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By Delphine Pierre, Jean-Marie Augustin, Anne-Sophie Alix, Charline Guérin, Cecile Cathalot, Yves Fouquet, Arnaud Gaillot, Ewan Pelleter, Carla Scalabrin, Florian Besson

With the world’s growing demand for metals, seafloor massive sulfides (SMS) deposits are now seen as a possible mineral resource that could contributes to secure metal supply for human needs. SMS deposits are characterized by high concentrations of base metals and at some place high contents of precious and rare metals. Since 1977 and the discovery of the first high temperature (HT) hydrothermal vent and its sulfide mineralization and high biodiversity, more than 300 sites are known today. If the exploration strategy for detection of active hydrothermal sites is now robust, their associated mineralization will not (and must not) constitute a potential target for deep-sea mining due to environmental concerns and technical limitations. Recent studies on SMS deposits are rather focused on extinct and buried mineralized sites characterized by a lower biomass. Several geophysical techniques to explore and detect extinct SMS (eSMS) and buried SMS (bSMS) have been developed (e.g. Kawada and Kasaya, 2017; Szitkar et al., 2017, 2014) using different approaches (e.g. regional or local scale; ship-based or using underwater vehicles) with several degrees of success or limitation. Here we present results from acoustic surveys performed on the TAG hydrothermal district during the BICOSE (2014) and LEVE-SMF (2016) cruises and direct observation provided by HOV (Nautile) dives carried out during HERMINE cruise (2017). Acoustic data were acquired using two different multibeam echosounders (MBES): the hull-mounted Kongsberg EM122 (12 kHz, R/V L’Atalante) and the ROV-mounted RESON SeaBat 7125 (400 kHz, ROV Victor) (Figure 1). After processing, acoustic seafloor backscatter data from both MBES provides complementary qualitative results in relation to the seafloor composition. The analysis of the seafloor backscatter data obtained by near-seafloor surveys with the high-resolution 400 kHz MBES shows a clear relationship between low backscatter strength values and areas covered with pelagic and hydrothermal sediments whereas high backscatter strength values are associated to pillow lavas and basaltic scree. Intermediate backscatter strength values are rather related to old and younger eSMS as well as to mineralization on TAG active mound.

Jan 1, 2018

By Winston Rocher Anda

Traditionally, mining activities have been developed in firm land, but technological advances and human needs have opened in the last year?s new opportunities in the maritime field. This has happened not only in the oil or hydrocarbons industries, but also in relation to the exploration or exploitation of other minerals, metallic and non-metallic. This has forced several countries to complement or create legal rules that make possible its own development and the International Law, through the United Nations Convention on the Law of the Sea, to regulate this activity in the space of its own, the calling area. Chile, as country with a long experience in mining and great advances in large deposits exploitation, possesses a special juridical frame that regulates this economic activity according if it is the geographical or territorial area in which is realizes, and it has been complemented lately with the international normative.

Jan 1, 2011

By Peter E. Halbach, Andreas Jahn

Co-rich hydrogenetic ferromanganese crusts are typical marine interface products of growth processes taking place on sediment-free substrate rocks on the seafloor. They grow very slowly and preferentially in water depths below the oxygen-minimum zone (OMZ) and have so far been found even in water depths of up to more than 5000 m, i.e. also below the calcite compensation depth (CCD); these deep ferromanganese crusts are particularly rich in Fe. It is assumed that the O2-minimum zone is the most important source layer of dissolved manganese, the decomposition of fecal pellets here also contributes to this Mn-budget. The process of hydrogenetic precipitation is basically an inorganic colloidal-chemical as well as a surface-chemical mechanism. Microbial mediations can be assumed, in particular since steps of redox-reactions are involved. The two main components of the hydrogenetic substance are hydrated d-MnO2 (vernadite) and x-ray amorphous Fe-oxyhydroxide, both of which are intimately intergrown with each other forming the extremely fine-grained hydrous oxidic material. In seawater, elements occur as dissolved hydrated ions or as inorganic as well as organic complexes which, in general, have either a positive or a negative surface charge depending on the pH of the respective marine environment. These complexes form hydrated colloids that interact with each other or with other dissolved hydrous metal ions. The main agent to oxidize the dissolved Mn2+ ions is oxygen, transported upwards from deeper water by turbulent eddy diffusion and turbulent rise processes at seamount slopes.

