeorus deceptivus (Heptageniidae). The rate of brook trout predation on drifting mayflies of both species in a 2-m long observation tank was higher during the day (60,75%) but still measurable at night (5,10%). Epeorus individuals released into the water column were more vulnerable to trout predation by both day and night than were Baetis larvae treated similarly. 4.,Drift of all mayfly taxa in five fishless streams was aperiodic, whereas their drift was nocturnal in five trout streams. The propensity of mayflies to drift was decreased during the day and increased during the night in trout streams compared with fishless streams. In contrast to the channel experiments, fish biomass and density did not alter the nocturnal nature nor magnitude of mayfly drift in natural streams. 5.,In combination, these results indicate that mayflies respond to subtle differences in concentration of fish cues in experimental channels. However, temporal and spatial variation in fish cues available to mayflies in natural streams may have obscured our ability to detect responses at larger scales. [source] Interregional comparisons of sediment microbial respiration in streamsFRESHWATER BIOLOGY, Issue 2 2000B. H. Hill Summary 1The rate of microbial respiration on fine-grained stream sediments was measured at 371 first to fourth-order streams in the Central Appalachian region (Maryland, Pennsylvania, Virginia, and West Virginia), Southern Rocky Mountains (Colorado), and California's Central Valley in 1994 and 1995. 2Study streams were randomly selected from the United States Environmental Protection Agency's (USEPA) River Reach File (RF3) using the sample design developed by USEPA's Environmental Monitoring and Assessment Program (EMAP). 3Respiration rate ranged from 0 to 0.621 g O2 g -1 AFDM h -1 in Central Appalachian streams, 0-0.254 g O2 g -1 AFDM h -1 in Rocky Mountain streams, and 0-0.436 g O2 g -1 AFDM h -1 in Central Valley streams. 4Respiration was significantly lower in Southern Rocky Mountain streams and in cold water streams (< 15 °C) of the Central Appalachians. 5Within a defined index period, respiration was not significantly different between years, and was significantly correlated with stream temperature and chemistry (DOC, total N, total P, K, Cl, and alkalinity). 6The uniformity of respiration estimates among the three study regions suggests that sediment microbial respiration may be collected at any number of scales above the site-level for reliable prediction of respiration patterns at larger spatial scales. [source] Residency and movement of stream-dwelling Japanese charr, Salvelinus leucomaenis, in a central Japanese mountain streamECOLOGY OF FRESHWATER FISH, Issue 3 2002T. Nakamura Abstract,,,The residency and movement of stream-dwelling adult (2+ and older) Japanese charr, Salvelinus leucomaenis, were studied by mark and recapture experiments in the Jadani Stream, a headwater tributary of the Tedori River, central Japan, from 1986 to 1989. Of the marked fish, 31.3,58.3% were recaptured in the same pools where they had been caught during the study periods of summer (June,August), autumn (August,November) and winter,spring (November to the next June) and no seasonal movement was observed. The mean distances that the fish moved during the study periods ranged from 139.0 to 502.3 m and many movements longer than 1000 m were observed. Between the resident and the moved fish, there was little difference in body length, growth rate or sex. For the fish that had been resident in the same pools and riffles at previous recaptures, most fish were recaptures in the same locations at the next recapture. Conversely, for the fish that moved previously, most fish were recaptured in different locations from previous sites at the next recapture. These results suggest that Japanese charr exhibit relatively high residency throughout the year, but many fish moved longer distance. The results also suggest the presence of static and mobile components in the charr population. [source] Dynamics of yeast populations recovered from decaying leaves in a nonpolluted stream: a 2-year study on the effects of leaf litter type and decomposition timeFEMS YEAST RESEARCH, Issue 4 2007Ana Sampaio Abstract Here we report on the results of a survey of the yeast populations occurring on submerged leaves (alder, eucalyptus and oak) in a natural mountain stream, during different phases of their decomposition and through two consecutive years. Leaf litter mass loss, total yeast counts, Shannon,Weiner index (H,), yeast community structure and physiologic abilities were analyzed to evaluate the dynamics of yeast communities during decay. Seventy-two yeast taxa were recorded, and in all litter types, species of basidiomycetous affinity predominated over ascomycetous ones. Discriminant analysis of presence/absence data (yeast