Environmental effects of North Sea oil operations

To appreciate the impact of large-scale industrial operations on the marine environment requires a range of scientific studies which ideally should include physical, chemical and biological surveys of the various environmental compartments likely to be contaminated, linked with experiments designed to detect and quantify effects. More finely focused studies can then provide an evaluation of the impact. In relation to North Sea oil activities, this type of approach suggests that at present significant offshore contamination is found only in the sediments close to platforms using oil-based drilling muds.     

Environmental effects of the use of oil-based drilling muds in the North Sea

The environmental effects of oil-based drilling mud cuttings have been evaluated using all the data available from monitoring around North Sea platforms. Beneath the platforms making extensive use of oil-based drilling muds the natural sediment is buried by cuttings and the hydrocarbon concentration 250 m from the platforms may be 1000 times background, but the concentration gradient is very steep and background levels are usually reached 2000–3000 m from the platform.The extent of the biological effects appear to be greater from the use of oil-based muds than from water-based muds. Beyond the area of physical smothering the effects of oil-based mud cuttings may be due to organic enrichment or to the toxicity of the aromatic fraction of the oil. Despite the large scale of inputs, in all the fields studied the major deleterious biological effects occurred within 500 m of the platform. Surrounding the area of major impact was a transition zone in which subtle biological effects could be detected as community parameters returned to normal, generally within 400–1000 m.The shape and extent of this zone varied and was largely determined by the current regime and scale of the drilling operation. Elevated hydrocarbon concentrations were detected beyond the areas of biological effects.     

The mixed-bed glacial landform imprint of the North Sea Lobe in the western North Sea

During the last glacial cycle an intriguing feature of the British-Irish Ice Sheet was the North Sea Lobe (NSL); fed from the Firth of Forth and which flowed south and parallel to the English east coast. The controls on the formation and behaviour of the NSL have long been debated, but in the southern North Sea recent work suggests the NSL formed a dynamic, oscillating terrestrial margin operating over a deforming bed. Further north, however, little is known of the behaviour of the NSL or under what conditions it operated. This paper analyses new acoustic, sedimentary and geomorphic data in order to evaluate the glacial landsystem imprint and deglacial history of the NSL offshore from NE England. Subglacial tills (AF2/3) form a discontinuous mosaic interspersed with bedrock outcrops across the seafloor, with the partial excavation and advection of subglacial sediment during both advance and retreat producing mega-scale glacial lineations and grounding zone wedges. The resultant ‘mixed-bed’ glacial landsystem is the product of a dynamic switch from a terrestrial piedmont-lobe margin with a net surplus of sediment to a partially erosive, quasi-stable, marine-terminating, ice stream lobe as the NSL withdrew northwards. Glaciomarine sediments (AF4) drape the underlying subglacial mixed-bed imprint and point to a switch to tidewater conditions between 19.9 and 16.5 ka cal BP as the North Sea became inundated. The dominant controls on NSL recession during this period were changing ice flux through the Firth of Forth ice stream onset zone and water depths at the grounding line; the development of the mixed-bed landsystem being a response to grounding line instability. © 2018 John Wiley & Sons, Ltd.     

Bottom irregularities in the North Sea

Summary A pressure transducer fixed to a sledge was towed over the bottom of the sea. Pressure variations corresponding to bottom displacement variations were recorded along different profiles in the area west of Sylt. From the time series obtained power spectra of bottom irregularities were computed as a function of wavenumberk or wavelength . Total rms bottom displacement in the wavelength band 50 to 500 m ranges from 3 cm to 36 cm depending on the location of the profile. Presumedly this is due to different types of sediment. Therefore the area cannot be considered as uniform or isotropic concerning the spatial and directional distribution of bottom irregularities. The approximation of spectra byE(k)k– yields -values between 0.4 and 2.9.

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Bodenunebenheiten in der Nordsee

Zusammenfassung Mit Hilfe einer Druckdose, die von einem Schiff aus über den Meeresboden gezogen wurde, konnten auf ausgewählten Profilen westlich von Sylt Bodenunebenheiten registriert werden. Aus den gewonnenen Zeitserien wurden SpektrenE(k) für die Wellenzahlenk bzw. für die Wellenlänge berechnet. Hieraus lassen sich die Amplituden der Bodenunebenheiten im Wellenlängenbereich von 20 bis 500 m bestimmen. Die effektive Bodenwelligkeit im Bereich von 50 bis 500 m liegt je nach Profil zwischen 3 cm und 36 cm. Die Ursache dafür ist möglicherweise in der unterschiedlichen Sedimentzusammensetzung zu suchen. Eine Isotropie des Bodenspektrums im Meßgebiet ist nicht vorhanden. Die Annäherung der Spektren durchE(k)k– ergibt -Werte zwischen 0,4 und 2,9.

