North American Streams Research Articles

Effects of Small Dams on Sunfish Assemblages in North Carolina Piedmont and Coastal Plain Streams

AbstractOver the past century dams have played a major role in restructuring North American stream communities. Effects of large dams on fish assemblages are well studied; however, effects of small dams are relatively unstudied. Sunfishes (family Centrarchidae) include many meso‐ and apex predators that are key components of North American lotic and lentic ecosystems. Additionally, centrarchids are widely introduced into impoundments well beyond their native ranges. Here, we examine sunfish assemblages at 75 sites associated with small dams in the Neuse, Tar, and Roanoke drainages in North Carolina. We predicted that streams with intact dams would have more introduced centrarchids than streams with breached or relict dams in response to dam‐induced shifts in assemblage structure. Contrary to our predictions, streams with breached dams had significantly higher numbers of introduced centrarchids, but total and native centrarchid richness were not significantly different from streams with intact dams. Streams with relict dams had significantly lower total and native centrarchid richness; exotic centrarchids did not differ between streams with intact and relict dams. Abundance of the most frequently encountered native taxon (Redbreast Sunfish Lepomis auritus) did not differ across dam types, and the abundance of the most frequently encountered exotic taxon (Bluegill L. macrochirus) was only significantly different (lower) in streams with relict dams. These data suggest that low‐head–small dams have unanticipated and potentially long‐lasting effects on stream fish communities. Moreover, they suggest a need to (1) reevaluate current views of breached dams as benign structures, and (2) develop a more holistic approach to prioritizing dams for removal.

Sampling Sufficiency for Fish Assemblage Surveys of Tropical Atlantic Forest Streams, Southeastern Brazil

AbstractKnowledge of the adequacy of field sampling protocols is critical for detecting species and assessing biological conditions. Several studies have been conducted to determine the appropriate electrofishing distance for estimating fish assemblage richness in temperate North American streams. We tested whether electrofishing 40 times the mean wetted channel width was sufficient for estimating species richness and developing precise metrics for Atlantic Forest streams in southeastern Brazil. We sampled 32 sites with differing gradients, substrates, and anthropogenic pressures. Our results show that 40 channel widths were not sufficient to estimate species richness in those systems, presumably because of the high number of rare species. However, 40 channel widths were sufficient for applying other metrics of assemblage condition (e.g., number of common species, percentage of tolerant individuals, percentage of Characiform species, percentage of Siluriform species, percentage of water column species, percentage benthic species, Shannon diversity, dominance). This suggests that 40 channel widths are an appropriate sampling distance for applying environmental assessment protocols to Atlantic Forest streams.

Triclosan inhibits arbuscular mycorrhizal colonization in three wetland plants

In terrestrial ecosystems, plant growth, plant community structure, and ultimately the ecosystem services provided by plants are dependent on the presence and composition of below ground arbuscular mycorrhizal (AM) fungal communities. AM fungi form obligate symbioses with plants providing nutrients to their host plants in exchange for photosynthates. While AM have been found in most wetland ecosystems, the effects of urban contaminants on AM associations are largely unknown. Triclosan (5-chloro-2-[2,4-dichlorophenoxy]phenol; TCS) is a widespread contaminant found in surface waters throughout North America and in addition to antimicrobial properties is purported to have antifungal properties. To determine the effects of TCS on arbuscular mycorrhizal associations, we exposed AM inoculated wetland plant species (Eclipta prostrata, Hibiscus laevis, and Sesbania herbacea) to TCS at concentrations of 0.0, 0.4 and 4.0μg/L in a continuous flow-through exposure system. TCS exposure caused significant reductions in hyphal and arbuscular colonization while no significant effect was detected for vesicular colonization. Across all species, hyphal colonization was significantly higher in controls (18.58±1.84%) compared to 0.4 and 4.0μg/L (10.20±1.34% and 9.86±1.32% respectively) TCS treatments. Similarly, arbuscular colonization was significantly higher in the controls (4.58±0.75%) compared to 0.4μg/L (2.20±0.38%) and 4.0μg/L (1.22±0.24%) TCS exposures. Since our lowest effect concentration, 0.4μg/L, lies within the range of concentrations found in North American streams it is plausible that AM colonization has been impacted in streams receiving WWTP effluent. Further studies are required to understand the mechanism of TCS inhibition of mycorrhizal colonization in wetland plant species as well as the potential ecological consequences that a decline in the AM colonization levels may represent.

