Use of phytoplankton species indicators to track the origin of phytoplankton blooms in Willapa Bay, Washington

We focus on the question of whether high phytoplankton production events observed in a United States Pacific Northwest estuary consist of estuarine species blooms fueled by oceanic nutrient input or reflect offshore oceanic blooms that have advected into the estuary. Our approach is to use certain phytoplankton species as indicators associated with water mass origin, either estuarine or oceanic, to help resolve this question in Willapa Bay, Washington. We used species analysis and primary production data from 10 selected dates in May–September of 1998 and 1999, representing periods of high through low productivity. Out of 108 phytoplankton species identified from Willapa Bay, nine were selected and tested as indicators of oceanic species, six as estuarine, and two as surf zone. Our test results demonstrated the oceanic and estuarine species to be satifactory indicators of source waters. The prevalence of these species indicators in our samples revealed that the highest primary production and the appearance ofPseudo-nitzschia spp. were associated with oceanic intrusions of phytoplankton biomass into Willapa Bay. While the largest blooms were oceanic in origin, numerous medium-sized production events were from either oceanic, surf zone, or estuarine sources, indicating a complex situation.     

H2O activity in concentrated NaCl solutions at high pressures and temperatures measured by the brucite-periclase equilibrium

 H₂O activities in concentrated NaCl solutions were measured in the ranges 600°–900° C and 2–15 kbar and at NaCl concentrations up to halite saturation by depression of the brucite (Mg(OH)₂) – periclase (MgO) dehydration equilibrium. Experiments were made in internally heated Ar pressure apparatus at 2 and 4.2 kbar and in 1.91-cm-diameter piston-cylinder apparatus with NaCl pressure medium at 4.2, 7, 10 and 15 kbar. Fluid compositions in equilibrium with brucite and periclase were reversed to closures of less than 2 mol% by measuring weight changes after drying of punctured Pt capsules. Brucite-periclase equilibrium in the binary system was redetermined using coarsely crystalline synthetic brucite and periclase to inhibit back-reaction in quenching. These data lead to a linear expression for the standard Gibbs free energy of the brucite dehydration reaction in the experimental temperature range: ΔG° (±120J)=73418–134.95T(K). Using this function as a baseline, the experimental dehydration points in the system MgO−H₂O−NaCl lead to a simple systematic relationship of high-temperature H₂O activity in NaCl solution. At low pressure and low fluid densities near 2 kbar the H₂O activity is closely approximated by its mole fraction. At pressures of 10 kbar and greater, with fluid densities approaching those of condensed H₂O, the H₂O activity becomes nearly equal to the square of its mole fraction. Isobaric halite saturation points terminating the univariant brucite-periclase curves were determined at each experimental pressure. The five temperature-composition points in the system NaCl−H₂O are in close agreement with the halite saturation curves (liquidus curves) given by existing data from differential thermal analysis to 6 kbar. Solubility of MgO in the vapor phase near halite saturation is much less than one mole percent and could not have influenced our determinations. Activity concentration relations in the experimental P-T range may be retrieved for the binary system H₂O-NaCl from our brucite-periclase data and from halite liquidus data with minor extrapolation. At two kbar, solutions closely approach an ideal gas mixture, whereas at 10 kbar and above the solutions closely approximate an ideal fused salt mixture, where the activities of H₂O and NaCl correspond to an ideal activity formulation. This profound pressure-induced change of state may be characterized by the activity (a) – concentration (X) expression: a _{H 2}O=X _{H 2}O/(1+αX _NaCl), and a _NaCl=(1+α)^(1+α)[X _NaCl/(1+αX _NaCl)]^(1+α). The parameter α is determined by regression of the brucite-periclase H₂O activity data: α=exp[A–B/ϱ_{H 2}O ]-CP/T, where A=4.226, B=2.9605, C=164.984, and P is in kbar, T is in Kelvins, and ϱ_{H 2}O is the density of H₂O at given P and T in g/cm³. These formulas reproduce both the H₂O activity data and the NaCl activity data with a standard deviation of ±0.010. The thermodynamic behavior of concentrated NaCl solutions at high temperature and pressure is thus much simpler than portrayed by extended Debye-Hückel theory. The low H₂O activity at high pressures in concentrated supercritical NaCl solutions (or hydrosaline melts) indicates that such solutions should be feasible as chemically active fluids capable of coexisting with solid rocks and silicate liquids (and a CO₂-rich vapor) in many processes of deep crustal and upper mantle metamorphism and metasomatism. Received: 1 September 1995 / Accepted: 24 March 1996     