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Irrégularités du fond en Mer du Nord

Résumé Un manomètre enregistreur fixé à un traîneau a été remorqué sur le fond de la mer. Les variations de pression correspondant aux variations du fond ont été enregistrées le long de différents profils dans la zone Ouest de Sylt. A partir de la série de mesures obtenues, on a calculé le spectre de puissance des irrégularités du fond en fonction du nombre d'ondek ou de la longueur d'onde . Globalement, les variations du fond dans la bande de longueurs d'onde de 50 à 500 m varient de 3 à 36 cm en moyenne quadratique selon la situation du profil. On présume que cela est dû aux différents types de sédiments. Aussi, la zone ne peut pas être considérée comme uniforme ou isotrope en ce qui concerne la distribution dans l'espace et en direction des irrégularités du fond. L'approximation de spectres parE(k)k– donne des valeurs de comprises entre 0,4 et 2,9.

     

Plankton prognoses in the North Sea

Ocean Dynamics - Our understanding of the marine ecosystem is expressed in our ability to predict ecological processes. Several approaches are compared to make such predictions on plankton...     

Trace metals in the North Sea

The distribution of zinc, manganese, nickel, copper and cadmium in water and biological material has been measured in the southern North Sea and Straits of Dover, and off the north-east coast of England. These investigations provide baseline values against which future pollution changes can be measured.     

Gas-induced erosion features in the North Sea

Pockmarks are prominent features on the seafloor at two main regions of the North Sea, the South Fladen area and the Norwegian Trench. The pockmarks vary in size from 5 m across to about 150 m and in depth from 1 m to about 20 m. Some of the features consist of several very small ‘unit-pockmarks’. These are probably gas-induced erosion features and found only in soft, finegrained, marine and glaciomarine sediments. They are probably caused by shallow- or deep-seated gas (or fluid) release through the seabed, whereby the finest particles are thrown into suspension and redistributed by nearbottom currents. On the North Sea Plateau a small pockmarked area has recently been found. A close relationship exists here between mobile gas in the upper sediments, faulting in the soft sediments and the morphology of the seabed. Other morphological features in the North Sea such as ‘coast parallel depressions’ and ‘elongated depressions’ or terraces are also interpreted here as gas-induced erosion products. This applies, yet again, to the ‘mottled seabed’ features, which appear as patches of high reflectivity on side scan sonar records from the North Sea Plateau; they correspond to shallow seabed depressions on the deep towed boomer records. Judging from reported observations from several shallow seas world wide volatile transport through the seabed is probably quite common and several morphological features are undoubtably induced by this process. Several erosion features of similar origin are probably common, also, in deep ocean basins.     

Trace metals in the northern North Sea

Cadmium, lead and copper have been determined in the dissolved and particulate phase for surface waters of the northern North Sea. Dissolved cadmium and copper show concentration gradients associated with salinity fronts which mark the boundary between coastal and ocean waters; lead does not. The particulate phase is shown to represent only a small fraction of the total metal concentration. Processes likely to be responsible for the observed distribution are discussed.     

Education challenges in the North Sea area

This paper introduces the North Sea as a fast evolving coastal ecosystem. The variability of natural conditions relates to the global climatic change and to human disturbances, which originate regionally. Education is an integral part of the strategy to improve environmental awareness. Considering contemporary challenges for educating the wider public about the main issues of environmental concern, attention is paid to various plans, which are being developed in North-Western Europe from primary schools to universities. "Learning for life" relies on an opening of the vocation of traditional universities and on the creation of a European university. Sharing resources in a competitive environment is one response given by British universities in the framework of a Discipline Network in Coastal Sciences and Management in 1996-2000. Networking is truly the key to a fast evolving teaching and learning context, notably in relation to ever developing information and communication technologies. The dissemination of scientific information is primordial in this context; a case study relating to the European project "Marine biodiversity in Europe" (BIOMARE) demonstrates the need for an elaborated strategy leading to socio-economic considerations. Empowering communities and governance are the main possible outcomes of such an enlarged approach to education, involving teachers, students, researchers, professionals, and volunteers. Proposals are made for amplifying the involvement of non-scientists into scientific research and its applications to management. Finally, a case is made for facilitating the mobility of all concerned, with a view to annihilate language and cultural barriers.     

At-sea detection of derelict fishing gear in the North Pacific: an overview

There are numerous known impacts of derelict fishing gear (DFG) to marine ecosystems and safe navigation around the world. To mitigate these impacts, the preemptive detection and removal of DFG at sea are being pursued. This special issue focuses on the North Pacific Ocean because of historic and ongoing research on DFG in the area, particularly as it relates to the Hawaiian Archipelago. In order to develop an effective detection strategy, information and expertise from three disciplines must be integrated: marine debris, oceanography, and remote sensing technology. Building upon results and discussions during a workshop held in December 2008, this special issue provides both results of original research and review papers, pursuing each discipline as it relates to DFG and outlining a multi-faceted strategy to effectively detect DFG at sea. This strategy serves as a roadmap, taking us closer to realizing the goal of detecting and removing DFG at sea.