Response of Wild Trout to Stream Restoration over Two Decades in the Blackfoot River Basin, Montana

AbstractAnthropogenic degradation of aquatic habitats has prompted worldwide efforts to improve or restore stream habitats for fisheries. However, little information exists on the long‐term responses of salmonids to restoration in North American streams. To recover wild trout populations in the Blackfoot River in western Montana, a collaborative approach to stream restoration began in 1990 to improve degraded stream habitats, primarily on private land. To assess the efficacy of various restoration techniques (channel reconstruction and placement of instream habitat structures, restoration of natural instream flows, installation of fish ladders and screens at irrigation diversions, and modification of grazing practices) in the recovery of wild trout, we examined long‐term (>5 years) trends in trout abundance on 18 tributaries treated between 1990 and 2005 and subsequently monitored between 1989 and 2010. At pretreatment conditions, average trout abundance was significantly lower in treatment versus reference sites (0.19 versus 0.62 trout/m; P = 0.0001). By 3 years posttreatment, trout abundance had increased significantly to an average of 0.47 trout/m across treatment sites (P = 0.01) and was no longer significantly different from the reference average (P = 0.12). These initial rapid increases were sustained over the long term (5–21 years) in 15 streams. However, trout abundance declined below pretreatment levels on three streams presumably due to the return of human impacts from heavy riparian grazing and detrimental irrigation practices. Although long‐term (12 year) average response trends were positive, trends varied spatially and native trout responded more strongly in the upper portion of the basin. Study results indicate that restoration should focus in the mid to upper basin and emulate features of natural channels to promote life history diversity and the recovery of native trout. Finally, long‐term monitoring led to adaptive management on most (10 of 18) projects, and thus proved vital to the overall sustainability of wild trout fisheries throughout the basin.

Increasing synchrony of high temperature and low flow in western North American streams: double trouble for coldwater biota?

Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (Tmax_w) and stream flow minima (Qmin) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and decreases in low flow during summer/fall have been reported. We hypothesized that an earlier peak flow could be shifting the timing of low flow and leading to a decrease in the interval between Tmax_w and Qmin. We also examined if years with extreme low Qmin were associated with years of extreme high Tmax_w. We tested these hypotheses using long-term data from 22 minimally human-influenced streams for the period 1950–2010. We found trends toward a shorter time lag between Tmax_w and Qmin over time and a strong negative association between their magnitudes. Our findings show that aquatic biota may be increasingly experiencing narrower time windows to recover or adapt between these extreme events of low flow and high temperature. This study highlights the importance of evaluating multiple environmental drivers to better gage the effects of the recent climate variability in freshwaters.

Regional species richness, hydrological characteristics and the local species richness of assemblages of North American stream fishes

Summary1. Local assemblage structure, from a deterministic perspective, is presumably dictated by the regional species pool as well as regulated by local factors. We examined the relationships of the regional species pool and local hydrological characteristics to local species richness of North American freshwater fishes using data sets collected during the National Water Quality Assessment program conducted by the United States Geological Survey.2. We predicted that local species richness is ultimately constrained by the composition of the regional species pool and further associated with local hydrological factors. Moreover, we predicted that variation in local species richness within major families can be explained by different combinations of hydrological characteristics that represent lineage‐specific responses to the environment.3. Daily discharge and regional and local species richness data were assembled from 41 stream localities across the United States. Multiple stepwise regressions were conducted to predict local species richness, based on regional species richness, mean discharge and hydrological characteristics quantified by nine variables characterising flow variability. Species richness at each site was calculated for the entire assemblage as well as within the four most species‐rich families in the data set (Catostomidae, Centrarchidae, Cyprinidae and Percidae).4. Local species richness was best predicted by a combination of regional species richness and discharge magnitude when all species were considered. Regional species richness was a significant explanatory variable of local species richness for three of four families (Catostomidae, Centrarchidae, Cyprinidae), but not for Percidae. Local richness in Centrarchidae and Cyprinidae was positively correlated with temporal flow variability as well as high and low flow duration, respectively, while richness in Catostomidae and Percidae tended to be associated with discharge volume. In addition, local species richness for three of the four major families was positively correlated with species richness of the other families in the assemblage, potentially suggesting the influence of local habitat quality and heterogeneity.5. Results suggest the importance of the combined influences of the regional species pool and local hydrological characteristics on local richness in freshwater fishes, with variation in richness within each family predicted by different characteristics of flow regimes.

