Dogger Bank Area Research Articles

Interconnection and generation from a North Sea power hub – A linear electricity model

We research effects on the electricity market of countries surrounding the North Sea after a proposed offshore wind park in the Dogger Bank area of the North Sea has been constructed. Interconnection and generation distribution are analysed separately. The supply price of electricity for each country is calculated by a linear regression analysis to simulate the supply price for higher or lower supply. The model uses the coupling of one supply with one receiver country. Linear modelling of the electricity market combines the results for each objective to find a final state for the market. Using the historic market and weather data for 2016, the results from interconnection show an average generated value of 0.275 [M€/hour] and 82.1 [GW] of average energy flow through the hub. The results of this interconnection between the countries bring between −26% and +11% change on average electricity prices. For hub generation added in, we found an average generated value of 0.573 [M€/hour] and an average price drop of 5% for each country for an average wind power generation of 6.3 [GW] at the hub. The results show that interconnecting the similarly sized electricity markets i.e. Great Britain and Germany & the Netherlands and Denmark, where one has a higher renewable share, would bring the most price stabilization between the two as well as generate the most financial return.

Economic and environmental benefits from integrated power grid infrastructure designs in the North Sea

The North Sea Offshore Grid (NSOG) is considered an important contributor towards large-scale integration of renewables and electricity market coupling. Different typologies have been studied for such a multinational power grid, ranging from radial point-to-point connections to more integrated meshed typologies. An artificial island enables a high level of integration of both offshore wind power and transnational trade due to economies of scale. This paper present multiple case studies of the Power Link Island (PLI) which is visioned by TenneT in the Doggerbank area. Our results demonstrate that the capabilities of such an island could add significant value to the system as a result of more efficient use of geographically spread, cost-efficient resources. However, depending on the future level of grid integration and generation mix, the added value of a PLI varies between e0.15bn to e20bn. Consequently, this could result in 18% more efficient utilization of renewable resources, primarily offshore wind, and significant reductions of CO2 emissions.

Extreme Wave Condition at Doggerbank

In design of offshore wind turbines, extreme wave conditions are of interest. Usually, the design wave condition is taken as the sea state corresponding to an annual exceedance probability of 2 × 10−2, i.e., a return period of 50 years. A possible location for a future wind farm, consisting of bottom fixed wind turbines, is the Doggerbank area. The water depth in this area varies from about 60 m in the north to about 20 m in the south. The hindcast database NORA10 provides sea state characteristics from 1957 to present over a domain covering Doggerbank. Regarding the deeper areas just north of Doggerbank, this hindcast model is found to be of good quality. Larger uncertainties are associated with the hindcast results as we approach shallower water further south. The purpose of the present study is to compare sea state evolution over Doggerbank as reflected by NORA10 with the results of the commonly used shallow water hindcast model SWAN. The adequacy of the default parameters of SWAN for reflecting changes in wave conditions over a sloping bottom is investigated by comparison with model test results. Extreme wave conditions for two locations 102.5 km apart in a north–south direction are established using NORA10. This is done using both, an all sea states approach and a peak over threshold (POT) approach. Assuming the extremes for the northern position to represent good estimates, the wave evolution southward is analyzed using SWAN. The extreme condition obtained from NORA10 in the northern position is used as input to SWAN and the results from the two hindcast models are compared in the southern position. SWAN seems to suggest a somewhat faster decay over Doggerbank compared to NORA10.

Functional composition of epifauna in the south-eastern North Sea in relation to habitat characteristics and fishing effort

