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US/EU-Baltic International Symposium, 2008 IEEE/OES

Date 27-29 May 2008

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Displaying Results 1 - 25 of 86
  • Enabling discovery based science with Webb Gliders

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1356 KB) |  | HTML iconHTML  

    Buoyancy driven Slocum Gliders were a vision of Douglas Webb, which Henry Stommel championed in a futuristic vision published in 1989. Slocum Gliders have transitioned from a concept to a technology serving basic research and environmental stewardship. The long duration and low operating costs of Gliders allow them to anchor spatial time series. Large distances, over 600 kilometers, can be covered using a single set of alkaline batteries. Since the initial tests, a wide range of physical and optical sensors have been integrated into the Glider allowing measurements of temperature, salinity, depth averaged currents, surface currents, fluorescence, apparent and inherent optical properties. The ability to operate Gliders for extended periods of time are making them the central in situ technology for the evolving ocean observatories. Off shore New Jersey Gliders have occupied a cross shelf transect and have documented the annual variability in shelf wide stratification on the Mid-Atlantic Bight and the role of storms in sediment resuspension. The sustained data permit scientists to gather regional data critical to addressing if, and how, the oceans are changing. One of next major regions we will use this technology is to study the climate induced impacts on the food webs along the West Antarctic Peninsula. View full abstract»

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  • Seatrack Web: A numerical tool to protect the Baltic Sea marine protected areas

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3209 KB) |  | HTML iconHTML  

    Shipping activities in the Baltic Sea, including oil transport and oil handled in harbors, have a number of negative impacts on the marine environment, marine protected areas (MPAs) and coastal zone. One of the main tasks in the ecological monitoring of the MPAs in the European seas is an operational satellite and aerial detection of oil spillages, determination of their characteristics, establishment of the pollution sources and forecast of probable trajectories of the oil spill transport. The interactive numerical model Seatrack Web SMHI is a powerful operational tool that can be used for a forecast of the oil spill drift in the vicinity of MPAs and for assessment of ecological risks related to potential oil pollution of every MPAs in the Baltic Sea. Three examples of oil spill drift modelling and of calculation a probability of the oil drift for specific points along main ship routes in the Gulf of Finland and southward of Gotland for July and August 2007 are shown. View full abstract»

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  • Expendable benthic lander (XBL)

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (930 KB) |  | HTML iconHTML  

    Observatories on the sea floor are about to permit long term observations of physical and chemical processes. Most of these observatories will deliver their measurements ashore in real time or near real time and many will derive power from a cable that connects them to shore. The cable is both empowering and limiting insofar as it permits long deployments and real time data return but restricts observations to regions where the cable has been laid. There remains a need for observatory type arrays of sensors where cables have not been emplaced. The expendable benthic lander is an instrument that can be deployed in such an array. The requirements for such an instrument are that it be inexpensive so that large numbers can be deployed in an array, easily deployed so that costs of laying the array are modest, capable so that physical and chemical properties can be resolved at the speed and sensitivity required to understand processes of importance, and recoverable so that the data may be analyzed in detail. Physical instrument recovery is a desirable attribute but not as important as data recovery. Since data may be recovered even if the instrument is lost, the term expendable is applied to this benthic lander although this is not the primary mode of use. View full abstract»

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  • Comprehensive estimation of marine economy and resource potential of coastal region

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1187 KB) |  | HTML iconHTML  

    For elaboration of strategy of sustainable coastal region development itpsilas very important to know a real potential of development of the region including estimation of the marine resources. As such parameter it is possible to use the concept of marine economy and resource potential of the coastal region which can be presented as united value of comprehensive characteristics of environment, socio-economic and political profits (damages) from coastal planning decisions. Some present results include example of the comprehensive estimation on the basic of the Baltic coastal regions. View full abstract»

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  • Water forecasts and data assimilation

    Page(s): 1 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1420 KB) |  | HTML iconHTML  

