Pharmaceuticals and personal care products in the Clark Fork River compared to national data

Pollution by pharmaceutical and personal care products (PPCPs) is an emerging concern because they are ubiquitous in freshwaters and may have adverse effects on ecosystem structure and function. Predicting PPCP abundance in freshwater systems is inhibited by the multiple controls on degradation and fate, as well as the unique characteristics of each individual compound. The Clark Fork River was one of 42 sites included in the RiverPACE project (Riverine Pharmaceutical Assessment, Collection, and Education Project), a collaborative effort to promote awareness of PPCPs in freshwater and develop a national database of PPCP concentrations in diverse river and stream ecosystems. Six different compounds were found at detectable levels in the waters of the Clark Fork River as it passes through Missoula. Those detected PPCPs were primarily associated with human antibiotics, antidepressants, and antihistamine medications, but sucralose (i.e., artificial sweetener) appeared at highest concentration. Compounds showing largest concentration ranges across the US, such as lincomycin (i.e., veterinary antibiotic) and triclosan (i.e., antiseptic present in toothpaste), were not detected in the Clark Fork River. Overall, concentrations of all compounds in the Clark Fork River were relatively low, especially when compared to nation- and world-wide concentrations of detectable PPCPs in water. Effects of PPCPs on humans through water consumption remain currently unknown, but the information derived from the RiverPACE project highlights the Clark Fork River as one of the ecosystems included in the national PPCPs database with a lowest risk for human health

Nutrient dynamics in the Upper Clark Fork River

Remediation and restoration of the Upper Clark Fork River (UCFR) is occurring under nutrient-rich conditions associated with non-point source and sewage treatment inputs. Restoration is designed to enhance river-floodplain interaction with potential influences on river nutrient loads. Assessment of the long-term record for nitrogen (N) and phosphorus (P) illustrate that the upper river consistently exceeds water quality standards for total N (300 μg N/L) and total P (20 μg/L P). However, data from the past three decades also show substantial reduction in nitrate-N loads during summer and autumn despite inputs from tributaries and sewage treatment facilities. During these time periods, benthic algal standing crops can be substantial (150 – 275 mg/m2 as chlorophyll) and measures of primary production support the potential for algal uptake to remove inorganic N and generate high atomic N:P ratios. Nutrient-diffusing assays suggest N-limitation of algal growth despite an overabundance of total N in the river water. Along with a plentiful supply of P, these conditions are optimal for the growth and proliferation of N-fixing microbes (i.e., bluegreen algae). Genetic assessment of epilithic biofilms along a 10-km reach near Drummond shows that bluegreens are indeed an abundant and diverse part of the microbial community. Preliminary assessment of the potential for N-fixation to add to nutrient enrichment and promote nuisance algal blooms points to the need to investigate elemental interactions and manage multiple water quality issues simultaneously as restoration continues concomitant with development of waste water and sewage treatment capacity on the UCFR

Remediation and restoration of the Upper Clark Fork River: influences on floodplain soil organic matter

Remediation and restoration of the Upper Clark Fork River (UCFR) represents an experiment addressing aquatic-terrestrial interaction at the landscape scale. Remediation and restoration along Reach A (from Warm Springs to Garrison) is designed to reconnect the channel and floodplain over ca. 70 km of river length. The process includes removal of metal-contaminated floodplain soils, lowering of the soil surface, introduction of new top soil, and re-vegetating the floodplain. Lowering the floodplain elevation should enhance river-floodplain interaction with potential influences on sediment deposition, and soil organic matter content and composition. In this study, we compared characteristics of soil organic matter, including % organic matter, water soluble dissolved organic carbon, and specific ultraviolet absorbance (SUVA) signatures among five sites associated with restoration of Reach A. The five sites were chosen to represent different soil types and ‘stages’ in the restoration process including: 1) pre-restoration conditions, 2) ongoing soil removal, 3) replacement top soil, 4) recently remediated and restored (i.e., \u3c1 \u3eyr), and 5) 5-yr post-remediation floodplain soils. Measures of organic matter abundance and composition (i.e., SUVA) were compared to autochthonous organic matter (i.e., benthic algae, Cladophora) to assess how potential organic matter sources may differ in terms of bioavailable carbon for river foodwebs

