Wisconsin River Research Articles

Picturing Indians: photographic encounters and tourist fantasies in H. H. Bennett's Wisconsin Dells

Today a tourist mecca, the area now known as the Wisconsin Dells was once wilderness - and a gathering place for the region's Native peoples, the Ho-Chunk, who for centuries migrated to this part of the Wisconsin River for both sustenance and spiritual renewal. By the late 1800s their numbers had dwindled through displacement or forcible removal, and it was this smaller band that caught the attention of photographer Henry Hamilton Bennett. Having built his reputation on his photographs of the Dells' steep gorges and fantastic rock formations, H. H. Bennett now turned his camera upon the Ho-Chunk themselves, and thus began the many-layered relationship unfolded by Steven D. Hoelscher in Picturing Indians: Photographic Encounters and Tourist Fantasies in H. H. Bennett's Wisconsin Dells.The interactions between Indian and white man, photographer and photographed, suggested a relationship in which commercial motives and friendly feelings mixed, though not necessarily in equal measure. The Ho-Chunk resourcefully sought new ways to survive in the increasingly tourist-driven economy of the Dells. Bennett, struggling to keep his photography business alive, capitalized on America's comfortably nostalgic image of Native peoples as a vanishing race, no longer threatening and now safe for white consumption.Hoelscher traces these developments through letters, diaries, financial records, guidebooks, and periodicals of the day. He places Bennett within the context of contemporary artists and photographers of American Indians and examines the receptions of this legacy by the Ho-Chunk today. In the final chapter, he juxtaposes Bennett's depictions of Native Americans with the work of present-day Ho-Chunk photographer Tom Jones, who documents the lives of his own people with a subtlety and depth foreshadowed, a century ago, in the flickers of irony, injury, humor, and pride conveyed by his Ho-Chunk ancestors as they posed before the lens of a white photographer.

A combined acoustic and electromagnetic wave-based techniques for bathymetry and subbottom profiling in shallow waters

Acoustic-wave based sub-bottom profiler (SBP) and electromagnetic-wave based ground penetrating radar (GPR) are two complementary geophysical tools that were used to map bathymetry and sediment sublayers in shallow waters. Near shore regions in Great Lakes, inland lakes, and rivers in Wisconsin, USA were examined using both geophysical tools. In areas with high silt and clay contents, such as Lake Superior, the SBP was able to image the sediment sublayers, whereas in the areas with sand cover and vegetation, the GPR provided sediment stratigraphic information. The higher vertical and horizontal resolutions of the SBP surveys provided more accurate and detailed bathymetry information than GPR surveys. In the Yahara River, SBP surveys imaged blurring contrasts between sublayers due to the gradual deposition of sediments; however, GPR provided sharp delineations of sediment layers but was only able to image the top two sublayers because of the high silt and clay electromagnetic wave attenuation. To confirm these findings, Shelby tubes and hydraulic jetting were used to collect ground-truth information. Sublayer thicknesses are estimated by evaluating acoustic and electromagnetic wave velocities using a mixture-based equation. In Lake Michigan, both techniques show similar sediment stratigraphy, indicating that the average sediment particle size ranges between silt and fine sand. Three-dimensional maps of bathymetry and subbottom sediments are also constructed. Overall it is shown that the combination of GPR and SBP techniques compensates each survey's strengths in an effective methodology for imaging bathymetry and sub-bottom profiles in shallow water environments.

Changes in The Floodplain Forest Vegetation of The Lower Wisconsin River Over The Last Fifty Years

Over the last five decades, the floodplain forests along the Lower Wisconsin River have experienced several events capable of shifting forest structure and composition, including river regulation, Dutch elm disease and increased levels of herbivory. This study analyzes changes in the structure and composition of the vegetation in the floodplain forests over the previous 50 y by comparing forest survey data collected in 2001 with data collected on the same sites by John Curtis in the 1950s. The results suggest that the forests are shifting to a previously unrecorded later successional stage, dominated increasingly by silver maple, hackberry and bitternut hickory, a possible result of river regulation. Early-successional stages, particularly those dominated by black willow and cottonwood, are disappearing. Disturbances, such as timber harvests, may be increasing the rate of this transition. Further, the forests have shown a large increase in the dominance of two thorny shrubs, prickly ash and European buckthorn, in the understory, suggesting browsing pressure may be affecting regeneration. Analysis of the ground layer parallels these findings, showing an increase in species more typical of higher elevations in the floodplain and mesic forests, as well as invasive species and dominance by several species less palatable to deer.

