David J. Velinsky

Dam Removal: Challenges and Opportunities for Ecological Research and River Restoration

W flow is a “master variable” (sensu Power et al. 1995) that governs the fundamental nature of streams and rivers (Poff et al. 1997, Hart and Finelli 1999), so it should come as no surprise that the modification of flow caused by dams alters the structure and function of river ecosystems. Much has been learned during the last several decades about the adverse effects of dams on the physical, chemical, and biological characteristics of rivers (Ward and Stanford 1979, Petts 1984, Poff et al. 1997, Poff and Hart 2002). Increasing concerns about these impacts, together with related social and economic forces, have led to a growing call for the restoration of rivers by removing dams (AR/FE/TU 1999, Pejchar and Warner 2001). For the purposes of this paper, we define restoration broadly as an effort to compensate for the negative effects of human activities on ecological systems by facilitating the establishment of natural components and regenerative processes, although we acknowledge that these efforts rarely eliminate all human impacts (see Williams et al. 1997 for alternative definitions). Interest in dam removal as a means of river restoration has focused attention on important new challenges for watershed management and simultaneously created opportunities for advancing the science of ecology. One challenge lies in determining the magnitude, timing, and range of physical, chemical, and biological responses that can be expected following dam removal. This information is needed to decide whether and how dam removals should be performed to achieve specific restoration objectives (Babbitt 2002). Opportunities for advancing ecological research also exist because dam removal represents a major, but partially controllable, perturbation that can help scientists test and refine models of complex ecosystems. In contrast to the small-scale experiments that traditionally have been employed in stream and river ecology, the unusually large magnitude and spatial extent of dam removal WE DEVELOP A RISK ASSESSMENT FRAME-

Ecological Benefits of Riparian Reforestation in Urban Watersheds: Study Design and Preliminary Results

Riparian forest restoration has become a major focus of watershed initiatives to improve degraded stream ecosystems. In urban watersheds, however, the ability of riparian forests to improve stream ecosystems may be diminished due to widespread, upland disturbance. This paper presents the methodology and some preliminary results from the first year of fieldwork on a 3-year project designed to assess the ecological benefits of riparian reforestation in urban watersheds. The study is based on an integrated, multidisciplinary sampling of physical, chemical, and biological attributes at forested and non-forested sections of 12 streams with different amounts of urban developement within their watersheds. Restored sections of three streams are also being monitored over the 3-year duration of the project. Sampling and analysis will continue through December 2000.

Effects of Small Ponds on Stream Water Chemistry

Abstract In many regions, small constructed ponds greatly exceed natural lakes in number and aggregate area. Many of these ponds are impoundments of small streams. Their effect in modifying stream water chemistry, however, remains poorly understood. Here we compare 19 physicochemical variables upstream vs. downstream of 11 ponds, sampled in March, May and July. The ponds greatly reduced inflow concentrations of SiO2 (by 71%), NO3 − (by 82%) and PO4 3− (by 46%), while exporting water of higher pH, alkalinity and dissolved oxygen content, and much higher quantities of particulate and dissolved organic C, N and P than were present upstream. Higher % removals of NO3 − and SiO2 were observed in ponds with longer hydraulic residence times. Based on ambient N:P ratios, algal periphyton below the ponds were likely P limited, but differential transformations of the components of total N vs. total P within the ponds greatly reduced N:P ratios downstream.

Effects of small dam removal on stream chemistry in southeastern Pennsylvania

Abstract We examined changes in stream chemistry following the removal of a 2-m-high dam on Manatawny Creek in southeastern Pennsylvania. Our primary objective was to determine the effect of small dam removal on the concentrations and forms of C, N, and P. Dissolved and particulate constituent concentrations were monitored at sites upstream and downstream of the dam and impoundment. Seasonal changes in alkalinity and N and P concentrations were observed before and after dam removal. However, the proportions of NO3− + NO2−, NH4+, and dissolved organic N (DON), and soluble reactive P (SRP) and dissolved organic P (DOP) in the total dissolved pools of N and P did not change seasonally. The dam and dam removal did not influence C, N, or P concentrations and forms (except for NH4+) in this stream. The lack of significant changes probably was a result of the short hydraulic residence time (<1.5 h at base flow), infrequent temperature stratification, and potential C limitation of bacterial activity in the small impoundment. Our results suggest that alterations in N and P concentrations and forms following dam removal may be site-specific. The characteristics of the dam, watershed, and impoundment (e.g., the amount of wetted streambed, hydraulic residence time, and organic enrichment of sediment and water) probably determine the influence of dam removal on stream water chemistry.

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 19.8 µg/g wet weight, approximately 60% of the experimentally determined lethal threshold. Concentrations of OC pesticides were generally similar to those in otters from areas of Oregon and Washington close to agricultural and industrial sources. The geometric mean total PCB concentration (540 ng/g wet wt) was similar to the concentration in otters from the heavily populated and industrialized lower Columbia River in Oregon and Washington. Seven liver samples that were among the highest in terms of total PCBs were analyzed for PCDDs and PCDFs. Polychlorinated dibenzo-p-dioxins were detected in six of the samples at total concentrations ranging from 172 to 2,783 pg/g wet weight. Polychlorinated dibenzofurans were detected in three of the samples at total concentrations ranging from 1.50 to 2,719 pg/g wet weight. The geometric mean PBDE concentration was 10.6 ng/g wet weight, with a range of 0.82 to 436 ng/g wet weight. No statistically significant relationship was observed between liver contaminant concentrations and land use within an 8-km radius of the trapping location. Overall, the data suggest that contaminant concentrations are not high enough to adversely affect the overall otter population in New Jersey. However, contaminant-related effects on the health or reproductive success of individual otters in some areas are possible.

