Annual cycle of fCO2 under sea-ice and in open water in Prydz Bay, East Antarctica

The annual cycle of dissolved nutrients and the fugacity of CO₂ (fCO₂), calculated from the concentration of dissolved inorganic carbon (DIC) and pH, was studied over a 14-month long period (December 1993 to February 1995) at a site in Prydz Bay near Davis Station, Vestfold Hills, East Antarctica. Significant spring decreases in fCO₂ began under the sea-ice in mid-October, when both water column and sea-ice algal activity resulted in the removal of nutrients and DIC and increased pH. Minimum fCO₂ (<100 μatm) and lowest nutrient and DIC concentrations occurred in December and January. The low summer fCO₂ values were clearly the result of biological activity. The seasonal depletion of dissolved nitrate reached 85% in mid-summer when chlorophyll-a concentrations exceeded 15 mg m⁻³. Oceanic uptake of carbon dioxide from the atmosphere, calculated from the fugacity difference and daily wind speeds, averaged more than 30 mmol m⁻² day⁻¹ during the summer ice-free period. This exchange replaced approximately half of the DIC consumed by biological activity. Apparent nutrient utilisation ratios (C/N/P) were close to Redfield values. In autumn fCO₂ began to rise, continuing slowly well into winter, and reaching a maximum close to modern atmospheric values between July and September. This increase can be attributed to a combination of local remineralisation of organic carbon in the water column and the steady increase in the mixing depth of the water column. At first glance, this suggests that air–sea equilibration occurred in winter despite the sea-ice cover, perhaps by horizontal circulation from regions outside the pack ice, or through openings in the ice. However, the persistent 15 to 20% undersaturation of dissolved oxygen throughout the winter suggests an alternate explanation. The late winter fCO₂ level may represent a characteristic established by global circulation, so that as a result of increasing atmospheric CO₂ concentrations, these Antarctic waters are in transition from being a winter-time source of CO₂ to the atmosphere to becoming a sink. Our fCO₂ observations emphasize the need to address seasonal variations in assessing Antarctic contributions to the oceanic control of atmospheric CO₂.     

Assessment of IUU fishing for Southern Bluefin Tuna

Illegal, unreported and unregulated (IUU) fishing is recognized as one of the largest threats to the sustainability of the world's fisheries. This paper focuses on IUU fishing in the context of unreported catches by members or co-operating non-members of regional fisheries management organizations (RFMOs) and their implications for scientific assessments of stock status and management advice. A review of Japanese market statistics was undertaken in 2006 by an independent panel in relation to catches of southern bluefin tuna (SBT). Based on this review, the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) concluded that very substantial and continuous unreported catches of SBT had been taken by longline vessels since at least the early 1990s. While uncertainty exists about the fleets contributing to these IUU catches, the assumption used within the CCSBT Scientific Committee is that a significant proportion of these were taken by Japanese longliners. Implications of these unreported catches for the stock assessments by RFMOs are discussed in light of the central role that Japanese vessel reported data have in the assessment of the world's tuna and billfish stocks. Results indicate that it is plausible that the unreported catches of SBT stem from the misreporting of catches as other tuna species and/or the location of fishing effort. The magnitude and extended period of the unreported SBT catches highlight the wide-spread risks of relying on fishery dependent logbook data in the absence of verification. An urgent need exists for minimum standards of verification of catch, effort and landing statistics for use in scientific assessments. The fisheries science community needs to be more pro-active in the development of such standards and the implementation of independent monitoring and verification. In addition, there is a need to reform the operation of the scientific bodies of RFMOs in terms of transparency, the treatment of uncertainty and the burden of proof if they are to be effective in providing objective scientific advice consistent with the intent of international agreements.     

Application of the Engineering-Geological Conditions in Land-Use Plans in the Petrvald Region(Czech Republic)

The objective of this paper is to demonstrate necessity to inform relevant parties about engineering-geological conditions for various practical purposes,especially including appropriate land-use planning.However,the relationship between relevant geological information and the geological environment is vital for foundation engineering purposes,especially where demanding structures are involved.This information is most conveniently structured when accumulated information concerning engineering-geological zones is utilized.This necessarily includes knowledge of rock workability and also of the pre-Quaternary bedrock,and these characteristics were then related to the current built-up area and future development according to the land-use plans in a case study are from the Petrvald Region(Czech Republic).The geological environment of area has been severely influenced by anthropogenic effects of deep black coal mining.Results of this research showed that future development should be founded on spoil banks,dumps,and settling basins. According to the land-use plan,this zone occupies 44.9%of the area of interest,and its materials predominantly emanate from mining in the Ostrava-Karvina Coal District.For future foundation structures planned there,it is imperative to consult detailed engineering-geological study.However, attention to and reliance on this necessity is not reflected in the existing land-use plan.     

Lack of population genetic structure in the marine nematodes Ptycholaimellus pandispiculatus and Terschellingia longicaudata in beaches of the Persian Gulf,Iran

We investigated genetic diversity and population genetic structure of two common benthic nematode species, Ptycholaimellus pandispiculatus and Terschellingia longicaudata, from sandy beaches in the area of Bandar Abbas (Iran), Persian Gulf. Based upon partial mitochondrial cytochrome oxidase c subunit 1 (COI) gene data, 17 and two haplotypes were found for P. pandispiculatus and Te. longicaudata, respectively. Analysis of molecular variance did not reveal a significant population genetic structure for either species. The absence of genetic structuring indicates substantial dispersal and gene flow in our study area. To assess the species structure of Te. longicaudata at a larger geographic scale, we compared 18S rDNA and COI sequences from Iran and the Scheldt Estuary in The Netherlands to ascertain whether they truly belong to the same species. Our data confirmed previous studies that Te. longicaudata likely constitutes a complex of multiple cryptic species, with one of these species having a (near) cosmopolitan distribution.     