Use of monitoring extreme data for the performance prediction of structures: Bayesian updating

Sensors of modern monitoring systems used in structural engineering provide data used for reliability assessment and maintenance planning. The storage and evaluation of sensor information are space and time-consuming activities. Therefore, it is necessary to process only the monitored data indicating a violation of defined performance thresholds. However, this process should not discard the knowledge gained from past monitored data and should allow the updating of prediction functions incorporating this knowledge. The objectives of this paper are to present: (a) a procedure for the effective incorporation of monitored data for the reliability assessment of structural components, (b) an approach for the updating of prediction functions and criteria for the interruption of monitoring, and (c) an effective use of the Bayesian approach for the incorporation of historical data in the structural reliability assessment. The proposed procedures and concepts are applied to the monitoring data obtained from the I-39 Northbound Bridge over the Wisconsin River in Wisconsin, USA. A monitoring program on that bridge was performed by the ATLSS Center at Lehigh University.

Development of a regional macroinvertebrate index for large river bioassessment

Abstract Large river bioassessment protocols lag far behind those of wadeable streams and often rely on fish assemblages of individual rivers. We developed a regional macroinvertebrate index and assessed relative condition of six large river tributaries to the upper Mississippi and Ohio rivers, Midwest USA. In 2004 and 2005, benthic macroinvertebrates, water chemistry, and habitat data were collected from randomly selected sites on each of the St. Croix, Wisconsin, Minnesota, Scioto, Wabash, and Illinois rivers. We first identified the human disturbance gradient using principal components analysis (PCA) of abiotic data. From the PCA, least disturbed sites showed strong separation from stressed sites along a gradient contrasting high water clarity, canopy cover, habitat scores, and plant-based substrates at one end and higher conductivity and nutrient concentrations at the other. Evaluation of 97 benthic metrics identified those with good range, responsiveness, and relative scope of impairment, as well as redundancies with other metrics. The final index was composed of Diptera taxa richness, EPT taxa richness, Coleoptera taxa richness, percent oligochaete and leech taxa, percent collector-filterer individuals, predator taxa richness, percent burrower taxa, tolerant taxa richness, and percent facultative individuals. Each of the selected metrics was scored using upper and lower thresholds based on all sites, and averaging across the nine metric scores, we obtained the Non-wadeable Macroinvertebrate Assemblage Condition Index (NMACI). The NMACI showed a strong response to disturbance using a validation data set and was highly correlated with non-metric multidimensional scaling (NMDS) ordination axes of benthic taxa. The cumulative distribution function of index scores for each river showed qualitative differences in condition among rivers. NMACI scores were highest for the federally protected St. Croix River and lowest for the Illinois River. Other rivers were intermediate and generally reflected the mixture of land use types within individual basins. Use of regional reference sites, though setting a high level of expectation, provides a valuable frame of reference for the potential of large river benthic communities that will aid management and restoration efforts.

Effect of flood regime on tree growth in the floodplain and surrounding uplands of the Wisconsin River

AbstractFlood regime and vegetation flood tolerance interact to influence tree growth in riverine landscapes. We studied tree growth in floodplain and upland forests of the Wisconsin River. About a century ago, levees set back from the river were constructed on this floodplain. The levee restricts some floodplain area from overbank flood events, but leaves a portion of active floodplain still inundated by floods. We addressed two questions: (1) how do growth rates of flood‐tolerant and flood‐intolerant tree species in the floodplain differ with flood regime? (2) At the stand level, how does growth rate differ with flood regime and between floodplain and upland areas? Annual tree growth rates from 1991 to 2000 were determined from tree increment cores for both individual species and stands. Tree growth rates of individual species varied between flood regimes. The most flood‐tolerant species (Betula nigra and Fraxinus pennsylvanica) grew faster in areas with active flooding, while the growth of less flood‐tolerant species (Quercus velutina and Q. ellipsoidalis) was depressed in swales and active floodplain. However, stand‐level tree growth did not differ between the floodplain and upland, or between flood regimes within the floodplain. Therefore, variation in the growth of individual species may not scale up to create differences in stand‐level tree growth because forest community composition varies spatially with flood regime. We suggest that growth rates are similar among sites because each community comprises of species adapted to their current flood regime. Copyright © 2008 John Wiley & Sons, Ltd.