Analysis of ecosystem functioning is essential to describe the ecological status of ecosystems and is therefore directly requested in international directives. There is a lack of knowledge regarding functional aspects of benthic communities and their environmental and anthropogenic driving forces in the southern North Sea. This study linked functional composition of epibenthic communities to environmental conditions and fishing effort and investigated spatial correlations between habitat characteristics to gain insight into potential synergistic and/or cumulative effects. Functional composition of epifauna was assessed by using biological trait analysis (BTA), which considered 15 ecological traits of 54 species. Functional composition was related to ten predictor variables derived from sediment composition, bottom temperature and salinity, hydrodynamics, annual primary production and fishing effort. Our results revealed significantly different functional composition between the Dogger Bank, the Oyster Ground, the West and North Frisian coast. Mobility, feeding type, size and adult longevity were the most important traits differentiating the communities. A high proportion of trait modalities related to an opportunistic life mode were obvious in coastal areas especially at the West Frisian coast and in the area of the Frisian Front indicating disturbed communities. In contrast, functional composition in the Dogger Bank area indicated undisturbed communities with prevalence of large, long-lived and permanently attached species being sensitive towards disturbance such as fishing. Tidal stress, mud content of sediments, salinity, stratification and fishing effort were found to be the most important habitat characteristics shaping functional composition. Strong correlations were found between variables, especially between those which changed gradually from the coast to offshore areas including fishing effort. Unfavourable extremes of these factors in coastal areas resulted in disturbed epibenthic communities, while the relative influence of a single factor on functional composition cannot be quantified. Coastal communities seemed to be well adapted to disturbance and the prevalence of opportunistic trait modalities not necessarily revealed a poor ecological status according to the Marine Strategy Framework Directive (MSFD). The integration of functional aspects into the assessment of ecosystem health is recommended, since widely used structural measures failed in naturally disturbed habitats.

Spatio-temporal dynamics of growth and survival of Lesser Sandeel early life-stages in the North Sea: Predictions from a coupled individual-based and hydrodynamic–biogeochemical model

Accounting for the individual variability and regional variations are important when predicting recruitment in fish species. Spatially explicit descriptions for recruitment in sandeels are necessary and sandeel growth and survival depend locally on zooplankton prey. We investigate the responses of larval and early juvenile Lesser Sandeel (Ammodytes marinus) in the North Sea to local feeding conditions by an adapted version of a generic bioenergetic individual-based model for larval fish describing growth and survival. Prey encounter and physiological processes are described explicitly in the model, which allows analyzing the influence of prey on the growth and survival of sandeel. The model is coupled to a hydrodynamic–biogeochemical model with physical and prey fields and implemented in temporal and three-dimensional spatial settings. Zooplankton biomass simulated by the biogeochemical model is validated by Continuous Plankton Recorder survey time series data. Spatio-temporal dynamics of the sandeel cohorts are simulated by the integrated model framework for the period 2004–2006 and five major area divisions of suitable sandeel habitats in the North Sea. This allows obtaining insight into the influence of temperature variation and zooplankton availability on the growth and survival. To determine areas promising for recruitment, area divisions are compared and optimal time of hatching for higher survival to recruitment due to match–mismatch with prey is determined by comparing different hatching times. The effect of vertical diel migration behavior of sandeel on the model outcomes is also examined. Vertical migration of sandeel results in increased feeding ability and growth and decreased starvation mortality of individuals. Results show that areas of German Bight and Southern Bight with high zooplankton production support high growth of sandeel. Most sandeel survive to settling in the Dogger Bank area that has large retention on average and still productive in zooplankton. Hatching at the optimal time of March/February with matching zooplankton peak concentrations enhances the growth and survival. Growth correlates positively with the observed temperature trend. Survival correlates negatively with temperature and prominently, when the hatching is in winter.

Biological processes in the North Sea: vertical distribution and reproduction of neritic copepods in relation to environmental factors

We studied the vertical distribution and reproduction of dominant neritic copepod species in the Dogger Bank area and surrounding North Sea to reveal (i) if these species are concentrated in the subsurface chlorophyll maximum layer, (ii) if the chlorophyll maximum offers superior food conditions for reproduction compared with surface waters and (iii) if the secondary production is thus higher in the frontal areas with a subsurface chlorophyll maximum. In addition, we wanted to (iv) identify the most important environmental factors determining the reproduction of neritic copepods in the North Sea. We observed a higher egg production of cultured Acartia tonsa when fed with the seston from chlorophyll maximum, but no evidence of a higher copepod abundance in this layer. Secondary production was highest at the station closest to the upwelling of new nutrients, although seasonal differences in environmental variables probably overrode the differences between frontal and stratified stations. Copepod egg production on an annual basis seemed to be best predicted by the body size and specific fatty acids, with a high egg production, but low hatching success associated with a high EPA:DHA ratio. Total secondary production of small copepods seemed mainly related to the species composition, suggesting that factors controlling abundance of specific species rather than reproduction might be more important in determining the secondary production of copepods.

