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Chesapeake Bay Region (chesapeake + bay_region)
Selected AbstractsPolybrominated diphenyl ether flame retardants in Chesapeake Bay region, USA, peregrine falcon (Falco peregrinus) eggs: Urban/rural trends,,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2009Katherine E. Potter Abstract A total of 23 peregrine falcon (Falco peregrinus) eggs were obtained between 1993 and 2002 from 13 nests, encompassing 11 locations in the Chesapeake Bay region, USA. When multiple eggs were available from the same clutch, average clutch contaminant concentrations were calculated. An overall median total polybrominated diphenyl ether (PBDE) level of 201 ng/g wet weight was determined for the eggs/clutches examined. The maximum in an individual egg, from an urban highway bridge site, was 354 ng/g. This egg also exhibited the highest BDE 209 burden (48.2 ng/g). Compared to distributions reported in fish and piscivorous birds, falcon eggs were enriched in the more brominated congeners. The BDE congeners 153, 99, and 100 constituted 26.0, 24.8, and 13.1%, respectively, of total PBDEs. In most aquatic species, BDE 47 is the most abundant congener reported; however, it constituted only 4.4% of total PBDEs in the eggs of the present study. The median BDE 209 concentration was 6.3 ng/g. The sum of the octa- to nonabrominated congeners (BDEs 196, 197, 206, 207, and 208) contributed, on average, 14.0% of total PBDEs, exceeding the contribution of BDE 209 (5.9%). Concentrations of polychlorinated biphenyls (PCBs) and 1,1-dichloro-2,2-bis(p -chlorophenyl)ethylene (4,4,-DDE) also were determined in a subset of 16 eggs (collected in 2001,2002 from six nests) and were an order of magnitude greater than the corresponding PBDEs. Median BDE 209 concentrations were significantly correlated (p < 0.01, Spearman R = 0.690) with the human population density of the area surrounding the nest. Total PBDEs, total PCBs, and 4,4,-DDE levels were not correlated to human population density. [source] Tumor prevalence and biomarkers of exposure and response in brown bullhead (Ameiurus nebulosus) from the Anacostia River, Washington, DC and Tuckahoe River, Maryland, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2004Alfred E. Pinkney Abstract We valuated liver and skin tumor prevalence and biomarkers of exposure and response in brown bullhead (Ameiurus nebulosus) from three locations in the Anacostia River (Washington, DC, USA), a Chesapeake Bay region of concern. The Tuckahoe River (Maryland, USA) served as a reference. Each river was sampled in fall 2000 and spring 2001. In the Anacostia, prevalence of liver tumors was 50 to 68%, and prevalence of skin tumors was 13 to 23% in large (,260 mm, age ,3 years) bullheads. Liver and skin tumor prevalence was 10 to 17% and 0%, respectively, in small (150,225 mm, age 1,2 years) bullheads. Tuckahoe bullhead liver tumor prevalence was 0 to 3% (large) and 0% (small); none had skin tumors. Biliary polynuclear aromatic hydrocarbon (PAH)-like fluorescent metabolites and liver DNA adduct concentrations were elevated in large and small Anacostia bullheads. Mean adduct concentrations were 16 to 28 times higher than those in Tuckahoe fish. Chromatograms revealed a diagonal radioactive zone, indicating polycyclic aromatic compound (PAC)-DNA adducts. The biomarker data and the 10 to 17% liver tumor prevalence at ages 1 to 2 suggest that these year classes are likely to have a high prevalence as they reach age 3 and older. This study provides the strongest evidence to date of the role of PAHs in tumor development in Anacostia bullheads. [source] Modeling and predicting complex space,time structures and patterns of coastal wind fieldsENVIRONMETRICS, Issue 5 2005Montserrat Fuentes Abstract A statistical technique is developed for wind field mapping that can be used to improve either the assimilation of surface wind observations into a model initial field or the accuracy of post-processing algorithms run on meteorological model output. The observed wind field at any particular location is treated as a function of the true (but unknown) wind and measurement error. The wind field from numerical weather prediction models is treated as a function of a linear and multiplicative bias and a term which represents random deviations with respect to the true wind process. A Bayesian approach is taken to provide information about the true underlying wind field, which is modeled as a stochastic process with a non-stationary and non-separable covariance. The method is applied to forecast wind fields from a widely used mesoscale numerical weather prediction (NWP) model (MM5). The statistical model tests are carried out for the wind speed over the Chesapeake Bay and the surrounding region for 21 July 2002. Coastal wind observations that have not been used in the MM5 initial conditions or forecasts are used in conjunction with the MM5 forecast wind field (valid at the same time that the observations were available) in a post-processing technique that combined these two sources of information to predict the true wind field. Based on the mean square error, this procedure provides a substantial correction to the MM5 wind field forecast over the Chesapeake Bay region. Copyright © 2005 John Wiley & Sons, Ltd. [source] An Introduction to a Special Issue on Large-Scale Submerged Aquatic Vegetation Restoration Research in the Chesapeake Bay: 2003,2008RESTORATION ECOLOGY, Issue 4 2010Deborah Shafer The Chesapeake Bay is one of the world's largest estuaries. Dramatic declines in the abundance and distribution of submerged aquatic vegetation (SAV) in the Chesapeake Bay over the last few decades led to a series of management decisions aimed at protecting and restoring SAV populations throughout the bay. In 2003, the Chesapeake Bay Program established a goal of planting 405 ha of SAV by 2008. Realizing that such an ambitious goal would require the development of large-scale approaches to SAV restoration, a comprehensive research effort was organized, involving federal and state agencies, academia, and the private sector. This effort differs from most other SAV restoration programs due to a strong emphasis on the use of seeds rather than plants as planting stock, a decision based on the relatively low labor requirements of seeding. Much of the research has focused on the development of tools and techniques for using seeds in large-scale SAV restoration. Since this research initiative began, an average of 13.4 ha/year of SAV has been planted in the Chesapeake Bay, compared to an average rate of 3.6 ha/year during the previous 21 years (1983,2003). The costs of conducting these plantings are on a downward trend as the understanding of the limiting factors increases and as new advances are made in applied research and technology development. Although this effort was focused in the Chesapeake Bay region, the tools and techniques developed as part of this research should be widely applicable to SAV restoration efforts in other areas. [source] Microzooplankton grazing on harmful dinoflagellate blooms: Are ciliates or heterotrophic dinoflagellates important?THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005DIANE K. STOECKER Microzooplankton grazing can be important in regulating growth of dinoflagellate populations, including species responsible for harmful algal blooms. In the Chesapeake Bay region, microzooplankton community grazing coefficients on small cell-size dinoflagellates are often greater than potential gross growth coefficients of dinoflagellates, and thus grazing may prevent bloom formation. Who are the major microzooplankton grazers on small dinoflagellates? Ciliates or other dinoflagellates? Data from Chesapeake Bay and its tributaries indicate both; sometimes ciliates and sometimes dinoflagellates are the major grazers. The importance of ciliates and heterotrophic dinoflagellates varies with season and location, but often one group dominates the microzooplankton assemblage. Specific clearance and division rates of ciliates are higher than that of heterotrophic dinoflagellates, thus it could be expected that ciliates would be the dominant microzooplankton grazers. However, during summer, small heterotrophic dinoflagellates are often the dominant grazers on small dinoflagelllates in the mesohaline Bay. Differential predation by copepods on ciliates may be responsible for this pattern. When microzooplankton community grazing is less than dinoflagellate cell division, red tides may result. Thus, it is important to understand the factors controlling both ciliate and heterotrophic dinoflagellate populations and their grazing impacts. [source] | ||||||||||