    The Waterforecast (http://www.waterforecast.com) has been operated since year 2001 providing a daily 5-day forecast on physical parameters such as wave climate, water levels, currents, salinity and temperature. However, also biogeochemical parameters have been included in the forecasts since 2001 providing similar 5-day forecasts for parameters such as dissolved oxygen and chlorophyll-a. Until now, data assimilation has not been carried out systematically. However, through different projects (MARCOAST (http://gmes-marcoast.com) and BALANCE (http://balance-eu.org)) new assimilation techniques have been implemented and tested improving the performance of the model forecast. Data assimilation has been carried out for physical parameters on basin to global scales for more than a decade and is now also advancing to regional systems forecasting, revealing some of the problems of data assimilation in frontal areas. Also, different modeling groups around the Baltic Sea work on improving biogeochemical model results by assimilation or by using more simple techniques attempting to improve forecasts of especially cyano-bacteria in the Baltic Sea. We have now successfully combined advanced data assimilation and water forecasting of both satellite images and profile measurements carrying out hindcast modeling of oxygen concentrations in the Baltic Sea and transition area and on-line assimilation of satellite images of SST and chlorophyll-a providing updated and improved forecasts on the state of the Baltic Sea, the North Sea and interconnecting seas. View full abstract»

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  • Fuzzy expert maps for risk management systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (839 KB) |  | HTML iconHTML  

    After widely known implementations of perfect ideas, expressed by researchers R. Axelrod, L. Zadeh and B. Kosko, the fuzzy cognitive map (FCM) became an important tool for decision makers in various practical areas, such as business evaluation, risk management, international policy making, medical diagnostics and others. The principle possibility of FCM involvement into a regional oceanic modeling system (ROMS) was presented during the US/EU Baltic International Symposium in Klaipeda in May 2006. Todaypsilas experience permits to extend the concept of FCM nodes, including additional fuzzy expert knowledge and enriching the representation of real situations under consideration. This paper presents a systematic approach, based on the authorspsila research, to the idea of FCM extension and its transformation into a rule-based fuzzy expert map (FEM), presents a simplified fragment of FEM use for a port security system, and discusses further perspectives of developing new tools for decision makers in risk management systems in general. View full abstract»

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  • United States IOOS - A national look

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (567 KB) |  | HTML iconHTML  

    The United States Integrated Ocean Observing System(IOOS) is a user-driven, coordinated network of people, organizations, and technology that generate and disseminate continuous data about our coastal waters, great lakes, and oceans. IOOS is intended to be a major shift in approach to ocean observing, drawing together the vast network of disparate, federal and non-federal observing systems to produce a cohesive suite of data, information, and products at a sufficient geographic and temporal scale to support decision-making. As the system matures, IOOS is expected to advance beyond its current science and management applications toward an instrument of policy and governance. Current efforts only scratch the surface of what we need to know about our oceans and coasts to fully assess their impact on commerce and transportation, weather and climate, and ecosystems. The power of IOOS is in its partnerships. Seventeen United States federal agencies and eleven regional coastal ocean observing systems (RCOOSs) share responsibility for the design, implementation, operation, and improvement of the United States. IOOS over time. Two interdependent components constitute the United State IOOS: (1) global ocean component and (2) coastal component. The latter includes the national set of observations for the Great Lakes and the EEZ, as well as the network of RCOOSs. Federal agencies are responsible for the design, operation, and improvement of both the global component and the national network of observations. RCOOSs augment existing federal observing capacity around the nation and ensure strong customer focus and connection. Each RCOOS, which is comprised of a series of sub-regional observing systems, is designed and managed by a single regional association (RA). View full abstract»

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  • Analysis and management of ecological risk for marine ecosystems and people in the Baltic Sea region

    Page(s): 1 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB) |  | HTML iconHTML  

    Presently there exists a contradiction; on the one hand, between the findings of the Commission of HELCOM CHEMU (1996) stating the lack of threat for the marine ecosystems and population from submerged chemical weapons in the Baltic Sea and, on the other hand, the statements of a number of politicians of the Baltic States (among others, the Prime Minister of Sweden) about the impermissibility of constructing the North Stream underwater gas pipeline due to extremely high environmental threat caused by the possibility of inflow of toxic agents into the nearby environment. The present research suggests an alternative problem-solving approach based on a new concept of scientific research. To illustrate the long-term prospects of the suggested research direction, on the basis of DPSIR (Driving Force-Pressure-State-Impact-Response) methodology we make a "through" estimation of the ecological risk significance. View full abstract»