Holocene relative sea-level change, isostatic subsidence and the radial viscosity structure of the mantle of northwest Europe (Belgium, the Netherlands, Germany, southern North Sea)

A comprehensive observational database of Holocene relative sea-level (RSL) index points from northwest Europe (Belgium, the Netherlands, northwest Germany, southern North Sea) has been compiled in order to compare and reassess the data collected from the different countries/regions and by different workers on a common time–depth scale. RSL rise varies in magnitude and form between these regions, revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity. It clearly contains a non-linear, glacio- and/or hydro-isostatic subsidence component, which is only small on the Belgian coastal plain but increases significantly to a value of ca 7.5m relative to Belgium since 8cal.kaBP along the northwest German coast. The subsidence is at least in part related to the Post-Glacial collapse of the so-called peripheral forebulge which developed around the Fennoscandian centre of ice loading during the Last Glacial Maximum. The RSL data have been compared to geodynamic Earth models in order to infer the radial viscosity structure of the Earth's mantle underneath NW Europe (lithosphere thickness, upper- and lower-mantle viscosity), and conversely to predict RSL in regions where we have only few observational data (e.g. in the southern North Sea). A very broad range of Earth parameters fit the Belgian RSL data, suggesting that glacial isostatic adjustment (GIA) only had a minor effect on Belgian crustal dynamics during and after the Last Ice Age. In contrast, a narrow range of Earth parameters define the southern North Sea region, reflecting the greater influence of GIA on these deeper/older samples. Modelled RSL data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow, WNW–ESE trending band connecting the German federal state of Lower Saxony with the Dogger Bank area in the southern North Sea. Identification of the effects of local-scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea-level index points based on model-data comparisons is possible but is still complicated by the relatively large range of Earth model parameters fitting each RSL curve, emphasising the need for more high-quality observational data.

Microphytobenthos of the Dogger Bank: a comparison between shallow and deep areas using phytopigment composition of the sediment

The surface sediment characteristics related to benthic microalgae primary production were studied at the Dogger Bank, North Sea, in order to evaluate the potential role of microphytobenthos as a food source for the macrobenthic fauna. Twenty-one stations were sampled in July 2001 and May 2002, with water depth ranging from 16.3 to 68.5 m. High-performance liquid chromatography pigment analyses revealed that concentrations of chlorophyll a, chlorophyll c and fucoxanthin are mainly associated with benthic diatom flora at most parts of the Dogger Bank. High percentage of phytopigments (>50%) was firmly attached to sand grains at the stations shallower than 40 m water depth. The deeper stations were characterized by a phytopigment composition originating from pelagic phytoplankton settled on the sea floor. Qualitative microscopy showed that the benthic microflora on top of the Bank mainly consists of small diatoms (5–10 μm), such as e.g., Diploneis spp., living attached to the sand grains. The results are discussed concerning possible implications for ecology and biogeochemistry of the Dogger Bank area.

Phospholipid fatty acid profiles at depositional and non-depositional sites in the North Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 241:57-70 (2002) - doi:10.3354/meps241057 Phospholipid fatty acid profiles at depositional and non-depositional sites in the North Sea Thorsten Stoeck1,*, Ingrid Kröncke1, Gerard C. A. Duineveld2, Ansa Palojärvi3 1Senckenberg Institute, Department of Marine Biology, Schleusenstrasse 39a, 26382 Wilhelmshaven, Germany 2Netherlands Institute for Sea Research, Department of Benthic Ecology, PO Box 59, 1790 AB Den Burg, The Netherlands 3MTT Agrifood Research Finland, Soils and Environment, 31600 Jokioinen, Finland *Present address: Marine Science Center, Northeastern University, East Point, Nahant, Massachusetts 01908, USA. E-mail: thorsten.stoeck@web.de ABSTRACT: The distribution of ester-linked phospholipid fatty acid (PLFA) in sediments of 12 sampling stations located in the German Bight, Skagerrak/northern Kattegat, Frisian Front, Oyster Ground, eastern North Sea and the Dogger Bank area was studied to compare the in situ microbial community structure of depositional and non-depositional sites. A total of 36 fatty acids in the range of C12 to C24 were determined. They consisted of saturated, branched, monounsaturated, polyunsaturated and hydroxy fatty acids, and variation was revealed in the relative proportions (mol %) of these fatty acids. The distribution of specific fatty acids was significantly different between depositional and non-depositional sites. Additionally, we could discriminate communities of sites which are intermediate in sedimentation regime. Highest total PLFA content was found at depositional sites. The PLFA profiles of all sites were dominated by bacteria, with highest bacterial contribution to the sedimentary PLFA pool at depositional sites. A high proportion of aerobic prokaryotes (up to 40%) at depositional sites indicated the occurrence of aerobic microniches in the corresponding anoxic sediments. Bacterial groups being a component of the degradation pathways of complex macromolecules (e.g. Cytophaga and Actinomycetes) were found in significant higher abundances at depositional sites compared to the other sites. At depositional sites, sulphate-reducing bacteria (SRB) (e.g. Desulfobacter spp.) were more abundant compared to the other stations. The relative contribution of microeukaryotes to the sedimentary PLFA pool was significantly higher at depositional sites. A nutritionally limited benthic system at non-depositional sites in the offshore is indicated by a microbial community exposed to higher physiological stress than those of the organically enriched sediments of the depositional sites. KEY WORDS: Microbial communities · Phospholipid fatty acids · North Sea · Sediment · Actinomycetes · Cytophaga · Sulphate-reducing bacteria Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 241. Online publication date: October 04, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Influence of Particle Mixing on Vertical Profiles of Chlorophyll a and Bacterial Biomass in Sediments of the German Bight, Oyster Ground and Dogger Bank (North Sea)

