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Factors controlling the spread of invasive earthworms in Minnesota’s Boundary Waters Canoe Area Wilderness are poorly known. Believed to have been introduced by anglers who use them as bait, invasive earthworms can alter the physical and... more
Factors controlling the spread of invasive earthworms in Minnesota’s Boundary Waters Canoe Area Wilderness are poorly known. Believed to have been introduced by anglers who use them as bait, invasive earthworms can alter the physical and chemical properties of soil and modify forest plant communities. To examine factors influencing earthworm distribution and abundance, we sampled 38 islands across five lakes to assess the effects of campsites, fire and entry point distance on earthworm density, biomass and species richness. We hypothesized that all three parameters would be greater on islands with campsites, lower on burned islands and would decrease with distance from the wilderness entry point. In addition to sampling earthworms, we collected soil cores to examine soil organic matter and recorded ground and vegetation cover. Campsite presence was the single most important factor affecting sampled earthworm communities; density, biomass and species richness were all higher on islan...
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ABSTRACT Background/Question/Methods Benthic production in streams can be exported to terrestrial habitats via emerging aquatic insects and therefore link aquatic and terrestrial ecosystems. Stream logjams could represent important nodes... more
ABSTRACT Background/Question/Methods Benthic production in streams can be exported to terrestrial habitats via emerging aquatic insects and therefore link aquatic and terrestrial ecosystems. Stream logjams could represent important nodes in this linkage because they enhance physical and hydrological complexity. This in turn could: 1) expand benthic microhabitats to increase aquatic insect abundance, which would subsequently 2) increase aquatic insect emergence at and near logjams, resulting in 3) enhanced aquatic-riparian exchange. To test these hypotheses, we sampled a 40-m stream reach centered on a logjam and its adjacent riparian habitat in and along Cabin Creek, a third order stream in northern Minnesota’s Superior National Forest during May of 2010 and 2011. Benthic and emergent insects were sampled, and physical parameters quantified (e.g., current velocity, submerged wood area, FPOM and CPOM) at 50 random locations sited upstream, downstream and at the logjam. Linkage to the adjoining riparian habitat was quantified by enumerating spider webs along the stream reach and 6-m inland. Hypotheses were tested by examining benthic abundance within functional feeding guilds, counting adult insects in floating emergence traps, and documenting the spatial distribution of spider webs. Data were analyzed using structural equation modeling. Results/Conclusions Our hypothesized chain of causation was supported by the data; specifically, 1) functional feeding guilds responded to logjam-modified habitat parameters, 2) emergent insect abundance correlated with benthic abundance, and 3) riparian spider web density increased near the logjam. We found that most benthic feeding guilds showed strong associations with wood and current velocity. In particular, all but shredders were associated with wood, and velocity was positively related to abundance of collectors, filterers, gatherers, scrapers, and predators. Emergence was directly related to benthic macroinvertebrate abundance, but also CPOM, which may intercept drifting insects. Other factors, particularly wood and FPOM, had indirect effects on emergence via their influence on benthic abundance. Our spider web data suggest that aquatic exchange along our 40-m reach was greatest at the logjam. Webs were concentrated near the logjam and extended further inland, implying deeper penetration by aquatic emergence. Although logjams and stream wood are known to influence lotic community structure and function, their effect on aquatic-terrestrial connectivity is poorly understood. Our results suggest that logjams, and more broadly, physical heterogeneity in streams, may be an important factor controlling the lotic-riparian linkage.
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Reach-scale effects of a stream logjam on benthic macroinvertebrate richness, evenness, diversity, and feeding guilds. Ong Xiong 1 , Jennifer N. Pomeroy 1 , Ashwin M. Sasidharan 1 , John P. Schoen 1 , Zachary R. Snobl 1 ...