Late Pleistocene dune construction in the Central Sand Plain of Wisconsin, USA

Wisconsin's Central Sand Plain east of the Wisconsin River is composed of eolian sand forming high-relief dunes surrounded by sand sheets and scattered low-relief dunes. To establish a maximum age for dune formation, three samples for optical dating were taken from glacial Lake Wisconsin lacustrine sediment that underlies eolian sand. These age estimates range from 19.3 to 13.6ka. Age estimates taken from within or at the base of the dunes range from 14.0 to 10.6ka. Samples taken from < 2m of the ground surface were slightly younger, indicating dunes were stabilized between 11.8 and 5.5ka. The younger ages near the surface of some dunes were most likely the result of pedoturbation or localized problems with applying the optical dating method. The majority of the optical age estimates from dunes (18 of 21) indicated that most of the dunes were active between 14 and 10ka and that most dune activity ended by 10ka. These ages suggest that localized activity on dune crests may have occurred in the Holocene but would have been limited to < 1m of sand accumulation. The timing of dune activity and the lack of any significant Holocene reactivation suggest that dune activation in this setting cannot be attributed solely to changes in aridity. Instead, we attribute dune formation to changes in sediment availability from either sand inputs from the Wisconsin River or the melting of permafrost.

Landscape genetics and the spatial distribution of chronic wasting disease

Predicting the spread of wildlife disease is critical for identifying populations at risk, targeting surveillance and designing proactive management programmes. We used a landscape genetics approach to identify landscape features that influenced gene flow and the distribution of chronic wasting disease (CWD) in Wisconsin white-tailed deer. CWD prevalence was negatively correlated with genetic differentiation of study area deer from deer in the area of disease origin (core-area). Genetic differentiation was greatest, and CWD prevalence lowest, in areas separated from the core-area by the Wisconsin River, indicating that this river reduced deer gene flow and probably disease spread. Features of the landscape that influence host dispersal and spatial patterns of disease can be identified based on host spatial genetic structure. Landscape genetics may be used to predict high-risk populations based on their genetic connection to infected populations and to target disease surveillance, control and preventative activities.

Landscape configuration and flood frequency influence invasive shrubs in floodplain forests of the Wisconsin River (USA)

Summary 1. Invasive species are present worldwide, yet predicting which invasive species will become problematic in which ecosystems remains an important ecological challenge. Floodplains are at particular risk for invasion, especially when subjected to anthropogenic disturbance. 2. We examined how components of flood regime, habitat quality and habitat configuration influenced the presence and abundance of three invasive shrubs in the floodplain of the Wisconsin River. Shrub taxa included two non-natives ( Lonicera spp. and Rhamnus spp.) and one native ( Zanthoxylum americanum ). Observations of taxa presence and abundance were recorded in nine forested river reaches, spanning three physiographic regions. We also compared the productivity of Z. americanum across a flood control levee in one reach. 3. Physiographic region significantly predicted the presence and abundance of these three taxa, acting as a synthetic indicator of differences in climate, geography and topography. Invasion was greatest in regions where modifications to flood regime and land use were most pronounced. Physiographic region was excluded from subsequent analyses to assess more specific predictors of shrub distributions. 4. Habitat configuration and quality both predicted shrub taxa presence and abundance. Shrub taxa were most frequently observed and most abundant in small forest patches, near roads, and in sandy soil with low nutrient content. Edge habitats have many of these characteristics. Edges appear to be favoured by avian shrub dispersers and provide conditions suitable for invasive establishment. 5. Flooding influenced non-native and native invaders differently. Non-native taxa were observed less frequently and at lower abundances in frequently flooded areas, probably because of a sensitivity to flooding. However, the presence, abundance and productivity of the native invader increased with flooding. Anthropogenic modifications to the flood regime limited hydrologic connectivity and may have reduced the competitive advantage of flood-tolerant traits, which allowed the invasion of upland species. 6. Synthesis . In the floodplain of the Wisconsin River, anthropogenic modifications that created edge habitat and altered flood regime facilitated shrub invasions, whereas unfragmented forest and intact flood regime limited invasion. Large patches of floodplain forest, less regulated flooding regimes, and lower road densities may help reduce the spread of invasive shrubs in temperate