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  • Air-Sea Interaction Profiler: Autonomous upper ocean measurements

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4078 KB) |  | HTML iconHTML  

    The Air-Sea Interaction Profiler (ASIP) is an autonomous profiling instrument for upper ocean measurements. The measurements from ASIP are well suited to enhancing research on air-sea interfacial and near surface processes. Autonomous profiling is accomplished with a thruster, which submerges ASIP to a programmed depth. Once this depth is reached the positively buoyant instrument will ascend to the surface acquiring data. ASIP can profile from a maximum depth of 100 m to the surface, allowing both mixed layer and near-surface measurements to be conducted. The sensor payload on ASIP include microstructure sensors (two shear probes and a thermistor); a slow response accurate thermometer; a pair of conductivity sensors; pressure for a record of depth; PAR for measurements of light absorption in the water column. Other non-environmental sensors are acceleration, rate, and heading for determination of vehicle motion. Power is provided with rechargable lithium-ion batteries, supplying 1000 W hr, allowing approximately 300 profiles. ASIP also contains an Iridium/GPS system, which allows realtime reporting of its position. View full abstract»

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  • Pathways of suspended particles released in the bottom boundary layer of the Bornholm Deep, Baltic Sea (numerical simulations)

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1655 KB) |  | HTML iconHTML  

    A model system consisting of a circulation model and a random-walk model is developed to simulate suspended particulate matter transport in the bottom boundary layer (BBL) of the southern Baltic Sea. The circulation model is based on POM, the Princeton Ocean Model, in which the vertical grid size is refined towards the bottom in order to resolve BBL properly. 3D fields of velocity, vertical and lateral apparent diffusivities generated by the circulation model are used as an input for the random walk model to simulate transport and dispersion of particles with prescribed settling velocity. The random-walk scheme allows for non-uniform vertical profiles of the vertical apparent diffusivity, and test runs have been done to make sure that the model does not display unrealistic removal of particles from highly turbulent BBL and further accumulation in low-diffusivity above-lying layers. A number of numerical experiments have been performed to study pathways of suspended particles released in the BBL in the centre of the Bornholm Deep at different wind conditions. At northerly and easterly winds the particles initially move westward and then get involved into either northern or southern detours around the Deep. The particles from the northern detour are finally absorbed into the Slupsk Furrow while those of the southern detour do not enter the Furrow keeping on cyclonic rotation within the Bornholm Basin. To the contrast, for the westerly and southerly wind conditions the particles move to the northeast for some 20 km and then get involved into the cyclonic rotation. The cyclonic rotation implies the convergence of currents in the BBL due the Ekman transport and, in view of continuity, the upwelling, so that the particles will remain trapped within the Bornholm Deep if the settling velocity is large enough to overcome the upwelling. Since the westerly wind conditions dominate in the climatic sense, the trapping effect may be considered as an important factor that controls- - dispersion of chemical warfare agents dumped in the Bornholm Deep after the World War II. View full abstract»

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  • Major advances in cabled ocean observatories (VENUS and NEPTUNE Canada) in coastal and deep sea settings

    Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1106 KB) |  | HTML iconHTML  

    VENUS (Victoria Experimental Network Under The Sea) is an advanced multi-node cabled ocean observatory now operational in the coastal ocean and NEPTUNE Canada (North-East Pacific Undersea Networked Experiments) is deploying into the deep ocean with on an 800 km loop with high power delivery. The abundant power, high bandwidth communications and hundreds of sensors delivering data in real or near real time will offer a new approach to acquisition of knowledge and interpretation of the ocean environment. Coupled with a powerful data repository and delivery system, ocean researchers have a powerful tool to explore ocean conditions. The development of cabled observatory technology is crucial given the current crises facing the ocean environment. View full abstract»

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  • Regional spatial distributions of organic carbon in coastal surface sediments of the Baltic Sea - A statistical approach and a rationale for geophysical surveying

