Looking back and moving forward: Health geography in Aotearoa and beyond

Health geography in Aotearoa New Zealand (NZ) has had a major impact on international sub‐disciplinary debates. It is timely to celebrate our domestic health geography achievements and alert ourselves to the challenges ahead. This reflection article provides a brief overview of Aotearoa NZ's maturing health geography community and includes the reflections of a panel discussion held during the bi‐annual NZ Geographical Society conference in 2016. We argue that the eclectism of health geography in NZ and beyond is both the sub‐discipline's major strength and challenge.     

Asteroid 6 Hebe: The probable parent body of the H-type ordinary chondrites and the IIE iron meteorites

Abstract— The S(IV)-type asteroid 6 Hebe is identified as the probable parent body of the H-type ordinary chondrites and of the IIE iron meteorites. The ordinary chondrites are the most common type of meteorites falling to Earth; but prior to the present study, no large mainbelt source bodies have been confirmed. Hebe is located adjacent to both the v₆ and 3:1 resonances and has been previously suggested as a major potential source of the terrestrial meteorite flux. Hebe exhibits subtle rotational spectral variations, indicating the presence of some compositional variations across its surface. The silicate portion of the surface assemblage of Hebe is consistent (both in overall average and in its range of variation) with the silicate components in the suite of H-type chondrites. The high albedo of Hebe rules out a lunar-style space weathering process to produce the weakened absorption features and reddish spectral slope in the S-type spectrum of Hebe. Linear unmixing models show that a typical Ni-Fe metal spectrum is consistent with the component that modifies an H-chondrite spectrum to produce the S-type spectrum of Hebe. On the basis of the association between the H chondrites and the HE iron meteorites, our model suggests that large impacts onto the relatively metal-rich H-chondrite target produced melt bodies (sheets or pods) that differentiated to form thin, laterally extensive near-surface layers of Ni-Fe metal. Fragments of the upper silicate portions of these melt bodies are apparently represented by some of the igneous inclusions in H-chondrite breccias. Alternately, masses of metal could have been deposited on the surface of Hebe by the impact of a core or core fragment from a differentiated parent body of H-chondrite composition. Subsequent impacts preferentially eroded and depleted the overlying silicate and regolith components, exposing and maintaining large masses of metal at the optical surface of Hebe. In this interpretation, the nonmagmatic IIE iron meteorites are samples of the Ni-Fe metal masses on the surface of Hebe, whereas the H chondrites are samples from between and/or beneath the metal masses.     

Controls on the chemical composition of groundwater from alluvial aquifers in the Wanaka and Wakatipu basins, Central Otago, New Zealand

 Groundwater in alluvial aquifers of the Wakatipu and Wanaka basins, Central Otago, New Zealand, has a composition expressed in equivalent units of Ca²⁺≫Mg²⁺≅Na⁺>K⁺ for cations, and HCO₃ ^–≫SO₄ ^2->NO₃ ^–≅Cl^– for anions. Ca²⁺ and HCO₃ ^– occur on a 1 : 1 equivalent basis and account for >80% of the ions in solution. However, some groundwater has increased proportions of Na⁺ and SO₄ ^2-, reflecting a different source for this water. The rock material of the alluvial aquifers of both basins is derived from the erosion and weathering of metamorphic Otago Schist (grey and green schists). Calcite is an accessory mineral in both the grey and green schists at <5% of the rock. Geological mapping of both basins indicates that dissolution of calcite from the schist is the only likely mechanism for producing groundwater with such a constant composition dominated by Ca²⁺ and HCO₃ ^– on a 1 : 1 equivalent basis. Groundwater with higher proportions of Na⁺ and SO₄ ^2- occurs near areas where the schist crops out at the surface, and this groundwater represents deeper and possibly older water derived from basement fluids. Anomalously high K⁺ in the Wakatipu basin and high NO₃ ^– concentrations in the Wanaka basin cannot be accounted for by interaction with basement lithologies, and these concentrations probably represent the influence of anthropogenic sources on groundwater composition. Received, June 1996 Revised, March 1997, July 1997 Accepted, July 1997     

The use of buffers to measure the pH of seawater

The pH of seawater can be measured in the field using potentiometric and spectrophotometric methods. The use of pH standards or buffers is an important aspect of the calibration of both methods in a laboratory on a common concentration scale. The buffers can also be used to monitor the performance of pH meter and spectrophotometer during a cruise. A procedure is described for the determination of the pH of seawater, where the proton concentration is expressed as moles kg-H₂O⁻¹ using seawater buffers. The buffers are prepared in synthetic seawater in the laboratory by the methods outlined by Bates and coworkers. We have prepared four buffers (Bis, Tris, Morpholine and 2-Aminopyridine) that cover a pH range from 6.8 to 8.8. The emf values of the buffers were measured with a H₂, Pt/AgCl, Ag electrode system after their preparation and bottling for use at sea. The measured emf values were found to be in good agreement (±0.05 mV) with the original measurements of Bates and coworkers from 0 to 45°C. The measured pH of these buffers are in good agreement (±0.001 pH units) with the values calculated from the equations of Dickson on the total pH scale based on Bates et al. Studies are underway to access the long term stability of these buffers. We have also used these buffers to calibrate systems used to make potentiometric and spectrophotometric measurements of pH on seawater relative to the H₂, Pt/Ag, AgCl electrode from 5 to 45°C.     