In May and September 1999 11 stations were sampled in the southern and central North Sea, located in the German Bight, eastern Oyster Ground and Dogger Bank. The study focused on the influence of particle mixing on transport of chlorophyll a to deeper sediment layers and vertical bacterial distribution (max. depth=10cm). The sampling stations were chosen to reflect a gradient in environmental conditions in the North Sea. The sampling stations differed in respect to redox potential (eH up to −243mV in the German Bight and up to 274mV in the offshore regions), silt content (up to 54% in the German Bight and 0·34% at the northern Dogger Bank) and different proportion of fresh organic material on total organic matter content (C/N ratios ranging from 9·27 in the German Bight up to 1·72 in the offshore sediments). Although bacterial densities (8·55×109g−1in the German Bight up to 0·35×109g−1in offshore sediments) were significantly correlated to chlorophyll a content in the sediment (P<0·01), inconsistencies in the temporal pattern of both variables in the surficial sediment layer suggested, that the dynamics of bacterial densities is generally controlled by food supply but also by other variables. The chlorophyll a content in the surficial sediments of the German Bight (up to 1·84μgg−1) was significantly higher than in the Oyster Ground (up to 0·58μgg−1) and the Dogger Bank area (up to 0·68μgg−1). With increasing chlorophyll a input to the benthic realm a subsequent enhanced burial of this compound into deeper sediment layers was expected either by biological (bioturbation) or by physical sediment mixing. However, the vertical profile of chlorophyll a decreased steeply in the sediments of the German Bight. Contrary, subsurface peaks were measured in the offshore areas. It was concluded from these results, that the vertical distribution of organic matter in sediments is less limited by the quantitative input from the water column but concomitant with particle mixing itself. The extent and possible mechanisms of particle mixing in the different study areas in relation to specific environmental factors is discussed.

Size-fractionated uptake of ammonium, nitrate and urea and phytoplankton growth in the North Sea during spring 1994

The growth of 2 different algal size classes was studied in March/April 1994 during the establishment of the spring bloom along a transect from the Dogger Bank to the Shetland Islands in the North Sea. Size-differential growth rates were estimated on the basis of independent measurements of carbon and nitrogen uptake. At the shallower stations near the Dogger Bank (DB) area, chlorophyll a (chl a) levels were up to 5.8 mu g l(-1). In the bloom 89 % of the chi a was in the >5 mu m fraction. In the central North Sea (cNS) and near the Shetland Islands (SI) total chi a was 0.52 and 0.38 mu g l(-1), respectively; 60 % was in the >5 mu m fraction. Depth-integrated primary production at the DB, cNS and SI was 46, 145 and 149 mg C m(-2) d(-1), respectively, for the 5 mu m size fraction. Since the calculated specific growth rates, based on either nitrogen uptake or inorganic carbon uptake, were in good agreement with each other for both size fractions, it was concluded that smaller algae apparently grow faster than larger ones in this typically light-controlled environment. The >5 mu m fraction, however, dominated the bloom at the Dogger Bank. Our findings consolidate the concept of size differential control of phytoplankton communities under typical spring bloom conditions which originally was demonstrated in a coastal area (Riegman et al. 1993; Neth J Sea Res 31:255-265). [KEYWORDS: phytoplankton growth; size fractionation; nitrogen uptake; carbon uptake; North Sea Marine diatoms; cell-size; nitrogen assimilation; carbon fixation; populations; plankton; station; system; waters; light]