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    The concentration of organic carbon in coastal sediments depends on several inter-related variables in a complex way. However, within a relatively small coastal area, several of these factors vary only little. Under these circumstances one variable, which to the largest extent determines the concentration of organic carbon is the mechanical energy of the bottom sediments. In this study we have collected sediment cores from two types of bottoms, transport (discontinuous deposition of fine particles and lower water content of sediments) and accumulation bottoms (continuous deposition of fine particles and higher water content of sediments), in a small area of the Stockholm Archipelago, in the Baltic Sea. The two bottom types are defined according to the water content of the sediment samples at the surface and distribution with depth. A statistical analysis of the organic concentration data by the means of an Analysis of variance (ANOVA) test with a 2-way layout, showed that the bottom type and not the sediment depth determines the concentration of organic carbon in these sediments. This result is believed to be universal under certain premises, and hence provides a rationale for surveying (with e g acoustic methods) the bottom dynamics whenever an estimate of the organic carbon concentration in the sediments of a given coastal area is desired. If the mean organic carbon concentration is estimated by considering these two sub-populations instead of a simple estimate, a smaller error will be obtained. View full abstract»

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  • Ocean observing technology and public-private partnerships

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (650 KB) |  | HTML iconHTML  

    The development and implementation of ocean observatories has primarily been driven by the research community and academic institutions. National governments have begun to take an increasingly more active role both in terms of fostering the development of individual observatories (the National Science Foundationpsilas Ocean Observatory Initiative) as well as the consideration of linking these individual observatories together into a national network (the Ocean.US Integrated Ocean Observing System). The role to be played by the private sector, both large and small companies, is also beginning to emerge. This paper explores some of the activities already undertaken by industry in ocean observing initiatives in the U.S. and other international initiatives. View full abstract»

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  • Effect of dumped chemical weapon on the Baltic Sea microbiota

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (651 KB) |  | HTML iconHTML  

    Seawater contamination with mustard gas and its derivatives substantially affects marine microorganisms. The mustard gas hydrolysis products (MGHPs) cause depletion of the species composition of microbiocenosis, as suggested by decreases in the Shannon and Pielou indices and the increase in the dominance index. Significant ecological shifts manifested as the decrease in the similarity indices. Decreased bacterial diversity suggests growth of a tolerant opportunistic species. From among bacterial cultures tolerant to mustard gas hydrolysis products the MGHPs-degrading microorganisms were isolated. The isolates were identified as Flavobacterium, Alcaligenes, Bacillus, or Pseudomonas spp. The main properties of these microorganisms are the tolerance to MGHPs, and the ability to utilize thiodiglycol. MGHPs-degrading bacteria can use mustard gas hydrolysis products as the sole source of carbon and energy at the organochlorine substances and thiodiglycol concentrations up to 240 mg/l and 6 g/l, respectively. The results suggest a potential for MGHPs biodegradation by natural occurring populations of near-bottom water and sediment microorganisms. Reduction in the species diversity of the marine microbiota suggests a decrease in the stability of the biosystem as a whole. View full abstract»

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  • Microbial indicators of contamination of water and sediments by warfare agents in Baltic Sea dump sites

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (629 KB) |  | HTML iconHTML  

    Our research revealed changes in the composition of the Baltic Sea microbial populations, namely, an increase in numbers of the physiological group of microorganisms that develop owing to organic compounds contaminating chemical weapon dump sites. We found that mustard gas hydrolysis products (MGHPs) - tolerant microorganisms were predominant in nearbottom water in many stations in the Baltic Sea dumping areas. The proportion of this group of indicator bacteria both in the total number of microorganisms and the amount of heterotrophic bacteria tended to increase. Comparison of the number of the indicator bacteria with the total number of heterotrophs allowed estimating the degree of contamination of marine ecosystem and characterizing the response of microbiota to the effect of warfare agents. Microbiological investigations revealed the concentration of MGHPs-tolerant microorganisms up to 20 - 98% of total number of heterotrophs in Gotland Deep, Strait of Skagerrack and Bornholm Basin. The ldquoabnormalrdquo sites characterized with a poor spectrum of heterotrophic microorganisms. At some stations the dominance of minimal number of species in near-bottom waters was observed. The species diversity of the microbial population in the dump sites was reduced because of an increase in the number of MGHPs-tolerant microorganisms. Thus, high number of microorganisms tolerant to MGHPs in near-bottom waters indicates possible leaking of CW agents into the environment and contamination of water and sediments with mustard gas and products of its hydrolysis in dumping areas. View full abstract»

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  • The impact of sea level rise and how it will effect on the Nile delta coast