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Research Interests: Ecology, Colonization, Colonisation, Bacteria, Oikos, and 4 moreStream, Substrate, Bloom, and Thallophyta
Background/Question/Methods Alteration of flow regimes is among the most serious threats to the ecological sustainability of streams and their associated communities. Water is being extracted from natural watercourses in growing... more
Background/Question/Methods Alteration of flow regimes is among the most serious threats to the ecological sustainability of streams and their associated communities. Water is being extracted from natural watercourses in growing quantities worldwide to meet basic human needs even as it becomes increasingly clear that water removal changes the way streams look, act and function. Decreased benthic current velocity resulting from reduced flows can alter the ability of stream grazer to remove benthic algae, and this has the potential to alter algal accrual, an important ecosystem process. To examine the effect of water abstraction on algal-grazer dynamics, we experimentally diverted 4, first order streams located at the Rocky Mountain Biological Laboratory in Gothic, CO. Benthic samples of macroinvertebrates and algae were collected from streams prior to diversion, and areas upstream of the diversions served as reference sites. During 4 weeks in July and August 2008, we diverted approxi...
Background/Question/Methods Water diverted from streams to meet human demands for freshwater alters current velocity near the streambed. Near-bed current provides an essential context for benthic organisms and can influence the ability of... more
Background/Question/Methods Water diverted from streams to meet human demands for freshwater alters current velocity near the streambed. Near-bed current provides an essential context for benthic organisms and can influence the ability of invertebrate grazers to remove or facilitate the growth of benthic algae. We hypothesized that lotic grazers adapted to fast current will lose their ability to control algae when near-bed current drops below a threshold velocity. To identify this putative threshold, and quantify the extent to which current mediates removal of benthic algal by grazers, we conducted a mesocosm experiment on the bank of Copper Creek, a high gradient mountain stream at the Rocky Mountain Biological Laboratory in Gothic, CO. Stream cobbles having small (6.45 cm2), attached ceramic tiles were colonized in the stream for 30 d prior to placement into 24, flow-through stream mesocosms. Each mesocosm maintained a gradient of near-bed current ranging 0-40 cm/s. Three grazers,...
Background/Question/Methods Streams and their adjacent riparian zones are tightly linked by reciprocal flows of materials and organisms. In mountain streams the strength of this linkage may exhibit altitudinal and seasonal variation.... more
Background/Question/Methods Streams and their adjacent riparian zones are tightly linked by reciprocal flows of materials and organisms. In mountain streams the strength of this linkage may exhibit altitudinal and seasonal variation. Elevation-specific environmental conditions may also influence exchange rates and modify connectivity across the gradient. In semi-arid regions where vegetation is restricted to grasses and small shrubs, subsidies such as leaf litter may be less important than terrestrial and aquatic invertebrates. To examine how elevation, seasonal variation and concomitant environmental variables affected lotic-riparian connectivity, we studied two reaches of the Arroyo Tambillos in the Andes Mountains of Argentina (2470 and 2630 m elevation, TD and TU respectively). We present a follow-up to a pilot study carried out during the 2012 austral summer in which no linkage between aquatic and riparian communities was found. The sampling period included spring, summer and f...
Background/Question/Methods Trophic cascades can be mediated by environmental conditions and are generally examined at large (> 10 m) scales; however, where fine-grained environmental heterogeneity exists, small-scale cascades may... more
Background/Question/Methods Trophic cascades can be mediated by environmental conditions and are generally examined at large (> 10 m) scales; however, where fine-grained environmental heterogeneity exists, small-scale cascades may occur and create mosaics of primary producer biomass. “Patchy” cascades may be particularly important for benthic stream habitats in which near-bed current velocity influences both small-scale heterogeneity and species interactions. To test this, we investigated a stonefly – mayfly – algae cascade in streamside mesocosms to replicate conditions in Copper Creek, a high gradient mountain stream by the Rocky Mountain Biological Laboratory in Gothic, CO, USA. Two experiments examined the effects of near-bed current on 1) Megarcys stonefly capture rates of Baetis prey, and 2) Megarcys influences on Baetis grazing. Algae was colonized on small stream cobbles placed in 24 circular channels in which near-bed current velocity averaged either 11 or 25 cm/sec. Bae...
