Bioavailability: the organism as sensor

The use of a system of continuous culture of phytoplankton at constant population density, the ‘cage-culture’ turbidostat, as a monitor of the bioavailability of pollutant materials, is illustrated. In the case of proposed dredge spoils from two polluted areas, it is shown that bulk analyses for scheduled materials cannot be equated with bioavailability. Monitoring for the effect of the whole pollutant mixture on a properly chosen test population could obviate the necessity for chemical analyses for each component.     

Geochemical characterization of the potential trace metal mobility in cohesive sediments

The Acid-Producing Potential (APP) and the Acid-Consuming Capacity (ACC) are introduced as basic parameters for long-term pollution assessment of mud disposal. They can be obtained by a four-step sequential leaching technique. The concentration of Ca extracted by the first Na-acetate step permits calculating the ACC. Both the Fe- and S-fractions deliberated by subsequent leaching steps are used to calculate the APP. When the APP of a sample is substacted from its ACC, a negative value indicates a potential increase of the bioavailability of the toxic metal load upon disposal of this mud in oxic environments.     

Quaternary evolution of the Gulf of İzmit (NW Turkey): a sedimentary basin under control of the North Anatolian Fault Zone

The Quaternary evolution of the Gulf of İzmit, situated on the tectonically active North Anatolian Fault Zone (NAFZ), was investigated using seismic reflection, paleontologic, and sediment textural data. On the basis of seismic stratigraphic and sedimentologic-paleontologic interpretations, four depositional units were distinguished within the Plio-Quaternary sequence of the Gulf of İzmit. According to these data, Plio-Quaternary deposits supplied from the northern terrestrial area started to accumulate during a progradational phase, in a south-facing half-graben. A coarse-grained sedimentary unit prograding into the gulf from the south since 200 ka b.p. indicates a dramatic variation in the evolution of the gulf, with the initiation of a new strike-slip fault of the NAFZ and a corresponding uplift of the Armutlu Peninsula in the south of the gulf. During the evolution of this fault from a wide shear zone consisting of right-stepped strike-slip faults and pull-apart basins to a localized principal fault zone, sediments were deposited under the influence of northerly prograding terrestrial and shallow-marine conditions due to relative sea-level fluctuations in the Marmara Sea. During this period, the Gulf of İzmit was invaded mainly by Mediterranean and partly by Black Sea waters. In the latest glacial period, shallow areas in the gulf became subaerially exposed, whereas the central and western sub-basins of the gulf turned into lakes. The present evolution of the Gulf of İzmit is controlled by the after effects of the new rupture of the NAFZ and the estuarine nature of the gulf environment.     

A climatology of mesoscale model simulated low-level wind jets over Cook Inlet and Shelikof Strait, Alaska

Weather in the North Gulf of Alaska is characterized by a high frequency of deep synoptic-scale low-pressure systems, especially during the cold season. The strong pressure gradients of these storms interact with the extremely rugged terrain of the coastal mountains to produce a variety of channeled flows. These surface wind regimes are not well documented in the scientific community, due to the paucity of observations. Modeling of these phenomena in regions of complex terrain is of great interest to those working with hydrodynamic, wave, and pollutant transport models in coastal and shelf areas. Such models, when coupled with ocean and coastal-ecology counterparts, give a broad view of the role surface winds play in shaping local coastal marine ecosystem in this region. This paper presents a climatology of simulated low-level wind jets over the domain of Cook Inlet and Shelikof Strait along Alaska's south-central coast. Daily simulations using the RAMS model were conducted in a 36-h forecast mode for the cold-season period 10/1/03 to 3/31/04. Systematic analysis of the resulting simulated low-level wind field makes it possible to characterize these jets and gap flows in spatial and temporal detail. The comparison between the RAMS winds and the Synthetic Aperture Radar (SAR)-derived winds when available verifies the existence of these wind jets and the capability of the model to simulate these cases. Clearly, the results of a study in this region depend on the fidelity of the model at these scales (O[5 km]). The SAR comparisons attempt to help establish this. From the 6 months of simulations over Cook Inlet and Shelikof Strait, the low-level wind jets are classified into 10 different regimes by location and orientation. These regimes are categorized into four more general groups: cross-channel westerly, easterly, and up and down Inlet flows. The nature of a particular regime is largely a function of pressure gradient orientation and local topography. Jets in the same group have a similar occurrence distribution with time. Some form of jet occurred in the study region almost daily each month of the period, with December 2003 having the highest frequency of wind jets.     