Structure of plankton communities in the Dogger Bank area (North Sea) during a stratified situation

Plankton dynamics and hydrography were invest~gated in the Dogger Bank area, southern North Sea, In May 1990 after the onset of stratification Greatest phytoplankton biomass and production rates were observed withln a subsurface maximum around the pycnochne. At all 51 stations investigated, fluorescence maxima were found at depths >l5 m and often at depths >30 m. Small flagellates (5 to 7 pm) dominated the phytoplankton. The vertical distributions of the smaller heterotrophs (bacteria, heterotrophic nanoflagellates and cihates) were closely related to the fluorescence distribution. Carbon budgets established for the southern North Sea suggest that, on and south of the Dogger Bank, ca 15 % of phytoplankton production was channelled directly into the larger zooplankton (copepods), while north of the Dogger Bank, ca 30 % was ingested by copepods. The production of the phytoplankton fraction >l 1 pm (i.e. potential copepod prey items) could not alone account for the daily carbon demand of the copepods. The carbon budgets suggest that ciliates could potentially have been of nutritional importance to the copepod populat~on. Calculations showed that copepods possessed the ability to clear a substantial fraction of ciliate production. The high biomass of bacteria, heterotroph~c flagellates and c~liates, as well as the fact that primary production of the larger (I.e. grazable) phytoplankton did not appear to be sufficient to meet copepod energy requirements, suggest the importance of the microbial loop in carbon cycling in the North Sea during the stratified period.

Evaluation of measurements and calculation of primary production in the Dogger Bank area (North Sea) in summer 1988

Primary production was measured during a survey in the Dogger Bank area, where both stratified and non-stratified conditions existed in July-August 1988. Daily primary production was calculated, based on I4C-fixation rates in an incubator with an artificial light source, depth profiles of in situ irradiance, and vertically heterogeneous phytoplankton distributions. Values ranged among sta- tions from 300 to 2200 mg C m-' d-l. Average primary production in the Dogger Bank area was estimated at 1.2 g C m-2 d-'. Variation in cloudiness affected primary production by a factor of 4.5. Calculations based on surface samples alone showed an average area1 primary production underesti- mate of 17 %. After correction for the uneven vertical biomass distribution, primary production was still underestimated by 12 % as a result of photoadaptation. Especially below 30 m, Ik was reduced from 310 to 174 pE m-2 S-', demonstrating the presence of shade-adapted phytoplankton at the thermocline. Calculated daily primary production rates based on in situ incubations and on incubator measurements deviated by only 5 %. Light quality did not have a significant effect on water column productivity. Size- dependent primary production based on post-incubation filtration onto 5 pm filters showed that, on average, 84 O/O of total primary production was in the > 5 pm fraction.

Cycling of nutrient elements in the North Sea

The cycling of elements of inorganic and organic nutrients (carbon, nitrogen, phosphorus and silicate) in the North Sea is described. The regional effects on nutrient cycling such as thermal and haline stratification, coastal interaction, river discharges, upwelling and frontal zones are discussed. The horizontal and vertical distribution of the inorganic nutrients (nitrate, phosphate, ammonia and silicate) at the surface is given for the whole North Sea during two situations: spring (1986) and winter (1987). In winter, highest nutrient concentrations were found at the northern boundary in the Atlantic inflow, and in the continental coastal waters. During the winter cruise, nutrient minima were detected in the Dogger Bank area. This is an indication that primary production continues during winter. Generally, the surface concentrations during winter were similar to the bottom concentrations. Except for phosphate, highest concentrations were measured just above the bottom. During late spring 1986 the concentrations of nutrients at the surface and below the densicline were generally significantly lower than during winter. Only at the Atlantic boundary in the north and near the estuaries higher concentrations were detected. In stratified parts of the North Sea, the decomposition of sedimented biomass caused the ammonia concentrations in the bottom layer to be significantly higher in spring than in winter. Incidents of frontal upwelling in the central North Sea introduce nutrient-rich bottom water into the euphotic zone, enhancing phytoplankton growth in the central North Sea during summer. The ratios of nitrogen nutrients to phosphate show that in the central North Sea nitrogen is a limiting factor rather than phosphorus, whereas in the continental coastal water and off England the opposite is true. Riverine input and trapping mechanisms in the estuaries and tidal flats cause the concentrations of organic matter (dissolved and particulate) to be highest in the coastal zones and to decrease seaward. During summer the concentration of dissolved organic carbon increases throughout the North Sea. It is calculated that about 60% of the biomass formed by primary production is converted into dissolved organic carbon, 40% directly goes into the foodweb. The biological impact of the plankton is readily apparent from increased surface concentrations of different dissolved organic substances during spring blooms. Examples of eutrophication and effects of nutrient limitation are given, together with other biological repercussions such as coupling of phytoplankton and nutrient succession. Budget calculations for the different nutrient elements show that in the North Sea the biological turnover greatly exceeds the estimated annual inflow and outflow of nutrient elements. Finally, recommendations are given for future research. They include analysing dissolved organic compounds and micronutrients and following multidisciplinary measurements strategies at one location in order to obtain more information for balancing budgets and for the detailed analysis of nutrient cycling in the North Sea.