North American Stream Hydrographers [NASH] Special Issue

The North American Stream Hydrographers (NASH) was conceived as a vehicle for bringing researchers and practitioners together in a community of practice for advancing the science of hydrometry and ...

Identifying the spatial pattern of wood distribution in northeastern North American streams

The spatial distribution of instream wood influences important ecological processes but has proven challenging to describe quantitatively. We present a modified version of a previously described metric used to quantify the spatial extent and pattern of instream wood distribution, then apply this approach in evaluating the distribution of wood habitat in forested northeastern North American streams. This revised metric, a ‘binned neighbor-K analysis’, provides greater resolution in evaluating the presence of aggregated, periodic, or segregated wood distributions in stream ecosystems. We employed this metric in evaluating the distribution of wood within 17 streams in two regions of northeastern North America. Our results indicate that the binned neighbor-K approach more accurately represents the spatial extent at which wood accumulates in streams by identifying recurring intervals in streams within which instream wood is not present and by more accurately quantifying the spatial extent of wood aggregations and periodically repeating occurrences of accumulated wood. We also used this metric to quantify the overall extent of wood ‘organization’ in streams, which revealed similarities and differences in instream wood distribution patterns in the two regions evaluated. Wood distribution patterns in both study regions were generally consistent with our expectations of increased organization at an intermediate stream size (up to 10 m bankfull width), then in larger streams (> 10 m) wood was less organized. These observed patterns result from landscape and ecosystem influences upon wood accumulation and movement in streams.

Secondary production in a southern Illinois headwater stream: relationships between organic matter standing stocks and macroinvertebrate productivity

We quantified macroinvertebrate production and organic matter standing stocks in riffle/run and pool habitats for 2 y in 2 reaches of Big Creek, a 3rd-order stream in southern Illinois, USA. Habitat-weighted secondary production was 24.9 and 26.2 g ash-free dry mass (AFDM) m−2 y−1 in the upper and lower reaches, respectively, in year 1 of the study and 17.6 and 15.1 AFDM m−2 y−1 in year 2. Annual production to biomass (P/B) ratios of the macroinvertebrate assemblages ranged from 7 to 10. Collector-gatherers, which were dominated by nontanypodine Chironomidae and Oligochaeta, accounted for >60% of total habitat-weighted production in both reaches, and consumption estimates based on production efficiencies indicated they consumed high proportions of available organic matter resources ≤250 µm. Macroinvertebrate production in Big Creek was strongly correlated with organic matter standing stocks, and our subsequent analyses of production and organic matter resources across several low-order North American streams suggested standing stocks of small wood, a relatively refractory component of organic matter, are an important component of the relationship between macroinvertebrate production and organic matter. However, the apparent influence of small wood on production may be related to associated physical characteristics of these streams, such as pH and canopy cover. Secondary production estimates in our data set were a function of both adjusted total organic matter exclusive of wood and wood standing stocks. Although production–organic matter relationships may be obscured by other factors at the local level, our results indicate that patterns of macroinvertebrate production across large geographic scales may be driven largely by the availability of detrital resources.

