02311nas a2200217 4500008004100000245016300041210006900204300001300273490000800286520157200294653001601866653001001882653001701892653002801909653001901937100001901956700001701975700001701992700001802009856006602027 2013 eng d00aInfluence of macroconsumers, stream position, and nutrient gradients on invertebrate assemblage development following flooding in intermittent prairie streams0 aInfluence of macroconsumers stream position and nutrient gradien a169 -1820 v7143 a

Climate change in the US Great Plains is expected to result in less frequent but more severe floods. This will affect hydrologic cycles, stream organisms, and ultimately ecosystem structure and function. We examined factors influencing invertebrate assemblages following flooding in 3 reaches (20 pools) of Kings Creek, an intermittent prairie stream on the Konza Prairie Biological Station, using replicated macroconsumer enclosures (fishless, dace, shiners, ambient). Invertebrate densities and biomass increased rapidly following scouring, including rapid colonizing taxa and relatively long-lived taxa, but macroconsumers had no significant effects. Rather, distance, which was negatively correlated with the concentration of dissolved inorganic nitrogen, from the downstream confluence with a larger stream significantly influenced assemblage structure, with higher richness and greater nutrient concentrations closer to the confluence. Results support previous findings that recovery patterns following flooding in this grassland stream are strongly influenced by proximity to refuges. Furthermore, physical rather than biological factors appear more influential in structuring invertebrate assemblages in these frequently disturbed systems. Predicted increases in the intensity and duration of hydrologic disturbances will increase direct impacts on stream communities, relative to indirect effects through potential changes in macroconsumer communities. Human activities that alter refuges may further impede recovery following hydrologic disturbances.

10adisturbance10aFlood10aInvertebrate10aMacroconsumer Gradients10aPrairie stream1 aBertrand, K.N.1 aWhiles, M.R.1 aGido, K., B.1 aMurdock, J.N. uhttps://link.springer.com/article/10.1007%2Fs10750-013-1534-500499nas a2200145 4500008004100000245009400041210006900135300001300204490000700217100001800224700001800242700001700260700001700277856005900294 2011 eng d00aDynamic influences of nutrients and grazing fish on periphyton during recovery from flood0 aDynamic influences of nutrients and grazing fish on periphyton d a331 -3450 v301 aMurdock, J.N.1 aDodds, W., K.1 aGido, K., B.1 aWhiles, M.R. uhttps://www.journals.uchicago.edu/doi/10.1899/10-039.102388nas a2200157 4500008004100000245012800041210006900169300001500238490000700253520182300260100001702083700001802100700001702118700001802135856007702153 2011 eng d00aNutrient loading and grazing by the minnow Phoxinus erythrogaster shift periphyton abundance and stoichiometry in mesocosms0 aNutrient loading and grazing by the minnow Phoxinus erythrogaste a1133 -11460 v563 a

1. Anthropogenic activities in prairie streams are increasing nutrient inputs and altering stream communities. Understanding the role of large consumers such as fish in regulating periphyton structure and nutritional content is necessary to predict how changing diversity will interact with nutrient enrichment to regulate stream nutrient processing and retention. 2. We characterised the importance of grazing fish on stream nutrient storage and cycling following a simulated flood under different nutrient regimes by crossing six nutrient concentrations with six densities of a grazing minnow (southern redbelly dace, Phoxinus erythrogaster) in large outdoor mesocosms. We measured the biomass and stoichiometry of overstory and understory periphyton layers, the stoichiometry of fish tissue and excretion, and compared fish diet composition with available algal assemblages in pools and riffles to evaluate whether fish were selectively foraging within or among habitats. 3. Model selection indicated nutrient loading and fish density were important to algal composition and periphyton carbon (C): nitrogen (N). Nutrient loading increased algal biomass, favoured diatom growth over green algae and decreased periphyton C : N. Increasing grazer density did not affect biomass and reduced the C : N of overstory, but not understory periphyton. Algal composition of dace diet was correlated with available algae, but there were proportionately more diatoms present in dace guts. We found no correlation between fish egestion/excretion nutrient ratios and nutrient loading or fish density despite varying N content of periphyton. 4. Large grazers and nutrient availability can have a spatially distinct influence at a microhabitat scale on the nutrient status of primary producers in streams.