A re-examination of the endangered Higgins eye pearlymussel Lampsilis higginsii in the upper Mississippi River, USA

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 3:229-237 (2007) - DOI: https://doi.org/10.3354/esr00033 A re-examination of the endangered Higgins eye pearlymussel Lampsilis higginsii in the upper Mississippi River, USA Andrew C. Miller*, Barry S. Payne Environmental Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180-6199, USA *Email: ecol_appl@earthlink.net ABSTRACT: We used our extensive data on freshwater mussels (Family: Unionidae), collected from 1984 to 2005 at multiple sites in the upper Mississippi River (UMR), USA, to examine the status of the endangered Higgins eye pearlymussel Lampsilis higginsii (Lea, 1857). Historically, this species inhabited an 850 km reach of the Mississippi River from Prescott, Wisconsin to Louisiana, Missouri, plus 9 UMR tributaries. After 1965 its range in the UMR declined by 50% and it was found in only 2 tributaries, the St. Croix and Wisconsin rivers. In river reaches unaffected by zebra mussels Dreissena polymorpha, L. higginsii mean density ranged from 0.0 to 1.4 m–2 (average = 0.25 m–2) and it comprised less than 2% of the unionid fauna. Recent distribution and abundance data indicate that the range of L. higginsii populations was misrepresented on historical maps and suggest that populations were in fact either absent or very uncommon both at the periphery of their historical range and in small tributaries where they were reported historically. Although this species has always been rare, it can usually be found in appropriate habitats within its current range. It was listed as endangered before there were data on its density, recruitment, and relative abundance. Although it was nearly extirpated by D. polymorpha in the late 1990s, L. higginsii appears to be resilient to zebra mussel infestations. A multi-agency conservation plan is now being implemented to reintroduce this species into small and medium-sized rivers within and outside its historical range. Our data indicate that this species is not in imminent danger of extinction, has always been rare, and is not adapted to small rivers. It would be more realistic, and beneficial to L. higginsii, to implement strategies that protect all unionid species and the habitats upon which they depend. KEY WORDS: Endangered Species Act · Upper Mississippi River · Lampsilis higginsii ·Zebra mussels · Freshwater mussels · Unionidae Full text in pdf format PreviousNextCite this article as: Miller AC, Payne BS (2007) A re-examination of the endangered Higgins eye pearlymussel Lampsilis higginsii in the upper Mississippi River, USA. Endang Species Res 3:229-237. https://doi.org/10.3354/esr00033 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 3, No. 2. Online publication date: September 04, 2007 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2007 Inter-Research.

Identifying Biotic Integrity and Water Chemistry Relations in Nonwadeable Rivers of Wisconsin: Toward the Development of Nutrient Criteria

We sampled 41 sites on 34 nonwadeable rivers that represent the types of rivers in Wisconsin, and the kinds and intensities of nutrient and other anthropogenic stressors upon each river type. Sites covered much of United States Environmental Protection Agency national nutrient ecoregions VII--Mostly Glaciated Dairy Region, and VIII--Nutrient Poor, Largely Glaciated upper Midwest. Fish, macroinvertebrates, and three categories of environmental variables including nutrients, other water chemistry, and watershed features were collected using standard protocols. We summarized fish assemblages by index of biotic integrity (IBI) and its 10 component measures, and macroinvertebrates by 2 organic pollution tolerance and 12 proportional richness measures. All biotic and environmental variables represented a wide range of conditions, with biotic measures ranging from poor to excellent status, despite nutrient concentrations being consistently higher than reference concentrations reported for the regions. Regression tree analyses of nutrients on a suite of biotic measures identified breakpoints in total phosphorus (approximately 0.06 mg/l) and total nitrogen (approximately 0.64 mg/l) concentrations at which biotic assemblages were consistently impaired. Redundancy analyses (RDA) were used to identify the most important variables within each of the three environmental variable categories, which were then used to determine the relative influence of each variable category on the biota. Nutrient measures, suspended chlorophyll a, water clarity, and watershed land cover type (forest or row-crop agriculture) were the most important variables and they explained significant amounts of variation within the macroinvertebrate (R(2) = 60.6%) and fish (R(2) = 43.6%) assemblages. The environmental variables selected in the macroinvertebrate model were correlated to such an extent that partial RDA analyses could not attribute variation explained to individual environmental categories, assigning 89% of the explained variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses.

