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Following decades of declines, populations of large fish recently started to increase in the North Sea, presumably due to reduced fishing pressure. However, population recovery may be too readily claimed, since standardised sampling of fish stocks commenced only in the 1970s, well after many species had already collapsed. A true recovery must be seen from a long-term perspective. The critically endangered common skate (Dipturus batis, Rajidae) species complex is an example of a large-bodied fish that mostly disappeared before standardised monitoring took place. Here, we put the recent increase in population size into a 120-year perspective, throughout three geographical divisions in the North Sea. We analysed a large range of mostly undisclosed historical data and contemporary sources. A reconstruction of Dutch commercial landings data confirms that the species used to be very abundant between 1901 and 1920, and shows how it steadily declined from 1920 onwards until it got extirpated around 1970. Based on a quantitative analysis of standardised catch numbers from fishery-independent surveys time, we conclude that the current abundance of the species is still below historical baselines and represents a local recovery at most. We further demonstrate a prominent and consistent pattern in size distribution, with larger (mature) individuals only occurring in the northern North Sea. A large dataset on historical stomach contents from the central North Sea confirmed the diet of young common skate, which consisted predominantly of shrimps. Our review exemplifies the importance of marine historical ecology to deduce the natural richness of the North Sea., Author(s): Roeland A. Bom [sup.1] , Aafke Brader [sup.2] , Jurgen Batsleer [sup.3] , Jan-Jaap Poos [sup.3] [sup.4] , Henk W. van der Veer [sup.1] , Anieke van Leeuwen [sup.1] [...]

The seismic character of slide deposits is typically described as structureless or chaotic. However, 3D seismic data from the northern flank of the North Sea Fan reveal recognizable internal, penetrative structures within the Tampen Slide deposits. The study of its seismic attributes allowed an integrated characterization of the slide deposits and has shown distinctive acoustic fabrics, both at the top and base of the slide deposit, which are interpreted to be the expression of internal deformation structures. Based on their geometry, four main seismic fabric types have been defined: anastomosing, curvilinear, rectilinear and wispy. The spatial distribution of the fabric was mainly controlled by a topographic high present on the sea-bed at the time of the gravitational collapse, which influenced the transport of material. Areas of distinct fabrics are thought to reflect different flow behaviour during the latest stages of the mass movement and could be considered kinematic indicators. The results give new insights into the transport and deformation processes of submarine mass movements and highlight the potential of detailed analysis of 3D seismic data. doi: 10.1144/0016-76492009-047.

In the past years the existence of freak waves has been affirmed by observations, registrations, and severe accidents. Many publications investigated the occurrence of extreme waves, their characteristics and their impact on offshore structures, but their formation process is still under discussion. One of the famous real world registrations is the so called 'New Year wave,' recorded in the North Sea at the Draupner jacket platform on January 1st, 1995. Since there is only a single point registration available, it is not possible to draw conclusions on the spatial development in front of and behind the point of registration, which is indispensable for a complete understanding of this phenomenon. This paper presents the spatial development of the New Year wave generated in a model basin. To transfer the recorded New Year wave into the wave tank, an optimization approach for the experimental generation of wave sequences with predefined characteristics is applied. The extreme sea state obtained with this method is measured at different locations in the tank, in a range from 2163 m (full scale) ahead of to 1470 m behind the target position--520 registrations altogether The focus lies on the detailed description of a possible evolution of the New Year wave over a large area and time interval. It is observed that the extreme wave at the target position develops mainly from a wave group of three smaller waves. The group velocity, wave propagation, and the energy flux of this wave group are analyzed, in particular. [DOI: 10.1115/1.3160533]

A shark-tooth apatite [delta][sup.18]O record of the early Palaeogene North Sea reflects changes in regional hydrography by showing variable temperatures and salinities. A 2-4 Ma period in the early Eocene was particularly influenced by substantial surface-water freshening, indicated by a 3-4[per thousand] reduction of [delta][sup.18] O values. The magnitude of the [delta][sup.18]O decrease indicates a depletion in [sup.18]O of surface waters by 2-3[per thousand] relative to Eocene mean ocean water. This value is lower than that of coeval lakes reconstructed from freshwater gastropod [delta][sup.18]O values from the Paris Basin, suggesting that large rivers with high-latitude catchment areas drained into the North Sea. The period of surface-water freshening began close to the Palaeocene--Eocene thermal maximum, when relative sea-level fall, tectonic uplift and basaltic volcanism caused a temporary isolation of the North Sea. North Atlantic and North Sea surface waters became reconnected during a series of early Eocene transgressions.