Jan 1, 2017

By Michael J. Cruickshank

The University of Hawaii, Ocean Basins Division (OBD) shares, equally with the University of Mississippi, Continental Shelf Division (CSD), congressional funding for the Marine Minerals Technology Center, a Generic Minerals Center under the U.S. Department of the Interior's Mineral Institutes Program. The State of Hawaii supports the program by the provision of salaries for the Executive and Technical Directors and by the provision of fiscal, administrative, and facilities support through the Hawaii Natural Energy Institute, the Research Corporation of the University of Hawaii, and the School of Ocean and Earth Science and Technology. The Center's program of research, technology development and education is multi-disciplinary and international in scope. Activities since the MMTC/OBD was established in June 1988 have included: Research projects * Development of a Free-Fall Seafloor Hard Substrate Corer. * The Microtopography of Manganese Crust deposits. * Evaluation of the Cobalt Crust Continuum on Seamounts in the Hawaiian Exclusive Economic Zone. * Graphite Furnace Atomic Absorption Spectrometer. * Computer Aided Design Methodology for Power, Communication and Strength Umbilicals. * Characterization and Environmental Impact Assessment of Tropical * Reef-derived sands for Beach Replenishment.

Jan 1, 1991

By Wilfred Lus

Meaningful and real time environmental monitoring of marine tailings placement is a clear sign of deeper commitment to the people of PNG in regard to impacts of mining on coastal environment and marine life. Today daily mine wastes and tailings are increasingly being delivered to the seabed offshore of project sites in Misima and Lihir islands. Ramu and Simberi mining projects also plan to dispose tailings out at deep sea. As tailings leave the tailings pipe and come out into the seabed, concentrations of the cations and other potential harmful particles in the tailings stream need to be quantifiably monitored each day during the life of the refinery. For continuous monitoring of the tailing?s true chemical characteristics submarine cables connected with ocean floor observation systems consisting of deep-sea underwater video, and cation sensors and electrodes will be laid. Power transport to the tailings site and data transfer from the tailings site will be via opto-electric cables. Various data center instruments will record and manage the collected data. Observation data will be transferred in real time to stake holder?s data centers via a dedicated line from on-land stations, and then distributed to company offices and government establishments. Japan Marine Science and Technology Center, Telikom PNG, and Australian Institute of Marine Sciences will be the key advisers in this project. The main role of the observatories is to monitor and collect background seabed geochemical data prior to start of tailings disposal, during tailings disposal period, and after the life of the refinery.

Jan 1, 2001

By Robert Ditchburn

Within New Zealand?s extended EEZ there exists a vast submarine hydrothermal mineral resource associated with the Kermadec intra-oceanic arc. Along this arc more than thirty submarine volcanoes have been explored by GNS-lead researchers and, of these, c. 60% are known to be hydrothermally active and a site of active seafloor mineralisation. Assessment of whether this mineralisation is economically viable in terms of grade and tonnage is now underway. A key aspect of these investigations is determining the age of the mineralization which will have a direct bearing on its mode of formation, the time elapsed to amass an economic deposit and, ultimately, its capacity for sustainable extraction. Intact barite-rich ?black-smoker? chimneys similar to that depicted here (86 cm long) have been recovered from Brothers volcano in the southern part of the arc. These and other hydrothermal deposits provide evidence of active volcanic massive sulphide (VMS) mineralisation along the arc, the age of which can be determined from the disequilibrium between isotopes within the thorium or uranium decay chains. A chimney from Mariana arc has also been dated using these radiometric methods. The principle dating technique for chimneys up to 15,000 years old uses the decrease in 226Ra/Ba due to radioactive decay after the VMS was deposited. An initial ratio is obtained from chimneys that are proven to be less than 100 years old and this involves dating with 210Pb, 228Ra and 228Th that have short half-lives compared with 226Ra.