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1308 KB) |  | HTML iconHTML  

    Records for more than 30 years of hourly sea level data at Alexandria and Port Said were used in these analyses. From these analyses the extreme sea level distribution was derived using a statistical analysis technique. A model for sea level prediction was constructed. The results indicate that the sea level rise if any will not exceed 15 cm in the worst weather condition for the next 50 years. View full abstract»

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  • The Mid-Atlantic Regional Coastal Ocean Observing System: Serving coast guard needs in the mid-atlantic bight

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (838 KB) |  | HTML iconHTML  

    The mid-atlantic regional coastal ocean observing system (MARCOOS) will implement an end-to-end regional ocean data acquisition, management, modeling and product generation system to satisfy user needs as defined by the middle atlantic coastal ocean observing regional association (MACOORA). MARCOOS will leverage extensive existing regional assets to augment federal backbone products in response to the MACOORA regional themes of maritime safety and ecological decision making. Regional products enabled by MARCOOS will in turn support the development of even higher resolution products at the sub-regional level, including supporting local MACOORA needs for Coastal Inundation and Water Quality. Through MARCOOS, regional scale observations from a network of HF-Radars, satellites, glider AUVs, and an array of meteorological stations will feed 4 operational numerical modeling systems. The HF radar network provides near realtime surface current observations along 1000 km of coastline with varying coverage from the coast out to the shelf break. The primary goal is to operate the regional system in a coordinated way to guarantee the delivery of quality ocean current and wave data. In this paper we present MARCOOS with an emphasis on the HF Radar network. Particular attention is placed on the setup, operation, and application of the network. Quality control metrics based on comparisons with coast guard deployed surface drifters (SLDMBs) have a specific focus to quantifying the uncertainty in the HF radar surface current estimates as applied to search and rescue observations. These metrics will be used to ensure that quality data is going to the coast guard and that this information is properly incorporated into existing search planning tools. View full abstract»

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  • Remote sensing of coastal ecosystems

    Page(s): 1 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (803 KB) |  | HTML iconHTML  

    Advances in sensor design and data analysis techniques are now making remote sensing systems practical and attractive for coastal ecosystem research and management. Multispectral and hyperspectral imagers are available for mapping coastal land cover and concentrations of organic/inorganic suspended particles and dissolved substances in coastal waters. Thermal infrared scanners can map sea surface temperatures accurately and chart coastal currents, while microwave radiometers can measure ocean salinity, soil moisture and other hydrologic parameters. Radar imagers, scatterometers and altimeters provide information on ocean waves, ocean winds, sea surface height and coastal currents. Using airborne LIDARs one can produce bathymetric maps, even in moderately turbid coastal waters. Since coastal ecosystems have high spatial complexity and temporal variability, they frequently have to be observed from both, satellite and aircraft , in order to obtain the required spatial, spectral and temporal resolutions. A reliable field data collection approach using ships, buoys, and field instruments with a valid sampling scheme is required to calibrate and validate the remotely sensed information. This paper presents a brief overview of recent advances in coastal remote sensing. View full abstract»

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  • Recent advances in ferrybox monitoring on board Finnmaid ferry

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2643 KB) |  | HTML iconHTML  

    Finnish Institute of Marine Research (FIMR) as a founding member of Alg@line consortium has been a forerunner in the field of monitoring research using commercial ferries. In 1992 FIMR started continuous measurements on board the ferry Finnjet, crossing the Baltic Sea Proper, using unattended recording and sampling system. During the spring of 2007 the ferrybox monitoring system was reinstalled in a new ferry Finnmaid providing real time observed data transmission with satellite connection. Chlorophyll-a (Chla) still remains the principal monitoring parameter. However, the distribution of cyanobacteria cannot be evaluated using Chla in vivo fluorescence, as most of their Chla is located in the poorly-fluorescing photosystem I. Instead, phycocyanin (PC) fluorescence is used in the detection of cyanobacterial blooms in 2005-07. PC fluorescence shows a linear relation to the biomass of the bloom forming filamentous cyanobacteria. During blooms of filamentous cyanobacteria the variability in Chla concentrations is better explained by PC fluorescence than by Chla fluorescence. Additionally, Chla records have been applied in validation of MODIS satellite monitoring for the water quality. View full abstract»