Comparison between in situ cone resistance and laboratory strength for overconsolidated north sea clays

Abstract

Cone resistance and laboratory strength measurements have been compared for stiff overconsolidated clays from five oil and gas fields in the North Sea. The clays considered are glacial in origin. The best agreement between cone resistance and laboratory strength is found by using an N_k factor equal to 17 in the formula

q_c = N_k . S_u + γZ.

The study shows that the cone gives highly reproducible results, whereas there is a considerable scatter in the laboratory strength determinations. When making use of CPTs for preliminary design, the authors recommend assuming an N_k of 15–20, depending on the type of problem under consideration.     

High-resolution Surveys for Geohazards and Shallow Gas: NW Adriatic (Italy) and Iskenderun Bay (Turkey)

The need for quantifying and understanding the distribution of shallow gas is both of academic interest and of relevance to offshore facilities. The combination of seafloor mapping, subbottom profiling, and multi-channel seismic data can provide information on regions of possible shallow gas, where the gas impacts the acoustic properties of the host material and the seafloor. In this paper, we present two case studies – one academic and one industry – that evaluate the distribution of shallow gas in two field areas in the Mediterranean. In the first case study, geophysical data from Iskenderun Bay, southeastern Turkey, indicate the presence and distribution of shallow gas. Pockmarks on the seafloor are associated with acoustic wipeout in the shallow subbottom data. Although deeper seismic data do not show bright spots or other indicators of possible gas, instantaneous frequency analysis clearly shows laterally restricted anomalies indicating gas-rich zones. The interpretation of possible shallow gas resulted in moving a proposed drilling location to a nearby area characterized by fewer (but still present) shallow gas signatures. In the second case study, cores acquired in the Po Delta, Adriatic Sea, provide quantitative ground-truthing of shallow gas – as suggested by geophysical data – and provide minimum estimates of the percentage of gas in the subsurface. Cores targeted on anomalous subbottom data yielded up to 41,000 ppm methane; cores with anomalous gas content are associated with thick recent flood deposits which may effectively isolate reactive terrigenous organic matter from biologic and physical re-working.     

Probability distributions for wave runup on beaches

Measured probability distributions of shoreline elevation, swash height (shoreline excursion length) and swash maxima and minima from a wide range of beach types are compared to theoretical probability distributions. The theoretical distributions are based on assumptions that the time series are weakly steady-state, ergodic and a linear sum of random variables. Despite the swash process being inherently non-linear, results indicate that these assumptions are not overly restrictive with respect to modeling exceedence statistics in the upper tail of the probability distribution. The RMS-errors for a range of exceedence level statistics (50, 10, 5, 2, and 1%) were restricted to < 10 cm (and often < 5 cm) for all of the swash variables that were investigated. The results presented here provide the basis for further refinement of coastal inundation modeling as well as stochastic-type morphodynamic modeling of beach response to waves. Further work is required, however, to relate the parameters of swash probability distributions to wave conditions further offshore.     

Late prehistoric soil fertility,irrigation management,and agricultural production in northwest coastal Peru

The Pampa de Chaparrí (Pampa) in hyperarid northwest coastal Peru is an ideal area to study late prehispanic agricultural technology and production because irrigation canals and furrowed fields have been preserved since abandonment approximately 500 years ago. We collected 55 samples for soil characterization, fertility, and micromorphic analyses and compared these results to a noncultivated control soil previously sampled in an adjacent valley. Natural soil fertility levels for maize, cotton, and bean production were generally high during late prehispanic cultivation in the Pampa. Maintaining adequate nitrogren levels for production, however, would have required external inputs from livestock manure, guano, or leguminous plants. The management of low soil salinity levels was possible because of rapidly permeable soils and irrigation waters low in salt. Based on available water capacity and climate conditions, the Blaney‐Criddle Equation yields evapotranspiration rates indicating that irrigation frequency was necessary in a range of every 10–16 days during the growing season. © 2004 Wiley Periodicals, Inc.     

A New Assessment Framework for Transience in Hydrogeological Systems

The importance of transience in the management of hydrogeologic systems is often uncertain. We propose a clear framework for determining the likely importance of transient behavior in groundwater systems in a management context. The framework incorporates information about aquifer hydraulics, hydrological drivers, and time scale of management. It is widely recognized that aquifers respond on different timescales to hydrological change and that hydrological drivers themselves, such as climate, are not stationary in time. We propose that in order to assess whether transient behavior is likely to be of practical importance, three factors need to be examined simultaneously: (1) aquifer response time, which can be expressed in terms of the response to a step hydrological change (τ_step) or periodic change (τ_cycle); (2) temporal variation of the dominant hydrological drivers, such as dominant climatic systems in a region; (3) the management timescale and spatial scale of interest. Graphical tools have been developed to examine these factors in conjunction, and assess how important transient behavior is likely to be in response to particular hydrological drivers, and thus which drivers are most likely to induce transience in a specified management timeframe. The method is demonstrated using two case studies; a local system that responds rapidly and is managed on yearly to decadal timeframes and a regional system that exhibits highly delayed responses and was until recently being assessed as a high level nuclear waste repository site. Any practical groundwater resource problem can easily be examined using the proposed framework.