Jan 1, 2005

By Alexander Malahoff

Six active Kermadec Arc submarine volcanoes located between 34°S and 36°30?S were mapped and sampled by an interdisciplinary inter-institutional research team between April and July 2005 using submersibles Pisces V and Pisces IV aboard the mother ship the RV Kai?mikai-O-Kanaloa. The purpose of the expedition was to study the relationship between hydrothermal activity, formation of hydrothermal mineral deposits and the biodiversity of life associated with the hydrothermal vents. Of the volcanoes examined, all showed evidence of hydrothermal activity, plume production and helium anomalies. Only two of the volcanoes, namely Brothers and Clark, showed chimneys and surficial poly-metallic sulphide deposition. Hydrothermal venting at a water depth of 1700 meters within the base of the northern wall of the summit caldera of Brothers Volcano has produced a field of chimneys, some of them 5 metres high with black smokers venting. Temperatures of 300°C were measured within the active vents. Clark Volcano has a double cone summit at a water depth of 875 metres. The shallowest cone has a near-summit hydrothermal vent field with 5-meter high venting chimneys and smaller structures around the periphery. Water temperatures of 200°C. Geochemical and petrological analysis of the massive poly-metallic sulphide samples taken from Brothers and Clark show a diversity of mineralogy. This diversity is clearly a function of hydrothermal water temperature. Chimneys sampled from Brothers are pyrite and sphalerite dominant with lesser chalcopyrite. Sulphides from Clark Volcano tend to be barite rich with lesser sphalerite and pyrite. Sulphides from Brothers Volcano have a range in gold composition of 4 to 58 ppb with silver composition of up to 38 ppb. A mineral formation model for the volcanoes suggests hydrothermal fluid boiling within the volcanic edifice for those volcanoes with shallow summits and massive sulphide deposition with the edifice as well. Surficial deposits include native sulphur and lower temperature oxides. Only the deeper water Brothers Volcano shows massive sulphide deposition along the marginal faults of the caldera floor.

Jan 1, 2005

By Mikhail P. Torokhov

Typical coastal placers leave no doubt that placer accumulation can result in significant concentration of heavy minerals in marine shallow water environment. However, the same situation is quite predictable for guyot?s slopes at stages of submarine volcano formation and later submersion of guyots to a depth of up to 3-4 km. Where these placers could be found is also clear ? in coastal facies (as typical coastal placers), and in morphological traps down guyot slopes in zones of active submarine currents. The latter could be cracks in rocks, shallow depressions, spurs, and structures, such as coral reefs, stromatholiths, and even ferromanganese crusts. The last of these have been studied carefully by the author in the Magellan Seamounts and on the Mid-Pacific Rise: tens of minerals, including mineral forms of PGE, REE, Mo, W, Te, Cr, Co, Ni, Cu, &Zn were identified as a xenogenic (trash) minerals. The detailed study of polished epoxydized sections, showed that interstitial spaces of Fe-Mn botryoids are enriched in heavy minerals (predominantly titanomagnetite). Taking into account the irregular character of crust surfaces and their position in active water environment, we can definitely state that they are the ideal traps for placer minerals. Study of guyot basaltic matter showed the presence of similar REE, PGE minerals that are in the crusts, and the same (mostly) micron sizes of minerals. High content of PGE in some basaltic varieties (up to 1 ppm) suggests that this is a reasonable source of these elements in the crusts, rather than the water column (which is normally considered to be the case by most marine scientists). Predominance of Pt in hydrogenous (?) crusts is interpreted as due to the better stability of Pt mineral forms during weathering and transportation (these are isoferroplatinum, and silicides). Comparison of 143Nd/144Nd values in bulk crusts, heavy fraction of crusts, basalts, and water column supports the author?s idea, that a significant part of REE also comes from basaltic matter (in form of monazite, CeO2 etc.).

