We evaluated patterns of denitrification and factors effecting in the upper Mississippi River. Measurements were taken over 2 years, during which river discharge ranged from record flooding to base flow conditions. Over period study, average enzyme activity was highest backwater lakes lowest main channel. Throughout study reach, occurred fall winter. Rates spring floods (2001) only slightly higher than preceding Mean unamended rates 0.02 (fall 2001 backwaters) 0.40 µg N·cm –2 ·h –1 (spring...

We measured nitrification rates in sediment samples collected from a variety of aquatic habitats Navigation Pool 8 the Upper Mississippi River (UMR) 7 times between May 2000 and October 2001. also conducted nutrient-enrichment experiments analyzed vertical profiles to determine factors regulating nitrification. Nitrification were relatively high compared other ecosystems (ranging 0–8.25 μg N cm−2 h−1) exhibited significant temporal spatial patterns. greatest during summer spring autumn...

1. Although it is well known that sediments can be hot spots for nitrogen transformation in streams, many previous studies have confined measurements of denitrification and nitrate retention to shallow (<5 cm deep). We determined the extent processing deeper a sand plains stream (Emmons Creek) by measuring core sections depth 25 assessing vertical profiles, with peepers piezometers, 70 cm. 2. Denitrification rates sediment slurries based on acetylene block were higher shallower sections....

Summary Photosynthesis and respiration are primary drivers of dissolved oxygen dynamics in rivers. We measured dynamics, aquatic ecosystem metabolism, algal abundance nutrient concentrations at main channel backwater sites on a reach the Upper Mississippi River that borders states Wisconsin Minnesota (U.S.A.). asked (i) how metabolism rates, differed backwaters, (ii) whether relates to solar irradiance, concentration, abundance, temperature river discharge (iii) relationships between these...

We assessed the effects of fish predation on zebra mussels (Dreissena polymorpha) in Navigation Pool 8 Upper Mississippi River from 13 May to 5 October, 1998. Concrete-block samplers were deployed at 18 randomly chosen sites main-channel border, with 6 upper, middle, and lower segments pool. Two blocks, 1 which was enclosed a cage exclude large predatory fishes, each site. After 145 d, blocks retrieved 12 sites, found all blocks. Densities higher caged than uncaged magnitudes differences...

Increased nutrient and sediment loading in rivers have caused observable changes algal community composition, thereby, altered the quality quantity of food resources available to native freshwater mussels. Our objective was characterize relationship between conditions mussel examine effects on fatty acid growth survival juvenile Juvenile Lampsilis cardium L. siliquoidea were deployed cages for 28 d at four riverine lacustrine sites lower St. Croix River, Minnesota/Wisconsin, USA. Mussel foot...

Abstract Contemporary land use can affect sediment nutrient processes in rivers draining heavily modified watersheds; however, studies linking to large river networks are limited. In this study, we developed and evaluated structural equation models for denitrification phosphorus retention capacity determine direct indirect linkages between current during base flow the Fox River watershed, WI, USA. A spatial‐scale dataset used study included nitrogen measurements information 106 sites. The...

Many estimates of nitrogen removal in streams and watersheds do not include or account for nitrate deep sediments, particularly gaining streams. We developed tested a conceptual model sediments nitrogen‐rich river network. The predicts that oxic, nitrate‐rich groundwater will become depleted as upwelling through encounters zone contains buried particulate organic carbon, which promotes redox conditions favorable removal. the at eight sites reaches lotic ecosystems Waupaca River Watershed...

Spatial variation in food resources strongly influences many aspects of aquatic consumer ecology. Although large-scale controls over spatial are well known, others have received little study. Here we investigated the fatty acid (FA) composition seston and primary consumers within (i.e., among habitats) tributary systems Lake Michigan, USA. FA is important because all metazoans require certain FAs for proper growth development that cannot be produced de novo, including polyunsaturated acids...

Restored riparian wetlands in the Upper Mississippi River basin have potential to remove sediment and nutrients from tributaries before they flow into River. For 3 yr we calculated retention efficiencies of a marsh complex, which consisted restored an adjacent natural that were connected Halfway Creek, small tributary Mississippi. We measured sediment, N, P removal through mass balance budget approach, N denitrification, mechanical soil excavation. The complex had average rates approximately...

Abstract Rivers affected by anthropogenic nutrient inputs can retain some of the phosphorus (P) load through sediment retention and burial. Determining influence land use management on P concentrations in fluvial ecosystems is challenging because different stressors operating at multiple spatial temporal scales. In this study, we sought to determine how influenced within a river network draining watershed modified mixed activities, Fox River, Wisconsin, USA. Results show that current had no...

Abstract Nitrogen (N) has been linked to increasing eutrophication in the Gulf of Mexico and as a result there is increased interest managing improving water quality Mississippi River system. Water level reductions, or ‘drawdowns’, are being used more frequently large river impoundments improve vegetation growth sediment compaction. We selected two areas Upper system (Navigation Pool 8 Swan Lake) examine effects drawdown on N dynamics. Navigation experienced summer drawdowns 2001 2002....

Sediments in the backwaters of Upper Mississippi River (UMR) are highly organic and provide an optimal environment for N removal. We monitored 8.6-ha UMR backwater site near La Crosse, Wisconsin, nearly 3 y to assess temporal variability, seasonal trends, factors regulating denitrification. measured rates unamended denitrification (DEN) enzyme activity (DEA) at ambient temperature DEA 30°C (DEA30). Seasonal mean (±1 SE) DEN ranged from 0.041 ± 0.015 0.47 0.23 μg cm−2 h−1 were highest winter...

The interface between ground water and surface in streams is a hotspot for N processing. However, the role of buried organic C transformation at this not well understood, inferences have been based largely on descriptive studies. Our main objective was to determine how particulate (POC) affected denitrification NO3− retention sediments an upwelling reach sand-plains stream Wisconsin. We manipulated POC mesocosms inserted sediments. Treatments included low high quantities conditioned red...

Abstract Carbon dioxide (CO 2 ) has shown promise as a tool to control movements of invasive Asian carp, but its effects on native freshwater biota have not been well studied. The authors evaluated lethal and sublethal responses juvenile fatmucket ( Lampsilis siliquoidea mussels CO at levels (43–269 mg/L, mean concentration) that bracket concentrations effective for deterring carp movement. 28‐d concentration 50% the was 87.0 mg/L (95% confidence interval [CI] 78.4–95.9) 16‐d postexposure,...

Eutrophic and hypoxic coastal waters are often associated with high nutrient inputs from riverine systems. For example, nitrogen (N) export the Mississippi River into Gulf of Mexico has been identified as an important factor causing eutrophication seasonal hypoxia. Modelling studies N flux in large rivers, including River, suggest that much enters rivers remains solution is exported downstream. However, patterns cycling complex vary according to habitat type season. Here we use spatial data...

Lake Erie is a large lake straddling the border of USA and Canada that has become increasingly eutrophic in recent years. Eutrophication particularly focused shallow western basin. The basin hydrodynamically similar to estuary, with riverine inputs from Detroit Maumee Rivers mixing together creating gradients chemical physical conditions. This study was driven by two questions: (1) How does secondary production food quality for consumers vary across this zone? (2) Are there correlations...