Seasonal Variation in the Biomass of Marine Macrophyta from Greek Coasts

Abstract. The marine plant communities of the littoral zone in different biotopes of the Greek coasts were investigated in 1980-81. Seasonal distribution and variation of marine plant biomass were assessed. The communities of Cystoseira crinita and C. compressa were outstanding with maximum biomass during the summer months. Corallina officinalis and Pterocladia capillacea + Viva rigida communities predominated with maximum biomass in autumn and exhibited a decrease in winter, except in stressed biotopes. The species diversity and productivity of seaweeds along the Greek coasts are interpreted in relation to a number of environmental parameters.     

Radioecological studies of activation products released from a nuclear power plant into the marine environment

The seaweeds Fucus vesiculosus, Fucus serratus, Ascophyllum nodosum and Cladophora glomerata and crustaceans of the Idothea and Gammarus families have proven to be excellent bioindicators for radioactive corrosion products released from a nuclear power plant into the marine environment. These bioindicators have been used to map the spatial and temporal distribution of the released radioactivity. The activity has been followed up to 150 km from the power plant, and the decrease in activity concentration C(z) in the bioindicators with distance z can be expressed by a power function C(z) = α. z^?1·4 where α is a constant.The variation with time of activity concentration very well reflects the amount of activity discharged from the power plant, with surprisingly good resolution in time.The bioindicators exhibit different uptake patterns of the radionuclides detected, and variations from summer to winter for the crustaceans Idothea, when compared to Fucus, has been found.     

Facies recognition of some Tertiary coals applied to prediction of oil source rock occurrence

Coals are oil source rocks in many of the Tertiary basins of Southeast Asia. The precursors of these hydrogen rich and oxygen poor coals are coastal plain peats which have mainly developed in an everwet and tropical climate. In these environments water flow and reworking can concentrate liptinitic kerogen in preference to vitrinitic kerogen. The distribution, petrography and chemistry of the coaly Miocene source rocks present in the Kutai Basin are described. The recognition of environmental controls on the accumulation of potentially oil-prone coals and coaly shales in deltaic environments is an aid to predictive source bed recognition in petroleum exploration. Comments on the environment of deposition of coaly sediments in the basins of the Norwegian Sea are discussed with reference to their possible oil and/or gas sourcing potential. The Triassic - Jurassic coals of the Haltenbanken area may become more oil-prone towards the delta margins, and facies mapping could aid oil exploration in this area.     

Mercury levels in some species of fish from the coast of Lebanon

The muscle tissue of 266 fish caught along the coast of Lebanon from Beirut to Tyre (85 km) were analysed for total mercury content. The mean levels for the 13 species ranged from 0·028 mg/kg of wet tissue for Siganus rivulatus to 0·0.54 mg/kg for Mullus barbatus. Whereas no significant differences (P < 0·05) in mercury levels were noted between species, in most cases a direct relationship was found between the weight or length of fish of the same species and total mercury content. Similarly, there were no significant differences (P < 0·05) between herbivore and carnivore species, nor between resident and migrant ones. All of the values obtained in the present study fall below the widely accepted limit of 0·5mg/kg of edible tissue.     

Field Placement and Evaluation of Stabilized Dredged Material (SDM) from the New York/New Jersey Harbor

Since the 1997 local ban on ocean dumping of dredged sediments, the States of New York and New Jersey have pursued a policy of environmentally sound solutions to the management of dredged material, including beneficial use of stabilized dredged material (SDM) in transportation applications. A pilot study was initiated in 1998 to evaluate the use of SDM in the construction of highway embankments. Utilizing 80,000 cubic yards of dredged material, two embankments were constructed from SDM on a commercial development area adjacent to the Harbor. Geotechnical properties and handling of SDM were evaluated both during and one year post - construction. This article presents the evaluation of the embankments themselves, including constructability and performance. The results demonstrate that SDM satisfies most of the geotechnical criteria for fill construction, except those for durability, requiring proper coverage and protection similar to that provided for fills constructed on cohesive soils. This same characteristic precludes long term stockpiling of SDM prior to final placement, limiting applications to those that have schedules overlapping with dredging projects. Increased costs for the use of SDM can be as high as $8 per cubic yard over traditional fills; however, this cost may be recouped through management fees collected from dredging projects.     

Past and present sedimentary activity in the Capbreton Canyon, southern Bay of Biscay

Located in the south-eastern part of the Bay of Biscay, the Capbreton Canyon incises the continental shelf up to the 30 m isobath contour, and acts as a natural conduit for continental and shelf-derived sediments. EM1000 multibeam bathymetry shows two main features characterising the canyon — a deeply entrenched meandering channel, bordered by fluvial-like terraces constituting large sediment traps. A dataset of cores and seismic profiles together with a multibeam bathymetry map has enabled the characterisation of recent sedimentary activity in the axial channel and on the terraces. Data analysis evidenced the major role of the canyon head in recent sediment dynamics. This part of the canyon is a temporary reservoir for sediments, accumulated by coastal hydrodynamic processes. Exceptional climatic, tectonic or hydrodynamic events can mobilise the sediments and generate gravity-driven flows. Under the present-day sea-level highstand conditions, these flows are not powerful enough to bring their bedload to the deep sea, and are confined mainly to the upper part of the canyon. Turbidity currents model the axial channel pathway and are at the origin of terrace formation. Terraces in the Capbreton Canyon are not typical but rather are reduced to confined levees. Three factors control the vertical growth of a terrace: (1) the amount of overspilled sediments brought by turbidity currents, (2) hemipelagic sedimentation and (3) terrace height. The amount of sediment spilling over a terrace decreases with increased terrace elevation. Concurrently, the proportion of hemipelagic fallout depositing on a terrace increases. Terraces are considered to be fossil when the height of the terrace prevents further deposition by overspilling. The terraces studied in this paper are interpreted as having formed during the Holocene, implying that the sediment dynamics of the Capbreton Canyon is continuous through time. Highstand periods differ from lowstand periods because they show a decrease in the energy of erosive processes. Temporal variations in erosive and depositional processes in the canyon are controlled by the Adour River, which delivers large amounts of sediment to the system.     