Jan 1, 2004

By Mikhail D. Ageev

The paper concerns with some questions of Autonomous Underwater Vehicle (AUV) control system design, which allows a motion at rough undersea terrain. The AUV advantages reveal itself completely during exploration of such objects as seamounts and reefs area. These objects are characterized by steep slopes (30 degrees and above) and chaotic situated obstacles (rock debris, pinnacles, escarpments). Uses of other technical facilities for operating in such formations are difficult, dangerous or impossible. These regions take an interest due to the presence of iron-manganese crusts. Modern AUV can estimate density of mineral by means of still camera or video recorder. For this reason the vehicle has to move with the distance of 3-5 meters from seabed. Under such conditions micro- and mesorelief presents a considerable danger for AUV. The AUV can bypass underwater obstacles in the various ways. However, in any case AUV motion will be characterized by intensive maneuvering on various speeds (from 0 up to 1.5 m/s), circular change of tractive force vector and, hence, a circular flow about the hull. So, AUV is equipped with the propulsion system, which provides free modes of motion.

Jan 1, 2003

By Tetsuo Yamazaki

Natural methane hydrate has been scientifically studied as a global carbon reservoir. However, in Japan, it?s potential as an energy resource has been industrially highlighted, because there are few domestic oil and natural gas resources in Japan, but many potential deposition areas for methane hydrate in the sea around Japan. Less CO2 discharge from methane compared with coal, oil and conventional natural gas for the same calorie value is considered an advantage for its use as an energy resource. Because methane hydrate is distributed at shallow depth in sediments on the ocean floor, accidental leakage of methane may occur while we utilize methane hydrate. Methane itself has a considerable impact on the greenhouse effect, if it reaches the atmosphere. Therefore, it is necessary to estimate its behavior in the environment after leakage if we want to use methane hydrate as energy resource. The mass balance after leakage of methane on the seafloor and in the water column can be studied through the analyses of natural cold seepages and hydrothermal activity.

Jan 1, 2004

A C-CORE study on behalf of the government of Newfoundland identified the inner continental shelf off northeast Newfoundland as having a relatively higher potential for hosting placer gold than other parts of the inner shelf. Under the auspices of the Canada-Newfoundland Cooperation Agreement on Mineral Development, the Geological Survey of Canada conducted a three-year project to map the distribution of surficial sediments and the abundance of placer minerals (particularly gold) from White Bay to Cape Freels. Much of the study area is a fjord coast, with steep rocky slopes and scattered gravel beaches. The extreme east, from Hamilton Sound to Cape Freels, has a wide, shallow inner shelf, sandy beaches, and extensive coastal dunes. Relative sea level was high in the late glacial period. It has fallen continuously in the west, but in the east it dropped to -19 m, before rising to within several metres of the present level by 3 ka. In terms of surficial sediments and processes, five zones are identified: (1) Deep offshore deep basins that contain thick postglacial mud overlying glacialmarine gravelly sandy mud. This zone is below a depth of 370 m in White Bay, 300 m in the Notre Dame Basin. 2) Basin transition zone in which the sea bed has been eroded by currents, so that glacialmarine sediments are exposed in places. Winnowing has formed an uppermost layer of muddy gravel. There is a slight potential for enhanced levels of fine particulate gold, but the gold would not be exploitable. (3) Iceberg impacted zone Above 200 m the keels of icebergs impact the sea bed, causing furrowing and pitting. Furrows predominate in deeper areas, and pits are concentrated at the inner boundary of this zone. Iceberg turbates have developed in shallow waters (60-100 m). Combined with winnowing, iceberg turbation could enhance the potential for concentration of fine particulate gold, but not into economic quantities. 4) Wave dominated zone Above approximately 60 m the sea-bed sediments are highly mobile due to waves, currents, and iceberg impact. Sand is either rippled or organised into sand waves. Gravel is either poorly sorted, and organised into