Spatial drivers of ecosystem structure and function in a floodplain riverscape: springbrook nutrient dynamics

On riverine flood plains, reorganization by fluvial processes creates and maintains a mosaic of aquatic and riparian landscape elements across a biophysical gradient of disturbance and succession. Across flood plains of gravel-bottom rivers, spring brooks emerge from points of groundwater discharge that may occur in distinct landscape positions. We investigated how ecosystem processes in spring brooks differ spatially across biophysical zones, reflecting how landscape position dictates severity of flood disturbance, allochthonous loading from riparian forests, and inputs from groundwater systems. Between July and October 2011, we quantified aspects of ecosystem structure and function among 6 spring brooks of the Nyack flood plain, Flathead River, Montana. Structural features varied predictably across near-channel (i.e., parafluvial) and late successional (i.e., orthofluvial) biophysical zones. Large wood standing stocks increased >40× (0.19–9.19 kg/m2), dominant particle size class differed by an order of magnitude (median particle size [D50] = 2–27), and measures of vertical hydraulic gradient (–0.06 to +0.12 cm/cm) reflected differences in landscape position. We found fine sediment accumulation, stronger groundwater inputs, and greater benthic and large wood standing stocks in orthofluvial than in parafluvial spring brooks. Algal biomass was negatively correlated with insolation and positively related to vertical hydraulic gradient. Results from microcosm experiments showed increasing N uptake across the gradient from parafluvial to orthofluvial spring brooks. Functional response to landscape-scale organization of springbrook structure underscores the need for a spatially explicit model of floodplain ecology.Peer reviewe

Effets de pulses de toxiques sur la capacité de prélèvement de phosphore du biofilm en cours d'eau intermittents

International audienceUse of Personal care products (PCPs) and herbicides has highly increased during last decades. These products can reach aquatic ecosystems, both through diffuse and/or local sources, where they are detected at low concentration. Under water scarcity, products reaching the river biota may have higher concentrations, and produce extended pulses. This situation may produce chronic contamination with unknown impacts on aquatic ecosystems. Among the commonly detected PCPs, Triclosan (TCS) is used as a broad-spectrum antimicrobial in several products as toothpaste, shampoos, etc. Several studies investigating removaI rates of TCS during wastewater treatment, detected TCS in the effluents and some of them showed the persistence in river water. Triclosan was also detected in wild living fishes and in human milk. Diuron (DIU) is a well known herbicide included into the list of priority pollutants of the EU Water Framework Directive (WFD). Several studies investigated effects of these compounds on aquatic organisms in a single-specie tests, though less have focused on the biofilm community response. In particular, no previous studies investigated effect of both compounds for ecosystem services as auto-depuration capacity (P uptake) of rivers. In this talk, results of a laboratory exposure of fluvial biofilms to both compounds will be presented. The results of the study confirm the effects that higher concentration of pollutants, occurring under poor dilution, produce in the biofilm. The mode of action of the two toxicants was different. TCS mainly affected the bacterial compartment, DIU affected mostly the algal compartment. Triclosan specially effected the P uptake capacity of the biofilm, which might determine a reduction of the self-depuration capacity in the river ecosystem. These compounds further affected the biofilm structure

Effects of relic low-head dams on stream denitrification potential: seasonality and biogeochemical controls

