Detailed visual seabed survey at drilling site 7218/11-1

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Figure14. Photosfrom Mercier(2012)showing(left) a sea-penfield and (right) developinglarvaeof the redfish Sebastestuckedamong the polypsof the seapens.Sizeof the seapensis not given,but the scalebarson the right are both 1 mm. The ecologicalrole of sponges,and their responsesto environmentalconditionsare to someextent documentedfor shallow-waters (seefor exampleBell & Smith,2004),we have few studieswhich clarify the role of coralsand spongesas autogenic engineersin deeperwater (Miller et al., 2012). Thoseauthors further state"[…]nevertheless,many fishes and macroinvertebratesinhabit deepwater coral (Rogers,1999, Husebøoet al., 2002, Mortensen & Buhl Mortensen, 2005 and Stone, 2006) and sponge(Beulieu,2001, Marliave et al., 2009) habitats. Unlike shallow-water systems, where the processesconnectinghabitat with populationsand communitiesof dependantorganisms are relatively well understood,the role of habitat structure, includingthat of autogenicecosystem engineers,in deep-water communitiesis still uncleardue to lack of small-scaleobservationaland experimentalstudies(Auster,2007). Obviously,the role of spongesas ecosystemengineersis a question of scale.At a small scale,an individual spongeprovides a habitat for a range of other organisms,but to be significantat an ecosystemscalerequiresthat large areasand/or large amountsof spongesare involved. Thisbegs the question to which we have no clear answer – how many sponges, or how large an area constitutes a resource of ecosystemsignificance?Further, how can we then assessissuesof vulnerabilityto humanactivities,or conservationstatus. The UK Biodiversity Action plan (http://jncc.defra.gov.uk/pdf/UKBAP_BAPHabitats -12- DeepSeaSpongeComms.pdf ) contains some interesting remarks, about sponge abundances, extractedfrom OSPAR(2008). "Densitiesof occurrenceare hard to quantify,but spongesin the class Hexactinellidahave been reported at densities of 4-5 per m², whilst ‘massive’growth forms of spongesfrom classDemospongiahave been reported at densitiesof 0.5-1 per m 2 (B. Bett, pers. comm.)." In this context,we canassumethat "massivegrowth forms" meanslargeindividuals,such asthe Geodiaspecimensin the BarentsSea, whichcanmeasure30-40 cm andmorein diameter. Akvaplan-niva AS, 9296 Tromsø 20 www.akvaplan.niva.no
4 Abundance quantification challenges - case study Salina, Juksa and Darwin 4.1 General Not only are spongesdifficult to identify, but they alsoare difficult to quantify from the type of data usuallycarriedout in connectionwith pre-drilling surveys.TheCENstandard(CENprEN16260)for visualassessmentsgivesguidanceon an abundancescale,but this requires knowledgeof numbersof spongesper unit area.Duringvisualsurveys,it is not alwayspossibleto uselaserbeamsduringall of the filming,andalsothe flight heightoften dependson individualconditions.Becausespongesin the south-westernpart of the BarentsSeaoften are verypatchilydistributed,estimatinga standardarea (m2)from a smaller(or larger)areausuallyisnot representativeof the realsituation. Duringvisualassessmentscarriedout during 2008,a 4-level abundancescalewas devisedby DNV, basedon minimum to maximumspongedensitiesrepresentativefor the RegionIX area. Thisscale alsowasusedat Salinain 2010(Akvaplan-niva)andJuksaandDarwinin 2011(DNV). Figure15. Abundancescaledefinedby DNV,2008.Upperleft rare,upperright, scattered,lowerleft, regularand lowerright, highdensity. At Salina,six of the imagesselectedfor detailed faunal analyseswere classifiedas havinga high densityof sponges,accordingto the abovescheme(Figure16). Detailed site survey at PL531 Darwin Akvaplan-niva AS Rapport 6051 - 1 21
Page 1 and 2: Detailed visual seabed survey at dr
Page 3: Akvaplan -niva AS Rådgivning og fo
Page 6 and 7: List of figures and tables FIGURE1.
Page 8 and 9: Preface In August,2012,Akvaplan-niv
Page 10 and 11: Figure2. ROVtransectsandrecordsof s
Page 12 and 13: 2 Materials and methods 2.1 Vessel
Page 14 and 15: 2.3 Survey track and waypoints Thep
Page 16 and 17: Akvaplan-niva haspreviouslyworked w
Page 18 and 19: Figure7. Over4 tonnesof sponges(pre
Page 20 and 21: Figure10. BarentsSea.Spongebycatchi
Page 22 and 23: Somespongesform densereefs,and prov
Page 26 and 27: Figure16. Imagefrom Salina,2010,cla
Page 28 and 29: It is clear that Cochraneadopted a
Page 30 and 31: 5.2 Seafloor conditions 5.2.1 Sedim
Page 32 and 33: 5.3.2 Plots of sponge distribution
Page 34 and 35: Figure24. Locationof the 30 imagess
Page 36 and 37: Position16. 0-1 % coverage Position
Page 38 and 39: Position15. 1-5 % coverage.Geodiaan
Page 40 and 41: 5.3.3 Overall assessment of sponge
Page 42 and 43: 5.3.5 Dominant sponge species recor
Page 44 and 45: Hymedesmia Hymedesmia Polymastia Po
Page 46 and 47: Figure34. Observationsof the yellow
Page 48 and 49: Figure36. Observationsfor the blues
Page 50 and 51: Figure38. Upper:spottedwolffishrest
Page 52 and 53: Figure40. Largestonein foreground,w
Page 54 and 55: Table 6. Summaryof environmentalcos
Page 56 and 57: 5.4.2.2 Deposition Case 2: to seafl
Page 58 and 59: 5.4.2.4 Deposition Case 7: Depositi
Page 60 and 61: 5.4.3 Comparative assessment Table7
Page 62 and 63: 6 References Auster, P.J. 2007. Lin
Page 64: Appendices Anelectronicsupplement(o

Detailed visual seabed survey at drilling site 7218/11-1

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