Biogeochemistry Commons^™

The Distribution And Comparative Biogeochemistry Of Silver With Other Selected Trace Metals In Coastal Waters Near Massachusetts, Usa, Christian F. Krahforst

Graduate Doctoral Dissertations

Water samples and hydrologic data were collected during 1994-1996 in New England coastal waters near Massachusetts, USA to examine the distribution of silver and other trace metals (Cu, Pb, Cd, Zn, and Fe) in the coastal systems of Massachusetts and Cape Cod Bays. These investigations were designed to test the hypothesis that silver could serve as a tracer of dispersion of municipal wastewater in Boston Harbor into Massachusetts and Cape Cod Bays and estimate the relative contribution of wastewater discharge to the overall silver budget of the Massachusetts Bays system. Silver concentrations in both particulate and filtered (<0.4 µm) fractions averaged 103 and 117 pmol kg-1 for Boston Harbor, 34 and 10 pmol kg-1 in western Massachusetts Bay, and 11 and 7 pmol kg-1 in the central portion of Massachusetts Bay, respectively. Average Ag concentrations in southern Gulf of Maine coastal waters were 10 and 2 pmol kg-1 for filtered and particulate fractions, respectively. While nearly half of the silver existed in particulate form in Boston Harbor, nearly 80% of the silver in Massachusetts and Cape Cod Bays occurred in the filterable fraction. Coastal water surveys revealed non-conservative Ag behavior and probably the result of incomplete mixing of three or more water masses with unique Ag signatures (e.g., Merrimack River, Boston Harbor, surface and intermediate Gulf of Maine waters). Quasi-steady state mass balance approaches estimate most of the silver entering into the Massachusetts Bays system during the study period was the result of municipal wastewater discharge to Boston Harbor (84-93%).

Multivariate analyses …

Fish Distributions And Nutrient Cycling In Streams: Can Fish Create Biogeochemical Hotspots, Peter B. Mcintyre, Alexander S. Flecker, Michael J. Vanni, James M. Hood, Brad W. Taylor, Steven A. Thomas

Dartmouth Scholarship

Rates of biogeochemical processes often vary widely in space and time, and characterizing this variation is critical for understanding ecosystem functioning. In streams, spatial hotspots of nutrient transformations are generally attributed to physical and microbial processes. Here we examine the potential for heterogeneous distributions of fish to generate hotspots of nutrient recycling. We measured nitrogen (N) and phosphorus (P) excretion rates of 47 species of fish in an N-limited Neotropical stream, and we combined these data with population densities in each of 49 stream channel units to estimate unit- and reach-scale nutrient recycling. Species varied widely in rates of N …

Environmental Controls On The Landscape-Scale Biogeography Of Stream Bacterial Communities, Noah Fierer, Jennifer L. Morse, Sean T. Berthrong, Emily S. Bernhardt, Robert B. Jackson

Environmental Science and Management Faculty Publications and Presentations

We determined the biogeographical distributions of stream bacteria and the biogeochemical factors that best explained heterogeneity for 23 locations within the Hubbard Brook watershed, a 3000-ha forested watershed in New Hampshire, USA. Our goal was to assess the factor, or set of factors, responsible for generating the biogeographical patterns exhibited by microorganisms at the landscape scale. We used DNA fingerprinting to characterize bacteria inhabiting fine benthic organic matter (FBOM) because of their important influence on stream nutrient dynamics. Across the watershed, streams of similar pH had similar FBOM bacterial communities. Streamwater pH was the single variable most strongly correlated with …

Biogeochemistry Of Arsenic And Antimony In The North Pacific Ocean, Gregory A. Cutter, Lynda S. Cutter

OES Faculty Publications

The biogeochemical cycles of the metalloid elements arsenic and antimony were examined along a 15,000 km surface water transect and at 9 vertical profile stations in the western North Pacific Ocean as part of the 2002 IOC Contaminant Baseline Survey. Results show that the speciation of dissolved arsenic (As III, As V, and methylated As) was subtly controlled by the arsenate (AsV)/phosphate ratio. An additional fraction of presumed organic arsenic previously reported in coastal waters was also present (~15% of the total As) in oceanic surface waters. Dissolved inorganic antimony displayed mildly scavenged behavior that was confirmed by correlations with …

Hydrographic Observations During The 2002 Ioc Contaminant Baseline Survey In The Western Pacific Ocean, C. I. Measures, Greg A. Cutter, W. M. Landing, R. T. Powell

OES Faculty Publications

The 2002 IOC Contaminant Baseline Survey in the western Pacific Ocean was the fourth in a series of cruises intended to establish the contemporary concentrations of trace elements and other materials in the major water masses of the ocean and to illuminate the pathways by which materials delivered to the surface ocean are incorporated in the subsurface waters. The expedition occupied 9 vertical profile stations encompassing the subtropical and subarctic gyre of the western North Pacific. In addition, underway surface water samples were collected during transits between the stations. This paper uses the temperature, salinity, nutrient, oxygen, and chlorophyll data …

Introduction To Special Section: Saz Project, T. W. Trull, Peter N. Sedwick, F. B. Griffiths, S. R. Rintoul

OES Faculty Publications

Oceanographic processes in the subantarctic region contribute crucially to the phys. and biogeochemical aspects of the global climate system. To explore and quantify these contributions, the Antarctic Cooperative Research Center organized the SAZ Project, a multidisciplinary, multiship study carried out south of Australia in the austral summer of 1997-1998. We present an overview of the SAZ Project and some of its major results.

Biogeochemical Control Of Phosphorus Cycling And Primary Production In Lake Michigan, R. S. Walsh, Gregory A. Cutter, W. M. Dunstan, J. Radford-Knoery, J. T. Elder

OES Faculty Publications

A 3-yr study in Lake Michigan has shown a 27 mmol P m^-2 increase in the mass of total P (TP) in the water during spring when the lake is mixed from surface to sediment. This value is an order of magnitude greater than the annual P input from external sources. TP changed in concert with increases in chlorophyll a and organic N and decreases in nitrate and soluble Si. The concentration of soluble reactive PO_4^-3 (SRP) remained relatively constant throughout the study. We hypothesize that the SRP concentration is maintained by a chemical equilibrium with calcium-phosphate …