Escaping the flow: boundary layer use by the darter Etheostoma tetrazonum (Percidae) during benthic station holding

Aquatic habitats characterized by directional water flow (lotic environments) pose numerous challenges to their inhabitants, including the constant threat of dislodgement and downstream transport. As a result, many organisms exhibit morphological and/or behavioral adaptations that facilitate midwater or benthic station holding in these environments, such as the ventral sucker disc of armored catfishes. However, a few groups, including the species-rich group of small (7-8 cm long and 1-2 cm high) North American stream fishes called darters, exhibit no obvious morphological adaptations to life in lotic habitats. We therefore asked whether small size itself facilitates benthic station holding in these fish. We first used digital particle image velocimetry to quantify the fluid dynamics of flow over a variety of substrates. We then visualized the patterns of flow over the darter Etheostoma tetrazonum during benthic station holding. The thickness of the region of decreased water velocity (i.e. the boundary layer) associated with several types of rocky substrate was large enough (∼2 cm high in some cases) for E. tetrazonum and many other darter species to escape the oncoming flow. We also found that, despite the large size of its pectoral fins, E. tetrazonum is capable of producing only very weak negative lift forces with fins. These substrate-directed forces likely act in conjunction with upstream-directed frictional forces between the tail, anal and pelvic fins and the substrate to facilitate station holding. Thus, we hypothesize that, in darters, small size is an adaptation to life in the benthic boundary layer of lotic environments.

Comparison of parametric and non-parametric estimations of the annual date of positive water temperature onset

The onset date of positive water temperature in the annual thermal cycle of North-American streams is modeled using parametric (regression) and non-parametric (artificial neural networks) approaches. Physiographic, land cover and weather-related variables are used to predict the date of positive temperature onset for 191 station-years at 48 locations in Canada and in Northern US. Preliminary correlation analysis is performed in order to test the relationships between the physiographic/land cover/weather variables and the date of positive temperature onset. Moreover, several different subsets of variables are tested as inputs to each model type. Artificial neural networks can predict the date of positive temperature onset for a given station-year, given its longitude, lake coverage of its drainage basin, and two January–February daily temperature indices, with a split-sample validation root mean square error (RMSE) ∼8.8 days. Ordinary least square (OLS) regression models allow to predict the onset date with RMSE ∼9.5 days, given the station’s latitude, longitude, lake coverage and one January–February daily temperature index. OLS regression models adjusted on canonical variates combining 13 physiographic/land cover and weather variables achieve prediction performance ∼9.1 days. The precipitation does not impact much on the onset date prediction for all tested models.

Living on the bottom: Kinematics of benthic station‐holding in darter fishes (Percidae: Etheostomatinae)

Darters represent a substantial radiation of freshwater fishes that live in close association with the substrate in North American streams and rivers. A key feature of any darter species is therefore its ability to stay in place or to "hold station" in flowing water. Here, we quantify the station-holding performance of two morphologically divergent darter species, the fantail darter Etheostoma flabellare and the Missouri saddled darter Etheostoma tetrazonum. We also characterize the primary kinematic responses of the two species when holding station in flow speeds ranging from 4 to 56 cm s(-1) in a flow tank on either plexiglas or small rock substrate. We then present a series of hypotheses about the potential hydrodynamic and functional consequences of the observed postural changes and the links among morphology, posture, and station-holding performance. On both substrates, E. tetrazonum was able to hold station at higher flow speeds than E. flabellare. On rocks, E. tetrazonum slipped at an average speed of 55.7 cm s(-1) whereas E. flabellare slipped at 40.2 cm s(-1). On plexiglas, E. tetrazonum slipped at an average speed of 24.7 cm s(-1) whereas E. flabellare slipped at 23.1 cm s(-1). We measured body and fin positions of the two species from individual frames of high-speed video while holding station on rocks and plexiglas. We found that on both substrates, the two species generally exhibited similar kinematic responses to increasing flow: the head was lowered and angled downward, the back became more arched, and the median and caudal fin rays contracted as water flow speed increased. The ventral halves of the pectoral fins were also expanded and the dorsal halves contracted. These changes in posture and fin position likely increase negative lift forces thereby increasing substrate contact forces and reducing the probability of downstream slip.