The majority of dams in the contiguous United States are small, low-head dams that are no longer operational but can influence the water quality of contemporary stream ecosystems. Potential effects of low-head dams on stream nitrogen removal (denitrification) have been rarely quantified, and yet they can be an important part of the decision-making process of removing low-head dams. Here, we provide novel empirical data on potential denitrification rates and their biogeochemical controls above and below two mid-Atlantic low-head dams over a 2-year period. Our results show that low-head dams did not increase streambed potential denitrification in comparison to dam-free sections in the same rivers. In our study sites, potential denitrification above low-head dams was generally low (15.7 ± 3.5 µg N [kg sediment]−1 h−1) despite recurring events of water hypoxia (\u3c 50% dissolved oxygen saturation) and high NO3− and DOC concentrations. Overall, we observed higher potential denitrification during winter samplings (9.2 and 50.1 µg N [kg sediment]−1 h−1 on average) and significant effects of sediment surface area and organic matter content on potential denitrification rates above the dams. Results from this study suggest limited effects of relic low-head dams on nitrogen removal and transport in stream ecosystems, and can contribute to the decision-making process of removing low-head dams

Draining the Landscape: How Do Nitrogen Concentrations in Riparian Groundwater and Stream Water Change Following Milldam Removal?

Dam removals are on the increase across the US with Pennsylvania currently leading the nation. While most dam removals are driven by aquatic habitat and public safety considerations, we know little about how dam removals impact water quality and riparian zone processes. Dam removals decrease the stream base level, which results in dewatering of the riparian zone. We hypothesized that this dewatering of the riparian zone would increase nitrification and decrease denitrification, and thus result in nitrogen (N) leakage from riparian zones. This hypothesis was tested for a 1.5 m high milldam removal. Stream, soil water, and groundwater N concentrations were monitored over 2 years. Soil N concentrations and process rates and δ15N values were also determined. Denitrification rates and soil δ15N values in riparian sediments decreased supporting our hypothesis but no significant changes in nitrification were observed. While surficial soil water nitrate-N concentrations were high (median 4.5 mg N L−1), riparian groundwater nitrate-N values were low (median 0.09 mg N L−1), indicating that nitrate-N leakage was minimal. We attribute the low groundwater nitrate-N to denitrification losses at the lower, more dynamic, groundwater interface and/or dissimilatory nitrate reduction to ammonium (DNRA). Stream water nitrate-N concentrations were high (median 7.6 mg N L−1) and contrary to our dam-removal hypothesis displayed a watershed-wide decline that was attributed to regional hydrologic changes. This study provided important first insights on how dam removals could affect N cycle processes in riparian zones and its implications for water quality and watershed management

Saturated, Suffocated, and Salty: Human Legacies Produce Hot Spots of Nitrogen in Riparian Zones

The compounding effects of anthropogenic legacies for environmental pollution are significant, but not well understood. Here, we show that centennial-scale legacies of milldams and decadal-scale legacies of road salt salinization interact in unexpected ways to produce hot spots of nitrogen (N) in riparian zones. Riparian groundwater and stream water concentrations upstream of two mid-Atlantic (Pennsylvania and Delaware) milldams, 2.4 and 4 m tall, were sampled over a 2 year period. Clay and silt-rich legacy sediments with low hydraulic conductivity, stagnant and poorly mixed hydrologic conditions, and persistent hypoxia in riparian sediments upstream of milldams produced a unique biogeochemical gradient with nitrate removal via denitrification at the upland riparian edge and ammonium-N accumulation in near-stream sediments and groundwaters. Riparian groundwater ammonium-N concentrations upstream of the milldams ranged from 0.006 to 30.6 mgN L−1 while soil-bound values were 0.11–456 mg kg−1. We attribute the elevated ammonium concentrations to ammonification with suppression of nitrification and/or dissimilatory nitrate reduction to ammonium (DNRA). Sodium inputs to riparian groundwater (25–1,504 mg L−1) from road salts may further enhance DNRA and ammonium production and displace sorbed soil ammonium-N into groundwaters. This study suggests that legacies of milldams and road salts may undercut the N buffering capacity of riparian zones and need to be considered in riparian buffer assessments, watershed management plans, and dam removal decisions. Given the widespread existence of dams and other barriers and the ubiquitous use of road salt, the potential for this synergistic N pollution is significant