Physical Sciences and Mathematics Commons^™

Tracking The Fate Of A High Concentration Groundwater Nitrate Plume Through A Fringing Marsh: A Combined Groundwater Tracer And In Situ Isotope Enrichment Study, Cr Tobias, Sa Macko, Iris C. Anderson, Elizabeth A. Canuel, Jw Harvey

VIMS Articles

A groundwater plume enriched in (15)NO(3)(-) was created upgradient of a mesohaline salt marsh. By measuring the changes in concentration and isotopic enrichment of NO(3)(-), N(2)O, N(2), NH(4)(+), and particulate organic nitrogen (PON) during plume transport through the marsh, in situ rates of dissimilatory nitrate reduction to ammonium (DNRA) and denitrification (DNF) were estimated, as well as N storage in the reduced N pools. For groundwater discharge within the top 10 cm of marsh, NO(3)(-) removal was 90% complete within the 50 cm of marsh nearest the upland border. The peak NO(3)(-) loss rate from the plume ranged from 208 …

Sources And Cycling Of Dissolved And Particulate Organic Radiocarbon In The Northwest Atlantic Continental Margin, Je Bauer, Erm Druffel, Dm Wolgast, S Griffin

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Continental shelves and slopes are productive and dynamic ocean margin systems that also regulate the fluxes of terrestrial, riverine, and estuarine materials between the continents and oceans. In order to evaluate the ages, potential sources, and transformations of organic matter in an ocean margin system, we measured the radiocarbon (Delta (14)C and delta (13)C distributions of total dissolved organic carbon (DOC), suspended particulate organic carbon (POC), and dissolved inorganic carbon (DIC) in waters of the Middle Atlantic Bight (MAB) continental shelf and slope in April-May 1994. The Delta (14)C of DOC was greatest (as high as -39 parts per thousand) …

Mitochondrial Gene Rearrangements Confirm The Parallel Evolution Of The Crab-Like Form, C. L. Morrison, A. W. Harvey, S. Lavery, K. Tieu, Y. Huang, C. W. Cunningham

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The repeated appearance of strikingly similar crab-like forms in independent decapod crustacean lineages represents a remarkable case of parallel evolution. Uncertainty surrounding the phylogenetic relationships among crab-like lineages has hampered evolutionary studies. As is often the case, aligned DNA sequences by themselves were unable to fully resolve these relationships. Four nested mitochondrial gene rearrangements—including one of the few reported movements of an arthropod protein-coding gene—are congruent with the DNA phylogeny and help to resolve a crucial node. A phylogenetic analysis of DNA sequences, and gene rearrangements, supported five independent origins of the crab-like form, and suggests that the evolution of …

Dynamic Bacterial And Viral Response To An Algal Bloom At Subzero Temperatures, Patricia L. Yager, Tara L. Connelly, Behzad Mortazavi, K. Eric Wommack, Nasreen Bano, James E. Bauer, Stephen Opsahl, James T. Hollibaugh

VIMS Articles

New evidence suggests that cold‐loving (psychrophilic) bacteria may be a dynamic component of the episodic bloom events of high‐latitude ecosystems. Here we report the results of an unusually early springtime study of pelagic microbial activity in the coastal Alaskan Arctic. Heterotrophic bacterioplankton clearly responded to an algal bloom by doubling cell size, increasing the fraction of actively respiring cells (up to an unprecedented 84% metabolically active using redox dye CTC), shifting substrate‐uptake capabilities from kinetic parameters better adapted to lower substrate concentrations to those more suited for higher concentrations, and more than doubling cell abundance. Community composition (determined by polymerase …

Quantifying Groundwater Discharge Through Fringing Wetlands To Estuaries: Seasonal Variability, Methods Comparison, And Implications For Wetland-Estuary Exchange, Cr Tobias, Jw Harvey, Iris C. Anderson

VIMS Articles

Because groundwater discharge along coastal shorelines is often concentrated in zones inhabited by fringing wetlands, accurately estimating discharge is essential for understanding its effect on the function and maintenance of these ecosystems. Most previous estimates of groundwater discharge to coastal wetlands have been temporally limited and have used only a single approach to estimate discharge. Furthermore, groundwater input has not been considered as a major mechanism controlling pore-water flushing. We estimated seasonally varying groundwater discharge into a fringing estuarine wetland using three independent methods (Darcy's Law, salt balance, and Br- tracer). Seasonal patterns of discharge predicted by both Darcy's Law …

Hydrography, Nutrients, And Carbon Pools In The Pacific Sector Of The Southern Ocean: Implications For Carbon Flux, Kendra L. Daly, Walker O. Smith Jr., Gregory C. Johnson, Et Al

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Abstract

We investigated the hydrography, nutrients, and dissolved and particulate carbon pools in the western Pacific sector of the Antarctic Circumpolar Current (ACC) during austral summer 1996 to assess the region's role in the carbon cycle. Low f CO₂ values along two transects indicated that much of the study area was a sink for atmospheric CO₂. The f CO₂ values were lowest near the Polar Front (PF) and the Subtropical Front (STF), concomitant with maxima of chlorophyll a and particulate and dissolved organic carbon. The largest biomass accumulations did not occur at fronts, …

The Paraguay-Paraná Hidrovía: Protecting The Pantanal With Lessons From The Past: Large-Scale Channelization Of The Northern Paraguay-Paraná Seems To Be On Hold, But An Ongoing Multitude Of Smaller-Scale Activities May Turn The Pantanal Into The Next Example Of The “Tyranny Of Small Decisions”, Johan F. Gottgens, James E. Perry, Et Al

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Because it is one of the most inaccessible places on earth, this large, rich ecosystem has remained relatively untouched. There is, however, increasing evidence that this area is threatened by a number of activities, including mining, illegal hunting and fishing, indiscriminate use of fire, agricultural development, and deforestation. Careless use of mercury in gold mining, particularly in the northern Pantanal, may have resulted in acute and chronic ecosystem disruption (Hylander et al. 1994, Nogueira et al. 1997, Leady and Gottgens 2001). Wildlife poaching and live animal trade are widespread although hard to quantify. During six months in 1985, the skins …

Doc Cycling In A Temperate Estuary: A Mass Balance Approach Using Natural 14c And 13c Isotopes, Peter Raymond, James E. Bauer

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We measured dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and their corresponding D14C and d13C values in order to study the sources and fates of DOC in the York River Estuary (Virginia, U.S.A.). The D14C and d13C values of DOC and DIC at the freshwater end-member indicate that during periods of moderate to high flow, riverine DOC entering the York was composed of decadal-aged terrestrially organic matter. In nearly all cases, DOC concentrations exceeded conservative mixing lines and were therefore indicative of a net DOC input flux from within the estuary that averaged 1.2 mM L21 d21 . The …