Jan 1, 1995

By Peter M. Bartlett

The Republic of South Africa ranks among the world leaders in both reserves and production of numerous land-based mineral commodities. Over the last three decades, however, South Africa has also identified several commodities that may exist in commercial quantities in the marine environment. The major targets include 1) placer diamonds; 2) titanium- and zirconium-rich beach sands; 3) sedimentary and concretionary phosphorite and glauconite deposits; 4) manganese nodules; and 5) hydrocarbons. South Africa ranks second in world reserves of diamonds and has potentially enormous sea resources. Diamonds are currently recovered on the Atlantic side from ancient beach gravels in the Northwest Cape Province and from the seabed south of the Orange River to Lamberts Bay. Approximately 100,000 carats (or just 1% of South Africa's total annual production) are produced each year from offshore operations. DeBeers is investing approximately $5 million per year on sea prospecting activities and currently operates three vessels in offshore recovery operations. Diamonds recovered at sea will remain a small percentage of total production because of huge land-based reserves that are mined at a fraction of the cost of seabed operations.

Jan 1, 1986

By Chan Min Yoo, Jung-Keuk Kang, Wonnyon Kim

Recently high-resolution paleomagnetic age determination of ferromanganese crust in less than millimeter scale has been successfully carried out using a superconducting quantum interference device microscopy magnetometer (SMM). However, it has not been clearly identified how the crust is keeping ancient geomagnetic field records. Here we try to identify magnetic mineralogy of the crust obtained in the Magellan Seamounts, the West Pacific (~20 °N). As a record, age of the crust used in this study is extended to ~10 Ma at ~40 mm depth and ~28 Ma at ~100 mm depth, respectively, based on the combination approach of SMM measurements, Be-isotope and Co-chronology. Thermal demagnetization revealed a Curie temperature of ~560oC, corresponding to (titano)magnetite. Component analysis of isothermal remanent magnetization identified a presence of two types of magnetite. Measurements of first order reverse curve showed a dominance of non-interacting single-domain magnetite, which is one of the intrinsic feature of biogenic magnetite. Although most of the magnetic particles on transmitted electron microscopy are covered by amorphous Fe-Mn minerals, some are observed as a prototype of biogenic magnetite showing a chain of ~10 nm sized magnetite cubes. However, a magnetite signal (i.e., Verway transition at ~ –120 oC) was not detected in low-temperature treatment probably due to surface oxidation of magnetite. Contribution of interacting magnetite of detrital origin is <30% throughout a crust. Interestingly, contribution of detrital magnetite is almost three times higher since ~10 Ma. At this boundary, a growth rate of the crust is double up and flux of other detrital signals, including Al, Mg, Ti and Zr, are also increased.

Jan 1, 2017

By David G. Jones

Radiometric surveys of the beach and nearshore zone of the Dutch Frisian Islands have identified sands enriched in heavy minerals. The areas of heavy mineral concentration have been mapped in detail using a state of the art towed gamma-ray detector, which gives improved sensitivity through the use of new detector materials and improved data processing techniques. The detector provides continuous measurement of sea floor radioactivity (and of a number of other parameters) and can be used simultaneously with other survey techniques, such as echo sounding, sidescan sonar and shallow seismic profiling. It enables a rapid, and cost effective, assessment of the surface distribution of heavy minerals to be made. The heavy mineral suite includes magnetite, ilmenite, garnet, rutile and zircon. These minerals contain 1-3 orders of magnitude more U and Th, in terms of their activity concentrations, than the accompanying light minerals (mainly quartz). Since the heavy mineral composition of the sands appears to be relatively constant along the Dutch Frisian Island chain, the U and Th concentrations can be used to provide a quick estimate of the heavy mineral content. The sea floor radiometric measurements allow sediment sampling for more detailed analysis to be highly targetted. The zones of heavy mineral enrichment are generally sub-parallel to the coast and are usually confined to water depths of 5-10 m. There is a close correlation with sand bars on the shoreface, the highest radioactivity typically occurring just seaward of the crest of these features. As well as being used for heavy mineral exploration, similar radiometric methods can be applied to mineral processing. Gamma-ray detection systems can be used to provide rapid analysis in the process stream enabling on-line grade control and optimisation of processing, from excavation of mineral sands to the final products.

