Detailed visual seabed survey at drilling site 7218/11-1
Detailed visual seabed survey at drilling site 7218/11-1
Detailed visual seabed survey at drilling site 7218/11-1
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5.4.3 Compar<strong>at</strong>ive assessment<br />
Table7 showsvariousexpressionsof extent of impactsunderthe variousdischargescenarios.Case7<br />
usesthe new SPUDloc<strong>at</strong>ionandis shownin bold.<br />
Table 7. Comparisonof the extent of impacts to the seafloor and spongeassemblages,under 5 different<br />
dischargescenarios.Note Case7 is calcul<strong>at</strong>edfor the new SPUDloc<strong>at</strong>ion (upd<strong>at</strong>ed21.09.2012)whereasthe<br />
otherscenariosarebasedon the originalSPUDloc<strong>at</strong>ion.<br />
Case1 Case2 Case6 Case7 Case6a<br />
Sp<strong>at</strong>ialextent of impacts<br />
Affectedarea1-3 mm (m2) 71426 <strong>11</strong>3031 71928 25341 71928<br />
Affectedarea3-10mm (m2) 44913 57388 45916 12249 45916<br />
Affectedarea10-30 mm (m2) 19767 18289 23587 7289 23587<br />
Numberof observ<strong>at</strong>ionsin affectedareas<br />
No.Observ<strong>at</strong>ions1-3mm0-1 %cover 27 42 19 16 57<br />
No.Observ<strong>at</strong>ions1-3mm1-5 %cover 272 397 233 <strong>11</strong>2 330<br />
No.Observ<strong>at</strong>ions1-3mm5-10 %cover 33 42 26 15 19<br />
No.Observ<strong>at</strong>ions1-3mm10-15 %cover 2 5 3 1 0<br />
No.Observ<strong>at</strong>ions1-3mm>15%cover 0 0 0 0 0<br />
Proportionsof observ<strong>at</strong>ionsin affectedareas<br />
%areaaffected1-3mm0-1%cover 8 % 9 % 7 % <strong>11</strong> % 14 %<br />
%areaaffected1-3mm1-5 %cover 81 % 82 % 83 % 78 % 81 %<br />
%areaaffected1-3mm5-10 %cover 10 % 9 % 9 % 10 % 5 %<br />
%areaaffected1-3mm10-15 %cover 1 % 1 % 1 % 1 % 0 %<br />
%areaaffected1-3mm>15%cover 0 % 0 % 0 % 0 % 0 %<br />
Case7 hasthe lowest sp<strong>at</strong>ialextent of impacts.Note th<strong>at</strong> areasaffected by higher sediment<strong>at</strong>ion<br />
than 30 mm thicknessarenot distinguishedin this exercise.<br />
5.5 Assessing vulnerability of sponge assemblages to <strong>drilling</strong><br />
discharges<br />
5.5.1 Wh<strong>at</strong> do sensitivity and vulnerability mean?<br />
We candefine sensitivityin terms of how muchreactionis causedby specificactions.In the caseof<br />
sponges,we canidentify wh<strong>at</strong> environmentalfactorshavea positiveandneg<strong>at</strong>iveeffect on sponges.<br />
Generally,sponges,likeother benthicorganisms,areaffectedby:<br />
Foodsupplyfrom the upperw<strong>at</strong>er layers<br />
Propertiesof the bottom w<strong>at</strong>er masses<br />
Sediment<strong>at</strong>ionof particles<br />
o Forspongesexcessivesediment<strong>at</strong>ionis assumedto causesmothering<br />
Exposureto chemicalsandphysicaldamage<br />
o May alter the ability to perform basic body functions (respir<strong>at</strong>ion, feeding and<br />
disposalof wasteproducts)<br />
Organismsare vulnerableif any of the abovefactorsare likely to be altered in the areain question,<br />
usuallyby ongoingclim<strong>at</strong>icchangesor humanactivities.<br />
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