Minerals Report - International Seabed Authority
Minerals Report - International Seabed Authority Minerals Report - International Seabed Authority
ackground levels and confined to a very restricted zone around mining vessels. � Effects of trace elements and pesticides on organisms in the water – Seabed sediments introduced to the continental shelf by the Orange River contain metals and pesticides that are remobilised through mining activity. The metals and pesticides are then liable to bio-accumulate if taken up by organisms. Small quantities of ferrosilicon are introduced to the gravel during the treatment process, and are lost overboard with the tailings, but this is considered to have no effect on water quality. The presence of trace elements and pesticides is considered to be limited both to a short time and over a small spatial extent. � The effect of low oxygen levels in the water as a result of tailings and mining on the seabed – Bacterial decomposition of organic matter in the sediments can deplete oxygen concentrations. Reduction in oxygen concentration of bottom waters was considered to be most significant as oxygen depleted bottom water is characteristic of the Benguela Ecosystem. Mobile animals such as fish migrate out of areas influenced by low oxygen concentrations whilst less mobile organisms perish since few can tolerate zero-oxygen water. Field measurements indicated that tailings would produce no measurable decrease in bottom water oxygen, but resedimentation could result in burial of organisms unable to escape [14,15,]. This aspect of the study considerably increased the understanding of the Benguela Ecosystem by providing new, higher-resolution datasets about currents and oxygen levels within the system. As a result of the baseline study, three years of current data and two years of oxygen measurements are now available. These provide the first time series analysis proving that low or zero oxygen events periodically occur naturally across large areas of the continental shelf. These data were recorded over an extended period by the Institute for Maritime Technology and further supplemented with data from RACAL. INTERNATIONAL SEABED AUTHORITY 630
3.1.2 Changes to the seabed and resident communities The mining process, treatment and the overboard discharge of tailings comprehensively mixes the sediment horizons overlying the footwall directly beneath the ore body. This alters the natural habitat of the infaunal communities. The process also destroys the organisms in the mined sediments, and others are smothered by resedimentation of the coarser-grained material discharged overboard as it settles on the seabed. Recolonisation of the mined areas (termed “chronically artificially disturbed”) [15] by benthic organisms requires time, and the structure of the communities is altered – benthic community structure is commonly considered to be an important indicator of environmental conditions. Researchers identified some 233 infaunal species, including at least one species that is new to science. The organisms range in size between worms of 20 cm in length to minute snails millimetres in diameter [16,17,18,19]. The spatial extent of this impact is restricted to the area in which mining occurs and most likely to a couple of hundred metres beyond due to the resedimentation of sediment put into suspension during the mining process. The analysis of the communities based on grab sampling from mined and unmined areas shows that recovery to a stable biological community may take from 4 to 8 years [19,20,21]. 3.1.3 Effects on fish and dolphins The initial study showed that within the mining area there are relatively few species, no fish spawning grounds and currently no commercial fishing activity. Rock lobster is the basis for an important fishery in Namibia, but DBM’s operations do not overlap with the optimal habitat or any rock lobster fishing activities. Consequently, potential for conflict between the deep-water diamond mining operations and the fishing industry is avoided. The potential for noise from vessels and/or from the mining process to impact on fish and marine mammals was considered. Measurements of noise levels established that the frequencies generated are lower than those used by marine mammals for communication [22,23,24]. INTERNATIONAL SEABED AUTHORITY 631
- Page 588 and 589: The deep-water ore body more closel
- Page 590 and 591: 4. The mineral resource management
- Page 592 and 593: deployed on a MacArtney FOCUS 400 R
- Page 594 and 595: Utilising Jago has made very detail
- Page 596 and 597: Although at first glance the nature
- Page 598 and 599: to levels capable of sustaining sea
