Richard J. Horwitz

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-

Influence of bank vegetation on channel morphology in rural and urban watersheds

Stream-bank vegetation significantly influences the morphology of streams in the Piedmont region of the United States. We surveyed the morphology of 26 paired stream reaches in southeastern Pennsylvania, northern Maryland, and Delaware. One member of each pair has a forested riparian zone, whereas the other has a riparian zone composed pri marily of grass. The paired reaches are nearly contiguous, so all significant channel-forming variables except riparian vegetation are held constant. The extent of urban development of the watersheds upstream of the paired reaches also varies considerably, allowing us to determine the combined influence of riparian vegetation and urbanization on channel morphology. Statistical analyses indicate that (1) channels with forested riparian zones are wider than channels with nonforested riparian zones, (2) channels in urbanized watersheds are wider than channels in nonurbanized watersheds, and (3) the effect of riparian vegetation is independent of the level of urbanization.

A comparison of congeneric PCB patterns in American eels and striped bass from the Hudson and Delaware River estuaries

The Hudson River estuary has enormous spatial variation in polychlorinated biphenyl (PCB) contamination due in large part to historical point source discharges above Troy Dam. The Delaware River estuary has accumulated significant levels of PCBs through decades of industrial, municipal, and non-point source inputs. The overall goal of this research was to use existing data sets to compare and contrast the patterns of accumulated PCB congeners in sub-populations of American eels and striped bass inhabiting these two estuaries and surrounding coastal waters. Using principal component analysis and analysis of covariance (ANCOVA), inter- and intra-estuarine differences in accumulated congeneric patterns were denoted for both species. Results from our study support the idea that migratory behaviors of striped bass hamper the use of accumulated congener-specific PCB patterns in providing information on localized contamination, although major regional differences were seen between upriver Hudson River fish, downriver Hudson River fish and fish from other areas within this study. This study provides additional evidence for the use of the American eel as a biomonitoring tool, since its limited home range provides finer resolution of regional contamination.

Effects of Bacillus thuringiensis israelensis on Black Flies and Nontarget Macroinvertebrates and Fish in a Large River

Abstract Six field experiments tested the effects of the microbial pesticide Bacillus thuringiensis israelensis (Bti) on pestiferous black flies (primarily the Simulium jenningsi group) as well as nontarget macroinvertebrates and fish in the Susquehanna River, Pennsylvania. The response of black fly drift after the Bti application was similar across all experiments. Black fly drift increased significantly within 0.5 h after application, peaked 2-3 h after application, and then remained high for several hours. Significant changes in drift were observed after Bti application for 31 of the 50 nontarget macroinvertebrate taxa examined, but none of these taxa exhibited an increase in drift density similar in magnitude and timing to that of black flies. Furthermore, none of the 31 taxa exhibited the same drift changes in all experiments, as was observed for black flies; most of the taxa exhibited a drift density change during only one posttreatment sample period within a single experiment. Most nontarget macroi...

Protozoan communities of the Flint River-Lake Blackshear ecosystem (Georgia, USA)

Freshwater protozoa are poorly characterized in river ecosystems. We report here the richness of the protozoan biotas in relation to environmental gradients from an ecosystematic survey of a large, coastal plain river. Communities were collected from natural and artificial substrates concurrent with water chemistry analysis at 11 sites along the Flint River and Lake Blackshear impoundment. Community similarity, the distribution of collected taxa in functional feeding groups, and the relation of communities to environmental gradients were evaluated. Two principal compenents determined from water chemistry data showed important downstream gradients of decreasing water hardness and increasing nutrient levels. Taxonomic richness was high; 200 to 450 taxa were collected depending on season and collecting technique. Artificial substrates provided the richest collections. Bactivorous species were the vast majority of all taxa collected. Community composition showed an orderly transition from upstream to downstream, and photosynthetic forms were enhanced at nutrient enriched sites. Communities were strongly influenced by increasing nutrient levels. Protozoan community analysis showed that microbial community composition reflects human influences on river ecosystems. Since microbial species exploit detrital resources and respond sensitively to human influences, they can provide important information regarding ecosystem conditions.

