Ozark Streams Research Articles

Validating Microbial Source Tracking Markers and Assessing the Efficacy of Culturable E. coli and Enterococcus Assays in Ozark Streams, USA

Fecal contamination threatens human health and contributes to the eutrophication of water resources. In Oklahoma, approximately 75% of assessed stream miles in the state are listed as impaired for fecal indicator bacteria (FIB). We tested the performance of seven microbial source tracking (MST) markers in six Northeast Oklahoma streams. All samples were tested with human (HF183), bovine (COWM2, COWM3), porcine (Pig-2-Bac), avian (Av4143), Escherichia coli, and Enterococcus markers using digital PCR (dPCR), as well as culturable assays for E. coli (Colisure) and Enterococcus (Enterolert). Rural and agricultural land uses were characterized by bovine sources of bacterial contamination. Human fecal contamination was found to be prominent in developed landscapes with several indicators for chronic human fecal pollution in an urban stream. All the streams met the criterion for Enterococcus impairment in 2019 and 2020; however, we found no relationships between culturable Enterococcus and the MST markers except in the urban stream, which had chronic human fecal pollution issues. The urban stream met the criterion for E. coli impairment, and E. coli was significantly correlated with the dominant MST markers in both rural and urban streams. We find that the culturable Enterococcus assay is not specific enough to be used for FIB water quality standards. We support the continued use of culturable E. coli assays to monitor for fecal contamination, and we recommend following-up with MST to verify fecal sources so informed mitigative actions can be taken to improve stream water quality.

Flight Capacity and Response to Habitat Drying of Endemic Diving Beetles (Coleoptera: Dytiscidae) in Arkansas (USA)

The ability to colonize new habitat is essential for wild populations affected by disturbance or other forms of habitat change. For aquatic insects in small streams, overland flight is an important strategy for dispersal when barriers to in-stream migration exist and when populations are isolated in upland habitats. Two Ozark-endemic water beetles (Heterosternuta sulphuria and Heterosternuta phoebeae) have shown little overlap in distributions, with the former frequently occurring in small upland watersheds and the latter occurring in aquatic habitats farther downstream in larger watersheds. Because H. sulphuria has been associated with perennial aquatic habitats, we hypothesized that H. sulphuria individuals could exhibit low capacity for flight, thereby affecting population distributions over time. Laboratory flight observations showed that zero individuals of H. sulphuria flew (n = 67), whereas 17 of 76 individuals of H. phoebeae were observed to fly. Stream habitat drying experiments provided further evidence of the weak capacity for flight and overland migration of H. sulphuria, with low probabilities of survivorship in microhabitats exposed to drying. Weak flight capacity and apparent intolerance to habitat drying have important implications for the evolutionary history and conservation of H. sulphuria in small Ozark streams exposed to variable flow regimes and stream margins vulnerable to disturbances.

Aquatic Macroinvertebrate Community Structure along a Continuum in a Spring Dominated River, Missouri, USA

The Current River is a cold-water, thermally constant Missouri Ozark stream and is one of the few remaining free-flowing rivers in the U.S. The Current River’s baseflow is largely fed by hundreds of springs, which include five first-magnitude springs. Little attention has been given to the influence of spring inflows on river temperature and spring influence on biodiversity. The objectives of this study were to demonstrate how large springs affect river macroinvertebrate communities, and to explore the relationships among macroinvertebrate diversity and habitat variables to estimate spring influences on community structure and diversity. Aquatic macroinvertebrates were collected from 42 riffle/run habitats of the Current River main-stem, tributaries, and springs during the winter season. Samples at each site were collected using a Slack-Surber sampler for macroinvertebrates with additional habitat variables collected: substrate size, embeddedness, periphyton, filamentous green algae, vegetation, depth, current velocity, temperature, dissolved oxygen, specific conductance, and pH. Beta diversity analysis was performed on consecutive pairs of site taxa richness values using the Wilson–Shmida calculation to determine the impact of main-stem confluences with either tributaries or springs, and invertebrate community relationships were explored using nonmetric multidimensional scaling (NMDS). Water temperature and taxa richness exhibited similar patterns, with higher temperatures being associated with lower taxa richness. Downstream of each large-magnitude spring, taxa richness sharply decreased, while taxa richness increased downstream of tributaries. Beta diversity usually declined downstream of the confluences with springs, but increased downstream of the tributaries. Data from large springs were closely grouped in NMDS, while tributaries and main-stem sites were more widely scattered. These data indicate spring inputs produce more homogenous conditions in the main-stem river compared to more heterogenous conditions produced by tributary inputs. Macroinvertebrate diversity along the Current River also does not follow predictions from the river continuum concept, but rather diversity peaks are downstream of springs. Our data clearly demonstrate the strong influence of large springs on macroinvertebrate communities in the Current River.

