The effect of nitrogen and phosphorus supply ratios and dilution rate on phosphorus uptake and mineralization in continuous flow microcosms

Continuous flow microcosms (50L volume, salinity 18-24 ppt) were used to examine the roles of heterotrophic protozoa and bacteria as phosphorus mineralizers. Nitrogen limitation was regulated by N:P supply ratios (5:1, 16:1) and growth rate was regulated by dilution rate (0.5, 0.25 volumes day&\sp{lcub}-1{rcub}&). Rates of carbon and phosphorus uptake from dissolved inorganic pools were determined using &\sp{14}&C and &\sp{lcub}32{rcub}&P tracer experiments and pre- and post-fractionation incubations. Based on uptake rates and on POP and POC values of the bacteria in the &\u3c&1.0 &\mu&m fraction, mass balance estimates of bacterial mineralization were determined. An isotope dilution method was used to determine phosphorus mineralization in the unfractionated sample. Heterotrophic protozoan mineralization was calculated as the difference. Results showed that bacteria had a minor role as remineralizers of phosphorus, more often taking-up inorganic phosphorus than remineralizing it. Heterotrophic protozoa were the major remineralizers of phosphorus. Microcosm treatments with a greater supply of inorganic phosphorus over nitrogen had increased POP concentrations and increased phosphorus remineralization. The effect of dilution on phosphorus remineralization was temperature dependent. Greater remineralization occurred in the high dilution rate in the July through October experiments and less remineralization occurred in the high dilution rate treatments in the December and January experiments

Two Paradoxes of Satisfaction

There are two paradoxes of satisfaction, and they are of different kinds. The classic satisfaction paradox is a version of Grelling's: does 'does not satisfy itself ' satisfy itself ? The Unsatisfied paradox finds a predicate, P, such that Px if and onl

Paradoxes and Hypodoxes of Time Travel

I distinguish paradoxes and hypodoxes among the conundrums of time travel. I introduce ‘hypodoxes’ as a term for seemingly consistent conundrums that seem to be related to various paradoxes, as the Truth-teller is related to the Liar. In this article, I briefly compare paradoxes and hypodoxes of time travel with Liar paradoxes and Truth-teller hypodoxes. I also discuss Lewis’ treatment of time travel paradoxes, which I characterise as a Laissez Faire theory of time travel. Time travel paradoxes are impossible according to Laissez Faire theories, while it seems hypodoxes are possible

Potential Impact of PCB's on Bluefish, Pomatomus saltatrix, Management

Since 1979, anglers along the U.S. Atlantic coast have landed by weight more bluefish, Pomatomus saltatrix, than any other marine species. A fishery management plan has been developed jointly by three fishery management councils and the Atlantic States Marine Fisheries Commission to preserve the bluefish resource. Major objectives of the plan include prevention of recruitment overfishing and reduction in waste of bluefish. In 1985, a Federal survey found PCB concentrations in larger bluefish (over 500 mm fork length) that exceeded the U.S. Food and Drug Administration tolerance level of 2 parts per million. Harvest strategies are presented in this article to protect the reproductive capability of bluefish while minimizing human health risks associated with dietary intake of PCB's

(E,E)-1-Methyl-2,6-distyrylpyridinium iodide

In the title compound, C22H20N+·I−, the dihedral angles between the central pyridine ring and two outer benzene rings are 15.30 (10) and 11.82 (11)°. There are inter­molecular π–π stacking inter­actions between the nearest phenyl ring over an inversion-related pyridyl ring, the shortest centroid–centroid distance being 3.672 (3) Å. The crystal structure of the compound indicates the 2,6-distyryl substituents have an E configuration

Effects of dredge deposits on seagrasses : an integrative model for Laguna Madre : concluding report. Volume I, Executive Summary.

Interagency Coordination Team, U.S. Army Corps of Engineers, Galveston District, The University of Texas Marine Science Institute, Texas A&M University Department of Oceanography, Texas Parks and Wildlife DepartmentThis report presents the results of an interdisciplinary collaborative effort to develop an integrative model for seagrass productivity in Laguna Madre. One of the major components of this integrative model is the Laguna Madre Seagrass Model (LMSM) which was designed to interface with other component models described in this report, including carbon and nitrogen allocation, sediment diagenesis, and spectral irradiance and radiative transfer. Linkage with hydrodynamic and sediment transport models provided a potentially valuable management tool to assess the effects of maintenance dredging and resuspension of dredged material deposits on seagrasses of Laguna Madre.Texas A&M University and the U.S. Army Corps of Engineers (Galveston District) 96-PL-03Marine Scienc