Catastrophic flooding from Glacial Lake Wisconsin

Glacial Lake Wisconsin was a large proglacial lake that formed along the southern margin of the Laurentide Ice Sheet during the Wisconsin glaciation. It was formed when ice of the Green Bay Lobe came into contact with the Baraboo Hills in southwestern Wisconsin and blocked the south-flowing Wisconsin River. During early glacial recession, the ice dam failed catastrophically and the lake drained in about a week. Despite early recognition of the former lake and the likelihood that it failed catastrophically, outflow rates during the failure have not been previously evaluated. Estimates based on step-backwater modeling indicate that peak discharge was between 3.6 and 5.3 × 10 4 m 3/s in the lower Wisconsin River. As an alternate method, we used a previously derived empirical relationship between lake volume and peak discharge for dam-break events. From a digital elevation model altered to incorporate isostatic depression, we estimated the lake volume to be 87 km 3 just prior to dam breach, suggesting that the flooding magnitude was as high as 1.5 × 10 5 m 3/s at the outlet. Adjusting these results for downstream flood wave attenuation gives a discharge of around 4.4 × 10 4 m 3/s in the lower reach, which closely matches the results of the step-backwater modeling. These estimates of discharge from the catastrophic failure of ice-marginal lakes improve our understanding of the processes that have produced the morphology and behavior of present-day upper Midwest river systems.

Using Stem Count as a Decision Aid in Turning Over Alfalfa Stands

Alfalfa stem density can be an indicator of when alfalfa stands no longer have potential for high yield. Studies were conducted at University of Wisconsin Arlington Research Station and River Falls Farm where areas of differing plant density were selected within 1-, 2- and 3-year-old fields of differing varieties each year, for three years. Stem density and yield were determined on the same plot areas for each cutting and plant density was determined at the end of the season. Plant density and stems per plant had little relationship to yield. Stem density below 40 stems/ft² had reduced yield potential.

Eight polymorphic microsatellite loci for the aquatic fungus Tetracladium marchalianum

AbstractWe have identified eight polymorphic microsatellite loci from the aquatic haploid fungus Tetracladium marchalianum. Microsatellite polymorphism was evaluated using 90 fungal isolates, each of single spore origin, from submerged leaves in Illinois and Wisconsin rivers in the USA. The number of alleles observed for a single locus ranged from three to 13, with up to 10 observed from a population. These genetic markers will be useful to evaluate population structure, genotypic diversity, and the reproductive mode of T. marchalianum.

Fish assemblages and biotic integrity of a highly modified floodplain river, the Upper Mississippi, and a large, relatively unimpacted tributary, the Lower Wisconsin

The Upper Mississippi River is a dynamic floodplain river that has been largely transformed by navigational levees and dams since the 1930s. The pools upstream of each dam are lake-like and only about the upper third of each reach retains a riverine character. In contrast, the Wisconsin River is not managed for commercial navigation and today its lower 149 km represent one of the least-degraded large river reaches in central North America. Riverine reaches in both the Mississippi and Wisconsin rivers have similar macro-habitats including numerous islands, large side channels, and connected backwaters and floodplain lakes. In this study, shoreline electrofishing samples were collected during summer 2002 and 2003 to characterize resident fish assemblages. We compared fish species abundance, biomass, and biotic integrity along main and side channel borders between the Upper Mississippi River and the Lower Wisconsin River. We expected that, in the absence of environmental degradation, fish composition and structure would be similar between the Mississippi and Wisconsin rivers, and between channel types within each river. Nonmetric multidimensional scaling and redundancy analysis revealed that fish species in the Mississippi River, unlike in the Wisconsin River, were characteristic of non-riverine habitats. We consider non-riverine fish assemblages indicative of environmental impairment. The main and side channel sites in the Mississippi River had more variable fish assemblages than the Wisconsin River. Analyses of fish index of biotic integrity scores showed that environmental condition was excellent for both channel types in the Wisconsin River, whereas in the Mississippi River the side channel was rated good and the main channel only fair. We conclude that differences between the two rivers and between channel types of the Mississippi River are consistent with direct and indirect effects of navigation. This study demonstrates the utility of a fish index of biotic integrity, an inexpensive and rapid bioassessment tool, for detecting change in ecological health on one of the world's largest rivers. Copyright © 2006 John Wiley & Sons, Ltd.

