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Don As A Source Of Bioavailable Nitrogen For Phytoplankton, D. A. Bronk, J. H. See, P. Bradley, L. Killberg
Don As A Source Of Bioavailable Nitrogen For Phytoplankton, D. A. Bronk, J. H. See, P. Bradley, L. Killberg
VIMS Articles
Relative to inorganic nitrogen, concentrations of dissolved organic nitrogen ( DON) are often high, even in regions believed to be nitrogen-limited. The persistence of these high concentrations led to the view that the DON pool was largely refractory and therefore unimportant to plankton nutrition. Any DON that was utilized was believed to fuel bacterial production. More recent work, however, indicates that fluxes into and out of the DON pool can be large, and that the constancy in concentration is a function of tightly coupled production and consumption processes. Evidence is also accumulating which indicates that phytoplankton, including a number of …
The Importance Of Tidal And Lateral Asymmetries In Stratification To Residual Circulation In Partially Mixed Estuaries, Me Scully, Carl T. Friedrichs
The Importance Of Tidal And Lateral Asymmetries In Stratification To Residual Circulation In Partially Mixed Estuaries, Me Scully, Carl T. Friedrichs
VIMS Articles
Measurements collected in the York River estuary, Virginia, demonstrate the important impact that tidal and lateral asymmetries in turbulent mixing have on the tidally averaged residual circulation. A reduction in turbulent mixing during the ebb phase of the tide caused by tidal straining of the axial density gradient results in increased vertical velocity shear throughout the water column during the ebb tide. In the absence of significant lateral differences in turbulent mixing, the enhanced ebb-directed transport caused by tidal straining is balanced by a reduction in the net seaward-directed barotropic pressure gradient, resulting in laterally uniform two-layer residual flow. However, …
Sediment Pumping By Tidal Asymmetry In A Partially Mixed Estuary, Malcolm Scully, Carl T. Friedrichs
Sediment Pumping By Tidal Asymmetry In A Partially Mixed Estuary, Malcolm Scully, Carl T. Friedrichs
VIMS Articles
[1] Observations collected at two laterally adjacent locations are used to examine the processes driving sediment transport in the partially mixed York River Estuary. Estimates of sediment flux are decomposed into advective and pumping components, to evaluate the importance of tidal asymmetries in turbulent mixing. At the instrumented location in the estuarine channel, a strong asymmetry in internal mixing due to tidal straining is documented, with higher values of eddy viscosity occurring during the less-stratified flood tide. As a result of this asymmetry, more sediment is resuspended during the flood phase of the tide resulting in up-estuary pumping of sediment …
Geology, Geography, And Humans Battle For Dominance Over The Delivery Of Fluvial Sediment To The Coastal Ocean, James P.M. Syvitski, John D. Milliman
Geology, Geography, And Humans Battle For Dominance Over The Delivery Of Fluvial Sediment To The Coastal Ocean, James P.M. Syvitski, John D. Milliman
VIMS Articles
Sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences (basin area and relief), geography (temperature, runoff), geology (lithology, ice cover), and human activities (reservoir trapping, soil erosion). A new model, termed “BQART” in recognition of those factors, accounts for these varied influences. When applied to a database of 488 rivers, the BQART model showed no ensemble over‐ or underprediction, had a bias of just 3% across six orders of magnitude in observational values, and accounted for 96% of the between‐river variation in the long‐term (±30 years) sediment load or yield of these rivers. The geographical range …
Eutrophication-Induced Phosphorus Limitation In The Mississippi River Plume: Evidence From Fast Repetition Rate Fluorometry, Jb Sylvan, A Quigg, S Tozzi, Jw Ammerman
Eutrophication-Induced Phosphorus Limitation In The Mississippi River Plume: Evidence From Fast Repetition Rate Fluorometry, Jb Sylvan, A Quigg, S Tozzi, Jw Ammerman
VIMS Articles
We assessed nutrient limitation in the Mississippi River plurne and Louisiana continental shelf during the summer of 2002 (04-08 July). We measured nutrient concentrations, alkaline phosphatase (AP) activities, chlorophyll a (Chl a) concentrations, and four fast repetition rate fluorescence (FRRF) parameters: the maximum quantum yield of photochemistry in photosystem II (PSII), F-v:F-m; the functional absorption cross section for PSII, sigma(psII); the time for photosynthetic electron transport on the acceptor side of PSII, tau(Qa); and the connectivity factor, p, in 24-h-long nutrient addition bioassays near the Mississippi River delta. Low phosphorus (P) concentrations, elevated inorganic nitrogen-to-phosphorus ratios, high AP activities, and …
Phytoplankton Carbon Fixation Gene (Rubisco) Transcripts And Air-Sea Co2 Flux In The Mississippi River Plume, De John, Zha Wang, Xw Liu, Rh Byrne, Je Corredor, Da Bronk, Et Al.
Phytoplankton Carbon Fixation Gene (Rubisco) Transcripts And Air-Sea Co2 Flux In The Mississippi River Plume, De John, Zha Wang, Xw Liu, Rh Byrne, Je Corredor, Da Bronk, Et Al.
VIMS Articles
River plumes deliver large quantities of nutrients to oligotrophic oceans, often resulting in significant CO2 drawdown. To determine the relationship between expression of the major gene in carbon fixation (large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBisCO) and CO2 dynamics, we evaluated rbcL mRNA abundance using novel quantitative PCR assays, phytoplankton cell analyses, photophysiological parameters, and pCO2 in and around the Mississippi River plume (MRP) in the Gulf of Mexico. Lower salinity (30-32) stations were dominated by rbcL mRNA concentrations from heterokonts, such as diatoms and pelagophytes, which were at least an order of magnitude greater than haptophytes, a-Synechococcus or high-light Prochlorococcus. …
Susceptibility Of Salt Marshes To Nutrient Enrichment And Predator Removal, La Deegan, Jl Bowen, D Drake, Jw Fleeger, Carl T. Friedrichs, Et Al.
Susceptibility Of Salt Marshes To Nutrient Enrichment And Predator Removal, La Deegan, Jl Bowen, D Drake, Jw Fleeger, Carl T. Friedrichs, Et Al.
VIMS Articles
Salt marsh ecosystems have been considered not susceptible to nitrogen overloading because early studies suggested that salt marshes adsorbed excess nutrients in plant growth. However, the possible effect of nutrient loading on species composition, and the combined effects of nutrients and altered species composition on structure and function, was largely ignored. Failure to understand interactions between nutrient loading and species composition may lead to severe underestimates of the impacts of stresses. We altered whole salt marsh ecosystems (similar to 60 000 m(2)/treatment) by addition of nutrients in flooding waters and by reduction of a key predatory fish, the mummichog. We …