H2O activity in concentrated KCl and KCl-NaCl solutions at high temperatures and pressures measured by the brucite-periclase equilibrium

H₂O activities in supercritical fluids in the system KCl-H₂O-(MgO) were measured at pressures of 1, 2, 4, 7, 10 and 15  kbar by numerous reversals of vapor compositions in equilibrium with brucite and periclase. Measurements spanned the range 550–900 °C. A change of state of solute KCl occurs as pressures increase above 2 kbar, by which H₂O activity becomes very low and, at pressures of 4 kbar and above, nearly coincident with the square of the mole fraction (x _H2O). The effect undoubtedly results primarily from ionic dissociation as H₂O density (ρ_H2O) approaches 1 gm/cm³, and is more pronounced than in the NaCl-H₂O system at the same P-T-X conditions. Six values of solute KCl activity were yielded by terminal points of the isobaric brucite-periclase T-x _H2O curves where sylvite saturation occurs. The H₂O mole fraction of the isobaric invariant assemblage brucite-periclase-sylvite-fluid is near 0.52 at all pressures, and the corresponding temperatures span only 100 °C between 1 and 15 kbar. This remarkable convergence of the isobaric equilibrium curves reflects the great influence of pressure on lowering of both KCl and H₂O activities. The H₂O and KCl activities can be expressed by the formulas: a _H2O = γ_H2O[x _H2O+(1 + (1 + α)x _KCl)], and a _KCL = γ_KCl[(1 + α)x _KCl/(x _H2O +(1 + α)x _KCl)]^(1 + α), where α is a degree of dissociation parameter which increases from zero at the lowest pressures to near one at high pressures and the γ's are activity coefficients based on an empirical regular solution parameter W: ln γ_i = (1 − x_i)²W. Least squares fitting of our H₂O and KCl activity data evaluates the parameters: α = exp(4.166 −2.709/ρ_H2O) − 212.1P/T, and W = (−589.6 − 23.10P) /T, with ρ_H2O in gm/cm³, P in kbar and T in K. The standard deviation from the measured activities is only ± 0.014. The equations define isobaric liquidus curves, which are in perfect agreement with previous DTA liquidus measurements at 0.5–2 kbar, but which depart progressively from their extrapolation to higher pressures because of the pressure-induced dissociation effect. The great similarity of the NaCl-H₂O and KCl-H₂O systems suggests that H₂O activities in the ternary NaCl-KCl-H₂O system can be described with reasonable accuracy by assuming proportionality between the binary systems. This assumption was verified by a few reconnaissance measurements at 10 kbar of the brucite-periclase equilibrium with a Na/(Na + K) ratio of 0.5 and of the saturation temperature for Na/(Na + K) of 0.35 and 0.50. At that pressure the brucite-periclase curves reach a lowest x _H2O of 0.45 and a temperature of 587 °C before salt saturation occurs, values considerably lower than in either binary. This double-salt eutectic effect may have a significant application to natural polyionic hypersaline solutions in the deep crust and upper mantle in that higher solute concentrations and very low H₂O activities may be realized in complex solutions before salt saturation occurs. Concentrated salt solutions seem, from this standpoint, and also because of high mechanical mobility and alkali-exchanging potential, feasible as metasomatic fluids for a variety of deep-crust and upper mantle processes. Received: 9 August 1996 / Accepted: 15 November 1996     

The most energetic particles

The 3rd International Workshop on Ultra High Energy Cosmic Rays covered such topics as results from experiments, theory and models, and the links with γ-rays, neutrinos, dark matter and the cosmic microwave background radiation. David Newton reports.     

Evidence for the enhanced lability of dissolved organic matter following permafrost slope disturbance in the Canadian High Arctic