- Page 600 and 601: In accordance with De Beers’ over
- Page 602 and 603: ACKNOWLEDGEMENTS I thank my many co
- Page 604 and 605: 16. I.B. Corbett (1989), The sedime
- Page 606 and 607: SUMMARY OF PRESENTATION AND DISCUSS
- Page 608 and 609: eroded during regression and transg
- Page 610 and 611: diamond mining business. Dr. Corbet
- Page 612 and 613: technological step, Dr. Corbett sug
- Page 614 and 615: and Ore Reserves (JORC). He also sa
- Page 616 and 617: With another slide, Dr. Corbett sho
- Page 618 and 619: of De Beers’ deepwater operation
- Page 620 and 621: system that allows other functions
- Page 622 and 623: CHAPTER 16 A CASE STUDY IN THE DEVE
- Page 624 and 625: change through heat transport and c
- Page 626 and 627: Main sites of oxygen minimum Flow o
- Page 628 and 629: • Undertake necessary mitigatory
- Page 630 and 631: State, by such spilling or pollutio
- Page 632 and 633: including diamonds, from non-fluore
- Page 634 and 635: agreements require that government
- Page 636 and 637: including current velocities, oxyge
- Page 640 and 641: Sonar equipment used on some DBM ve
- Page 642 and 643: advocated this approach for environ
- Page 644 and 645: local geology, sedimentology and mi
- Page 646 and 647: Levene’s test could also be used
- Page 648 and 649: unquestionably be alarming, and the
- Page 650 and 651: 3.4 Future Innovation in Video Tran
- Page 652 and 653: sponges and bryozoans to more gener
- Page 654 and 655: esearch contributions of Mark Gibbo
- Page 656 and 657: 16. Craig R. Smith (1998), The Biol
- Page 658 and 659: magellanicus, Gmein) populations. J
- Page 660 and 661: SUMMARY OF PRESENTATION AND DISCUSS
- Page 662 and 663: presentation he would show that kno
- Page 664 and 665: process of self-regulatory checking
- Page 666 and 667: initial mining, but that within a v
- Page 668 and 669: continental shelf. He suggested tha
- Page 670 and 671: would result in the extermination o
- Page 672 and 673: The participant from Saudi Arabia r
- Page 674 and 675: of the Namibian government would be
- Page 676 and 677: With the exception of the West Paci
- Page 678 and 679: 1.3 Resources The oceanic regions o
- Page 680 and 681: 2 Physiography of the Ocean Floor a
- Page 682 and 683: INTERNATIONAL SEABED AUTHORITY 674
- Page 684 and 685: partially separated continental fra
- Page 686 and 687: occur beneath the continental shelf
ackground levels and confined to a very restricted zone<br />
around mining vessels.<br />
� Effects of trace elements and pesticides on organisms in the<br />
water – <strong>Seabed</strong> sediments introduced to the continental shelf<br />
by the Orange River contain metals and pesticides that are<br />
remobilised through mining activity. The metals and pesticides<br />
are then liable to bio-accumulate if taken up by organisms.<br />
Small quantities of ferrosilicon are introduced to the gravel<br />
during the treatment process, and are lost overboard with the<br />
tailings, but this is considered to have no effect on water<br />
quality. The presence of trace elements and pesticides is<br />
considered to be limited both to a short time and over a small<br />
spatial extent.<br />
� The effect of low oxygen levels in the water as a result of<br />
tailings and mining on the seabed – Bacterial decomposition<br />
of organic matter in the sediments can deplete oxygen<br />
concentrations. Reduction in oxygen concentration of bottom<br />
waters was considered to be most significant as oxygen<br />
depleted bottom water is characteristic of the Benguela<br />
Ecosystem.<br />
Mobile animals such as fish migrate out of areas influenced by<br />
low oxygen concentrations whilst less mobile organisms perish<br />
since few can tolerate zero-oxygen water. Field measurements<br />
indicated that tailings would produce no measurable decrease<br />
in bottom water oxygen, but resedimentation could result in<br />
burial of organisms unable to escape [14,15,].<br />
This aspect of the study considerably increased the understanding<br />
of the Benguela Ecosystem by providing new, higher-resolution datasets<br />
about currents and oxygen levels within the system. As a result of the<br />
baseline study, three years of current data and two years of oxygen<br />
measurements are now available. These provide the first time series<br />
analysis proving that low or zero oxygen events periodically occur<br />
naturally across large areas of the continental shelf. These data were<br />
recorded over an extended period by the Institute for Maritime<br />
Technology and further supplemented with data from RACAL.<br />
INTERNATIONAL SEABED AUTHORITY 630
Change language