Drought and nutrient pollution produce multiple interactive effects in stream ecosystems.

Drought and nutrient pollution can affect the dynamics of stream ecosystems in diverse ways. While the individual effects of both stressors are broadly examined in the literature, we still know relatively little about if and how these stressors interact. Here, we performed a mesocosm experiment that explores the compounded effects of seasonal drought via water withdrawals and nutrient pollution (1.0 mg/L of N and 0.1 mg/L of P) on a subset of Ozark stream community fauna and ecosystem processes. We observed biological responses to individual stressors as well as both synergistic and antagonistic stressor interactions. We found that drying negatively affected periphyton assemblages, macroinvertebrate colonization, and leaf litter decomposition in shallow habitats. However, in deep habitats, drought-based increases in fish density caused trophic cascades that released algal communities from grazing pressures; while nutrient enrichment caused bottom-up cascades that influenced periphyton variables and crayfish growth rates. Finally, the combined effects of drought and nutrient enrichment interacted antagonistically to increase survival in longear sunfish; and stressors acted synergistically on grazers causing a trophic cascade that increased periphyton variables. Because stressors can directly and indirectly impact biota—and that the same stressor pairing can act differentially on various portions of the community simultaneously—our broad understanding of individual stressors might not adequately inform our knowledge of multi-stressor systems.

Measurable microcystin in Ozark streams was rare during summer 2018 baseflow conditions

AbstractAccelerated eutrophication due to human activity has been linked to an increase in the occurrence of cyanobacteria in freshwater systems. The purpose of this study was to document the occurrence of microcystin, a common cyanotoxin, within northwest Arkansas streams. Twenty streams were sampled from May through October 2018, and water and periphyton samples were analyzed for microcystin and chlorophyll‐a (CHL‐a). Mean microcystin concentrations in water samples were low across sites, ranging from < 0.10 to 0.21 μg L−1. Mean microcystin in the periphyton across sites ranged from 2.6 to 9.9 μg m−2 and were within values observed in the literature. All microcystin concentrations measured in these Ozark streams were well below the current USEPA recreational guidelines of 8.0 μg L−1 and the drinking water guidelines of 0.3 μg L−1 for infants and 1.6 μg L−1 for adults.

Hydrologic variation influences stream fish assemblage dynamics through flow regime and drought

Hydrologic variation can play a major role in structuring stream fish assemblages and relationships between hydrology and biology are likely to be influenced by flow regime. We hypothesized that more variable flow regimes would have lower and more variable species richness, higher species turnover and lower assemblage stability, and greater abiotic environment-fish relationships than more stable flow regimes. We sampled habitats (pool, run, and riffle) in three Runoff/Intermittent Flashy streams (highly variable flow regime) and three Groundwater Flashy streams (less variable flow regime) seasonally (spring, early summer, summer and autumn) in 2002 (drought year) and 2003 (wet year). We used backpack electrofishing and three-pass removal techniques to estimate fish species richness, abundance and density. Fish species richness and abundance remained relatively stable within streams and across seasons, but densities changed substantially as a result of decreased habitat volume. Mixed model analysis showed weak response variable-habitat relationships with strong season effects in 2002, and stronger habitat relationships and no season effect in 2003, and flow regime was not important in structuring these relationships. Seasonal fish species turnover was significantly greater in 2002 than 2003, but did not differ between flow regimes. Fish assemblage stability was significantly lower in Runoff/Intermittent Flashy than Groundwater Flashy streams in 2002, but did not differ between flow regimes in 2003. Redundancy analysis showed fish species densities were well separated by flow regime in both years. Periodic and opportunistic species were characteristic of Runoff/Intermittent Flashy streams, whereas mainly equilibrium species were characteristic of Groundwater Flashy streams. We found that spatial and temporal variation in hydrology had a strong influence on fish assemblage dynamics in Ozark streams with lower assemblage stability and greater fluctuations in density in more hydrologically variable streams and years. Understanding relationships between fish assemblage structure and hydrologic variation is vital for conservation of fish biodiversity. Future work should consider addressing how alteration of hydrologic variation will affect biotic assemblages.