Background/Question/Methods Streambed current can have direct and indirect effects on benthic organisms. The distribution and abundance of streambed algae, for example, may be directly influenced by current velocity via subsidy/stress... more
Background/Question/Methods Streambed current can have direct and indirect effects on benthic organisms. The distribution and abundance of streambed algae, for example, may be directly influenced by current velocity via subsidy/stress effects. Current may indirectly affect algae by influencing the distribution of benthic organisms, such as retreat-building hydropsychid caddisfly larve. As passive filter-feeders, hydropsychid larvae respond to current and may negatively influence algal abundance by competing for space, altering microhabitats and by actively removing algae. We hypothesized that algal abundance and hydropsychid density would each show a positive relationship to current, but an inverse relationship to one another. To test this, we examined the streambed community in a reach of the Chippewa River in Eau Claire, WI, USA, underlain with exposed bedrock and colonized by hydropsychids of the genus Ceratopsyche. Forty-five benthic samples were collected across a range of curr...
Background/Question/Methods Chase’s (2007) model of community assembly predicts that communities experiencing high stress will show lower species diversity and greater similarity than communities having low stress. The model predicts that... more
Background/Question/Methods Chase’s (2007) model of community assembly predicts that communities experiencing high stress will show lower species diversity and greater similarity than communities having low stress. The model predicts that stress gradients will cause communities to converge on a small number of stress-tolerant species, which will be similar among high stress sites. To test this, we studied lichen communities on rocky shorelines of the Boundary Water Canoe Area Wilderness in northern Minnesota. We hypothesized that wave action and ice formation near the shore establishes a stress gradient that attenuates with increasing distance from the shoreline. Lichen communities were sampled at 22 lakeshore sites by placing a 900 cm2 quadrat 1, 2 and 3 m from the shoreline, which approximated areas of high, medium and low stress, respectively. Results/Conclusions Shoreline lichen assemblages showed a similar ranking of morphologies in terms of percent cover, such that crustose &g...
Los arroyos andinos se caracterizan por tener variaciones espacio temporales en las variables ambientales que afectan la estructura de las comunidades bentónicas. Para examinar cómo la altura y las fluctuaciones estacionales en las... more
Los arroyos andinos se caracterizan por tener variaciones espacio temporales en las variables ambientales que afectan la estructura de las comunidades bentónicas. Para examinar cómo la altura y las fluctuaciones estacionales en las variables físico-químicas afectan la distribución de las comunidades de invertebrados, se estudiaron dos tramos (TU= 2630 y TD= 2470 m) del arroyo Tambillos localizado en la Cordillera Frontal de los Andes (Mendoza, Argentina). Los muestreos fueron efectuados durante primavera, verano y otoño (2012-2013). Para la colecta de los macroinvertebrados se tomaron 12 muestras con red Surber en cada sitio de muestreo siguiendo un gradiente longitudinal y en el perfil transversal del arroyo. Para explorar las relaciones existentes entre las variables ambientales y el ensamble de especies acuáticas se realizó un Análisis de Correspondencia (CCA), y regresiones lineales generalizadas (GLM) para examinar los cambios en la densidad de los invertebrados a nivel espacio...
Background/Question/Methods Substrate surfaces provide an essential habitat template for sessile organisms. The orientation and type of substrate on which sessile organisms grow are an important determinant of community composition and... more
Background/Question/Methods Substrate surfaces provide an essential habitat template for sessile organisms. The orientation and type of substrate on which sessile organisms grow are an important determinant of community composition and influence its resistance and resilience to perturbation. Saxicolous, or rock inhabiting, lichens are important pioneer species of bare rock and dominate the aquatic-terrestrial transition zones in lakeshore habitats. To investigate how substrate type, slope and aspect influenced lichen communities, we surveyed the rocky shores of glacial lakes within the Boundary Waters Canoe Area Wilderness (BWCAW) of northern Minnesota. We quantified lichen distribution and abundance from sixteen shoreline sites on six lakes. At each site, a 1 X 2 meter plot was placed perpendicular to the high water mark (HWM) and divided into 32, 0.25m2 quadrats. Eight quadrats from each plot were randomly selected and measured for species abundance and total percent cover as a pr...