Jan 1, 1995

In the western Woodlark Basin, propagation of seafloor spreading is occurring directly into the continental crust of Papua new Guinea. The spreading is not strictly in a back-arc tectonic setting, rather it appears associated with microplate rotations related to the complex convergence of the Indo-Australian and Pacific plates in the southeastern Pacific region. Volcanic rocks along the western Woodlark spreading axis range from normal mid- ocean ridge basalts to basaltic andesites with back-arc geochemical affinities. Rare peralkaline rhyolites also occur. Hydrothermal deposits occur at a basaltic andesite volcano located on the neovolcanic zone near its westernmost propagating tip. Franklin Seamount is a 250m-high cone constructed largely of pillow lavas and talus which sits astride a 450m-high ridge of similar lavas oriented subnormal to the spreading direction. At its crest, 2150m below sea level, there is a 100m-deep caldera.

Jan 1, 1993

By Wilhelm Schwarz

Manganese nodules lay in vast areas of the deep sea floor. Ideal harvesting conditions for a manganese nodule field are dense nodule abundances of nodules between 20 and 60 mm diameter and a metal content as high as possible. With regard to the development of collector technology, the properties of the deep sea soil, in which the nodules are embedded and to which the nodules stick, are of major interest. The forces for loosening the nodules have to be provided by the collector. For this purpose water jets and/or mechanical devices can be employed. For the choice of the best collecting procedure, various criteria, such as collecting rate, energy consumption and the environmental impact on the eco system of the deep sea floor, have to be considered and weighted as to their importance. Nowadays, the concept of a mining system with a flexible transport hose and a self propelled collecting machine is increasingly accepted among the expert community. With regard to the trafficability of the deep sea soil with a self propelled mining machine, the mechanic properties of the soil and the morphology of the deep sea floor are of special importance. The manganese nodule fields, which are interesting with regard to their recoverability, are mostly in the areas of tectonic fracture zones, at which the morphology of the sea floor is formed by vulcanic activities. In these areas, deep sea mountains, pits and other obstacles exist that have to be driven around if not trafficable.

