The First Data Release of the Sloan Digital Sky Survey

The Sloan Digital Sky Survey has validated and made publicly available its First Data Release. This consists of 2099 square degrees of five-band (u, g, r, i, z) imaging data, 186,240 spectra of galaxies, quasars, stars and calibrating blank sky patches selected over 1360 square degrees of this area, and tables of measured parameters from these data. The imaging data go to a depth of r ~ 22.6 and are photometrically and astrometrically calibrated to 2% rms and 100 milli-arcsec rms per coordinate, respectively. The spectra cover the range 3800--9200 A, with a resolution of 1800--2100. Further characteristics of the data are described, as are the data products themselves.Comment: Submitted to The Astronomical Journal. 16 pages. For associated documentation, see http://www.sdss.org/dr

Urbanization alters coastal plain stream carbon export and dissolved oxygen dynamics

Coastal plain streams in the southeastern United States supply carbon that supports important coastal ecosystems, but the effects of urbanization on carbon export from these streams have not been extensively studied. This study aimed to determine how urbanization changes coastal plain stream organic matter quality, rates of carbon export, and dissolved oxygen dynamics that have implications for stream ecosystem function. Organic matter quality, organic carbon export, and dissolved oxygen concentrations were measured for multiple years (2009 & 2013–2015) in North Carolina coastal plain streams that spanned a gradient of urbanization. Based on spectral characteristics, dissolved organic matter (DOM) quality appeared to shift from characteristic blackwater in minimally impacted streams to clear streamwater in urban streams due to large reductions in chromophoric DOM concentrations, aromaticity, and molecular weight. Differences in spectral indices and characteristics of dissolved organic carbon export suggest that urbanization reduced natural sources of DOM and provided various urban sources of DOM that were likely more bioavailable. Particulate organic matter in the urban streams was indicative of more labile autochthonous sources than that of the less impacted streams, and rates of particulate carbon export increased and shifted to higher flows with watershed impervious surface cover. Diel variation of dissolved oxygen increased with watershed impervious surface cover, indicating that urbanization and associated changes in carbon and nutrient cycling altered stream function. While the effects of urbanization on carbon export were similar to previous studies in other regions, the unique blackwater state of natural streams and receiving waters in the study area make them especially susceptible to negative ecological impacts from altered carbon and nutrient export. Management actions that conserve or restore natural carbon sources to the stream may help mitigate multiple negative effects of urbanization in southeastern US coastal plain streams