We study the spatial and seasonal variability of phytoplankton biomass (as phytoplankton color) in relation to the environmental conditions in the North Sea using data from the Continuous Plankton Recorder survey. By using only environmental fields and location as predictor variables we developed a nonparametric model (generalized additive model) to empirically explore how key environmental factors modulate the spatio-temporal patterns of the seasonal cycle of algal biomass as well as how these relate to the ~1988 North Sea regime shift. Solar radiation, as manifest through changes of sea surface temperature (SST), was a key factor not only in the seasonal cycle but also as a driver of the shift. The pronounced increase in SST and in wind speed after the 1980s resulted in an extension of the season favorable for phytoplankton growth. Nutrients appeared to be unimportant as explanatory variables for the observed spatio-temporal pattern, implying that they were not generally limiting factors. Under the new climatic regime the carrying capacity of the whole system has been increased and the southern North Sea, where the environmental changes have been more pronounced, reached a new maximum.

Abstract: We have calculated a time series of larval transport indices for the central and southern North Sea covering 1970-2004, using a combined three-dimensional hydrodynamic and individual-based modelling framework for [...]

Abstract: Acoustic data are often collected during bottom trawl surveys. Their use can potentially improve the precision and accuracy of fish abundance estimates if acoustic data collected between trawl stations [...]

The 36- square kilometer dune area along the North Sea Coast, which is used by the Amsterdam Water Supply since 1853 to provide drinking water to Amsterdam, is studied to illustrate the need for calibration of a suitable model, the forecast of which can influence property and livelihood. The study suggests from the perspective of modeling and calibration that in addition to applying the best statistical calibration methods, all available information should be included simultaneously, which covers all small- and large-scale situations/stresses for which data are available.

Abstract: We analysed 12 microsatellite DNA loci in temporal samples (1980, 1994, and 2002) from the only remaining indigenous population of the North Sea houting (Coregonus oxyrhynchus) in the Vidaa [...]

Since the substantial loss of subtidal eelgrass (Zostera marina L.) in the 1930s, seagrass beds in the Wadden Sea are limited to the intertidal zone and dominated by Z. noltii Hornem. This study deals with the effect of vegetated tidal flats on quantities of mobile epifauna and proves empirically the function of seagrass canopies as a refuge for marine animals remaining in the intertidal zone at ebb tide. Drop-trap samples were taken in the Sylt-Romo Bight, a shallow tidal basin in the northern Wadden Sea, on vegetated and unvegetated tidal flats during July and August 2002, and during the entire growth period of Z. noltii from May to September in 2003. The species composition in Z. noltii and bare sand flats showed minor differences since only two isopod species (Idotea baltica and I. chelipes) occurred on Z. noltii flats exclusively. Juvenile shore crabs (Carcinus maenas L.), brown shrimps (Crangon crangon L.) and common gobies (Pomatoschistus microps Kroyer) were also found abundantly on bare sand flats. However, the results showed significantly higher abundances and production of these dominant species on vegetated tidal flats. Additionally, the analyses of faunal size classes indicated higher percentages of small individuals in the seagrass bed during the entire sampling period. Despite drastic diurnal fluctuations of dissolved oxygen at low tide, faunal density in the residual water layer remaining in seagrass canopies at ebb tide was found to be consistently higher than that found in artificially created tide-pool units. Although species composition of mobile epifauna did not basically differ between vegetated and unvegetated tidal flats, Z. noltii beds are considered to contribute quantitatively to the function of tidal flats, as an extended juvenile habitat for some of the most important species of the Wadden Sea food web., Introduction The shallow waters of the Wadden Sea are generally considered as important juvenile habitats contributing to the development of species stocks and faunal composition of the North Sea (Zijlstra [...]