A Review of Factors Affecting PIT Tag Detection Using Mobile Arrays and Use of Mobile Antennas to Detect PIT‐Tagged Suckers in a Wadeable Ozark Stream

AbstractAdvantages of PIT tags are their small size, longevity, and low cost compared to other tags. They are often used in fisheries to study movement patterns and survival or to estimate population size. However, PIT tags are limited by their short detection distance. Mobile PIT antennas may increase the utility of PIT tags in fisheries. In this study, we synthesized current detection efficiency literature for mobile PIT antennas, determined physical factors that decreased PIT tag detection probabilities for our antenna, determined factors that influenced the proportion of PIT‐tagged suckers detected by our mobile antenna, and summarized techniques used to increase detections of PIT‐tagged suckers using mobile antennas in a wadable stream. Our literature review indicated that tag size and orientation were the most important factors affecting detection probabilities. However, our manual testing suggested that the detection probability for our antenna was primarily influenced by water depth of the tag and distance from the antenna. Our sucker detection data showed that detection efficiency in our stream was most influenced by discharge, turbidity, and sample date. Tracking methods that include targeting key habitats (e.g., rootwads) and using natural features to congregate tagged fishes (e.g., riffles or pinch points) may increase detection efficiency in wadable streams. This is the first formal review of factors affecting mobile PIT antenna detection efficiency. The published literature, combined with our study results, indicates that several factors need to be considered prior to mobile PIT antenna tracking.

A low-water crossing impacts Northern Hog Sucker Hypentelium nigricans movement in an Ozark stream

Streams are complex systems that rely on connectivity to maintain natural ecological function. Low-water crossings are common in small-intermediate sized streams and can restrict longitudinal movement of fishes. The Current River in Missouri (USA) contains a single anthropogenic barrier to longitudinal connectivity: the Cedar Grove low-water crossing, which spans the main channel (10 culverts) and a side channel (4 culverts). In July 2017, we radio-tagged Northern Hog Sucker Hypentelium nigricans upstream (henceforth ‘above’; N = 24) and downstream (henceforth ‘below’; N = 26) of the crossing and followed their movements monthly for a year to assess fish passage and maximum displacement. Passage was limited to four below-tagged fish passing upstream of the crossing with one fish making an additional downstream and then upstream passage. Passage was more likely to occur during high flow. On average, below-tagged fish exhibited more than seven times greater maximum displacement (Mean (M) = 6.55 km, Standard Error (SE) = 2.91 km) than above-tagged fish (M = 0.92 km, SE = 0.33 km). The majority (71%) of fish exhibited stationary behavior (<1 km) compared to mobile behavior (>1 km). Among mobile individuals, maximum displacement was greatest away from the crossing, with above-tagged fish favoring upstream movements (100%) and below-tagged fish favoring downstream movements (67%). Our results suggest the crossing is a semi-permeable barrier in which fish passage primarily occurs during high flows. Alternatives to the low-water crossings at Cedar Grove should be considered to promote natural longitudinal movement of fishes. The side channel provides a potentially impactful and economically feasible management opportunity to act as a fish bypass channel on the Current River.

Smallmouth Bass Population Demographics in Missouri Ozark Streams and an Evaluation of a Statewide 305‐mm Minimum Length Limit

AbstractThe Ozark streams of Missouri provide anglers with unique Smallmouth Bass Micropterus dolomieu fishing opportunities. To ensure the sustainability and potential of these fisheries, we sampled five streams in the Ozark highland ecoregion of southern Missouri via recreational angling methods. From our samples, we developed estimates of recruitment, growth, and mortality, and assessed current regulations for Smallmouth Bass. To accomplish these objectives, we aged otoliths from 75 legal (305‐mm) fish on each stream. Back‐calculated length‐at‐age estimates were formed for sublegal lengths, and were paired with electrofishing length distributions on each stream using an age‐length key. These data were used to develop estimates of dynamic rate functions and models of yield, spawning potential, and number of memorable fish for each study population. We found that recruitment was stable on each stream, but growth and mortality varied among streams. We also found that models of yield, spawning potential, and number of memorable fish varied greatly among streams. Our results showed that the current 305‐mm statewide minimum length limit is applicable for some of our study streams, but yield, spawning potential, and trophy potential could increase with more restrictive length limits on some of our study streams. More spatially explicit length limits can help these Smallmouth Bass populations reach their growth potential. This information can help inform stream management in Missouri and across the Ozark region of the Midwest.