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  • Biodiversity of microzooplankton (ciliates and rotifers) in the Baltic Sea

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (617 KB) |  | HTML iconHTML  

    Microzooplankton (e.g. ciliates and rotifers) is an important ecosystem compartment responsible for the transfer and recycling of nutrients in pelagic ecosystems. In the Baltic Sea, species diversity of microzooplankton is high. The characteristic feature of the Baltic Sea planktonic fauna is that great part of it is represented by the freshwater species. In comparison with other seas, species composition of the Baltic Sea's ciliates and rotifers have been studied more completely. Now, 789 species of ciliates are known for the Baltic Sea, and only 160 of them are true planktonic. Thus, the need to define better the diversity of planktonic ciliates is essential. In particular, nanociliates (<20 mum) and their functional role in the Baltic pelagic ecosystems are poorly known. Several species of ciliates that are new for the Baltic Sea were discovered by the authors in the Neva Estuary (eastern Baltic Sea). Diversity of rotifers in the Baltic estuarine ecosystems was investigated in more details and accounts to ca. 150 species; meanwhile the species composition of rotifer assemblages in the open Baltic Sea is still in need of revision. View full abstract»

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  • Complex satellite monitoring of the nord stream gas pipeline construction

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3214 KB) |  | HTML iconHTML  

    Shipping The Nord Stream is a more than 1200-km long gas pipeline that will link Russia to Europe via the Baltic Sea from Vyborg in Russia to Greifswald in Germany. The construction process of the pipeline may cause, in particular, the following impact on the marine environment: (i) oil pollution due to the operation of ships, pipelay vessel, dredge ships and mechanisms in the sea; (ii) increase of suspended matter concentration due to dumping of sand and gravel, and dredging operations; (iii) provoking of local algal bloom events in summertime due to vertical mixing resulted from dumping and dredging works. Thus, there are two very important and interrelated tasks: (i) to monitor in the operational regime the ecological state of the sea at the site of the pipeline construction, and (ii) to discriminate between natural effects and anthropogenic impacts, related to the construction itself. View full abstract»

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  • Electromagnetic footprint measurements from a towed platform for characterizing sub-bottom conductivities and structures in the Stockholm archipelago

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1510 KB) |  | HTML iconHTML  

    In the ocean there are mainly two ways of characterizing the properties of the sediment structure. One technique is to observe the properties by physically collecting core samples by in-situ instrumentation. The other is to use remote techniques to estimate the acoustic properties of the sediment and from these observations invert the sediment thickness and sound velocity by interpreting the reflected sound. One of the drawbacks of the acoustic technique is that its range sometimes may be limited by gas trapped in the sediments, which severely impedes the sound propagation. This situation is often encountered in the Stockholm archipelago. For these areas it is possible to use low-frequency electromagnetic fields to achieve basically the same type of sediment property description. A model-based technique has been developed for characterizing the sediment conductivity and thickness by inversion of electromagnetic data. A field trial was undertaken in May 2007 where electromagnetic data was collected by a towed sensor which also included a one-axis electromagnetic multi-frequency source in addition to the electric receiver. Results from the analysis are presented and discussed in terms of its appropriateness for use in footprint techniques for determining sediment layer thickness and sediment conductivity along the tow track. View full abstract»

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  • Progress toward a sea-floor observatory at a carbonate/hydrate mound in the northern Gulf of Mexico

    Page(s): 1 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1138 KB) |  | HTML iconHTML  