species) showed significant differences both among substrate types (P<0.0026) and with decomposition time (P<0.0001). Carbon and nitrogen source utilization by yeast strains also varied with the substrate (P<0.0001) and decomposition time (P<0.0001). Further conclusions were that: (1) all litter types have in common ubiquitous yeast species, such as Cryptococcus albidus, Debaryomyces hansenii and Rhodotorula glutinis, among the common 20 yeast species; (2) only a few species were dominant, and most species were rare, being recorded once or twice throughout decomposition; and (3) the order of yeast appearance, and their substrate assimilation patterns, strongly suggest a succession phenomenon. Finally, explanations for the distribution patterns and variations in yeast communities are discussed. [source] Suspended sediment dynamics in a steep, glacier-fed mountain stream, Place Creek, CanadaHYDROLOGICAL PROCESSES, Issue 9 2003G. Richards Abstract This study examined suspended sediment concentration (SSC) during the ablation seasons of 2000 and 2001 in Place Creek, Canada, a steep, glacier-fed mountain stream. Comparison of stream flow in Place Creek with that in an adjacent, almost unglacierized catchment provided a rational basis for separating the ablation seasons into nival, nival,glacial, glacial and autumn recession subseasons. Distinct groupings of points in plots of electrical conductivity against discharge supported the validity of the subseasonal divisions in terms of varying hydrological conditions. Relationships between SSC and discharge (Q) varied between the two study seasons, and between subseasons. Hysteresis in the SSC,Q relationship was evident at both event and weekly time-scales. Some suspended sediment released from pro-glacial Place Lake (the source of Place Creek) appeared to be lost to channel storage at low flows, especially early in the ablation season, with re-entrainment at higher flows. Multiple regression models were derived for the subseasons using predictor variables including Q, Q2, the change in Q over the previous 3 h, cumulative discharge over the ablation season, total precipitation over the previous 24 h and SSC measured at 1500 hours as an index value for each day. The models produced adjusted R2 values ranging from 0·71 to 0·91, and provided tentative insights into the differences in SSC dynamics amongst subseasons. Introduction of the index value of SSC significantly improved the model fit during the nival,glacial and glacial subseasons for both years, as it adjusts the model to the current condition of sediment supply. Copyright © 2003 John Wiley & Sons, Ltd. [source] Leaf Decomposition in a Mountain Stream in the Sultanate of OmanINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2009Maha Al-Riyami Abstract Decomposition of Juglans regia leaves was studied in fine and coarse mesh bags in a permanent mountain stream in Oman. A rapid initial mass loss, attributed to leaching, was followed by a more gradual decline. Daily exponential decay rates (k) calculated over 32 days were 0.011 (fine mesh litter bags) and 0.014 (coarse mesh litter bags). The difference between bag types was not significant, suggesting limited impact of leaf-shredding invertebrates. Ergosterol levels on leaves from fine mesh bags peaked at 0.3 mg g,1 AFDM after 16 days of stream exposure. During the experimental period, which followed the annual leaf fall, the concentration of aquatic hyphomycete conidia in the stream varied between 82 and 1362 l,1. Based on the morphology of conidia found in the water column or released from leaves, we identified 14 species of aquatic hyphomycetes. Tetracladium apiense was the most common taxon (62.2% of conidia in water column during the field experiment). Three other Tetracladium species contributed another 8%. Plating out leaf particles yielded common epiphytic taxa such as Alternaria sp., Aureobasidium pullulans and Phoma sp. The measured metrics of leaf decay in this desert stream fall within the range of values observed in temperate and tropical streams, with clear evidence for an early leaching phase, and no evidence of a strong impact of leaf shredders. The community of aquatic hyphomycetes appears impoverished. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Population Ecology of the Riparian Frog Eleutherodactylus cuneatus in CubaBIOTROPICA, Issue 3 2010Ansel Fong G. ABSTRACT A population of the poorly known riparian frog Eleutherodactylus cuneatus was studied for 1 yr along a mountain stream in eastern Cuba. We examined population structure, seasonal and daily activity, growth, and habitat use using mark-recapture and call-point counts. Juveniles were observed during all survey periods with a spike in March. Higher numbers of adults were present in May,July, associated with longer day length, warmer temperatures, and the onset of the rainy season. This was coincident with higher calling activity away from the stream, suggesting an increase in both reproductive and nonreproductive activity in the warmer months between May and September. The number of individuals peaked at 2000,2200 h, but high numbers of individuals were visible throughout the night. Lower activity levels were observed throughout the day. Population size estimates were 84,131 adults and 124,304 juveniles, with averages of 110 and 236 individuals, survival rates were high but capture probabilities were low for a 5-d period in March 2004. Growth rate was negatively related to the size of recaptured individuals, although decreases in growth rate were slight. Frogs were found either in the water (49.7%), or in the banks and on the ground adjacent to the stream where most individuals were found on the ground under the cover of rocks, leaf litter, or large palm fronds. These results provide baseline knowledge of E. cuneatus population dynamics and ecology needed for a rapid detection of any decline this population may undergo in the future. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp [source] Assessing trace-metal exposure to American dippers in mountain streams of southwestern British Columbia, CanadaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2005Christy A. Morrissey Abstract To develop a suitable biomonitor of metal pollution in watersheds, we examined trends in exposure to nine trace elements in the diet (benthic invertebrates and fish), feathers (n = 104), and feces (n = 14) of an aquatic passerine, the American dipper (Cinclus mexicanus), from the Chilliwack watershed in British Columbia, Canada. We hypothesized that key differences may exist in exposure to metals for resident dippers that occupy the main river year-round and altitudinal migrants that breed on higher elevation tributaries because of differences in prey metal levels between locations or possible differences in diet composition. Metals most commonly detected in dipper feather samples in decreasing order were Zn > Cu > Hg > Se > Pb > Mn > Cd > Al > As. Resident dipper feathers contained significantly higher mean concentrations of mercury (0.64 ,g/g dry wt), cadmium (0.19 ,g/g dry wt), and copper (10.8 ,g/g dry wt) relative to migrants. Mass balance models used to predict daily metal exposure for dippers with different diets and breeding locations within a watershed showed that variation in metal levels primarily was attributed to differences in the proportion offish and invertebrates in the diet of residents and migrants. In comparing predicted metal exposure values to tolerable daily intakes (TDI), we found that most metals were below or within the range of TDI, except selenium, aluminum, and zinc. Other metals, such as cadmium, copper, and arsenic, were only of concern for dippers mainly feeding on insects; mercury was only of concern for dippers consuming high fish diets. The models were useful tools to demonstrate how shifts in diet and breeding location within a single watershed can result in changes in exposure that may be of toxicological significance. [source] Ecological responses to nutrients in streams and rivers of the Colorado mountains and foothillsFRESHWATER BIOLOGY, Issue 9 2010WILLIAM M. LEWIS Summary 1. Abundance and composition of periphyton and benthic macroinvertebrates were treated as potential nutrient response variables for 74 streams in montane Colorado. The streams ranged from unenriched to mildly enriched with nutrients (N, P). 2. The study showed no meaningful relationship between periphyton biomass accumulation and concentrations of total or dissolved forms of nitrogen or phosphorus. Nutrient concentrations were also unrelated to periphyton and macroinvertebrate richness, diversity and community composition. Macroinvertebrate communities did, however, show a strong positive relationship to periphyton abundance. 3. A positive response of periphyton biomass to increasing nutrient concentrations has been well documented over large ranges of nutrient concentrations. Our study suggests that the nutrient response is suppressed by other controlling factors on the lower limb of the nutrient response curve (i.e. at low nutrient concentrations); a quantitatively significant response occurs only in excess of a threshold beyond which nutrients become dominant over other controlling factors. This interpretation of the results is consistent with published meta-analyses showing lack of nutrient response for a high proportion of experimentally enriched periphyton communities, and division of responses between N and P for communities that do show growth in response to enrichment. 