Hyporheic secondary production and life history of a common Ozark stonefly

The hyporheic zone plays a key role in stream ecosystem function, but the quantity of biomass produced in this unique and rarely sampled habitat remains underappreciated. We measured hyporheic secondary production and life history characteristics of a stonefly, Leuctra tenuis (Pictet, 1841), in two Ozark streams with extensive gravel beds: a mainstem perennial stream and a tributary with ephemeral surface flow. L. tenuis nymphs were collected 30–45 cm below the streambed surface in both locations monthly for a year (2017–2018). Annual hyporheic secondary production of L. tenuis was 15.23 mg m−2 of streambed (95% CI 12.00–20.41) in the mainstem and 2.61 mg m−2 (95% CI 0.95–4.83) in the tributary. Annual benthic production of L. tenuis collected concurrently from the mainstem was 12.06 mg m−2 (95% CI 6.77–17.73). L. tenuis was univoltine and completed nymphal development in 8 months and approximately 3900 degree days (starting 20 January). This study is the first to measure hyporheic secondary production in the Ozarks, where many streams have deep hyporheic zones that could contribute substantial biomass to stream and riparian food webs. Our results, based on just one species of a diverse hyporheos, indicate the need for more ecological research in this habitat.

Movement and Diel Habitat Use of Juvenile Neosho Smallmouth Bass in an Ozark Stream

AbstractDocumenting fish movement patterns and examining relationships with both fish and habitat characteristics are essential aspects of sound conservation and management. Stream fish movement and habitat use have been associated with a myriad of factors, and variability among individuals is common. Movement and habitat use patterns of juvenile Smallmouth Bass Micropterus dolomieu in streams are poorly understood, particularly for the Neosho subspecies M. dolomieu velox. Our study objective was to determine diel movement patterns and microhabitat use by juvenile Neosho Smallmouth Bass during late autumn. In 2016, we surgically implanted radio transmitters into 13 juvenile Smallmouth Bass in Honey Creek, Oklahoma. We tracked the fish by using radiotelemetry on 41 occasions over the 26‐d tag life and located fish throughout the diel cycle to characterize movement and habitat use. Movement patterns varied among individual fish, with cumulative movements ranging from 33 to 1,302 m. Incremental displacement (the distance moved between two consecutive relocations) increased slightly with warmer water temperatures and increasing fish size. Although there was also considerable individual variation in habitat use patterns, deeper habitats were associated with larger juvenile Smallmouth Bass and daytime. Fish also tended to use higher‐velocity habitats during the day, and this trend increased over the duration of the study. Our results suggest high individual variation in both movement and habitat use by juvenile Neosho Smallmouth Bass across the diel cycle. We show that juvenile Smallmouth Bass move among microhabitats and would benefit from management actions that maintain and promote instream habitat complexity. Future efforts focused on juvenile Smallmouth Bass movement over longer time periods would be beneficial for understanding movement and habitat use dynamics across a greater range of seasonal and environmental variability.