Jan 1, 2003

By Yves Fouquet

Recent exploration demonstrates that hydrothermal systems related to upper mantle ultramafic outcrops are common in the modern ocean. Most sites are located on slow spreading ridges with a low magmatic budget. Volcanogenic Massive Sulfide (VMS) deposits, associated with basalt, along the Mid Atlantic Ridge (MAR) are volcanically controlled near the topographic highs at the center of the segments. Three preferential settings are identified for ultramafic sulfide mineralization: 1) Off axis, on rift valley walls, near the amagmatic ends of the segments; 2) Non-transform offsets and 3) Ultramafic dome structures at the ridge transform fault intersection. The upper surface of these domes is often interpreted as a detachment fault. Three processes are considered for driving hydrothermal cells in ultramafic rocks: 1) regional heat flow at the ridge axis 2) Cooling of a deep gabbroic intrusion and 3) exothermic heat produced during serpentinisation. Along the Mid Atlantic Ridge, four types of ultramafic hydrothermal mineralization are observed: 1) High temperature (>350°C) sulfide mineralization related to low pH fluids, (ex. The Logachev field at 14°45? N and the Rainbow field at 36°14 N); 2) Medium temperature carbonate chimneys (<100°C) related to high pH fluids (ex. The Lost City site at 30°N); 3) Low temperature diffuse venting associated with extremely high methane discharge and pervasive alteration and silicification of both volcanic and ultramafic rocks (ex : The Saldanha field at 36°34 N); 4) Stockwork mineralization and quartz veins with sulfides related to gabbroic intrusions within ultramafic rocks (15°N). When compared to mineralization in a basaltic environment, sulfide deposits are enriched in copper, zinc and specific elements related to an ultramafic rock source such as Ni and Co. They are also significantly enriched in gold which, unlike in basaltic environments, has a bimodal occurrence both in low temperature Zn-rich assemblages and in high temperature Cu-rich mineral assemblages. The Cu-Zn-Co-Au deposits along the Mid Atlantic Ridge seem to be more common than on land where few similar VMS deposits are known. We consider that ultramafic VMS deposits on slow spreading ridges constitute a specific marine type of mineralization that is less easily than back arc deposits, incorporated into the continent during obduction processes.

Jan 1, 2004

By S. Rajendran

India?s interest in the resources of the deep seabed particularly the manganese nodules in the Indian Ocean can be traced back to the Indian Ocean Expedition of 1960 ? 65. The collection of Manganese Nodule samples from the Indian Ocean in January 1981 aroused considerable interest within the scientific community. Following several surveying expeditions, the Central Indian Ocean was identified as the most promising area for exploitation. India was accorded ?Pioneer Investor? status and further research and development programs were launched to establish the techno-economic viability of deep seabed mining. India has also shown considerable progress in the field of development and testing of methods for processing the nodules. The Department of Ocean Development manages the program.

Jan 1, 2003

By Virginie Tilot

Recommendations have been drafted following an international multidisciplinary panel discussion organized at UNESCO/IOC by the Académie des Sciences d?Outre-Mer on 15 December 2010 conveyed, according to its mandate, to the French government and to an international pool of scientists and stakeholders. These take into consideration the relevant Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982, the Rio ?Earth Summit? Convention of Biological Diversity of 5 June 1992 as well as the activities and recommendations implemented for the world?s oceans and seas, in particular by the International Seabed Authority (ISA) and the recent reports and scientific works (including those implemented by the ISA Kaplan, Ifremer, COI-Unesco). The recommendations integrate, for one of the ecosystems, the conclusions of the project of the conclusions of an IOC-UNESCO / Government of Flanders project (2004-2010) implemented by Dr. V. Tilot from 2004 to 2010, during which were published three volumes describing the referential state of the polymetallic nodule ecosystem and proposing options for the management and conservation of the nodule ecosystem in the Clarion Clipperton Fracture Zone, NE Pacific Ocean: http://unesdoc.unesco.org/images/0014/001495/149556f.pdf, http://unesdoc.unesco.org/images/0014/001495/149556e.pdf; http://unesdoc.unesco.org/images/0014/001495/149556e.pdf#223

Jan 1, 2011

By Siân E. Boyd

Studies of benthic recolonization in the aftermath of marine aggregate dredging in the U.K. and elsewhere are limited and are largely confined to experimental circumstances. Investigations of the physical and biological status of licensed extraction sites in the U.K. at various times following cessation of commercial dredging are very limited, and so judgments as to the likely progress towards environmental restoration and the time-scales involved continue to be based on predictions rather than real data. This field-based research programme was commissioned to enhance the understanding of processes leading to physical and biological recovery of the seabed following dredging, thereby aiding the identification of practices to minimize environmental harm at licensed sites, and to promote rehabilitation on cessation. The outcome of survey work will have the notable benefit of allowing questions about the present status of locations hitherto subject to commercial exploitation to be answered directly, rather than by inference.

Jan 1, 2002