4. Grazing probably is not the key controlling variable for periphyton in Colorado mountain streams, given that the highest chlorophyll concentrations are associated with the highest abundances of macroinvertebrates. Modelling indicates that the initial amount of periphyton biomass at the start of the growing season, in conjunction with elevation-related length of the growing season and water temperature, explains most of the variation in periphyton accumulation among these streams, but there is a yet unexplained suppression of periphyton growth rates across all elevations. [source] Assessment of European streams with diatoms, macrophytes, macroinvertebrates and fish: a comparative metric-based analysis of organism response to stressFRESHWATER BIOLOGY, Issue 9 2006DANIEL HERING Summary 1. Periphytic diatoms, macrophytes, benthic macroinvertebrates and fish were sampled with standard methods in 185 streams in nine European countries to compare their response to degradation. Streams were classified into two main stream type groups (i.e. lowland, mountain streams); in addition, the lowland streams were grouped into four more specific stream types. 2. Principal components analysis with altogether 43 environmental parameters was used to construct complex stressor gradients for physical,chemical, hydromorphological and land use data. About 30 metrics were calculated for each sample and organism group. Metric responses to different stress types were analysed by Spearman Rank Correlation. 3. All four organism groups showed significant response to eutrophication/organic pollution gradients. Generally, diatom metrics were most strongly correlated to eutrophication gradients (85% and 89% of the diatom metrics tested correlated significantly in mountain and lowland streams, respectively), followed by invertebrate metrics (91% and 59%). 4. Responses of the four organism groups to other gradients were less strong; all organism groups responded to varying degrees to land use changes, hydromorphological degradation on the microhabitat scale and general degradation gradients, while the response to hydromorphological gradients on the reach scale was mainly limited to benthic macroinvertebrates (50% and 44% of the metrics tested correlated significantly in mountain and lowland streams, respectively) and fish (29% and 47%). 5. Fish and macrophyte metrics generally showed a poor response to degradation gradients in mountain streams and a strong response in lowland streams. 6. General recommendations on European bioassessment of streams were derived from the results. [source] Biological and ecological traits of benthic freshwater macroinvertebrates: relationships and definition of groups with similar traitsFRESHWATER BIOLOGY, Issue 2 2000Philippe Usseglio-Polatera Summary 1Relating species traits to habitat characteristics can provide important insights into the structure and functioning of stream communities. However, trade-offs among species traits make it difficult to predict accurately the functional diversity of freshwater communities. Many authors have pointed to the value of working with groups of organisms as similar as possible in terms of relationships among traits and have called for definition of groups of organisms with similar suites of attributes. 2We used multivariate analyses to examine separately the relationships among 11 biological traits and among 11 ecological traits of 472 benthic macroinvertebrate taxa (mainly genera). The main objective was to demonstrate (1) potential trade-offs among traits; (2) the importance of the different traits to separate systematic units or functional groupings; and (3) uniform functional groups of taxa that should allow a more effective use of macroinvertebrate biological and ecological traits. 3We defined eight groups and 15 subgroups according to a biological trait ordination which highlighted size (large to small), reproductive traits (K to r strategists), food (animal to plant material) and feeding habits (predator to scraper and/or deposit feeder) as ,significant' factors determining the ordination of taxa. This ordination partly preserved phylogenetic relationships among groups. 4Seven ecological groups and 13 ecological subgroups included organisms with combinations of traits which should be successively more adequate in habitats from the main channel to temporary waters, and from the crenon to the potamic sections of rivers, and to systems situated outside the river floodplain. These gradients corresponded to a gradual shift from (1) rheophilic organisms that lived in the main channel of cold oligotrophic mountain streams to (2) animals that preferred eutrophic habitats of still or temporary waters in lowlands. The groups with similar ecological traits had a more diverse systematic structure than those with similar biological traits. 