Simulated recruitment of riparian trees and shrubs under natural and regulated flow regimes on the Wisconsin River, USA

Models that link ecological responses to hydrologic changes are important for assessing the effects of flow regulation on aquatic and riparian ecosystems. Based on the Recruitment Box Model, a graphical model used to prescribe environmental flows for cottonwood (Populus spp.) recruitment, we designed a simulation model to represent the influence of river flow dynamics on seedling recruitment of riparian pioneer woody plants. The model simulates the influence of temporal patterns of river stage on dispersal, germination, initial recruitment and over-winter survival of first-year seedlings of riparian pioneer shrubs and trees. We used the model to simulate seedling recruitment patterns for five species (Acer saccharinum, Betula nigra, Populus deltoides, Salix nigra and Salix exigua) on the Wisconsin River (Wisconsin, USA) under three flow scenarios: historic (1935–2002), simulated natural (1915–1975) and simulated regulated flows (1915–1975). Simulation results agreed well with field-observed relative differences among years (1997–2000) in seedling densities for the five focal species. Simulated successful recruitment years were highly synchronous among species, but species differed in their sensitivity to flows at different times during the growing season, consistent with among-species differences in seed dispersal timing. Comparison of simulated natural and regulated flows for 1915–1975 showed that flow regulation decreased monthly flow variability, increased late summer to winter baseflow and reduced the magnitude of spring peaks. Simulated recruitment and over-winter survival of tree seedlings of all species was enhanced under the regulated flow scenario, likely due to increased summer baseflow and reductions in peak flood magnitude. Our analyses show the utility of extending the Recruitment Box Model to include multiple species of riparian shrubs and trees, and the effects of post-colonization flows on their recruitment success. However, some key functional relationships between flow patterns and woody seedling demography (e.g. shear stress thresholds for seedling mortality) have not been adequately quantified and merit further study. Copyright © 2006 John Wiley & Sons, Ltd.

Identification of groundwater flowpaths and denitrification zones in a dynamic floodpain aquifier

The groundwater flow system in the thick sand and gravel aquifer of the wide forested floodplain along the Lower Wisconsin River was characterized using major ion and oxygen and deuterium stable isotope analyses to explain nitrate attenuation in the floodplain. Critical to the groundwater flow system are the 60–90 m bluffs, the Pleistocene river terrace, and the modern floodplain with ridge and swale microtopography. Upland nitrate concentrations reached 12 mg NO 3–N/L, but were largely below the detection limit in the downgradient floodplain wetlands. A transect of monitoring wells and multilevel samplers, with depths of up to 6 m, were installed to characterize spatial and temporal variability in the floodplain groundwater flowpaths. Results showed that the topography induces deep, intermediate, and shallow flow systems and that temporal variability causes mixing between water from different sources. Nitrate attenuation in this system is likely a combination of dilution, plant uptake and denitrification. The absence of dissolved oxygen and nitrate and presence of high soluble iron concentrations in the lower floodplain indicate an ample supply of electron donors for oxygen consumption, denitrification and subsequent iron reduction. The data indicate that conditions created by the topography and temporal variability of the system are suitable for denitrification to occur at depth.

