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... BY Robert R. Christian and Cassondra R. Thomas Biology Department, East Carolina University, Greenville, NC, 27858 USA. ... 6 3. Fate of 1 atom of nitrogen as it leaves the Neuse River Estuary having entered as nitrate plus nitrite in... more
... BY Robert R. Christian and Cassondra R. Thomas Biology Department, East Carolina University, Greenville, NC, 27858 USA. ... 6 3. Fate of 1 atom of nitrogen as it leaves the Neuse River Estuary having entered as nitrate plus nitrite in spring ..... 14 ...
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The age and ability of salt marshes to accumulate and sequester carbon is often assessed using the carbon isotopic signatures (ΔC and δC) of sedimentary organic matter. However, transfers of allochthonous refractory carbon (C) from the... more
The age and ability of salt marshes to accumulate and sequester carbon is often assessed using the carbon isotopic signatures (ΔC and δC) of sedimentary organic matter. However, transfers of allochthonous refractory carbon (C) from the watershed to marshes would not represent new C sequestration. To better understand how refractory carbon (C) inputs affect assessments of marsh age and C sequestration, ΔC and δC of both total organic carbon (TOC), C, and non-C organic matter fractions were measured in salt marshes from four contrasting systems on the North Atlantic coast. To our knowledge, no salt marsh sediment study has considered refractory or allochthonous carbon in carbon budget calculations or the impact on chronologies. Stable and radiogenic isotope data suggest that while TOC was dominated by autochthonous plant inputs, C was dominated by locally recycled or allochthonous C, the delivery of which was controlled by the size and slope of each watershed. Steep-gradient rivers an...
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Research Interests: Earth Sciences, Ecology, Stratification, Biological Sciences, Environmental Sciences, and 14 moreWater Quality Management, Nutrient Management, Estuaries, North Carolina, Trophic Level, Primary Production, Storm surge, Dissolved Oxygen, Nutrient Loading, Chemical Properties, Organic Matter, Residence Time, Community Composition, and Vertical mixing
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Most headwater streams in coastal North Carolina have been altered by agricultural and silvicultural activities. This study was conducted to evaluate effects of these alterations so that methods could be developed to assess the condition... more
Most headwater streams in coastal North Carolina have been altered by agricultural and silvicultural activities. This study was conducted to evaluate effects of these alterations so that methods could be developed to assess the condition of headwater reaches from hydrologic, biogeochemical, and habitat perspectives. Findings of this research and relevant studies on riparian areas elsewhere provided the basis for developing reference-based assessment protocols for the North Carolina Ecosystem Enhancement Program. The nineteen sites used in the study represented a range of both natural variation and variation caused by human alteration. Sites were primarily first to second order reaches ranging from forested riparian zones with natural stream channels to severely altered riparian areas that had been channelized, had their buffers removed, and were subjected to drainage. Data from a subset of six reaches showed quantifiable differences in functioning among reaches spanning the gradient...
A reference framework was used to structure a rapid assessment method for estimating the ecological condition of riparian ecosystems in the inner coastal plain of North Carolina. Four versions with identical format were developed for low... more
A reference framework was used to structure a rapid assessment method for estimating the ecological condition of riparian ecosystems in the inner coastal plain of North Carolina. Four versions with identical format were developed for low order (first and second) and high order (third and fourth) rural landscapes, and for low and high order urban landscapes. Assessments were conducted in six watersheds: four in the Tar- Pamlico basin, one in the Neuse River basin, and one in the Lumber River basin. Sampling sites were selected randomly within each of the watersheds at a density of approximately one per kilometer of stream length. A sampling unit for assessment was 100 yards in length, usually requiring less than 0.5 h for a pair of experienced professionals to assess. Indicator scores were then assembled to combine those that were pertinent to the stream channel and to the riparian zone for the 277 assessed reaches. The condition of reaches varied widely along the scale of relatively...
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It has recently been proposed that the frequency of dividing bacterial cells (FDC) can be used to predict growth rates of natural aquatic bacterial assemblages. We have examined the relationship between FDC and growth rate in bacteria... more
It has recently been proposed that the frequency of dividing bacterial cells (FDC) can be used to predict growth rates of natural aquatic bacterial assemblages. We have examined the relationship between FDC and growth rate in bacteria from southern-temperate, coastal marine waters by using incubation under conditions of manipulated nutrient availability and exclusion of bacterivores. The regression of the natural logarithm of bacterial instantaneous growth rate (mu) on FDC resulted in a better fit than regression of untransformed mu on FDC. The regression equation was ln mu = 0.299FDC - 4.961. The coefficient of variation for predicted ln mu at mean FDC was 7%. The range of FDC-estimated bacterial instantaneous generation times for coastal Georgia waters was 12 to 68 h, and range of calculated bacterial production rates was 0.6 to 17.6 mg of C.m. h. Unresolved problems of and suggested improvements on the FDC method of predicting growth rate are discussed.