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.

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). The objectives of this study were to evaluate congener-specific PCB concentrations in 13 over-the-counter childrens dietary supplements containing fish oils/powders and assess potential PCB exposures through ingestion of these products on a daily basis. Every supplement analysed contained PCBs, with a mean concentration of 9 ± 8 ng PCBs/g supplement. When following serving size suggestions, mean daily exposure values ranged from 2.5 to 50.3 ng PCBs/day. Daily exposures for childrens supplements were significantly lower than those previously reported for adult supplements and may be explained, in part, by the variability in the amount of fish oil (and PUFA content) in a serving size. Based on this study, factors such as fish oil purification methods (e.g., molecular distillation) and the trophic level of the fish species used to make the fish oil cannot be used as indicators of PCB levels within childrens supplements. Fish supplements may decrease or increase daily PCB exposure compared with ingestion of fresh fish. However, eating fish high in omega-3 PUFAs and low in PCBs may reduce PCB exposure compared with daily supplementation with fish oils for some products studied.

Validation of a Macroinvertebrate-Based Index of Nutrient Status in Streams Using Macroinvertebrate, Water-Chemistry, and Diatom Data

Abstract Determination of the causes of water-impairment is a critical part of bioassessment, and it is useful to be able to infer causes from the same sampling data used to assess the impairment. Determination of excess nutrient inputs to a waterbody as a cause of impairment is especially important because of the severity and ubiquity of nutrient-related water-quality problems nationwide. To that end, we tested and validated in New Jersey waters a macroinvertebrate-based nutrient biotic index (NBI) for phosphorus and nitrogen developed by the New York State Department of Environmental Conservation (NYSDEC). We used macroinvertebrate, water-chemistry, and diatom data from New Jersey streams collected in the state biomonitoring program and a study of diatom—nutrient relationships. We calculated tolerance values for widespread taxa based on frequency of occurrence in samples from sites with a range of nutrient concentrations. The NBI of a sample was calculated as a sum of the tolerance values of taxa in a sample weighted by the relative abundances of taxa. We developed tolerance values from the New Jersey data because relatively few taxa present in the New Jersey samples were rated in the New York study. NBIs for the New Jersey data calculated using the New Jersey-based tolerance values were significantly related to nutrient concentrations with correlations similar to, or greater than, those observed in the New York study. For taxa in common, the New Jersey-based tolerance values were only weakly correlated with the analogous New York values. To validate the NBI approach, we calculated NBI scores via a “leave-one-out” procedure for a data set not used to estimate tolerance values. These comparisons yielded statistically significant but weak correlations between the NBIs and nutrient concentrations. Factors that weaken these relationships are related to: (1) the specific data used (e.g., the lack of tolerance values for many taxa in independent data sets and weak temporal matching of macroinvertebrate and nutrient samples), (2) estimation issues (e.g., variability in estimates of tolerance values and NBIs), and (3) problems inherent in the approach (e.g., the effects of other factors on macroinvertebrate relationships). However, for all data sets examined, nitrogen and phosphorus concentrations were positively correlated, as were nitrogen and phosphorus tolerance values for taxa, and nitrogen and phosphorus NBI scores for sites. These correlations need to be considered in the selection of sampling sites for the development of tolerance values, the weighting of taxa in calculation of NBIs, and the interpretation of NBI values for the 2 nutrients.

Trophic transfer of polybrominated diphenyl ethers and polychlorinated biphenyls in a tidal freshwater marsh

The John Heinz National Wildlife Refuge (NWR) at Tinicum Marsh contains one of the last remaining tidal freshwater marsh communities along the Pennsylvania side of the Delaware River Estuary. The marsh receives a significant load of nutrients and sediment-associated contaminants and is hypothesised to act as an effective trap for these chemicals. The goal of this study was to quantify the levels of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) at various trophic levels at two sites within Tinicum Marsh and assess the factors important in determining their bioaccumulation and trophic transfer. For both PCBs and PBDEs, lipid variation for all species was a large factor in determining contaminant body burden. Also, concentrations in biota increased with increasing trophic level as determined by nitrogen isotope analysis (δ15N values) at the downstream site within Tinicum Marsh. This trend was less apparent at the upstream site and may be due to differences in feeding behaviours among species between the two sites and/or differences in carbon and nitrogen sources and recycling. These data are valuable in assisting bioaccumulation/trophic transfer studies and serve as benchmarks to which future PCB and PBDE concentrations will be compared.