Emerging fisheries,emerging fishery interactions with sea turtles: A case study of the large-mesh gillnet fishery for flounder in Pamlico Sound,North Carolina,USA

Emerging fisheries and changes in fishery practices are not always readily apparent, nor are their impacts on non-target species such as seabirds, sea turtles, and marine mammals. Data from several different sources led managers to discover high rates of sea turtle bycatch in an inshore large-mesh gillnet fishery in North Carolina, USA, particularly the emerging deep-water gillnet fishery. This paper reviews the history of how increased numbers of observed stranded sea turtles in 1999 led to the discovery that turtles were becoming entangled in the large-mesh gillnet fishery in Pamlico Sound, North Carolina. It also demonstrates how a variety of data sets from fisheries observers, aerial surveys, and fisheries statistics programs contributed to shaping management of the large-mesh gillnet fishery in Pamlico Sound to decrease turtle bycatch and now point towards the need of additional assessment of gillnet bycatch in other parts of North Carolina. Finally, potential approaches are discussed for a more timely detection of future fishery conflicts and development of a plan to reduce otherwise inevitable bycatch and disruptions to fishing effort.     

A parametric study on seakeeping assessment of fast ships in conceptual design stage

The paper presents an approach to investigate the effects of some parameters on seakeeping assessment of fast ships in conceptual design stage. Hull form parameters have been classified into two groups: main dimensions (L, B and T) and secondary form parameters (LCB and C_P). To demonstrate the approach a fast ship is redesigned as parent hull and alternative hull forms are generated by changing these parameters systematically. Some hull forms are selected related the geometric limits and seakeeping analyzes are here investigated and discussed. The obtained results are satisfactory for seakeeping predictions during the conceptual design stage.     

Corrections to ocean surface forcing in the California Current System using 4D variational data assimilation

The option for surface forcing correction, recently developed in the 4D-variational (4DVAR) data assimilation systems of the Regional Ocean Model System (ROMS), is presented. Assimilation of remotely-sensed (satellite sea surface height anomaly and sea surface temperature) and in situ (from mechanical and expendable bathythermographs, Argo floats and CTD profiles) oceanic observations has been applied in a realistic, high resolution configuration of the California Current System (CCS) to sequentially correct model initial conditions and surface forcing, using the Incremental Strong constraint version of ROMS-4DVAR (ROMS-IS4DVAR). Results from both twin and real data experiments are presented where it is demonstrated that ROMS-IS4DVAR always reduces the difference between the model and the observations that are assimilated. However, without corrections to the surface forcing, the assimilation of surface data can degrade the temperature structure at depth. When using surface forcing adjustment in ROMS-IS4DVAR the system does not degrade the temperature structure at depth, because differences between the model and surface observations can be reduced through corrections to surface forcing rather than to temperature at depth. However, corrections to surface forcing can generate abnormal spatial and temporal variability in the structure of the wind stress or surface heat flux fields if not properly constrained. This behavior can be partially controlled via the choice of decorrelation length scales that are assumed for the forcing errors. Abnormal forcing corrections may also arise due to the effects of model error which are not accounted for in IS4DVAR. In particular, data assimilation tends to weaken the alongshore wind stress in an attempt to reduce the rate of coastal upwelling, which seems to be too strong due to other sources of error. However, corrections to wind stress and surface heat flux improve systematically the ocean state analyses. Trends in the correction of surface heat fluxes indicate that, given the ocean model used and its potential limitations, the heat flux data from the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) used to impose surface conditions in the model are generally too low except in spring-summer, in the upwelling region, where they are too high. Comparisons with independent data provide confidence in the resulting forecast ocean circulation on timescales ～14 days, with less than 1.5 °C, 0.3 psu, and 9 cm RMS error in temperature, salinity and sea surface height anomaly, respectively, compared to observations.     