Fishing has wide-ranging impacts on marine ecosystems. One of the most pervasive signs of intensive fishing is 'fishing down the food web', with landings increasingly dominated by smaller species from lower trophic levels. Decreases in the trophic level of landings are assumed to reflect those in fish communities, because size-selective mortality causes decreases in the relative abundance of larger species and in mean body size within species. However, existing analyses of fishing impacts on the trophic level of fish communities have focused on the role of changes in species composition rather than size composition. This will provide a biased assessment of the magnitude of fishing impacts, because fishes feed at different trophic levels as they grow. Here, we combine body size versus trophic level relationships for North Sea fishes (trophic level assessed using nitrogen stable-isotope analysis) with species--size--abundance data from two time-series of trawl-survey data (whole North Sea 1982-2000, central and northern North Sea 1925-1996) to predict long-term trends in the trophic structure of the North Sea fish community. Analyses of the 1982-2000 time-series showed that there was a slow but progressive decline in the trophic level of the demersal community, while there was no trend in the trophic level of the combined pelagic and demersal community. Analyses of the longer time-series suggested that there was no trend in the trophic level of the demersal community. We related temporal changes in trophic level to temporal changes in the slopes of normalised biomass size-spectra (which theoretically represent the trophic structure of the community), mean [log.sub.2] body mass and mean [log.sub.2] maximum body mass. While the size-based metrics of community structure showed long-term trends that were consistent with the effects of increased fishery exploitation, these trends were only correlated with trophic level for the demersal community. Our analysis suggests that the effects of fishing on the trophic structure of fish communities can be much more complex than previously assumed. This is a consequence of sampled communities not reflecting all the pathways of energy transfer in a marine ecosystem and of the absence of historical data on temporal and spatial changes in the trophic level of individuals. For the North Sea fish community, changes in size structure due to the differential effects of fishing on species and populations with different life histories are a stronger and more universal indicator of fishing effects than changes in mean trophic level.

The interannual variations in abundance of the calanoid copepod Centropages typicus (Kroyer) in the North Sea are significantly positively correlated with seasurface temperature. The same is true of Calanus helgolandicus Claus. In both cases there was a deviation from the close relationship with temperature for several years in the early to mid-1980s. Centropages typicus was less abundant than expected from 1981 to 1984, but Calanus helgolandicus recovered from a period of lower than expected abundance from 1980 to 1982, to become more abundant than expected from 1983 to 1987. The difference between the responses of the two species to climate-driven changes in seasonal cycles of phytoplankton is interpreted in relation to their biology. Geographical variations of the interannual variability and seasonal cycles of Centropages typicus in the North Sea are analysed. The centre of the population of this species in the North Sea is in the German and Southern Bights, but the variations in abundance may be partly influenced by advection from areas to the west of Britain.

Haplotype frequency distribution and discriminatory power of two mtDNA fragments has been studied in a marine pelagic teleost, Atlantic herring. Data suggest that the very skewed haplotype distribution of many mtDNA markers may be one of the reasons for the more infrequent detection of population differentiation compared to microsatellites.

The optics of chromophoric dissolved organic matter (CDOM) in the Greenland Sea were investigated and compared to results from earlier studies in the Southeastern North Sea. Absorption at 375 nm ([a.sub.375]) in the Greenland Sea varied from 0.77 [m.sup.-1] to the detection limit of our instrument (0.05 [m.sup.-1]), with the highest values found during summer. The spectral slope coefficient (S) ranged from 8.2 to 26.4 [micro][m.sup.-1] with the highest values occurring during winter. Seasonal variations in the in situ production and degradation of CDOM where shown to be responsible for the trends seen. A negative correlation between S and [a.sub.375] was evident in the Greenland Sea and differed noticeably from that found in coastal waters. The differing S-[a.sub.375] behavior of CDOM known to be of terrestrial origin allowed the development of an algorithm for the differentiation between marine and terrestrial organic matter. The behavior of marine CDOM was modeled by S = 7.4 + 1.1/[a.sub.375].