Routine monitoring of toxics in fish-year 4 - Atlantic Coastal Inland Region: Office of Science research project summary

The Routine Monitoring for Toxics in Fish Program is a 5-year, geographically based rotating program to generate data on chemical contaminants in fish for the issuance, update and revision of fish consumption advisories. The monitoring program design is built upon fish contaminant research conducted by NJDEP since the early 1980’s. In order to investigate regional patterns in fish contamination the program includes rotating sample collections among geographic regions within the state. In addition to analyze fish contaminant temporal trends and to identify unknown hotspots, re-sampling selected waterbodies and sampling “new” (not previously sampled) locations was part of the sampling regime. This Year 4 study provides the results for the Atlantic Coastal Inland Region. The study design incorporated a variety of considerations, including sampling species that are important to recreational fishing, targeting fish species of specific trophic position that are known to bioaccumulate mercury and/or organic chemical contaminants, consider the target species body lipid content (important in organic contaminants), as well as species longevity and/or lifestyle proximity to bottom sediments. The data generated through this study are useful in developing credible consumption risk assessments, since they include the size ranges and species that are generally targeted by recreational anglers and can be used in an evaluation of contaminant trends in this region and comparable throughout the state. The results show that mercury in fish concentrations varied among species, but typically increased with fish size and are usually higher in predatory fish, such as chain pickerel and largemouth bass. Mercury levels in chain pickerel were highest in waters with pH less than 7, and for largemouth bass in lakes with pH between 5 and 6. The highest mercury concentrations were observed at drainage sites within and marginal to the Pine Barrens. As observed in this and previous studies lower pH waterbodies typically reflect conditions promoting high mercury bioavailability through methylation, and sources of mercury in the environment are both natural and anthropogenic. PCB levels in the fish sampled, however, showed a different contamination pattern with only relatively low to moderate PCB concentrations identified from these same locations. In general, PCBs and OCPs were typically higher in samples of American eel than other fish species examined. DDXs showed high variability within all sites of the study area, with some of the lowest and highest average concentrations observed when compared to previously studied regions. The variations in these xenobiotics (PCBs, OCPs, DDX) may highlight the differing contaminant sources and geo-chemistry of these contaminants, and may also reflect legacy industrial practices of production, disposal and/or use. Although these xenobiotic concentrations were variable among sites, the highest average concentrations were seen in fish from Deal Lake (PCBs and chlordanes), North Branch Metedeconk River (DDXs and chlordanes), Maurice River (PCBs), and several other smaller lakes (DDXs). Although there are large differences in contaminant concentrations in samples within regions, a comparison of fish tissue chemical data among sites from the previous studies on the Passaic and Raritan Regions, and this study show some regional contaminant differences. In general concentrations of mercury were higher in the Atlantic Coastal Region while PCBs were higher in the Raritan Region. Where comparisons between 1992 and 2007datasets for this study were possible, there was no clear trend in contaminant concentrations at previously sampled locations. When comparing these data to available health criteria, with the exception of mercury, few of the samples analyzed exceeded the USFDA action levels for advisories on commercial fish. However, the NJDEP/DHSS use USEPA supported risk-based health criteria, in establishing consumption advisories for recreationally caught fish. These criteria are typically lower than FDA thresholds for mercury, PCBs, dioxins, and OCPs. The majority of the fish samples tested in this study exceeded the various individual NJDEP/DHSS/USEPA contaminant risk-based thresholds and several samples examined exceeded thresholds for multiple contaminants. The data from this study were used by NJDEP/DHSS to develop the most recent fish consumption advisories for a variety of recreationally caught fish in New Jersey.