Background/Question/Methods The exchange of energy at ecotones is influential in shaping the communities of adjacent ecosystems. The riparian-stream boundary is an ecotone in which emergent aquatic prey provide an important subsidy to... more
Background/Question/Methods The exchange of energy at ecotones is influential in shaping the communities of adjacent ecosystems. The riparian-stream boundary is an ecotone in which emergent aquatic prey provide an important subsidy to riparian consumers, such as web-building spiders. Terrestrial spiders have been shown to be positively correlated with aquatic insect emergence, and emergence is linked to benthic productivity. Logjams, or accumulations of wood in streams, can increase aquatic macroinvertebrate production through their retention of organic materials and diversification of habitat. Because of this, we hypothesized that there would be an increase in spider density situated near logjams. To test this, spider webs were counted, classified and mapped within 6-m of the stream bank of a 40-m reach in a northern Minnesota stream. In addition, a Web Space Index (WSI) was developed to estimate availability of web-building substrate and structure. Data were collected during two p...
Background/Question/Methods Benthic production in streams can be exported to terrestrial habitats via emerging aquatic insects and therefore link aquatic and terrestrial ecosystems. Stream logjams could represent important nodes in this... more
Background/Question/Methods Benthic production in streams can be exported to terrestrial habitats via emerging aquatic insects and therefore link aquatic and terrestrial ecosystems. Stream logjams could represent important nodes in this linkage because they enhance physical and hydrological complexity. This in turn could: 1) expand benthic microhabitats to increase aquatic insect abundance, which would subsequently 2) increase aquatic insect emergence at and near logjams, resulting in 3) enhanced aquatic-riparian exchange. To test these hypotheses, we sampled a 40-m stream reach centered on a logjam and its adjacent riparian habitat in and along Cabin Creek, a third order stream in northern Minnesota’s Superior National Forest during May of 2010 and 2011. Benthic and emergent insects were sampled, and physical parameters quantified (e.g., current velocity, submerged wood area, FPOM and CPOM) at 50 random locations sited upstream, downstream and at the logjam. Linkage to the adjoinin...
Artificial streams hold great promise for examining ecological processes. They lend themselves to manipulations of discharge, sediment load, water chemistry, and other parameters difficult or impossible to control in natural streams.... more
Artificial streams hold great promise for examining ecological processes. They lend themselves to manipulations of discharge, sediment load, water chemistry, and other parameters difficult or impossible to control in natural streams. However, artificial streams also have important limitations. In this presentation we describe insights gained from several ecological studies conducted at the St. Anthony Falls Laboratory's Outdoor StreamLab, including, 1) short-term turbidity exposure effects on fish health, 2) macroinvertebrate grazing rates on periphyton as a function of velocity, 3) rates of macroinvertebrate colonization as related to velocity, and 4) fine-scale correlations of periphytic biomass with hydraulic conditions. Several lessons emerge from these initial attempts at ecological research in the Outdoor StreamLab. We have learned that the size, flow rate, substrate, water chemistry, and available colonization population of the artificial stream limit the kinds of organis...