Arctic landscapes are believed to be highly sensitive to climate change and accelerated disturbance of permafrost is expected to significantly impact the rate of carbon cycling. While half the global soil organic matter (SOM) is estimated to reside in Arctic soils, projected warmer temperatures and permafrost disturbance will release much of this SOM into waterways in the form of dissolved organic matter (DOM). The spring thaw and subsequent flushing of soils releases the highest contributions of DOM annually but has historically been undersampled due to the difficulties of sampling during this period. In this study, passive samplers were placed throughout paired High Arctic watersheds during the duration of the 2008 spring flush in Nunavut, Canada. The watersheds are very similar with the exception of widespread active layer detachments (ALDs) that occurred within one of the catchments during a period of elevated temperatures in the summer of 2007. DOM samples were analyzed for structural and spectral characteristics via nuclear magnetic resonance (NMR) and fluorescence spectroscopy as well as vulnerability to degradation with simulated solar exposure. Lignin-derived phenols were further assessed utilizing copper(II) oxide (CuO) oxidation and gas chromatography/mass spectrometry (GC/MS). The samples were found to have very low dissolved lignin phenol content (∼0.07% of DOC) and appear to originate from primarily non-woody angiosperm vegetation. The acid/aldehyde ratios for dissolved vanillyl phenols were found to be high (up to 3.6), indicating the presence of highly oxidized lignin. Differences between DOM released from the ALD vs. the undisturbed watershed suggest that these shallow detachment slides have significantly impacted the quality of Arctic DOM. Although material released from the disturbed catchment was found to be highly oxidized, DOM in the lake into which this catchment drained had chemical characteristics indicating high contributions from microbial and/or primary productivity. The resulting pool of dissolved carbon within the lake appears to be more biologically- and photochemically-labile than material from the undisturbed system. These disturbances may have implications for projected climate warming; sustained elevated temperatures would likely perpetuate widespread ALDs and further affect carbon cycling in this environment.     

Responsible fisheries: An overview of FAO policy developments (1945–1994)

The paper outlines the evolution of fisheries development policies (aquaculture excluded), from an international perspective as seen within the various UN and FAO fishery committees. It begins with the first FAO Technical Committee on Fisheries in 1945 and extends through the various periods corresponding to post-war reconstruction (1945–1958), geographical expansion (1959–1972), establishment of a new economic order of the oceans (1973–1982), and transition towards global concerns (1983–1992). It underlines the gaps between government resolutions at the international level and effective implementation at national policy level. This identifies the elements to be considered in responsible fishing policies. Finally, the FAO International Code of Conduct for Responsible fisheries is presented as the conceptual framework for achieving sustainable fisheries development and UNCED's objectives within the framework of the 1992 Convention.     

The water status of Terminalia brownii Fresen. seedlings during establishment in semi-arid sites in Kenya

The water status of Terminalia brownii seedlings was assessed in relation to incident microclimate and initial irrigation treatments, during establishment at Olorgesailie in the Rift Valley of Kenya. Experimental treatments involved incorporation of a water-absorbing polymer with the root systems of the plants during establishment, and repeated irrigation, in a factorial design. The maximum photosynthetically active radiation of over 2500 μmol/m²/s recorded during the first 9 days after outplanting was associated with air temperatures of up to 47·4°C, and leaf-to-air vapour pressure deficits (VPDs) of up to 8·04 kPa. Water potentials declined to a minimum of -3·7 MPa, 9 days after outplanting, indicating severe water deficits. Stomatal conductances were generally below 0·2 cm/s, reflecting a high degree of stomatal closure. However, conductances of over 1·3 cm/s were observed on the 6th day after outplanting, associated with VPDs below 1·5 kPa. These relatively high conductances were restricted to plants which had received irrigation; overall, irrigation was found to significantly increase stomatal conductance on three of the four measurement days. Although the application of synthetic polymers increased stomatal conductances on two of the measurement days, the effects were very slight (treated means 0·02-0·03 cm/s higher than controls). These results indicate the severity of the transplant shock in semi-arid sites for seedling water status, and imply that initial irrigation treatments are more likely to increase establishment rates of tree seedlings than application of synthetic polymers.     

THE NEW DECADE: DIGITS AND DIVERSITY

The President of the Photogrammetric Society, Mr. I Newton, chaired a panel discussion concerned with those developments in photogrammetry which may take place during the 1990s.     

Identification of regions enriched or depleted in radioelements through nondistributional analysis of aerial radiometric data

Throughout the aerial radiometric reconnaissance survey portion of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program, the identification of outliers (anomalies) was an important approach to locating regions with radio-element concentrations that are either higher or lower than expected. The method introduced herein to locate such regions involves three steps: selection of a high (or low) threshold for the variate of interest; use of the sample percentile to identify all points of interest; and movement of a window over the selected data to locate significant clusters of observations. These steps, applied to aerial radiometric ²¹⁴Bi (equivalent uranium) data collected over the Copper Mountain area in Wyoming, resulted in the identification of areas enriched in that variate.