Morphological variation of the Caloneis schumanniana species complex (Bacillariophyceae) from different environmental conditions in North American streams

Morphological variations of the Caloneis schumanniana (Grunow) Cleve species complex were studied using multivariate analysis. Populations of three species, synonymized in the literature, i.e., C. schumanniana, Caloneis limosa (Kutzing) Patrick and Caloneis lewisii Patrick, were analyzed. Their morphological and ecological characteristics were evaluated and outlined for the sampled streams by US EPA’s Western Environmental Monitoring and Assessment Program. Geographic separation among the three taxa was not resolved. This study showed that C. schumanniana has wider ecological tolerance than C. limosa and C. lewisii. Despite the ecological overlap, specific ecological preferences of C. limosa and C. lewisii were described.

Convergence of temperate and tropical stream fish assemblages

The hypothesis of convergence takes the deterministic view that community (or assemblage) structure can be predicted from the environment, and that the environment is expected to drive evolution in a predictable direction. Here we present results of a comparative study of freshwater fish assemblages from headwater streams in four continents (Europe, North America, Africa and South America), with the general objective of testing whether these assemblages display convergent structures under comparable environmental conditions (i.e. assemblage position in the stream longitudinal continuum). We tested this hypothesis by comparing species richness and trophic guilds of those stream fish assemblages represented in available data from multiple sites on each continent. Independent of phylogenetic and historical constraints, fish assemblage richness and trophic structure in the four continents converged along the stream continua to a substantial degree. For the four continents, assemblage richness increased, the proportion of invertivorous species decreased, and the proportion of omnivorous species increased from upstream to downstream, supporting theoretical predictions of the river continuum concept. However, the herbivore/detritivore and piscivore guilds were virtually absent from our small European and North American stream sites, unlike our African and South American stream sites. This divergence can be linked to differences in energy availability between temperate and tropical systems.

Diagnostic study and modeling of the annual positive water temperature onset

A data-driven model is designed using artificial neural networks (ANN) to predict the average onset for the annual water temperature cycle of North-American streams. The data base is composed of daily water temperature time series recorded at 48 hydrometric stations in Quebec (Canada) and northern US, as well as the geographic and physiographic variables extracted from the 48 associated drainage basins. The impact of individual and combined drainage area characteristics on the stream annual temperature cycle starting date is investigated by testing different combinations of input variables. The best model allows to predict the average temperature onset for a site, given its geographical coordinates and vegetation and lake coverage characteristics, with a root mean square error (RMSE) of 5.6 days. The best ANN model was compared favourably with parametric approaches.

Niche characteristics explain the reciprocal invasion success of stream salmonids in different continents

An ability to understand and predict invasions is elemental for controlling the detrimental effects of introduced organisms on native biota. In eastern North America, European brown trout generally dominates over, and eventually replaces, the native brook trout. We show here that in northern Europe the pattern of replacement between these two species is reversed: when transferred to North European streams, brook trout spread extensively and partially replaced the native brown trout. The effect of brook trout on brown trout was habitat-specific: brook trout excluded the native species only in small tributary streams where the reproduction of brown trout was severely reduced, whereas in larger streams brown trout was largely unaffected. Thus, the pattern of coexistence among the two salmonids in our study area is approaching that typically observed in North American streams. In both areas, brook trout ultimately settles in small headwater streams, but the process of replacement differs profoundly: in North Europe, brook trout replaces brown trout in headwater streams, whereas in North America these same streams are the ultimate refuge area for brook trout under the invasion pressure by brown trout. Our results underline the importance of knowing species' niche characteristics to explain and predict biological invasions.

Stream channel geomorphology influences mussel abundance in southern Appalachian streams, U.S.A.