1 aKohler, T.J.1 aMurdock, J.N.1 aGido, K., B.1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2427.2010.02557.x03055nas a2200157 4500008004100000245013200041210006900173300001300242520245800255100001702713700001902730700001802749700001802767700001702785856009502802 2010 eng d00aDisturbance mediated effects of stream fishes on ecosystem processes: concepts and results from highly variable prairie streams0 aDisturbance mediated effects of stream fishes on ecosystem proce a593 -6173 a

Stream fishes can have strong top-down and bottom-up effects on ecosystem processes. However, the dynamic nature of streams constrains our ability to generalize these effects across systems with different disturbance regimes and species composition. To evaluate the role of fishes following disturbance, we used a series of field and mesocosm experiments that quantified the influence of grazers and water column minnows on primary productivity, periphyton structure, organic matter pools, and invertebrate communities following either scouring floods or drying of prairie streams. Results from individual experiments revealed highly significant effects of fishes, but the direction or magnitude of effects varied among experiments. Meta-analyses across experiments indicated that grazers consistently reduced the relative amount of fine benthic organic matter (FBOM) and chironomid abundance within 2 weeks after disturbances. However, effect sizes (log response ratios) were heterogeneous across experiments for algal biomass and algal filament lengths measured more than 4 weeks after a disturbance and potentially associated with system productivity and grazer densities. A similar analysis of 3–4 experiments using water column minnows only found a consistent trend of decreasing FBOM in fish treatments relative to controls when measured less than 2 weeks after disturbances and increase in gross primary productivity measured more than 4 weeks after disturbance. These results, along with those of others, were used to develop a conceptual framework for predicting the potential role of fishes in streams following disturbances (flood and drying). Both theoretical and empirical research shows that recovery of stream ecosystem processes will depend on the resilience of autotrophic and heterotrophic communities following disturbance. Fish effects may vary among functional groups but are generally predicted to be greatest during early stages of succession when algal and invertebrate communities are less complex and their biomass is low relative to fish biomass. Our analysis underscores the context dependency of consumer effects on ecosystem structure and function in nonequilibrium conditions and suggests that factors regulating fish densities and colonization of algal and invertebrate taxa need to be evaluated to predict the consequences of biodiversity loss in streams with variable or human-modified disturbance regimes.

1 aGido, K., B.1 aBertrand, K.N.1 aMurdock, J.N.1 aDodds, W., K.1 aWhiles, M.R. uhttps://www.k-state.edu/fishecology/msreprints/Gido%20et%20al.2010%20AFSbook%20chapter.pdf02518nas a2200169 4500008004100000245009700041210006900138300001300207490000800220520195400228100001902182700001702201700001802218700001802236700001702254856007702271 2009 eng d00aDisturbance frequency and functional identity mediate ecosystem processes in prairie streams0 aDisturbance frequency and functional identity mediate ecosystem  a917 -9330 v1183 a

A major consequence of climate change will be the alteration of precipitation patterns and concomitant changes in the flood frequencies in streams. Species losses or introductions will accompany these changes, which necessitates understanding the interactions between altered disturbance regimes and consumer functional identity to predict dynamics of streams. We used experimental mesocosms and field enclosures to test the interactive effects of flood frequency and two fishes from distinct consumer groups (benthic grazers and water-column minnows) on recovery of stream ecosystem properties (algal form and biomass, invertebrate densities, metabolism and nutrient uptake rates). Our results generally suggest that periphyton communities under nutrient limitation are likely to recover more quickly when grazing and water-column minnows are present and these effects can diminish or reverse with time since the disturbance. We hypothesized that increased periphyton production and biomass was the result of increased nutrient turnover, but decreased light limitation and indirect effects on other trophic levels are alternative explanations. Recovery of stream ecosystem properties after a natural flood differed from mesocosms (e.g. lower algal biomass and no long algal filaments present) and species manipulations did not explain recovery of ecosystem properties; rather, ecosystem processes varied along a downstream gradient of increasing temperature and nutrient concentrations. Different results between field enclosures and experimental mesocosms are attributable to a number of factors including differences in algal and invertebrate communities in the natural stream and relatively short enclosure lengths (mean area=35.8 m2) compared with recirculating water in the experimental mesocosms. These differences may provide insight into conditions necessary to elicit a strong interaction between consumers and ecosystem properties.