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ABSTRACT Installed logjams constructed of wood are commonly used in stream restoration projects to provide habitat for lotic organisms. Macroinvertebrate densities are known to increase on logjam surfaces; how-ever, less is known about... more
ABSTRACT Installed logjams constructed of wood are commonly used in stream restoration projects to provide habitat for lotic organisms. Macroinvertebrate densities are known to increase on logjam surfaces; how-ever, less is known about the influence logjams have on benthic organisms inhabiting the surrounding streambed. To examine this, we conducted a before-after-control-impact (BACI) study in a stream in northern Minnesota, USA, to determine how an installed logjam affected the richness and abundance of three insect orders commonly used in biotic indices, the Ephemeroptera, Plecoptera, and Trichoptera (i.e., EPT taxa). A spanning logjam composed of three logs bound together was installed perpendicular to stream flow at the impact site. Initial sampling of the impact site and an upstream control found no differences among the ETP taxa. A year after installation, the logjam accumulated woody debris and altered flow so that near-bed current at the impact site was faster and more heterogeneous than at the control site. Although the richness and abundance of the macroinvertebrate community as a whole did not differ between sites after one year, it did for the Ephemeroptera and Plecoptera at the impact site. By contrast, Trichoptera richness and abundance did not change. Our results lend support to the hypoth-esis that installed logjams may enhance stream habitat not only by providing colonization surfaces for macroinverbrates, but also by altering the benthic environment of the surrounding habitat.
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Background/Question/Methods Traditionally, benthic macroinvertebrate communities have been characterized by taxonomic groupings and diversity indices. Recently, a trait-based approach has emerged that allows comparisons of... more
Background/Question/Methods Traditionally, benthic macroinvertebrate communities have been characterized by taxonomic groupings and diversity indices. Recently, a trait-based approach has emerged that allows comparisons of macroinvertebrates by functional traits rather than their taxonomic affiliation. This approach has the potential to identify traits necessary for maintaining stream ecosystem function. Here we explore how benthic macroinvertebrate diversity and functional trait composition vary with streambed heterogeneity. Heterogeneity was assessed in terms of near-bed velocity, stream depth, and substrate size. We collected Surber samples from Copper Creek, a montane stream flowing through the Rocky Mountain Biological Laboratory in Gothic, Colorado. For each sampled area, nine measurements of near-bed velocity and depth were taken, and substrate size was measured. Standard deviations (SD) of near-bed velocity, depth, and substrate size were used to quantify heterogeneity, such...
ABSTRACT Trophic cascades can be context-dependent in that they occur under some conditions but not others. An important context for stream benthic communities is near-bed current velocity, which varies at the spatial scale at which... more
ABSTRACT Trophic cascades can be context-dependent in that they occur under some conditions but not others. An important context for stream benthic communities is near-bed current velocity, which varies at the spatial scale at which benthic species interactions occur.To investigate how centimetre-scale variation in near-bed current velocity influenced the occurrence of benthic cascades, I studied a stonefly/mayfly/algal system in a high-gradient Rocky Mountain stream and examined the effect of 10 and 25 cm s−1 current (i.e. ‘slow’ and ‘fast’, respectively) on stonefly predation and its top-down effects.There were two experiments using stream-side mesocosms and a third using in-stream troughs. The two mesocosm experiments had known numbers of stoneflies and mayflies and examined how near-bed current influenced (i) top-down cascades driven by non-trophic, behaviourally mediated predator effects (stonefly mouthparts were glued shut) and (ii) direct predation. The in-stream experiment allowed mayfly grazers to arrive and depart freely and examined how near-bed current and stoneflies influenced algal accumulation and community structure.Results from these experiments showed that top-down cascades occurred in slow, but not fast current, and that these cascades are driven largely by the non-trophic effects of predation. The mesocosm experiment showed that mayflies removed less algae in slow current when stoneflies with glued mouthparts were present. There was 33% greater algal biomass in slow compared with fast current, and algal biomass in the slow current did not differ from that in the grazer-free controls. The predation experiment showed that stoneflies captured approximately twice as many mayflies in slow as compared to fast current.The in-stream experiment found that algal biomass increased when stoneflies were present, but grazer densities did not differ from stonefly-free controls, supporting the hypothesis that effects mediated by behaviour drove the cascade.This study suggests that near-bed current can turn stonefly/mayfly/algae cascades ‘on’ and ‘off’ at small spatial scales and provides a new perspective for understanding algal heterogeneity on natural streambeds.