Summary1. Studies of North American streams have shown that hydraulic parameters and stream geomorphology can explain unionid mussel abundance at both the reach and catchment scale. However, few studies have examined applicability of hydrogeomorphic variables across broader spatial scales, such as across whole catchments, or have elucidated conditions under which spates can affect mussel populations in streams.2. We quantified freshwater mussel abundance and species richness and their physical habitat at 24 sites in eight streams in southern Appalachian catchments in 2000 and 2001. In addition, we modelled site‐specific hydraulic parameters during summer baseflow and bankfull stages to estimate high‐ and low‐discharge conditions, respectively.3. Mussel abundance was related to stream geomorphology, whereas richness was related to stream size. Baseflow habitat parameters explained only minor variation in abundance or richness, and both measures were highly correlated with mean current velocity or stream size. Bankfull shear stress composed a relatively low proportion of overall mussel habitat variability, but it accounted for significant variation in abundance and richness.4. Mussel abundance was highly variable at sites subject to low‐shear stress during spates, whereas abundance always was low at sites subject to high‐shear stress. These data suggest that habitat conditions during floods, rather than those at summer baseflow, limit the abundance of mussels in Appalachian streams. These data also suggest that mussel abundance and assemblage structure may be sensitive to any changes in channel geomorphology and hydraulic conditions that might result from land use in the catchment.

Facilitation between herons and smallmouth bass foraging on common prey

Understanding how multiple predators affect one another and their shared prey is an increasingly important goal for ecologists examining predator–prey dynamics and food-web structure. In a field experiment, we examined the outcome of interactions between terrestrial and freshwater predators foraging for the same prey in two temperate North American streams. We used a factorial design to examine the combined foraging effects of herons and smallmouth bass on striped shiners and central stonerollers. We found that there was facilitation between the two predators, resulting in risk-enhancement for the prey species, with particularly pronounced effects on the smallest (<70 mm) size classes. Facilitation is the least well-documented predator–predator interaction and has not been quantitatively demonstrated for freshwater and terrestrial predators. Our results indicate that bass may gain a net benefit from the presence of wading birds such as herons and egrets, and that concerns about the negative effects of birds on fish stocks through competition may be unwarranted.

MORPHOLOGICAL STUDIES ON SELECTED TAXA IN THE GENUS STAUROSIRELLA WILLIAMS ET ROUND (BACILLARIOPHYCEAE) FROM RIVERS IN NORTH AMERICA

Morphological studies at the light microscopy (LM) and scanning electron microscopy (SEM) levels of selected fragilarioid diatoms within the genus Staurosirella Williams et Round occurring in North American streams and rivers are presented herein. The studied samples were collected by the U.S. Geological Survey's National Water Quality Assessment Program (NAWQA), which concentrates on stream water quality monitoring throughout the continental United States and Hawaii. Two new species (Staurosirella ovata Morales and Staurosirella subrobusta Morales), one new combination (Staurosirella martyi (Héribaud) Morales), and three new combinations/new status (Staurosirella dubia (Grunow) Morales, S. rhomboides (Grunow) Morales, and S. subcapitata (Frenguelli) Morales) are presented. Additionally, detailed morphological information of one additional taxon (Staurosirella leptostauron (Ehrenberg) Williams et Round,) is provided. The taxonomie affinities of all these taxa, as well as some ecological aspects are discussed in the light of published and newly collected material.

Human-induced changes in animal populations and distributions, and the subsequent effects on fluvial systems

Humans have profoundly altered hydrological pathways and fluvial systems through their near-extirpation of native populations of animal species that strongly influenced hydrology and removal of surface sediment, and through the introduction of now-feral populations of animals that bring to bear a suite of different geomorphic effects on the fluvial system. In the category of effects of extirpation, examples are offered through an examination of the geomorphic effects and former spatial extent of beavers, bison, prairie dogs, and grizzly bears. Beavers entrapped hundreds of billions of cubic meters of sediment in North American stream systems prior to European contact. Individual bison wallows, that numbered in the range of 100 million wallows, each displaced up to 23 m 3 of sediment. Burrowing by prairie dogs displaced more than 5000 kg and possibly up to 67,500 kg of sediment per hectare. In the category of feral populations, the roles of feral rabbits, burros and horses, and pigs are highlighted. Much work remains to adequately quantify the geomorphic effects animals have on fluvial systems, but the influence is undeniable.