Surface drag and turbulence over an inhomogeneous land surface

Data collected over an inhomogeneous semi-rural area are presented. The data are compared with previous surface-layer data to determine how representative the fixed-point flux measurements are of area averages. Departures from the standard surface-layer results are found to be relatively small (~10–20%), which supports the concept of a blending height above which the flow ceases to respond to variations in the underlying surface and becomes horizontally homogeneous.Effective roughness lengths are derived for different wind directions and the relationship between the effective roughness length and upwind surface is examined in the light of recent ideas on averaging surface roughness lengths. It is found that by averaging drag coefficients, realistic values of the effective roughness length can be calculated which are not very sensitive to the precise choice of the component roughness lengths.     

Framing in geographical analysis of environmental conflicts: Theory, methodology and three case studies

When applied to environmental concerns, framing offers a rigorous conceptual and analytic approach with potentially practical significance for dealing with complex issues relevant to geography. The purpose of this article is to introduce framing concepts, typology and modes of analysis to address issues which geographers commonly treat: disputes over land ownership and uses, competition for water resources, cultural clashes over control of territory and resources and the impact of spatial patterns and structures when siting noxious sites. Framing analysis is applied to three cases of environmental conflict in Israel and, more generally, for understanding conflicts revolving around the management of human habitats in relation to the physical environment.     

Sulfur in peridotites and gabbros at Lost City (30°N, MAR): Implications for hydrothermal alteration and microbial activity during serpentinization

Variations in sulfur mineralogy and chemistry of serpentinized peridotites and gabbros beneath the Lost City Hydrothermal Field at the southern face of the Atlantis Massif (Mid-Atlantic Ridge, 30°N) were examined to better understand serpentinization and alteration processes and to study fluid fluxes, redox conditions, and the influence of microbial activity in this active, peridotite-hosted hydrothermal system. The serpentinized peridotites are characterized by low total sulfur contents and high bulk δ³⁴S values close to seawater composition. Low concentrations of ³⁴S-enriched sulfide phases and the predominance of sulfate with seawater-like δ³⁴S values indicate oxidation, loss of sulfide minerals and incorporation of seawater sulfate into the serpentinites. The predominance of pyrite in both serpentinites and gabbros indicates relatively high fO₂ conditions during progressive serpentinization and alteration, which likely result from high fluid fluxes during hydrothermal circulation and evolution of the Lost City system from temperatures of ∼250 to 150 °C. Sulfate and sulfide minerals in samples from near the base of hydrothermal carbonate towers at Lost City show δ³⁴S values that reflect the influence of microbial activity. Our study highlights the variations in sulfur chemistry of serpentinized peridotites in different marine environments and the influence of long-lived, moderate temperature peridotite-hosted hydrothermal system and high seawater fluxes on the global sulfur cycle.     

Modification of an acoustic pinger to transmit temperature data

An acoustic pinger can be modified to transmit two pings per second with the delay time between pings controlled by the temperature of an external thermistor. The precision of the temperature measurements is on the order of 0.1°C. This modification does not interfere with the normal depth indicating function of the pinger and is an inexpensive means of obtaining water temperature data.     

Modern swathe sounding and sub-bottom profiling technology for research applications: The Atlas Hydrosweep and Parasound Systems

This chapter describes two separate but complementary research echosounder systems originally developed by Krupp Atlas Elektronik GmbH for the new German oceanographic research vessel Meteor.The Hydrosweep is a Hydrographic wide-swathe sweep survey echosounder for both shallow and deep water applications providing accurate bathymetric surveys and terrain-following navigation capabilities.The Parasound system is a hull-mounted dual channel parametric narrow-beam deep sea survey and sub-bottom profiling echosounder enabling particularly high vertical and horizontal resolution of seabed features.     

