Marine pipeline dynamic response to waves from directional wave spectra

A methodology has been developed to calculate the dynamic probabilistic movement and resulting stresses for marine pipelines subjected to storm waves. A directional wave spectrum is used with a Fourier series expansion to simulate short-crested waves and calculate their loads on the pipeline. The pipeline displacements resulting from these loads are solutions to the time-dependent beam-column equation which also includes the soil resistance as external loading. The statistics of the displacements for individual waves are combined with the wave statistics for a given period of time, e.g. pipeline lifetime, to generate probabilistic estimates for net pipeline movement. On the basis of displacements for specified probability levels the pipeline configuration is obtained from which pipeline stresses can be estimated using structural considerations, e.g. pipeline stiffness, end restraints, etc.     

Some General Properties of Transverse Motions of the Geostrophic Front

Within the framework of the reduced-gravity model of the ocean taking into account the effect of friction in the Rayleigh form, we study the two-dimensional problem of nonlinear motions of a subsurface front of finite width. We consider the conservation laws and the character of motion of the center-of-mass of the cross section of the front and their variations caused by the losses of energy. For fields with special structure, the problem is reduced to the solution of a system of nonlinear ordinary differential equations. It is shown that the initially geostrophic frontal current decays with time according to a power law. The deviations of the initial state of the front from the state of geostrophic balance result in the generation of superinertial oscillations of the hydrodynamic fields.     

Histopathological biomarkers in estuarine fish species for the assessment of biological effects of contaminants

The increasing emphasis on the assessment and monitoring of estuarine ecosystems has highlighted the need to deploy appropriate biological indices for these locations. Fish diseases and histopathology, with a broad range of causes, are increasingly being used as indicators of environmental stress since they provide a definite biological end-point of historical exposure. This study reports on the histopathological alterations observed in selected organs and tissues of three species of estuarine fish (Platichthys flesus, Pomatoschistus minutus and Zoarces viviparus), captured from four British estuaries (the Tyne, Tees, Mersey and Alde), differently impacted by contaminants, including PAHs. A biannual sampling regime was used to identify the important seasonal variations that occur in terms of the observed biological effects. Inflammatory lesions and hepatocellular fibrillar inclusions attained their highest prevalence in P. flesus captured from the Tyne, Tees and Mersey. The presence of pre-neoplastic and neoplastic toxicopathic lesions was highest in P. flesus captured from these sites, when compared to fish from the Aide reference site. In particular, the prevalence of hepatic foci of cellular alteration (up to 43.3%) and hepatocellular adenoma (up to 10%) were highest in P. flesus captured from the Mersey estuary. Intersex (ovotestis) was only recorded in male P.flesus captured from the Mersey estuary (up to 8.3%) and from male Z. viviparous captured from the Tyne estuary (25%). Pathologies associated with the gill and the kidney were also most prevalent in fish captured from the Tyne, Tees and Mersey estuaries. This study has successfully applied histopathology to an estuarine monitoring program, both for the recording of toxicopathic lesions in the liver and other organs, and for the detection of the endpoint of endocrine disruption, intersex. As such, it provides a powerful integrative tool for the assessment of biological effects of contaminants in these environments.     

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.     

Eastern and Western Poor Cod (Trisopterus minutus capelanus) Populations in the Mediterranean Sea: Evidence from Allozyme and Minisatellite Loci

Abstract. Nine allozyme and two minisatellite loci were used to investigate potential genetic differentiation among three samples of Mediterranean poor cod, Trisopterus minutus capelanus, from the Gulf of Lion, the Tuscan Archipelago and the Aegean Sea. Both types of markers showed consistent results, with F_ST values of 0.0262 and 0.0296 (P < 0.0015, after Bonferroni correction for multiple tests) for allozymes and minisatellites, respectively. Allele frequency heterogeneity tests between pairs of samples showed a clear separation between the two western Mediterranean samples (Gulf of Lion, Tuscan Archipelago) and the eastern one (Aegean Sea). The results indicate that at least two reproductively isolated populations of poor cod occur in the Mediterranean.     