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. Triplicate grabs were taken at each station for benthic community analysis and the Benthic Index of Biotic Integrity (B-IBI) was used to interpret the data. Only one station, #92, exhibited toxicity related to sediment contamination. Sediments from this station significantly inhibited growth of both test species, had the highest concentrations of contaminants, and had a degraded benthic community, indicated by a B-IBI of less than 3. Additional sediment from this station was tested and sediment toxicity identification evaluation (TIE) procedures tentatively characterized organic compounds as the cause of toxicity. Overall, forty percent of the stations were classified as degraded by the B-IBI. However, qualitative and quantitative comparisons with sediment quality benchmarks indicated no clear relationship between benthic community health and contaminant concentrations. This study provides a baseline for assessing the effectiveness of management actions in the Anacostia River.

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

Fish oil supplements have become a popular means of increasing ones 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. Based on manufacturers’ recommended dosages, daily intakes of PCBs and PBDEs ranged from 5 to 686 ng day−1 and from 1 to 13 ng day−1, respectively. Daily consumption of fish oil supplements expose consumers to PCBs and PBDEs. However, in comparison with fish ingestion, fish supplements may decrease daily PCB exposure and provide a safer pathway for individuals seeking to maintain daily recommended levels of polyunsaturated fatty acids.

Spatial variability of estuarine environmental drivers and response by phytoplankton: A multivariate modeling approach

Abstract Environmental variables such as river inflow, dissolved chemicals, temperature, total suspended solids, dissolved oxygen, and pH are the environmental drivers that maintain phytoplankton growth in estuaries. Spatial variability of environmental drivers in Barnegat Bay, New Jersey, and their roles in the distribution of phytoplankton were investigated in order to identify spatial variability in phytoplankton production in the bay. The water quality data collected and analyzed by New Jersey Department of Environmental Protection from 14 different stations in Barnegat Bay were divided into two different data sets, i.e. Northern Barnegat Bay (NB) and Southern Barnegat Bay (SB) data. Structural equation modeling, Bayesian linear regression, and kriging interpolation were used for the modeling study. The study identified higher dissolved N:P(88:1) in NB as compared to SB (19:1). The NB phytoplankton growth was maintained by the dissolved chemicals transported by inflow, whereas, the SB phytoplankton growth was maintained by sediment–water processes and regeneration. The lower ratio of regression coefficients of dissolved N to P throughout SB, as compared to that of NB, indicates low dissolved nitrogen concentrations in SB. In addition, higher inflow induced transport of dissolved nutrients and carbon may explain the significant north–south chlorophyll-α concentration gradient. The findings identified indirect effects of inflow and direct effects of nutrients on NB phytoplankton growth. Within SB, there were direct effects of nutrients, carbon dynamics, dissolved oxygen, pH, and turbidity on phytoplankton growth. Therefore, the results of this study are useful to state and federal water quality agencies in developing management strategies for northern and southern Barnegat Bay.

Polychlorinated Biphenyls in Sediment and Biota From the Delaware River Estuary

ABSTRACT. A spatially comprehensive evaluation of poly chlorinated biphenyl (PCB) inventories in white perch, channel catfish, small prey fish, amphipods and sediment within four zones of the Delaware River Estuary was completed during two seasons (fall 2001 and spring 2002). Highest sediment PCB concentrations occurred adjacent to urbanized and industrialized stretches of the estuary. Whole organism t-PCB body burdens (on a wet weight basis) reflected the spatial distributions in sediment PCB concentrations. However, there was considerable variation in PCB concentrations among individual catfish and perch fillets within zones that were not significantly reduced by lipid normalization. This variation suggests that within a zone many factors (e.g., dietary shifts, small-scale heterogeneity in sediment contamination, and non-equilibrium conditions in contaminant partitioning) drive PCB bioaccumulation. With increasing down-estuary distances, all biota except for perch had enhanced concentrations of more chlorinated congeners, especially nona- and deca-chlorinated biphenyls. Specific congeners such as PCB 206 and 209 may act as indicators of unique local sources of contamination within the lower portions of the Delaware River Estuary.

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. Nitrate was taken up by the marsh during all seasons. In the spring, the high rate of NH production from the sediment was correlated with NO uptake, suggesting dissimilatory reduction to NH as a potentially important process. Denitrification rates were greatest in July, averaging 5.5 ± 0.6 mg N m h. Adjusted for tidal inundation using a refined digital elevation model, denitrification averaged 0.08, 0.5, and 0.2 g N m mo for April, July, and October, respectively. Less than 10% of the modeled N load was estimated to have been removed in the months measured. A combination of high N load, limited marsh area that represented ∼1% of the watershed area, and conservative extrapolation of denitrification rates contributed to the low estimate of the N load attenuated.