Clay mineral analyses of 300 surface sediment samples in the Skagerrak, Kattegatt, and the southwestern Baltic Sea have yielded qualitative evidence of considerable advective transport of suspended fine-grained terrigenous matter from the North Sea to the Baltic Sea. The transport is related to periodic near-bottom saltwater inflows, whereas the outflow of less saline surface water carries little suspended matter of Baltic origin. Although there are not enough data at this stage for exact budgeting, it is evident that this process contributes considerably to the sedimentation in the southwestern Baltic Sea and has probably done so during the past 6 k.y. It has been neglected so far. Hence, the southwestern Baltic Sea is believed to be a final sink for fine-grained North Sea material. This fact is corroborated by a compilation of sediment thickness data in the major basins of the Baltic Sea, which shows that the shallow southwestern basins accumulate more Holocene mud than the eastern and central basins. The external terrigenous matter also has far-reaching implications concerning the assessment of organic and inorganic pollutants, which are bound to fine-grained, clayey material. The Baltic Sea can no longer be regarded as a closed sedimentary system, and pollution assessment and control must be considered with a wider perspective. Keywords: Baltic Sea, clay minerals, advection, suspended materials, North Sea.

The Baltic Sea, its environmental status and its ecosystem from the 1940s to today and looking ahead are discussed with attention to eutrophication, water transparency and effects on bladderwrack, a seaweed. Adequate knowledge of the ecosystem and elimination of toxics is available to guide in restoration of the environment of the sea, but large societal changes, especially in transportation, industry and agriculture, would be necessary to eliminate pollution, and political issues are being given higher priority.

The effects the Siberian tundra and its rivers have on the environment of the seas of the Siberian shelf and the Arctic Ocean have been studied as part of the Tundra Ecology -94 expedition. Inflow of inorganic and organic carbon was investigated. The transformation of the carbon forms by biochemical processes were investigated. Anthropogenic radionuclides were studied in water and sediments. The distribution of dissolved inorganic carbon shows the majority of the Yenisey and Ob outflow goes into the Laptev Sea and then to the Arctic Ocean. Even close to mouths of large rivers, benthic fluxes are low vs coastal areas of the North Sea region where human activities have a larger effect. A significant part of the radioisotopes found come from water from the Atlantic Ocean.

Phytoplankton blooms are examined in relation to manganese and iron cycling in coastal waters of the North Sea. Topics include seasonal succession of plankton, Mn and Fe; regeneration of Fe and Mn; the role of aggregates, pelagic heterotrophs and sediments; contribution of Mn and Fe by rivers; and other processes.

In this paper we consider the estimation of North Sea storm severity, for storms with return periods in the interval 100 to 500 yr. The analysis consists of: modeling the tail-distribution for a set of data for storm severity (using, e.g., storm hindcast data); estimating extreme storm severity; estimating confidence intervals for extreme storm severity; validating the bias and variance of estimates using simulation studies, for known underlying model forms; and estimating the robustness of extreme quantile estimates with respect to misspecification of the underlying model for the tail-distribution of storm severity. Applications to NESS (Northern European Hindcast Study) hindcast data at clusters of locations in the northern, central and southern North Sea are considered. Results suggest, in particular, the existence of a physical upper limit for storm severity in the North Sea and a close to constant value for the extreme value index, (gamma) approximately -0.2.

The relationship between argument and social identity is a largely unexplored topic. In general, social psychologists examining this issue tend to view language from the perspective of one's cultural heritage, [...]

The area of the Central North Sea is notorious for the occurrence of very high waves in certain wave trains. The short-term distribution of these wave trains includes waves which are far steeper than predicted by the Rayleigh distribution. Such waves are often termed 'extreme waves' or 'freak waves.' An analysis of the extreme statistical properties of these waves has been made. The analysis is based on more than 12 yr of wave records from the Maersk Olie og Gas AS operated Gorm Field which is located in the Danish sector of the Central North Sea. From the wave recordings more than 400 freak wave candidates were found. The ratio between the extreme crest height and the significant wave height (20-min value) has been found to be about 1.8, and the ratio between extreme crest height and extreme wave height has been found to be 0.69. The latter ratio is clearly outside the range of Gaussian waves, and it is higher than the maximum value for steep nonlinear long-crested waves, thus indicating that freak waves are not of a permanent form, and probably of short-crested nature. The extreme statistical distribution is represented by a Weibull distribution with an upper bound, where the upper bound is the value for a depth-limited breaking wave. Based on the measured data, a procedure for determining the freak wave crest height with a given return period is proposed. A sensitivity analysis of the extreme value of the crest height is also made.