Field Evidence of a Natural Capillary Barrier in a Gravel Alluvial Aquifer

Core Ideas A tracer test in a gravel aquifer detected a natural capillary barrier. Electrical resistivity data combined with well data found two separate vadose zone flow paths. Phosphorus transport is limited, as it needs to migrate through soil before gravel. Ozark streams commonly feature “composite” floodplains, in which the vadose zone consists of silt or silt loam soils (∼1 m thick) overlying gravel subsoil. Previous work has shown that preferential flow paths can exist within the gravel subsoil, which can conduct water and P at rates exceeding the sorption capacity of the gravel. At a site on Barren Fork Creek, a 1‐ by 1‐m infiltration plot was constructed and an infiltration experiment was performed using sequentially introduced solutes including P (the constituent of regulatory interest), Rhodamine‐WT (Rh‐WT, a visual tracer), and Cl− (an electrical tracer). The solute transport was measured with monitoring wells (MWs) placed 1 m from the plot boundary and 5 m down the groundwater flow gradient using an electrical resistivity imaging (ERI) array. The ERI method utilized differences between a pre‐infiltration background image and subsequent temporal images taken during the test to quantify changes induced by the tracers. The infiltration test maintained a steady‐state flow rate of 4.5 L min−1 for 84.75 h. Electrical resistivity imaging data showed significant changes in resistivity induced by the tracers within the soil vadose zone under the plot but no similar changes within the gravel, indicating that the interface was acting as a capillary barrier. Electrical resistivity images 5 m away from the plot showed tracer breakthrough into the gravel in areas not sampled by the MWs. Solute detection was limited in MWs, indicating that MWs could not adequately monitor movement below the capillary barrier because it controlled migration of solute to the heterogeneous phreatic zone.

Diversity and Longitudinal Patterns of Stoneflies (Plecoptera) in a Southwestern Missouri Ozark Stream

Abstract Plecoptera species are documented from 6 longitudinal sites over a 10-year period 2002 - 2012 in a southwestern Missouri Ozark stream, including a Missouri Department of Natural Resources reference reach. Benthos, light trapping, net, and hand collections were used to capture Plecoptera every month of the year with highest sampling Nov - Jun. We collected 5,645 individuals representing 7 families, 17 genera, and 29 species including 4 confirmed species of Capniidae (38% of total), 3 Leuctridae (29%), 2 Taeniopterygidae (1.2%), 1 Nemouridae (0.81%), 3 Chloroperlidae (0.95%), 12 Perlidae (27%), and 5 Perlodidae (3.1%). Allocapnia rickeri, followed by Zealeuctra claasseni, Agnetina capitata, Acroneuria frisoni, and Perlesta decipiens were the most commonly collected species. An expected longitudinal downstream gradient of increasing Plecoptera richness was apparent, ranging from 9 species collected in stream headwaters to 21 species at the most downstream site. Identifiable richness throughout the watershed was highest between January and May (19 species present in April). Plecoptera richness in this stream compares favorably to collections in two high-quality streams in the western Ozarks in northeastern Oklahoma and streams in the Ouachita Mountains of central Arkansas.

Differences Found in the Macroinvertebrate Community Composition in the Presence or Absence of the Invasive Alien Crayfish, Orconectes hylas.

Introductions of alien species into aquatic ecosystems have been well documented, including invasions of crayfish species; however, little is known about the effects of these introductions on macroinvertebrate communities. The woodland crayfish (Orconectes hylas (Faxon)) has been introduced into the St. Francis River watershed in southeast Missouri and has displaced populations of native crayfish. The effects of O. hylas on macroinvertebrate community composition were investigated in a fourth-order Ozark stream at two locations, one with the presence of O. hylas and one without. Significant differences between sites and across four sampling periods and two habitats were found in five categories of benthic macroinvertebrate metrics: species richness, percent/composition, dominance/diversity, functional feeding groups, and biotic indices. In most seasons and habitat combinations, the invaded site had significantly higher relative abundance of riffle beetles (Coleoptera: Elmidae), and significantly lower Missouri biotic index values, total taxa richness, and both richness and relative abundance of midges (Diptera: Chironomidae). Overall study results indicate that some macroinvertebrate community differences due to the O. hylas invasion were not consistent between seasons and habitats, suggesting that further research on spatial and temporal habitat use and feeding ecology of Ozark crayfish species is needed to improve our understanding of the effects of these invasions on aquatic communities.

Influence of a Spring on Fish Communities and Habitat in an Ozark Stream

ABSTRACT: Springs influence water temperature and flow of streams; however, little information exists on the effects of springs on fish communities and their potential as refugia. This study examined the impacts of a spring on a wadeable stream. Fish, water quality, and physical habitat data were collected seasonally in 2011–2012 upstream and downstream of Double Spring, located on Terrell Creek within Wilson's Creek National Battlefield, Missouri. Downstream of the spring, stream width was similar among seasons, and temperature, dissolved oxygen, and depth were less variable than upstream throughout the year. Temperature was significantly higher and dissolved oxygen was significantly lower at the upstream reach in summer, which completely dried by fall. During spring and winter, temperature and dissolved oxygen did not vary between reaches. The fish community differed between the upstream and downstream sites, particularly in summer when community similarity (Bray-Curtis) was 30.2%. Species richness and ...