Persistent volcanic signature observed around Barren Island, Andaman Sea, India

This study delineates the formation of a warm pool (>34°C) of air to the west (downwind) of the active volcano of the Barren Island during October–November 2005. Barren Island is located in the Sumatra–Andaman region, about 135 km east of Port Blair, and lies within the Burma microplate, the southern tip of which experienced a submarine earthquake (M _w 9.3) causing a tsunami in December 2004. Barren Island is the only volcano, which has shown sustained eruptive activity since shortly after the Great Sumatran Earthquake of December 2004. Our observations require further corroboration to relate how submarine earthquakes activate volcanoes and how far these thermal emissions influence climate changes. Because it links global warming and climate changes to the frequent emissions from a volcano activated by submarine earthquakes, this case study is of special interest to the earth-ocean-atmosphere sciences community.     

Parameterization of the depth of the upper quasi-homogeneous layer based on measurements in the North Atlantic (Section along 53° N)

The dependence of the variation in the depth of the upper mixed layer (MLD) on the governing parameters (the momentum flux, the buoyancy fluxes at the ocean surface, and the density gradient in the pycnocline) is considered. It is shown that, in the spring storm season, wind mixing dominates over convective mixing. In this case, the MLD is linearly correlated with the Ekman scale calculated from the friction velocity observed approximately 12 h before the measurement of the MLD.     

Primary production in the eastern tropical Pacific: A review

The eastern tropical Pacific includes 28 million km² of ocean between 23.5°N and S and Central/South America and 140°W, and contains the eastern and equatorial branches of the north and South Pacific subtropical gyres plus two equatorial and two coastal countercurrents. Spatial patterns of primary production are in general determined by supply of macronutrients (nitrate, phosphate) from below the thermocline. Where the thermocline is shallow and intersects the lighted euphotic zone, biological production is enhanced. In the eastern tropical Pacific thermocline depth is controlled by three interrelated processes: a basin-scale east/west thermocline tilt, a basin-scale thermocline shoaling at the gyre margins, and local wind-driven upwelling. These processes regulate supply of nutrient-rich subsurface waters to the euphotic zone, and on their basis we have divided the eastern tropical Pacific into seven main regions. Primary production and its physical and chemical controls are described for each.Enhanced rates of macronutrient supply maintains levels of primary production in the eastern tropical Pacific above those of the oligotrophic subtropical gyres to the north and south. On the other hand lack of the micronutrient iron limits phytoplankton growth (and nitrogen fixation) over large portions of the open-ocean eastern tropical Pacific, depressing rates of primary production and resulting in the so-called high nitrate-low chlorophyll condition. Very high rates of primary production can occur in those coastal areas where both macronutrients and iron are supplied in abundance to surface waters. In these eutrophic coastal areas large phytoplankton cells dominate; conversely, in the open-ocean small cells are dominant. In a ‘shadow zone’ between the subtropical gyres with limited subsurface ventilation, enough production sinks and decays to produce anoxic and denitrified waters which spread beneath very large parts of the eastern tropical Pacific.Seasonal cycles are weak over much of the open-ocean eastern tropical Pacific, although several eutrophic coastal areas do exhibit substantial seasonality. The ENSO fluctuation, however, is an exceedingly important source of interannual variability in this region. El Niño in general results in a depressed thermocline and thus reduced rates of macronutrient supply and primary production. The multi-decadal PDO is likely also an important source of variability, with the ‘El Viejo’ phase of the PDO resulting in warmer and lower nutrient and productivity conditions similar to El Niño.On average the eastern tropical Pacific is moderately productive and, relative to Pacific and global means, its productivity and area are roughly equivalent. For example, it occupies about 18% of the Pacific Ocean by area and accounts for 22–23% of its productivity. Similarly, it occupies about 9% of the global ocean and accounts for 10% of its productivity. While representative, these average values obscure very substantial spatial and temporal variability that characterizes the dynamics of this tropical ocean.     

The STRATAGEM project: Stratigraphic development of the glaciated European margin

The EC-funded STRATAGEM project ran from 2000 to 2003 and was a study of the Neogene evolution of the glaciated northeast Atlantic margin from Lofoten to Porcupine, an area extending over nearly 20 degrees of latitude. An extensive seismic, borehole and sample database has been used, much of it supplied by the oil industry. The main products of STRATAGEM have been an integrated, unified stratigraphic framework in the form of an atlas documenting and illustrating the detailed stratigraphy of the entire margin, and a detailed evolution model for this margin. A brief summary of the background to, and organisation of, the project is presented, together with an outline of the main objectives, the physiographic setting of the area and the database.