1 aBertrand, K.N.1 aGido, K., B.1 aDodds, W., K.1 aMurdock, J.N.1 aWhiles, M.R. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0706.2008.16849.x02263nas a2200205 4500008004100000245006600041210006600107300001300173490000700186520162600193653002401819653002201843653001601865653001501881653001401896653001701910100001801927700001801945856009401963 2007 eng d00aLinking benthic algal biomass to stream substratum topography0 aLinking benthic algal biomass to stream substratum topography a449 -4600 v433 aThe physical properties of substrata significantly influence benthic algal development. We explored the relationships among substratum surface texture and orientation with epilithic microphytobenthic biomass accumulation at the whole-substratum and micrometer scales. Unglazed clay tiles set at three orientations (horizontal, vertical, and 45°), and six substrata of varying surface roughness were deployed in a prairie stream for 3 weeks. Substrata were analyzed for loosely attached, adnate, and total benthic algal biomass as chl a, and confocal laser scanning microscopy was used to measure substrata microtopography (i.e., roughness, microscale slope angles, and three-dimensional surface area). At the whole-substratum level, vertical substrata collected significantly (P < 0.05) less algal biomass, averaging 34% and 36% less than horizontal and 45° substrata, respectively. Benthic algal biomass was also significantly less on smoother surfaces; glass averaged 29% less biomass than stream rocks. At the microscale level, benthic algal biomass was the greatest at intermediate values, peaking at a mean roughness of approximately 17 μm, a mean microscale slope of 50°, and a projected/areal surface area ratio of 2:1. The proportion of adnate algae increased with surface roughness (26% and 67% for glass and brick, respectively), suggesting that substratum type changes the efficiency of algal removal by brushing. Individual substrata and microsubstrata characteristics can have a strong effect on benthic algae development and potentially affect reach scale algal variability as mediated by geomorphology.10aconfocal microscopy10amicrophytobenthos10aorientation10aperiphyton10aroughness10asurface area1 aMurdock, J.N.1 aDodds, W., K. uhttp://knz.lternet.edu/content/linking-benthic-algal-biomass-stream-substratum-topography02551nas a2200241 4500008004100000245012500041210006900166300001100235490000700246520175400253653002002007653001202027653001802039653001502057653001102072653001102083100001802094700001802112700001702130700001802147700001902165856012502184 2007 eng d00aThe saturation of N cycling in Central Plains streams: 15N experiments across a broad gradient of nitrate concentrations0 asaturation of N cycling in Central Plains streams 15N experiment a31 -490 v843 aWe conducted 15NO 3 − stable isotope tracer releases in nine streams with varied intensities and types of human impacts in the upstream watershed to measure nitrate (NO 3 − ) cycling dynamics. Mean ambient NO 3 − concentrations of the streams ranged from 0.9 to 21,000 μg l−1 NO 3 − –N. Major N-transforming processes, including uptake, nitrification, and denitrification, all increased approximately two to three orders of magnitude along the same gradient. Despite increases in transformation rates, the efficiency with which stream biota utilized available NO 3 − -decreased along the gradient of increasing NO 3 − . Observed functional relationships of biological N transformations (uptake and nitrification) with NO 3 − concentration did not support a 1st order model and did not show signs of Michaelis–Menten type saturation. The empirical relationship was best described by a Efficiency Loss model, in which log-transformed rates (uptake and nitrification) increase with log-transformed nitrate concentration with a slope less than one. Denitrification increased linearly across the gradient of NO 3 − concentrations, but only accounted for ∼1% of total NO 3 − uptake. On average, 20% of stream water NO 3 − was lost to denitrification per km, but the percentage removed in most streams was <5% km−1. Although the rate of cycling was greater in streams with larger NO 3 − concentrations, the relative proportion of NO 3 − retained per unit length of stream decreased as NO 3 − concentration increased. Due to the rapid rate of NO 3 − turnover, these streams have a great potential for short-term retention of N from the landscape, but the ability to remove N through denitrification is highly variable.10adenitrification10aNitrate10anitrification10aSaturation10astream10aUptake1 aO'Brien, J.M.1 aDodds, W., K.1 aWilson, K.C.1 aMurdock, J.N.1 aEichmiller, J. uhttp://knz.lternet.edu/content/saturation-n-cycling-central-plains-streams-15n-experiments-across-broad-gradient-nitrate