Temporal and spatial variations in the biogeochemical cycling of cobalt in two urban estuaries: Hudson River Estuary and San Francisco Bay

Despite the fact that Co is an essential trace element for the growth of marine phytoplankton, there is very limited information on the cycling of this trace metal in the marine environment. We report here the distribution of dissolved (<0.4 μm) and particulate (>0.4 μm) Co in surface waters of the Hudson River Estuary (HRE) and San Francisco Bay (SFB). Samples were collected during several cruises (from 1990 to 1995 in SFB and from 1995 to 1997 in the HRE) along the whole salinity gradient. Dissolved Co concentrations (mean±1 standard deviation) were nearly identical in magnitude in both estuaries despite differences in climate, hydrography, riverine-flow conditions and land-usage (HRE=0.91±0.61 nM; SFB=1.12±0.69 nM). Dissolved Co levels in each system showed non-conservative distributions when plotted as a function of salinity, with increasing concentrations downstream from the riverine end-members. Desorption from suspended particulates and sewage inputs, therefore, seems to be the major processes responsible for the non-conservative behavior of Co observed. Mass balance estimates also indicated that most of the estuarine Co is exported out of both estuaries, indicating that they and other estuarine systems are principal sources of this essential trace element to the open ocean.     

Semisubmersible response to transient ice forces

The paper presents an analytical and experimental study on the transient response of semisubmersibles to bergybit impact and the strength of bergybit ice to high strain-rate loadings. Two approaches have been proposed for the solution of the semisubmersible-bergybit interaction problem, one using the energy approach and the other using the conventional structural dynamics approach with initial velocity conditions. In addition the local behaviour of the impacted regions have been analysed for deformation and failure. Numerical results have been given for local behaviour of an impacted column and global behaviour of semisubmersible-bergybit system. Experimental study has been reported on the impact strength of iceberg ice at strain rates of 10⁻³, 10⁻² and 10⁻¹; the indentation impact strength of ice is found to be 3–4 times the unaixial compressive strength, at the same strain rate.     

Distributions of dissolved and particulate biogenic thiols in the subartic Pacific Ocean

Dissolved and particulate concentrations of the biogenic thiols cysteine (Cys), arginine–cysteine (Arg–Cys), glutamine–cysteine (Gln–Cys), γ-glutamate–cysteine (γ-Glu–Cys) and glutathione (GSH) were measured in the subartic Pacific Ocean in the summer of 2003 using high performance liquid chromatography (HPLC) with precolumn derivatization as reported in previous work. In this study, a preconcentration protocol for the derivatized thiols was utilized to extend detection limits of dissolved thiols to picomolar levels. The measured concentrations of particulate and dissolved thiols were uncoupled, with distinctive depth profiles and large differences in the particulate to dissolved ratios between individual compounds. Glutathione was the most abundant particulate thiol whereas the most abundant dissolved thiol was γ-Glu–Cys, with concentrations as high as 15 nM. Given the relatively small pool of intracellular γ-Glu–Cys and the very low dissolved concentrations of GSH, we hypothesize that glutathione released from cells is rapidly converted to the potentially degradation resistant γ-Glu–Cys outside the cell. The relatively high concentrations of other dissolved thiols compared to particulate concentrations implies both biological exudation and slow degradation rates. Some thiols appear to vary with changes in nutrient availability but this effect is difficult to decouple from changes in community structure inferred from pigment analyses. Dissolved thiol concentrations also exceed typical metal concentrations in the subartic Pacific, supporting previous arguments that they may be important in metal speciation.     

Different cardiac response to copper in limpets from metal polluted and clean shores of Hong Kong

The gastropod limpet, Cellana grata, is common on moderately exposed to exposed Hong Kong rocky shores. On the basis of the existing literature on trace metal contamination in Hong Kong, four sites were identified, representative of highly polluted (Aberdeen and Lei Yue Mun) and clean (Cape d'Aguilar and Clear Water Bay) conditions. Limpets from the two polluted sites showed similar, but significantly higher body concentrations of copper than limpets from the two clean sites, which were also similar. Non-invasive measurements of cardiac activity of limpets from the four sites showed between site differences in baseline heart rates under standard seawater, irrespective of pollution level. When acutely exposed to water borne copper (2 h, 0.5+/-0.06 SD ppm), however, limpets from clean sites showed a significantly higher increase in inter-beating time (bradycardia) than those from polluted sites. These results highlight the potential use of cardiac activity to assess the exposure of natural populations of limpets to trace metal pollution.     

Geologic evolution of the Canarian Islands of Lanzarote, Fuerteventura, Gran Canaria and La Gomera and comparison of landslides at these islands with those at Tenerife, La Palma and El Hierro

In this paper we discuss the results of a swath bathymetric investigation of the Canary archipelago offshore area. These new data indicate that volcanism is pervasive throughout the seafloor in the region, much more that would be suggested by the islands. We have mapped tens of volcanic edifices between Fuerteventura and Gran Canaria and offshore Tenerife, La Gomera, El Hierro and La Palma. Volcanic flows are present between Tenerife and La Gomera and salic necks dominate the eastern insular slope of La Gomera. This bathymetry also supports land geologic studies that indicate that the oceanic archipelago has acquired its present morphology in part by mass wasting, a consequence of the collapse of the volcanic edifices. In the younger islands, Tenerife, La Palma and El Hierro, the Quaternary (1.2 to 0.15 Ma) debris avalanches are readily recognizable and can be traced offshore for distances measured in tens of km. Off the older islands, Lanzarote, Fuerteventura, Gran Canaria and La Gomera (<20 to 3.5 Ma), the avalanches have been obscured by subsequent turbidity current deposition and erosion as well as hemipelagic processes. The failure offshore western Lanzarote is in the form of a ramp at the base of the insular slope bound on the seaward side by a scarp. Its size and the lack of evidence of rotation along its landwards side precludes the possibility that it is a slump. It probably represents a slide whose outer scarp is caused by break-up of the slide. Mounds on the ramp’s surface may represent post-displacement volcanic structures or exotic blocks transported to their present locations by the slide. The failures offshore Fuerteventura are so large that, although they occurred in the Miocene-Pliocene, exotic blocks displaced from upslope are still recognizable in the insular margin morphology. The Canary Island insular margin appears to be a creation of Miocene-Pliocene mass wasting and more recent turbidity current deposition and erosion, and hemilepagic deposition. Failures offshore La Gomera are due to debris flows and/or turbidity currents. These events have obscured earlier mass wasting events. An erratum to this article is available at .     

On the use of grate-turbulators for tests of microstructural probes

Highly sensitive microstructural probes subjected to noise disturbances are free of these in laboratory tests. This leads necessarily to the working out of methods for complex testsin situ. The paper reports on the successful use for this purpose of a grate (net) suspended from a free-falling probe. The grate sets up turbulence with reproducible structure in the area of sensor location.UDK 551.46.085     

New sets of wavelet-forming functions

One of the most efficient tools of studying meteorological and climatic time series is wavelet analysis, which allows local properties of a nonstationary time series to be examined. New sets of continuous and discrete wavelet-forming functions are proposed. All proposed wavelets are finite (have a bounded carrier), even, and well localized in the spectral space.