A study of the North Sea atmosphere was conducted to identify the different Ca-containing particle types and to determine the relationship between their occurrence and the source regions of the corresponding air masses. Electron probe X-ray microanalysis was undertaken to examine the composition of some 50,000 aerosol samples colleted above the Southern Bight of the North Sea. Nonhierarchical cluster analysis was conducted to identify the different types, their abundances and their sources. CaSO4 is the most abundant type of Ca-containing particles. A large fraction comes from anthropogenic sources in central Germany, with extremely large amounts of CaSO4 particles found in northeastern winds coming from this region.

Individual aerosol particles in samples collected over the North Sea were analyzed using x-ray electron probe microanalysis. Some 45,000 individual particles were studied and approximately 45,000 of these contained substantial concentrations of one or more of the heavy metals Cr, Pb and Zn. There were significant differences in abundances detected in the North Sea aerosol.

Electron-probe X-ray microanalysis was used to study variations in individual aerosol inorganic particle composition of air masses crossing the North Sea. Hierarchical cluster analysis using the Ward error sum method revealed three to eight different aerosol types. Principal factor analysis revealed that aluminosilicates and NaCl, seawater crystallization products and two industrial sources are the four main sources of air mass composition in the North Sea.

Aerosol particle samples taken from over the North Sea were analyzed using laser microprobe mass analysis (LAMMA) to determine if the sources of individual particles were natural or man-made. LAMMA is more labor-intensive than electron probe X-ray microanalysis (EPXMA), but can detect smaller concentrations of trace elements. 6000 particles from various altitudes over the southern corner of the North Sea were analyzed. Methodology, results and conclusions are presented.

Analysis of samples of giant aerosol particles taken over the North Sea shows the source of these particles to be aluminosilicates, combustion processes, industrial processes and marine sources. The samples were collected by an aircraft flying at various altitudes over the southern corner of the North Sea. 12,500 samples were analysed using electron probe X-ray microanalysis.

Byline: H. Marx (1), B. Brunner (1) Keywords: Key wordsaHeavy metals; Lead; Cadmium; Mercury; Shrimp Abstract: aCadmium (Cd), lead (Pb) and mercury (Hg) contents of common shrimp (Crangon crangon L.) from the German mud flats in the North Sea were investigated by means of atomic absorption spectrometry. The heavy metal contents of the 32 samples were low: 0.043+-0.026 mg Cd, 0.019+-0.011 mg Pb and 0.033+-0.016 mg Hg (mean+-SD) per kg wet weight. All of the samples contained lower amounts of the investigated elements than the levels of concern of the Federal Institute for Health Protection of Consumers and Veterinary Medicine, i.e. 0.5 mg Pb/kg, 0.1 mg Cd/kg and 0.5 mg Hg/kg wet weight most of the samples showed significantly lower levels of contamination. Therefore, no risk to the consumer arises from the Cd, Pb and Hg contents of the shrimp caught in this area. The main reasons for the overall low levels of contamination might be the short period of feeding of the shrimp and, with respect to Pb, an active mechanism of secretion. Besides this, the heavy metal load of the shrimp depended on the fishing season (November or May). Author Affiliation: (1) Institut fur Hygiene und Technologie der Lebensmittel tierischen Ursprungs, Ludwig-Maximilians-Universitat, Veterinarstrasse 13, D-80539 Munchen, Germany, DE Article note: Received: 23 February 1998 / Revised version: 30 April 1998

Several historic marine data are analyzed to explain the impact of fisheries and other human activities on the changes that have been observed in the North Sea benthos. The marine invertebrates of the studied region are shown to exhibit extremely high levels of mortality due to the high population turnover rates.