Rapid Nitrate Loss and Denitrification in a Temperate River Floodplain

Nitrogen (N) pollution is a problem in many large temperate zone rivers, and N retention in river channels is often small in these systems. To determine the potential for floodplains to act as N sinks during overbank flooding, we combined monitoring, denitrification assays, and experi- mental nitrate (NO3 � -N) additions to determine how the amount and form of N changed during flooding and the processes responsible for these changes in the Wisconsin River floodplain (USA). Spring flooding increased N concentrations in the floodplain to levels equal to the river. As dis- charge declined and connectivity between the river and floodplain was disrupted, total dissolved N decreased over 75% from 1.41 mg l � 1 , equivalent to source water in the Wisconsin River on 14 April 2001, to 0.34 mg l � 1 on 22 April 2001. Simultaneously NO3 � -N was attenuated almost 100% from 1.09 to 60%) of NO3 � -N mass loss was not attributable to hydrologic losses or conversion to other forms of N, suggesting that denitrification was likely responsible for most of the NO3 � -N disap- pearance. Floodplain capacity to decrease the dominant fraction of river borne N within days of inundation demonstrates that the Wisconsin River floodplain was an active N sink, that denitri- fication often drives N losses, and that enhancing connections between rivers and their floodplains may enhance overall retention and reduce N exports from large basins.

Association of polychlorinated biphenyls (PCBs) with live algae and total lipids in rivers—a field-based approach

The association of PCBs and live algal cells in rivers was studied at four locations during four seasons in two Wisconsin rivers. Positive relations between particle-associated PCBs and both chlorophyll-a and algal carbon concentrations indicated that live algal cells were a significant sorption phase for dissolved PCBs. Large Pennate diatoms ( Navicula, Synedra, Pinnularia, Diatoma, and Cocconeis), or more rarely, Euglenoids ( Trachelomonas sp .), dominated most sample assemblages on an algal carbon basis. These assemblages made up the highest percentage of total SOC during spring (average=50%) and lowest during summer (average=15%). At the three impounded sites, most individual PCB congeners were relatively enriched in samples characterized by: (1) high concentrations of algal carbon (as a percent of SOC), (2) algal assemblages dominated (or co-dominated) by Euglenoids, and (3) high concentrations of total lipids. Despite relatively higher masses of sorbed PCBs in the most lipid-rich samples, there was no robust correlation between total lipid content and particle-associated PCBs when aggregating all samples from the study. A possible explanation is that PCBs are associated with other structural components in live algae and (or) departure from chemical equilibrium in the river due to algal growth kinetics. A kinetic uptake model was used to calculate the mass of PCBs associated with the total organic carbon content of live algae. Based on this model, PCBs were enriched in algal cells during bloom seasons (spring and fall) compared to non-bloom seasons (summer and winter). Further, although individual PCB congener partition coefficients (log) to live algal cells (range=5.3–6.4) overlapped to those for detritus (range=3.6–7.4), PCBs tended to be enriched in detrital carbon pools during non-bloom conditions. The larger range of estimated PCB partition coefficients for detritus likely reflects the more heterogeneous nature of this material compared to live algal cells.

Biodiversity of floodplain forests in Europe and eastern North America: A comparative study of the Rhine and Mississippi Valleys

In this study, we investigate the mechanisms driving biodiversity in floodplain forests with a comparison of the composition and dynamics in the warm-temperate floodplain forests of the lower Mississippi Valley and the cool-temperate floodplain forests of the lower Wisconsin and Rhine River Valleys. We employ data from original research, as well as from the literature. We compare species, genus, and family diversity across regions with respect to species richness, numbers of species per family and genus, and a similarity index. We examine these results within a historical context, as well as with respect to river-floodplain dynamics. We also compare productivity data and successional stages for each region. We find a lower species, genus, and family richness in the cool-temperate forests of the Rhine compared to the cool-temperate forests of the Wisconsin, a probable result of the lack of available refugia for Rhine species in times of glacial expansion. We find the highest richness in the lower Mississippi Valley, likely a result of climatic factors and the availability of refugia in this region. In each of the regions, floodplain forests are more diverse than their upland counterparts, demonstrating the role of river-floodplain dynamics in maintaining species diversity. Each region maintains a high and relatively similar level of productivity in the floodplain forests. They also experience similar stages of succession, although succession becomes more complex in the warm-temperate forests of the Lower Mississippi.