Rates of nitrification and nitrate reduction in nearshore marine sediments at near ambient substrate concentrations

Nitrification and nitrate reduction were measured simultaneously by a ¹⁵N-isotope dilution technique in the top 2 cm of sandy sediments in Great South Bay, Long Island, New York. Experiments were done at three times, under three different sets of environmental conditions. Nitrification rates remained between 0.010 and 0.015 μg-at N (g dry wt)⁻¹ (24 h)⁻¹ despite decreasing temperature. Nitrate reduction ranged from 0.02 to 0.11 μg-at N (g dry wt)⁻¹ (24 h)⁻¹. Nitrate reduction exceeded nitrification in two experiments. In the third, at low temperature and apparently high oxygen levels, rates of nitrification and nitrate reduction were comparable. We conclude that there is not a constant relationship between nitrification and nitrate reduction in this environment. Attempts to measure rates of nitrification by using the inhibitor chlorate were not successful.     

The role of iron chelates in the NAD(P)H-dependent oxidation of 2-keto-4-thiomethylbutyric acid (KMBA) by rainbow trout and pacific salmon microsomal fractions

Uninduced microsomes from three different species of the genus Oncorhynchus catalyzed a NAD(P)H-dependent oxidation of the radical scavenging agent 2-keto-4-thiomethylbutyric acid (KMBA). This reaction was stimulated by the addition of iron-EDTA, hemoglobin and myoblobin but inhibited by catalase and benzoate. Superoxide dismutase (SOD) did not substantially inhibit the oxidation in the presence of iron-EDTA. This hydroxyl radical (·OH)-generating system was mainly NADH-dependent which is similar to observations in aquatic invertebrates but in contrast to mammalian systems. This study demonstrates that this radical-generating activity is wide ranging and requires consideration in evaluating xenobiotic metabolism.     

Succession in Gulf of Mexico Cold Seep Vestimentiferan Aggregations: The Importance of Spatial Variability

Abstract. The slow rate of change in hydrocarbon seep communities on the upper ­Louisiana slope prevents the use of direct observation in studying successional trends. We used a chronosequence consisting of three presumed stages – juvenile, adult and senescent – to test a previous model which proposed that sulfide availability and vestimentiferan growth and physiological health decline over the lifespan of a vestimenti­feran aggregation. We replicated the chronosequence at two sites to simultaneously ­explore the influence of spatial heterogeneity on the characteristics of these communities. We determined environmental sulfide concentrations and vestimentiferan growth and condition in at least two vestimentiferan aggregations representative of each stage at each of these two sites. Hydrogen sulfide concentrations were highly variable both above and below the sediment's surface, and sulfide was present in high concentrations to sediment depths of 70  cm. Vestimentiferan growth and condition varied significantly on multiple spatial scales from sites separated by tens of kilometers, to aggregations separated by tens to hundreds of meters within a site, to individual vestimentiferans ­separated by tens of centimeters within an aggregation. The striking variability in both environmental sulfide and vestimentiferan growth and condition within individual ­aggregations suggests a crucial role for microhabitat variability in the persistence of vestimentiferan aggregations at these sites. Few significant successional trends in ­environmental sulfide or vestimentiferan growth and condition were found over the three stages tested.     

Co-management and “consciousness”: Fishers’ assimilation of management principles in Chile

Chile's new Management Area system delegates management responsibility to organizations of artisanal shell-fishers on the condition that they team with professionally trained marine biologists. A survey of participating fishers in Chile's Fourth and Fifth regions examined four social benefits predicted to result from this type of co-management: (1) improved rapport between fishers and the state, (2) greater awareness among fishers of ecology and the benefits of management, (3) cooperation between fishers and scientists, and (4) unity between fishers. A discussion analyzes the principal benefit encountered—fishers’ newfound “consciousness” of the value of management—within the context of co-management and territorial use rights.     

Using Kolmogorov-Smirnov Statistics to Compare Geostrophic Velocities Measured by the Jason, TOPEX, and Poseidon Altimeters

The Kolmogorov-Smirnov (K-S) test is used to compare probability density functions (PDFs) of geostrophic velocities measured by the TOPEX, Poseidon, and Jason altimeters. Velocity PDFs are computed in 2.5° by 2.5° boxes for regions equatorward of 60° latitude. Although velocities measured by the TOPEX and Jason altimeters can differ, on the basis of the K-S test the velocities are statistically equivalent during the ∼200 day period when the satellites followed the same orbit. Full records from TOPEX, Poseidon, and Jason show less agreement, which can be attributed to temporal variability in ocean surface velocities and differing levels of measurement noise.