The composition and origin of metal in howardites

Howardites can be divided into two main groups, Ni-rich (>350ppm Ni) and Ni-poor (<150ppm Ni). In the Ni-rich group Ni occurs principally in metal grains associated with melt rocks and is largely derived from projectiles which caused the melting. The metal in Bununu, Kapoeta and Malvern melt rocks plots in the meteoritic Ni-Co range and in Bununu and Kapoeta is enriched in P. By contrast, most metal grains in primary lithic and crystal clasts in howardites are Ni-poor and plot mainly in the composition field of pristine lunar anorthosite metal. However, there are variations in the abundance and exact composition of primary metal from howardite to howardite and each therefore represents a discrete source region. The matrix metal in Bholgati, Bununu, and Kapoeta shows the diversity of compositions expected in a polymict breccia, with compositions plotting in and between the anorthositic and meteoritic Ni-Co fields. Other howardites show a more limited range of matrix metal compositions, because of limited metal-bearing clasts.Petersburg differs from other howardites in several ways. The metal in primary clasts has a unique $\text{Ni}\text{Co}$ ratio of about 40, which indicates derivation from a different reservoir from other howardite primary clasts. The metal in the matrix consists of large grains intergrown with silicates with compositions clustering tightly at 3.3% Ni, 0.2% Co. This is interpreted as equilibration, possibly as the result of deeper burial for Petersburg than for other howardites.     

Characteristics and implications of some Loch Lomond Stadial moraine ridges and later landforms,eastern Lake District,northern England

Moraine ridges and mounds of inferred Loch Lomond Stadial (LLS) age have been mapped at three sites (Fordingdale, Swindale and Wet Sleddale) in part of the eastern Lake District, northern England, and indicate glaciers were more widespread than envisaged by Sissons (1980, Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 71, pp. 13–27). The moraines delimit closely the downslope/downvalley limits of the former glaciers but there is no geomorphological evidence with which to define their upslope/upvalley margins. The former glaciers are considered to have been nourished within the confines of their individual valley, cirque and hillside embayment respectively, rather than being outlet glaciers of plateau icefields. Estimated equilibrium line altitudes (ELAs) are within the range of values determined previously for LLS glaciers in the Lake District and do not necessitate revision of established palaeoclimatic parameters. Individual ELAs were probably influenced by local factors; all three former glaciers had accumulation-area aspects between north and east, limiting the impact of direct solar radiation during the ablation season, and were adjacent to extensive areas of high ground to the west and/or south that would have facilitated transfer of snow to their surfaces by winds from those directions. In Fordingdale, three essentially contemporaneous depositional landforms occur upslope of the moraines and are considered to represent hillslope adjustments following wastage of glacier ice from the site. © 1998 John Wiley & Sons, Ltd.     

The Biology of Upogebia pusilla (Petagna) (Decapoda, Thalassinidea) I. The Burrows

Abstract. The biology of the thalassinidean shrimp Upogebia pusilla was studied on a tidal flat in the Lagoon of Grado (Northern Adriatic). Burrows were investigated using in situ resin casting and with additional in situ and laboratory observations. Burrows show a basic pattern consisting of a U or a double U with turning chambers and a vertical shaft. Mean burrow diameter depends on animal size, it is smaller than the rigid carapace of the animal. Dimensions, distance between openings, depth of U, total depth, volume and surface are size dependent. The burrow wall is smooth and oxidized. Burrows are always inhabited by a single shrimp. Although they overlap, they are never interconnected. They are mainly constructed by compression of the sediment and are relatively permanent structures. A comparison of the burrows of Thalassinidea with regard to shape, number and appearance of openings, dimensions, properties of the burrow wall and dynamics is given.