Nutrient early diagenesis in the sandy sediments of the dogger bank area, north sea: Pore water results

Nutrient pore water profiles from the upper 100 mm of the sandy and organic-poor sediments of 12 stations in the Dogger Bank area (North Sea) were obtained during July – August 1988. O 2 penetration, as measured with microelectrodes, varied between 4 and 15 mm. Silicate, ammonium, nitrate, and phosphate concentrations were low compared with values reported in the literature for other marine interstitial waters. Nitrate showed clear nitrification peaks in the upper 10 mm of the sediment, while the other constituents reached their maximum levels between 20 and 40 mm. In some cores the latter concentrations declined again below these depths. Averaged over all stations, benthic respiration, measured in whole-core incubations, was 12 mmol(O 2)·m −2·day −1, while measured nutrient sediment-water exchange rates were 333 (Si), 167 (NH 4 +), 161 (NO 3 −) and 32 (P) μmol·m −2·day −1. Compared with the daily phytoplankton nutrient requirements, these fluxes amount to less than 10% for Si, ∼2% for N, and ∼ 3% for P. This suggests that nutrient regeneration largely occurs in the water-column. The pore-water profiles were evaluated quantitatively, using one-dimensional steady-state diagenetical models in which the apparent diffusion coefficient is calibrated against experimentally obtained fluxes. Results indicate that apparent diffusion is 1 to 6 times molecular diffusion. For Si the first-order dissolution rate estimated from the Si model is 0.2 to 9.3·10 −6·s −1 at the sediment surface, declining to less than 5% of these values at 7.5 to 37.5 mm. The combined ammonium - nitrate model revealed that mineralization of organic nitrogen into ammonium is restricted to the upper 6 to 59 mm. First-order nitrification and denitrification rates were estimated at 0.3 to 16.5·10 −4 and 0.06 to 5.5·10 −4·s −1, respectively. Total nitrification was calculated at 155 to 1930 μmol·m −2·day −1, total denitrification at 54 to 546 μmol·m −2·day −1. Denitrification is completely fuelled by nitrate produced during nitrification in the upper mm's. According to the model, 70 to 80% of the organic N being mineralized within the sediment is released to the water column, largely as nitrate. The P model includes both first-order sorption in the upper oxidized sediment layer and first-order phosphate removal in the zone below. Oxic sorption rate is estimated at 1 to 120·10 −6·s −1, sorption equilibrium concentration is ∼1.7 mmol·m −3. For the removal rate below oxygen penetration, two situations were observed. At 8 stations, removal rate in the reduced zone was 3 orders of magnitude less than oxic sorption. At 4 stations, both rates and equilibria were equal to those in the oxic layers, probably indicating the absence of substantial Fe(III) reduction in the upper cm's at these stations. Average benthic P-mineralization was calculated at 80 μmol·m −2·day −1, of which ∼ 60 μmol·m −2·day −1 was at least temporarily removed from the pore water by sorption. This implies that ∼25% of the organic P mineralized within the sediment is directly regenerated to the water column.