5Monitoring and assessment tools for the management of water resources are generally more effective if they are based on a clear understanding of the mechanisms that lead to the presence or absence of species groups in the environment. We believe that groups with similar relationships among their species traits may be useful in developing tools that measure the functional diversity of communities. [source] Retracted and replaced: A modelling study of hyporheic exchange pattern and the sequence, size, and spacing of stream bedforms in mountain stream networks, Oregon, USAHYDROLOGICAL PROCESSES, Issue 15 2005Michael N. Gooseff Abstract This article has been retracted and replaced. See Retraction and Replacement Notice DOI: 10.1002/hyp.6350 Studies of hyporheic exchange flows have identified physical features of channels that control exchange flow at the channel unit scale, namely slope breaks in the longitudinal profile of streams that generate subsurface head distributions. We recently completed a field study that suggested channel unit spacing in stream longitudinal profiles can be used to predict the spacing between zones of upwelling (flux of hyporheic water into the stream) and downwelling (flux of stream water into the hyporheic zone) in the beds of mountain streams. Here, we use two-dimensional groundwater flow and particle tracking models to simulate vertical and longitudinal hyporheic exchange along the longitudinal axis of stream flow in second-, third-, and fourth-order mountain stream reaches. Modelling allowed us to (1) represent visually the effect that the shape of the longitudinal profile has on the flow net beneath streambeds; (2) isolate channel unit sequence and spacing as individual factors controlling the depth that stream water penetrates the hyporheic zone and the length of upwelling and downwelling zones; (3) evaluate the degree to which the effects of regular patterns in bedform size and sequence are masked by irregularities in real streams. We simulated hyporheic exchange in two sets of idealized stream reaches and one set of observed stream reaches. Idealized profiles were constructed using regression equations relating channel form to basin area. The size and length of channel units (step size, pool length, etc.) increased with increasing stream order. Simulations of hyporheic exchange flows in these reaches suggested that upwelling lengths increased (from 2·7 m to 7·6 m), and downwelling lengths increased (from 2·9 m to 6·0 m) with increase in stream order from second to fourth order. Step spacing in the idealized reaches increased from 5·3 m to 13·7 m as stream size increased from second to fourth order. Simulated upwelling lengths increased from 4·3 m in second-order streams to 9·7 m in fourth-order streams with a POOL,RIFFLE,STEP channel unit sequence, and increased from 2·5 m to 6·1 m from second- to fourth-order streams with a POOL,STEP,RIFFLE channel unit sequence. Downwelling lengths also increased with stream order in these idealized channels. Our results suggest that channel unit spacing, size, and sequence are all important in determining hyporheic exchange patterns of upwelling and downwelling. Though irregularities in the size and spacing of bedforms caused flow nets to be much more complex in surveyed stream reaches than in idealized stream reaches, similar trends emerged relating the average geomorphic wavelength to the average hyporheic wavelength in both surveyed and idealized reaches. Copyright © 2005 John Wiley & Sons, Ltd. [source] Stream Macroinvertebrate Community Affected by Point-Source Metal PollutionINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2007Hideyuki Doi Abstract The impacts of mining activities on aquatic biota have been documented in many stream ecosystems. In mining streams, point-source heavy metal pollution often appears in the stream. We hypothesize that this pollution is toxic to macroinvertebrates owing to high concentrations of metals and therefore affects macroinvertebrate community structure. We investigated macroinvertebrate community structure in mountain streams, including heavy metal-polluted sites and neutral-pH streams, to determine the relationship between community structure and environmental factors such as low pH and heavy metal concentrations. Based on multidimensional scaling ordination, the macroinvertebrate community at heavy metal pollution sites was remarkably different from that at the other sites. Inductively coupled plasma mass spectrometry revealed high concentrations of aluminum and iron in surface water at the polluted sites. Macroinvertebrate community structure at the metal pollution sites was significantly different from that at other sites in the same stream and in neutral-pH streams. Thus, point-source metal pollution may reduce the density and diversity of in situ macroinvertebrates. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Benthic Invertebrates and Metabolism of West Carpathian (Slovakia) RiversINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3-4 2003Ferdinand, porka Abstract We examined benthic invertebrates and metabolism on the basis of the annual sampling of 9 types of running waters in the West Carpathians. Headwaters in general represent typical heterotrophic systems, except where they are high mountain streams, which are autotrophic. Lower down, the upper reaches of brooks are transition zones between heterotrophic and autotrophic systems. After the transition to an autotrophic system (which depends mainly on the primary producers) there is a considerable decrease in secondary production. Production is higher in the rivers of the Carpathian basin, as well as lower down the valley (submontane rivers and lower tributaries of submontane streams) where, within the autotrophic systems, there is a shift of metabolism from the bottom to the water column. The temperature days, altitude and slope of the stream and concentration of calcium influence production of macrozoobenthos. [source] Behavioural interactions between native smokey dace and introduced yellowfin shiner: implications from habitat selection theory for an ongoing invasionJOURNAL OF FISH BIOLOGY, Issue 2003C. M. Wagner The occupation of adjacent, non-overlapping positions along environmental gradients by closely related and ecologically similar species has drawn considerable attention from ecologists over the past decades. Condition-specific competition, wherein competitive superiority varies with the abiotic environmental gradient, has been proposed as the major structuring force behind such distributions. These concepts, however, are generally applied to explain the contemporary distribution of organisms that share an evolutionary history. Our aim was to apply these concepts to the naive interactions between native and introduced fishes. In 1990 yellowfin shiner (Notropis lutipinnis) were introduced into the headwaters of the Little Tennessee River of western North Carolina, U.S.A. where it exhibits microhabitat preferences that overlap significantly with those of a threatened native minnow, the smokey dace (Clinostomus funduloides raneyi). Previous research has established that these drift-feeding minnows: (1) differ in their average ability to intercept drifting prey as a function of water velocity; (2) generally occupy focal-point velocities that maximize the rate of prey capture; and, (3) occasionally defend the forward positions in foraging aggregations that form in high quality patches. We present the results of a series of experiments designed to: (1) evaluate the role of aggression in the establishment and maintenance of preferred foraging positions in drift-feeding minnows; (2) test the effects of prey availability, group size, and velocity on dominance rank, spatial position in groups, and feeding rates of individuals; and, (3) evaluate the potential for condition-specific competition to establish competitive refugia for the native within the natural heterogeneity of mountain streams. [source] Differences in the structure, growth and survival of Parasenecio yatabei ramets with contrasting water relations on the slope of a stream bankPLANT SPECIES BIOLOGY, Issue 2 2009HAJIME TOMIMATSU Abstract Parasenecio yatabei (Asteraceae), a summer-green perennial herb, is widely distributed on sloping mountain stream banks in cool-temperate zone forests of Japan. We investigated the growth pattern, leaf longevity and leaf water relations of vegetatively independent plants (ramets) growing in two contrasting soil water conditions, that is, upper and lower stream banks (U ramets and L ramets, respectively). The objective of the present study was to clarify the physiological and morphological responses of the ramets to soil water conditions. Dry matter allocation to subterranean parts was higher in U ramets than in L ramets. The U ramet leaves survived for approximately 2 months longer than L ramet leaves. The ratio of subterranean part to aerial part dry matter was greater in U ramets than L ramets. Leaf mass per leaf area (LMA) tended to be greater in U ramets than L ramets throughout the growing season. The leaf bulk modulus of elasticity at full hydration was significantly higher in U ramets. Thus, ramet growth patterns and morphological traits varied with changing soil water conditions. The greater longevity of U ramet leaves may play a role in compensating for the reduced annual net carbon gain caused by lower photosynthetic activity. U ramets growing in environments with less water availability achieved high water-use efficiency by a high passive water absorption capacity via a progressed root system and high productivity via longer leaf longevity with higher LMA and elasticity. Therefore, P. yatabei growing along mountain streams could have the ability to colonize the upper bank through higher survivorship based on these traits. [source] | |||||||||||||