Spatial variation of the intertidal sediments and macrozoo-benthic assemblages along Eighty-mile Beach, North-western Australia

The extensive intertidal flats along Eighty-mile Beach in North-western Australia appear to be monotonous and homogeneous and seem ideally suited to study tidal zonation in macrozoo-benthic communities and their possible correlates with characteristics of the sediment. In October 1999, we sampled benthic invertebrates and sediments at a total of 895 sampling stations distributed over six different locations, each location separated by 15 km of unsampled foreshore along Eighty-mile Beach. To test for the presence or absence of patterns of tidal zonation (distinct height-related zones of specific sediment grain sizes or zoobenthic taxonomic groups) or patchiness (distinct patches of specific sediment grain sizes or zoobenthic taxonomic groups not related to tidal height) each location was divided into three along-shore sections and each section (transect) was examined at two or three tidal heights. Zonation was observed for sediment grain sizes. Sediments were coarser at the highest intertidal level and finer towards the low water line. Benthic assemblages also differed among tidal heights, but in terms of species-composition the differences were not consistent among the locations. Each location supported a unique collection of benthic invertebrates. Therefore the hypothesis of the presence of distinct zones of specific species or zoobenthic taxonomic groups was rejected; the presence of benthic patches was confirmed. The distribution of sediments and the composition of benthic assemblages were surprisingly poorly correlated compared to those reported in 12 previous quantitative studies around the world. One possible explanation might be that super-cyclone Vance, which hit the study-area only six months before this study, contributed to this poor correlation. Alternatively, the poor correlation may indicate that biotic interactions are more important than the assumed abiotic structuring.     

Can turbidity caused by Corophium volutator (Pallas) activity be used to assess sediment toxicity rapidly?

The standard toxicity test organism, Corophium volutator, exhibits a behavioural response to contaminated sediments that causes increased turbidity of overlying water. We quantify the effects of this response to an estuarine sediment spiked with copper and hydrocarbon contaminated sediments from an oil installation in the North Sea. Turbidity measured 24 h after the start of a toxicity test shows a strong relationship with contaminant concentrations and with mortality after 10 days. Turbidity measurements can therefore give a rapid indication of sediment toxicity, permitting a reduction in storage time of sediments to be used in dilution series and toxicity identification evaluation (TIE) tests, reducing the likelihood of contaminants degrading prior to testing.     

Nitrogen uptake kinetics in the Ross Sea, Antarctica

The first estimates of uptake kinetic parameters for NH₄⁺, NO₃⁻, and urea in the Ross Sea, Antarctica were measured on three cruises during austral late winter–early spring 1996 (pre-bloom), late spring 1997 (bloom development), and summer 1997 (bloom decline). Nitrogen (N) uptake experiments were conducted with water collected at the 50% light penetration depth using trace-metal clean protocols and ¹⁵N tracer techniques. At all sites, ambient NO₃⁻ concentrations ranged from 5.8 to 30.5 μg-at N l⁻¹ and silicic acid concentrations were greater than 62.0 μg-at Si l⁻¹. The following trends were observed. First, based on maximum uptake rates (V_max), apparent N utilization followed the order NO₃⁻>NH₄⁺>urea during the pre-bloom and bloom development cruises. During the summer cruise, as the bloom was declining, the apparent order of utilization was NH₄⁺>NO₃⁻>urea. Second, evidence for possible repression of NO₃⁻ uptake by elevated NH₄⁺ concentrations was only observed at one site. Third, the kinetic parameters of NH₄⁺ uptake rates corrected for isotope dilution were compared with the kinetic parameters determined from uncorrected rates. In this comparison, the measure of substrate affinity, α (α=V_max/K_s) increased by an average of 4.6-fold when rates were corrected for isotope dilution, but values of V_max remained unchanged. Fourth, using bacterial production data, the magnitude of bacterial N uptake was estimated. Assuming that all bacterial N demands were met with NH₄⁺, the estimated bacterial portion of NH₄⁺ uptake ranged from <1%, when the ratio of bacteria to autotrophic biomass was low, to 35%, when bacterial abundance and biomass were highest. Finally, dramatic changes in NH₄⁺ uptake capacity were observed at one station (Stn. O), where kinetic parameters were measured during all three cruises. We hypothesize that a mutualistic relationship exists between phytoplankton and heterotrophic bacteria, and that the creation of microzones of high NH₄⁺ concentrations contributed to the changes seen at this station.