@article {KNZ001544, title = {Influence of macroconsumers, stream position, and nutrient gradients on invertebrate assemblage development following flooding in intermittent prairie streams}, journal = {Hydrobiologia}, volume = {714}, year = {2013}, pages = {169 -182}, abstract = {

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.

}, keywords = {LTER-KNZ, disturbance, Flood, Invertebrate, Macroconsumer Gradients, Prairie stream}, doi = {10.1007/s10750-013-1534-5}, url = {https://link.springer.com/article/10.1007\%2Fs10750-013-1534-5}, author = {Bertrand, K.N. and M.R. Whiles and K. B. Gido and Murdock, J.N.} } @article {KNZ001433, title = {Dynamic influences of nutrients and grazing fish on periphyton during recovery from flood}, journal = {Journal of the North American Benthological Society}, volume = {30}, year = {2011}, pages = {331 -345}, keywords = {LTER-KNZ}, doi = {10.1899/10-039.1}, url = {https://www.journals.uchicago.edu/doi/10.1899/10-039.1}, author = {Murdock, J.N. and W. K. Dodds and K. B. Gido and M.R. Whiles} } @article {KNZ001386, title = {Nutrient loading and grazing by the minnow Phoxinus erythrogaster shift periphyton abundance and stoichiometry in mesocosms}, journal = {Freshwater Biology}, volume = {56}, year = {2011}, pages = {1133 -1146}, abstract = {

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.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2427.2010.02557.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2427.2010.02557.x}, author = {Kohler, T.J. and Murdock, J.N. and K. B. Gido and W. K. Dodds} } @proceedings {KNZ001432, title = {Disturbance mediated effects of stream fishes on ecosystem processes: concepts and results from highly variable prairie streams}, journal = {Advances in Stream Fish Community Ecology: Concepts, Approaches and Techniques}, year = {2010}, pages = {593 -617}, abstract = {

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.

}, keywords = {LTER-KNZ}, url = {https://www.k-state.edu/fishecology/msreprints/Gido\%20et\%20al.2010\%20AFSbook\%20chapter.pdf}, author = {K. B. Gido and Bertrand, K.N. and Murdock, J.N. and W. K. Dodds and M.R. Whiles} } @article {KNZ001237, title = {Disturbance frequency and functional identity mediate ecosystem processes in prairie streams}, journal = {Oikos}, volume = {118}, year = {2009}, pages = {917 -933}, abstract = {

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.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1600-0706.2008.16849.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0706.2008.16849.x}, author = {Bertrand, K.N. and K. B. Gido and W. K. Dodds and Murdock, J.N. and M.R. Whiles} } @article {KNZ001117, title = {Linking benthic algal biomass to stream substratum topography}, journal = {Journal of Phycology}, volume = {43}, year = {2007}, pages = {449 -460}, abstract = {The 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{\textdegree}), 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{\textdegree} 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{\textdegree}, 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.}, keywords = {LTER-KNZ, confocal microscopy, microphytobenthos, orientation, periphyton, roughness, surface area}, doi = {10.1111/j.1529-8817.2007.00357.x}, author = {Murdock, J.N. and W. K. Dodds} } @article {KNZ001116, title = {The saturation of N cycling in Central Plains streams: 15N experiments across a broad gradient of nitrate concentrations}, journal = {Biogeochemistry}, volume = {84}, year = {2007}, pages = {31 -49}, abstract = {We 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 - {\textendash}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{\textendash}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.}, keywords = {LTER-KNZ, denitrification, Nitrate, nitrification, Saturation, stream, Uptake}, doi = {10.1007/s10533-007-9073-7}, author = {O{\textquoteright}Brien, J.M. and W. K. Dodds and Wilson, K.C. and Murdock, J.N. and Eichmiller, J.} }