Two Catastrophic Floods: Similarities and Differences in Effects on an Ozark Stream Fish Community

In December 1982 a devastating flood occurred in Piney Creek, in the rural Ozark Mountains in Izard County, Arkansas, with vertical stage rises of 2–4 m in the headwaters, 11–12 m at downstream locations, and an estimated return time of 50–100 years. Physical effects in the watershed were catastrophic, with extreme scour and rearrangement of the stream bed, destruction of riparian forest, and deposition of huge amounts of sand from the creek in adjacent pastures or forest. In spite of the extreme nature of this winter flood, residual effects on the overall fish community of the watershed were minimal, and by eight months after the event, the community was virtually indistinguishable from that in the previous summer. In March–April 2008 flooding of equal or greater magnitude than the 1982 flood again occurred in Piney Creek. We followed effects of the spring 2008 flood on local fishes at five long-term fixed sites in the watershed, and on the fish community pooled across those sites, four months after the 2008 flood, and again in 2010 and 2012. In spite of the severity of the 2008 springtime flood, the community before and after was relatively similar qualitatively and quantitatively. But multivariate analyses of the fish community showed more change after the 2008 flood, and in a directional trajectory, than had occurred after the 1982 flood. At the five individual sites, changes in fishes after the 2008 flood were idiosyncratic, with two sites showing marked changes immediately after the flood, with only one subsequently returning toward its former structure. Fishes at all five sites showed more change in multivariate space after the 2008 than after the 1982 flood. In the summers after both floods some cyprinid and catostomid species showed sharp increases in numbers of young-of-year. Differences in the effects of the two floods on the fish community could relate to their timing, with springtime flooding having more effects on fish than the winter flood. Similarities between the two floods with respect to increased production of young-of-year could relate to the scouring of fines (silt and sand) by the floods, providing clean gravel and cobble with more interstitial spaces that could provide protection for fish eggs or larvae, and more microhabitat for food organisms used by young fishes such as micro- or macroinvertebrates. Regardless of mechanisms, much remains to be learned about the effects of extreme floods on stream fish communities, particularly in light of the potential for increased frequency of extreme events as global climate changes continue.

Stream and shallow groundwater nutrient concentrations in an Ozark forested riparian zone of the central USA

Characterizing spatiotemporal variations in surface water (SW)–shallow groundwater (GW) nutrient concentrations is important to predict stream ecosystem responses to disturbance. Unfortunately, there is a lack of such information from mixed-deciduous semi-karst hydro-geological regions. Nitrate (NO3−), total phosphorous (P), potassium (K) and ammonium (NH4+) concentrations were monitored in a case study between an Ozark stream and riparian hardwood forest GW over the 2011 water year in the central USA. Average SW NO3−, P, K and NH4+ concentrations were 0.53, 0.13, 3.29 and 0.06 mg L−1, respectively. Nine meters from the streambank, average GW NO3− concentration was 0.01 mg L−1, while P, K and NH4+ concentrations were 0.03, 1.7 and 0.04 mg L−1, respectively. Hyperbolic dilution model results indicated that NO3− and K exhibited dilution behavior, while NH4+ had a concentration effect and P was hydrologically constant. Observed seasonal NO3− concentration patterns of winter maxima and summer minima in SW (1.164 and 0.133 mg L−1) and GW (0.019 and 0.011 mg L−1) were supported by previous studies yet exhibited distinct semi-karst characteristics. Results indicate that in addition to relatively low residence time, lower nutrient concentrations in GW (relative to SW) may suggest that shallow GW flow processes are important for vegetation removal and retention of nutrients from streams in semi-karst shallow groundwater systems of the central USA.

Climate change simulations predict altered biotic response in a thermally heterogeneous stream system.