    The Gulf of Mexico hydrates research consortium has been designing a sea-floor observatory to monitor natural gas hydrates in the gulf of Mexico for almost ten years. The observatory will consist of seismo-acoustic receiving arrays, geochemical arrays in the lower water column and upper sediments as well as systems for observing microbial activity. Mississippi Canyon Lease Block 118 (MC118) in the northern part of the Gulf has been selected as the site of the observatory. A carbonate/hydrate mound approximately one kilometer in diameter occurs in the south-central portion of MC118 at a water depth of about 900 m. The surface morphology of the mound has been imaged by multi-beam bathymetric sonar from an autonomous underwater vehicle (AUV) operating 40 m above the sea floor, by video cameras deployed on and a few meters above the sea floor from surface vessels and by visual observations from manned submarines. Gravity and box cores have been collected for lithologic and bio-geochemical studies of the near-surface sediments on the mound. Microbial sulfate reduction, anaerobic methane oxidation, and methanogenesis are all important processes in the upper four meters of sediment. These microbial processes seem to control the diffusive flux of methane from the sediments into the overlying water column. The activity of microbes is also focused within patches or dasiahot spotspsila at the main, active mounds. This activity is primarily dependent upon an active fluid flux of hydrocarbon-rich fluids. The geochemical evidence suggests that the fluid flux waxes and wanes over time and that the microbial activity is sensitive to such change. The subsurface structure of the mound has been investigated by chirp-sonar profiles acquired by the AUV simultaneously with acquisition of the swath bathymetry data and by a psuedo-3D grid of high-resolution seismic profiles obtained using the surface-source/deep-receiver technique. Also, deep seismic 3D volumes obtained by the petroleum in- - dustry have been viewed. The surface of the mound is pocked by craters apparently formed during episodic fluid expulsion events. Gases venting from the mound, as well as those contained in outcropping hydrates, have been analyzed and found to be thermogenic, perhaps having migrated up faults from a deep, as yet undiscovered, petroleum reservoir. The deep seismic data show that the faults emanate from a salt diapir located some hundreds of meters below the mound. It was observed during a cruise in November, 2007, that craters and outcrops had changed significantly during the 14-month period since the previous cruise in September, 2006. The mound therefore has been shown to be sufficiently dynamic to warrant continuous monitoring over the five-to-ten years that the observatory is expected to be operational. View full abstract»

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  • Iron plaque formation on seagrasses: Why not?

    Page(s): 1 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2841 KB) |  | HTML iconHTML  

    Iron (Fe) plaque formation is a well known phenomenon in wetland, freshwater and salt marsh species; however there are no reports about Fe plaque occurrence in seagrasses. Here we review the main factors regulating Fe deposition on the roots and rhizomes of plants from reduced sediments/soils, and discuss these factors in relation to marine environment. Moreover, we present some early observations and quantification of Fe plaque on the tropical seagrass Cymodocea serrulata. Based on these first results and literature data, we compare the seagrass C. serrulata with the freshwater macrophyte Lobelia dortmanna performance and efficiency with regard to plaque formation. The comparison shows that regardless of the lower oxygen release to the sediment and less favourable sediment conditions with high pH, low organic matter content, high carbonate content and actively ongoing sulphate reduction, the seagrass is able to develop significant Fe plaques on roots and rhizomes. Thus we conclude that seagrasses have the necessary characteristics for plaque formation, and that marine sediments may be a favourable environment for Fe plaque development. Moreover, we suggest the likelihood of finding Fe deposits also on other species than C. serrulata and in other geographical locations. View full abstract»

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  • Geophysical investigations of a chemical munition dumpsite in the Baltic Sea

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    Very high resolution seismic and magnetic investigations were carried out over a chemical munition dumpsite in the Bornholm Basin, south-western Baltic. The main goal of the investigations was to image the internal structure of the dumpsite and to map the lateral and vertical distribution of the dumped weapons. The shallow geology was imaged in great detail on the seismic data. Seven seismic-stratigraphic units were identified, related to different stages in the Holocene and late-glacial history. A large number of diapir-like features were observed that most likely represent fluid expulsion phenomena. Four shipwrecks were identified in the dumpsite area. The wrecks have partly sunk into the soft upper sediments, their height above the sea floor reaching no more than 2 m. Seismic and magnetic data indicate the presence of a large number of buried objects. In most cases there is a good correlation between the two data sets. The objects are generally buried no deeper than 1 to 2 m. Their size varies between 1.5 and 5 m, occasionally up to 10 m. Shallow pits in the sea bed are likely due to the impact of dumping. The data confirm the wide variety of dumped war material ranging from bombs and shells to encasements and containers. The distribution of the buried objects seems rather heterogeneous, with locally high object concentrations surrounded by areas of lower object density. The results of this case study demonstrate the benefit of complementary, concurrent geophysical investigations for munition dumpsite research. Finally this will yield a better assessment of the current status of the dumpsite and the possible ecological risks related to the dumped war material. View full abstract»

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