Size-dependent effects of dams on river ecosystems and implications for dam removal outcomes.

Understanding the relationship between a dam's size and its ecological effects is important for prioritization of river restoration efforts based on dam removal. Although much is known about the effects of large storage dams, this information may not be applicable to small dams, which represent the vast majority of dams being considered for removal. To better understand how dam effects vary with size, we conducted a multidisciplinary study of the downstream effect of dams on a range of ecological characteristics including geomorphology, water chemistry, periphyton, riparian vegetation, benthic macroinvertebrates, and fish.

Relationships between ecosystem properties and sea-level rise vulnerability of tidal wetlands of the U.S. Mid-Atlantic.

Tidal wetlands in the Mid-Atlantic, USA, are experiencing high rates of relative sea level rise, and it is unclear whether they will be resilient in the face of future flooding increases. In a previous study, we found 80% of our study areas in tidal freshwater and salt marshes in the Delaware Estuary and Barnegat Bay had elevation change rates lower than the 19-year increase in mean sea level. Here, we examine relationships between marsh elevation dynamics and abiotic and biotic parameters in order to assess their utility as indicators of vulnerability to relative sea level rise.

Author Correction: Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Reconstruction of historical 2,3,7,8-tetrachlorodibenzo-p-dioxin discharges from a former pesticide manufacturing plant to the Lower Passaic River.

Based on chemical fingerprinting and other lines of scientific evidence, a former pesticide manufacturing plant in Newark, New Jersey (U.S.A.

Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States.

Tidal wetlands produce long-term soil organic carbon (C) stocks. Thus for carbon accounting purposes, we need accurate and precise information on the magnitude and spatial distribution of those stocks. We assembled and analyzed an unprecedented soil core dataset, and tested three strategies for mapping carbon stocks: applying the average value from the synthesis to mapped tidal wetlands, applying models fit using empirical data and applied using soil, vegetation and salinity maps, and relying on independently generated soil carbon maps.

Linking otolith microchemistry and surface water contamination from natural gas mining.

Unconventional natural gas drilling and the use of hydraulic fracturing technology have expanded rapidly in North America. This expansion has raised concerns of surface water contamination by way of spills and leaks, which may be sporadic, small, and therefore difficult to detect. Here we explore the use of otolith microchemistry as a tool for monitoring surface water contamination from generated waters (GW) of unconventional natural gas drilling.

Stable isotopes of C and N reveal habitat dependent dietary overlap between native and introduced turtles Pseudemys rubriventris and Trachemys scripta.

Habitat degradation and species introductions are two of the leading causes of species declines on a global scale. Invasive species negatively impact native species through predation and competition for limited resources. The impacts of invasive species may be increased in habitats where habitat degradation is higher due to reductions of prey abundance and distribution.

Exchange of Nitrogen through an Urban Tidal Freshwater Wetland in Philadelphia, Pennsylvania.

Tidal freshwater wetlands in urban settings can be subject to elevated N concentrations, which can promote the exchange of N between the marsh, water, and atmosphere, including denitrification. We used a multitiered approach consisting of direct measurements of N fluxes and denitrification, tidal hypsometry, and N load modeling to examine N exchanges in an urban tidal freshwater wetland of the Delaware River Estuary, Philadelphia, PA. Sediment cores and aboveground biomass were collected at 20 locations across a range of elevations and plant communities in April, July, and October 2010.

Children's daily exposure to polychlorinated biphenyls from dietary supplements containing fish oils.

In children, omega-3 polyunsaturated fatty acids (PUFAs) may elicit a suite of health benefits including enhancement of cognitive development. Subsequently, dietary supplements containing omega-3 PUFAs have become increasingly popular. Often, the largest source of beneficial PUFAs in these supplements is fish oil, which may contain significant levels of contaminants such as polychlorinated biphenyls (PCBs).

Bacterial community profiles from sediments of the Anacostia River using metabolic and molecular analyses.

Unlabelled: BACKGROUND AIM AND SCOPE: Though the tidal Anacostia River, a highly polluted riverine system, has been well characterized with regard to contaminants, its overall resident bacterial populations have remained largely unknown. Improving the health of this system will rely upon enhanced understanding of the diversity and functions of these communities. Bacterial DNA was extracted from archived (AR, year 2000) and fresh sediments (RE, year 2006) collected from various locations within the Anacostia River.

Historical contamination of the Anacostia River, Washington, D.C.

The tidal Anacostia River in Washington DC has long been impacted by various sources of chemical pollution over the past 200 years. To explore more recent inputs of various chemicals, six sediment cores were collected for dating and chemical analysis in the downstream section of the tidal Anacostia River. Profiles of contaminants in sediment cores can be useful in determining management direction and effectiveness of pollution controls over time.

Mercury and halogenated organic contaminants in river otters (Lontra canadensis) in New Jersey, USA.

Liver samples collected from New Jersey river otters (Lontra canadensis) in 2005 and 2007 were tested for Hg, organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polybrominated diphenyl ethers (PBDEs). The highest mercury concentrations were found in otters living in the Pinelands region, where acidic soils and surface waters enhance Hg bioavailability. The highest individual Hg concentration was 19.

Evaluating daily exposure to polychlorinated biphenyls and polybrominated diphenyl ethers in fish oil supplements.

Fish oil supplements have become a popular means of increasing one's dietary intake of essential polyunsaturated fatty acids. However, there is growing concern that the levels and potential health effects of lipophilic organic contaminants such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) may diminish some of the health benefits associated with the daily consumption of fish oil supplements. In this study, ten over-the-counter fish oil supplements available in the United States were analysed for PCBs and PBDEs and daily exposures calculated.

Using the Sediment Quality Triad to characterize baseline conditions in the Anacostia River, Washington, DC, USA.

The Sediment Quality Triad (SQT) consists of complementary measures of sediment chemistry, benthic community structure, and sediment toxicity. We applied the SQT at 20 stations in the tidal portion of the Anacostia River from Bladensburg, MD to Washington, DC to establish a baseline of conditions to evaluate the effects of management actions. Sediment toxicity was assessed using 10-day survival and growth tests with the freshwater amphipod, Hyalella azteca and the midge, Chironomus dilutus.

The effects of small dam removal on the distribution of sedimentary contaminants.

With increasing concern over degradation of aquatic resources, issues of liability, and maintenance costs, removal of small dams has become increasing popular. Although the benefits of removal seem to outweigh the drawbacks, there is a relative paucity of studies documenting the extent and magnitude of biological and chemical changes associated with dam removal, especially those evaluating potential changes in contaminant inventories. In August and November of 2000, a run-of-the-river dam on Manatawny Creek (southeast Pennsylvania) was removed in a two-stage process.

Stable carbon isotope analysis of nucleic acids to trace sources of dissolved substrates used by estuarine bacteria.

The natural abundance of stable carbon isotopes measured in bacterial nucleic acids extracted from estuarine bacterial concentrates was used to trace sources of organic matter for bacteria in aquatic environments. The stable carbon isotope ratios of Pseudomonas aeruginosa and nucleic acids extracted from cultures resembled those of the carbon source on which bacteria were grown. The carbon isotope discrimination between the substrate and total cell carbon from bacterial cultures averaged 2.