Primary production of phytoplankton at a frontal zone located at the northern slope of the Dogger Bank (North Sea)

In July 1988 a survey was made in the Dogger Bank area of the North Sea. As a result of wind stress the area was found to be frequently well mixed. At the northerly slope a transition zone was observed between the stratified central North Sea and the well-mixed Dogger Bank area. Low nutrient concentrations were observed in surface waters; especially for nitrate ( 0,5µM), nitrate (>1µM), ammonium (>2µM) and silicate (>2µM) only prevailed below the thermocline. Chlorophylla values were below 1µg l−1 near the surface. Enhanced values (up to 4µg l−1) were observed in the deeper layer at the transition zone and just below the thermocline at well-stratified locations. At the transition zone high specific C-fixation rates (up to 100 mg C mg−1 chla d−1) at the surface indicated the presence of enhanced productivity. The compensation depth for primary production was found to coincide with a specific C-fixation rate of 5 mg C mg−1 chla d−1. At greater depths, phytoplankton was only found where tidally induced vertical mixing allowed a regular exposure to higher light intensities. Storms resulted in a rapid redistribution of chlorophylla and enhancement of the C-fixation rate in the upper layer of the water column.

Dogger Bank Itch. 4. an eczema-causing sulfoxonium ion from the marine animal, Alcyonidium gelatinosum [bryozoa

Repeated exposure to the marine bryozoan, Alcyonidium gelatinosum, frequently provokes an eczematous allergic contact dermatitis known as the “Dogger Bank Itch”. The dermatitis, representing a severe occupational disease, is especially widely distributed among trawlermen working in the Dogger Bank area in the North Sea. The allergy is shown to belong to the type of cell-mediated hypersensitivity. The hapten has been identified as the (2-hydroxyethyl) dimethylsulfoxonium ion. The isolation, structure determination and synthesis are discussed.

Dogger bank itch. 2. An allergic contact dermatitis

AbstractDogger Bank Itch is an allergic contact dermatitis representing a severe occupational hazard among trawlermen of the Dogger Bank Area in the North Sea. Allergic sensitivity is acquired following exposure to the marine bryozoan Alcyonidium gelatinosum. The allergen has been identified as (2‐hydroxyethyl) dimethylsulfoxonium ion. The isolation, structure determination and synthesis of the allergen is discussed.

Geology of the Dogger Bank area, North Sea

A sediment survey carried out on board H.M.S. “Luymes” in 1963 in the area between 53°50′N–54°50′N and 2°E–4°20′E brought to light that the Dogger Bank (average depth 25 m) is built up of medium-grained sand and coarse material, whereas east of the Dogger Bank is an extensive area (average depth 50 m) where fine silty sand is found. In the southwestern part of the area investigated clay occurs in a deep gully (average depth 70 m) which is connected with the Outer Silver Pit. With the help of an echo sounder a buried relief at an average level of 3 m below the sea floor was discovered in the last two regions mentioned. Most likely this relief represents a former glacial landscape covered with soft sediments. With a gravity corer (120 kg weight) 40 cores were taken in the eastern and southern part of the area described. It appeared that in all the cores the original stratification was disturbed by organisms such as sea urchins and worms. In the areas with fine sediments an average rate of sedimentation of only 0.3 mm/year can be estimated from the 14C-age determinations of Preboreal peat samples from the Dogger Bank, and from the thickness of the soft sediment cover. On the higher grounds, the Dogger Bank and Cleaver Bank (Fig.2), are patches covered with pebbles. Moreover, grab samples of boulder clay were collected in a few places. These indicate that the substratum of the Dogger Bank consists of moraine ridges belonging presumably to the Weichsel glaciation, the last Pleistocene glaciation. The pebbles on top of the banks are coarser than those on the flanks, a phenomenon the author attributes to the selective transport of fine gravel during a former period when the sea-level was lower. Regarding the shells caught with a 0.1 m 2 Van Veen grab, one can observe that the majority were not living on the Bank when sampled (autumn, 1963). Even a number of species among them are only known from shallow water; these shells lived on the Dogger Bank when sea level was at least 20 m lower, i.e., during the Boreal (Lower Holocene). The presence of these shells near the surface proves that no sedimentation of any importance occurs on the Bank at present.

Sea Surface Temperature in Coastal Waters of the British Isles

MR. A. J. LEE has recently commented1 on my paper dealing with variations of sea surface temperature in coastal waters of the British Isles. He points out that I made no mention of the part played by currents in determining the winter pattern of sea surface temperature. I was, however, primarily concerned with the shape of the isotherm patterns. The presence of the relatively shallow water of the Dogger Bank area will, in itself, ensure that the pattern will consist of two tongues, although the level of temperature of these tongues will be largely determined by the strength of the currents mentioned by Mr. Lee.