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Research Interests: Ecology, Colonization, Colonisation, Bacteria, Oikos, and 4 moreStream, Substrate, Bloom, and Thallophyta
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... in a stream ecosystem: responses by primary producers and consumers. Ecology 76:1297309.Jasper, S. & Bothwell, ML 1986. Photosynthetic characteristics of lotic periphyton. Can. ... Arch. Hydrobiol. 109:13945. Meyns, S.,... more
... in a stream ecosystem: responses by primary producers and consumers. Ecology 76:1297309.Jasper, S. & Bothwell, ML 1986. Photosynthetic characteristics of lotic periphyton. Can. ... Arch. Hydrobiol. 109:13945. Meyns, S., Illi, R. & Ribi, B. 1994. Comparison of chlorophyll-a ...
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ABSTRACT An inexpensive, portable suction device for collecting aquatic insects is described. The sampler can be operated by one person and is particularly effective for collecting invertebrates from the interstitial spaces of stream... more
ABSTRACT An inexpensive, portable suction device for collecting aquatic insects is described. The sampler can be operated by one person and is particularly effective for collecting invertebrates from the interstitial spaces of stream cobble. It can be constructed easily using materials commonly available in most hardware stores.
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ABSTRACT The effects of light regime and nutrient enrichment on periphytic algae in a second-order Rocky Mountain stream were determined in a field experiment. We established a light gradient along a 400 m stretch of West St. Louis Creek... more
ABSTRACT The effects of light regime and nutrient enrichment on periphytic algae in a second-order Rocky Mountain stream were determined in a field experiment. We established a light gradient along a 400 m stretch of West St. Louis Creek using the following four light treatments: artificially shaded in the open reach, closed-canopy, artificially illuminated in the closed reach, and open-canopy. Nitrate and phosphorus were manipulated with nutrient-diffusing substrata. Despite order-of-magnitude differences in light levels, metrics of periphytic and algal abundance were very similar under the open and closed canopy treatments. Under the artificially illuminated treatment, however, all parameters were two to four times greater, indicating that light was limiting under both of the natural light regimes, (i.e., insufficient light under the closed canopy and photoinhibition in the open section). Addition of phosphorus caused significant increases in Chl-a, periphytic ash-free-dry-mass, and algal cell density, but it did not increase algal biovolume. Nitrate, by contrast, increased only algal biovolume. Nitrate + phosphorus caused the greatest increases in all metrics. Eleven of 53 algal species dominated the periphytic assemblages in treatments, but patterns of relative abundance shifted under different light and nutrient regimes. Light had a greater effect than did nutrients on changes in community structure.
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ABSTRACT In field measurements and laboratory experiments we assessed the influence of high levels of iron, manganese, and concurrent blooms of iron-depositing bacteria, Leptothrix ochracea, on macroinvertebrates. Macroinvertebrate... more
ABSTRACT In field measurements and laboratory experiments we assessed the influence of high levels of iron, manganese, and concurrent blooms of iron-depositing bacteria, Leptothrix ochracea, on macroinvertebrates. Macroinvertebrate communities in five of six streams were depauerate inside blooms. Reasons for the decreased abundance vary among taxa, with our experiments demonstrating the importance, for one or more species, of (1) direct toxic effects, and,/or smothering, (2) behavioral avoidance of bacterial-coated substrates, and (3) an inability to use bacteria as food. Three mayfly species showed increased mortality when caged inside the blooms, but five trichopterans and one plecopteran did not. Five invertebrates avoided Leptothrix-coated substrate in choice trials, while three did not. Stenonema fuscum could not ingest Leptothrix, and Neophylax nacatus had reduced growth feeding on it, but Heptagenia umbratica grew equally well on diets of Leptothrix or diatoms. This study demonstrates the important role epilithic organisms play in modifying substrates, and how these changes may act to influence benthic abundance and distribution in streams.