Climate change is predicted to increase water temperatures in many lotic systems, but little is known about how changes in air temperature affect lotic systems heavily influenced by groundwater. Our objectives were to document spatial variation in temperature for spring-fed Ozark streams in Southern Missouri USA, create a spatially explicit model of mean daily water temperature, and use downscaled climate models to predict the number of days meeting suitable stream temperature for three aquatic species of concern to conservation and management. Longitudinal temperature transects and stationary temperature loggers were used in the Current and Jacks Fork Rivers during 2012 to determine spatial and temporal variability of water temperature. Groundwater spring influence affected river water temperatures in both winter and summer, but springs that contributed less than 5% of the main stem discharge did not affect river temperatures beyond a few hundred meters downstream. A multiple regression model using variables related to season, mean daily air temperature, and a spatial influence factor (metric to account for groundwater influence) was a strong predictor of mean daily water temperature (r2 = 0.98; RMSE = 0.82). Data from two downscaled climate simulations under the A2 emissions scenario were used to predict daily water temperatures for time steps of 1995, 2040, 2060, and 2080. By 2080, peak numbers of optimal growth temperature days for smallmouth bass are expected to shift to areas with more spring influence, largemouth bass are expected to experience more optimal growth days (21 – 317% increase) regardless of spring influence, and Ozark hellbenders may experience a reduction in the number of optimal growth days in areas with the highest spring influence. Our results provide a framework for assessing fine-scale (10 s m) thermal heterogeneity and predict shifts in thermal conditions at the watershed and reach scale.

Movement patterns of southern redbelly dace, Chrosomus erythrogaster, in a headwater reach of an Ozark stream

AbstractPrevious research on fish movement has focused primarily on recreationally important fishes in perennial streams; however, fewer studies have examined movement patterns of small‐bodied fishes in intermittent streams where abiotic and biotic conditions can be extreme compared with perennial systems. Using mark–recapture, we examined movement patterns of southern redbelly dace, Chrosomus erythrogaster, in an intermittent Ozark stream having both permanently connected and temporally isolated sections. Juvenile (60–88%) and adult (55–83%) residency rates were not significantly different for any mark–recapture sample, and movement was primarily within a section for both groups. Ontogenetic differences were detected for kurtosis, distance moved and population spread, with adults exhibiting greater variability in movement, moving more often and further. When considering only adults, there was a significantly higher number of individuals that exhibited intermovement from isolated sections compared with connected sections. In addition, a higher proportion of adults exhibiting intermovement moved to connected stream sections in May and July compared to January and March. Dace exhibited upstream bias in July, with 76% of emigrates moving to an upstream connected section. Although there were no statistically significant associations between the proportion of intermovers from connected and isolated sections and measured water quality and habitat variables, noteworthy trends were observed, and these trends were always stronger for connected sections. Understanding the factors that influence population dynamics in headwater streams is important for the survival and persistence of stream fish populations, especially considering the anticipated expansion of intermittent headwater streams as a result of future climatic changes.

Life between predators and a small space: substrate selection of an interstitial space‐dwelling stream salamander

AbstractPhysical space is a fundamental habitat constraint for interstitial space‐dwelling organisms; however, few studies have examined how physical space variation structures predator/prey interactions within such communities. Streambeds in the western Ozark Plateau are composed of Silurian/Ordovician chert gravel and contain a rich assemblage of interstitial space‐dwelling species, including macroinvertebrates, fishes and aquatic salamanders. Here, we used field and lab experiments to examine interstitial space size preference and structure of an Ozark streambed community, with emphasis on the Oklahoma salamander, Eurycea tynerensis, and its predators (crayfish) and prey (isopods and amphipods). In the field, we implemented a three by six grid of enclosures containing three distinct size classes of well‐sorted substrate (small, medium and large) that represented three categories of interstitial space size. Isopods and amphipods were the most abundant macroinvertebrates at the site, and the average size of isopods increased with substrate size. Salamanders were significantly more abundant in medium‐sized substrate enclosures, whereas isopods of consumable size and amphipods were more abundant in small and medium substrate, and crayfish were found exclusively in large substrate enclosures. Pairwise choice experiments in the lab showed that salamanders always preferred the largest gravel size (i.e. large or medium to small, and large to medium). A subsequent experiment performed with uniformly large gravel demonstrated that salamanders avoided positions near and adjacent to crayfish. We suggest that the finite interstitial space distribution of Oklahoma salamanders is limited by physical constraints of small, prey‐rich spaces, and avoidance of predators and prey scarcity in the interstitial spaces among large substrates. This study demonstrates the strong influence of interstitial space size on community structure and predator/prey interactions in chert‐bottomed Ozark streams.