Seasonality and selectivity in the feeding ecology and reproductive biology of deep-sea bathyal holothurians

Chlorophyll and carotenoid pigments were determined from the gut sediments of five species of bathyal holothurian in the NE Atlantic, sampled shortly after the spring/summer phytoplankton bloom in 2001 and prior to the spring bloom in 2002. Three species, Laetmogone violacea, Paroriza pallens and Bathyplotes natans, sampled within a similar depth range (900–1100 m) in the summer of 2001 showed significant differences in their chlorophyll and carotenoid pigment concentrations. This suggests they may select for slightly different components from the available food resource. Four species sampled in early spring 2002, Laetmogone violacea, Paroriza pallens, Benthogone rosea and Benthothuria funebris, also had significant differences in their pigment concentrations. These species were sampled over a wider depth range (1000–3100 m) showing a bathymetric trend in pigment concentrations. There was a distinct seasonal change in the composition and concentration of the pigments, linked to a reduction in the availability of fresh organic material during autumn and winter periods.Ovarian tissue was also examined. The carotenoid pigments found in the ovary also occurred in the OM ingested by the holothurians. The dominant gonadal carotenoid pigments were β-carotene, echinenone and zeaxanthin. The potential for using these carotenoids to gain a competitive advantage through selectivity of chlorophyll and carotenoid pigment biomarkers are discussed in relation to competition for food resources by deposit-feeders. The results were also compared with selectivity in abyssal species.     

Changes in the hydrography of Central California waters associated with the 1997–98 El Niño

Oceanographic conditions off Central California were monitored by means of a series of 13 hydrographic cruises between February 1997 and January 1999, which measured water properties along an oceanographic section perpendicular to the California Coast. The 1997–98 El Niño event was defined by higher than normal sea levels at Monterey, which began in June 1997, peaked in November 1997, and returned to normal in March 1998. The warming took place in two distinct periods. During June and July 1997, the sea level increased as a result of stronger than normal coastal warming below 200 dbars and within 100 km of the coast, which was associated with poleward flow of saltier waters. During this period, deeper (400–1000 dbar) waters between 150–200 km from shore were also warmed and became more saline. Subsequently, sea level continued to rise through January 1998, mostly as a result of the warming above 200 dbars although, after a brief period of cooling in September 1997, waters below 200 dbar were also warmer than normal during this period. This winter warm anomaly was also coastally trapped, extending 200 km from shore and was accompanied by cooler and fresher water in the offshore California current. In March and April 1998, sea level dropped quickly to normal levels and inshore waters were fresher and warmer than the previous spring and flowed southward.The warming was consistent with equatorial forcing of Central California waters via propagation of Kelvin or coastally-trapped waves. The observed change in heat content associated with the 1997–98 El Niño was the same as that observed during the previous seasonal cycle. The warming and freshening events were similar to events observed during the 1957–58 and 1982–83 El Niños.     

Stratigraphy of the sediment infill in Bosphorus Strait: water exchange between the Black and Mediterranean Seas during the last glacial Holocene

The sediment infill over the Paleozoic bedrock in the Bosphorus Strait consists of four sedimentary units which were deposited in the last 26,000 ¹⁴C years B.P. The stratigraphy of these units suggests that this part of the Bosphorus was a freshwater lake between 26,000 and 5,300 ¹⁴C years B.P., depositing sands with a freshwater mollusc fauna of Black Sea neo-euxinian affinity (Dreissena rostriformis, Dreissena polymorpha, and Monodacna pontica). The first appearance of euryhaline Mediterranean molluscs (e.g., Ostrea edulis, Mytilus edulis) was observed at 5,300 ¹⁴C years B.P. in this part of the Bosphorus. Deposition of coarse Mytilus-bank and Ostrea-bank units suggests that the establishment of the present dual-flow regime in the Bosphorus took place at about 4,400 ¹⁴C years B.P.