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

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Akvaplan-niva haspreviouslyworked with iSURVEYto developa systemwhich allowsthe biological events (i.e. observations)to be taken without havingto stop the surveyorlogging.Usually,event recordingrequiresa 'fix' procedure,whichtakesapproximately3 minutesto complete.Thiswould be too time-consumingfor all our biologicalobservations,and would have forced us to restrict the number of geo-referencedobservationsmade. The surveyorson-board from iSURVEYproduceda customised recording system, which allowed biologists to click on a number of pre-defined categories,asbiologicalrecordingsweremade. 2.4.2 Event logging In the ROVcontrol room, the biologistsweregivena PClinkedto the surveylog,andcouldmakegeoreferencedobservationsas event logs. A number of pre-defined categorieswere made, allowing rapidrecording.Additionalnotescouldbemadefor eachof these. o Sediment(absenceof recordingmeansonly mud andsmallerstoneswereobserved): Stone Stonewith growth Boulder Boulderwith growth o Fauna(alphabeticalorder,latin namefirst, colloquialdescriptivecharacteristicgiven) Sponges Aplysilla (yellow) Candelabrum(string) Axinella(funnel) Farreaocca(bumpy) Geodia(potato) Hymedesmia(blue) Polymastia(dog'sball; with spikes) Stylochordyla(stalked) Otherfauna Ascidiacea(seasquirts) Annelida(worms) Anthozoa(seaanemonesandseapens) Bryozoa Crustacea o Decapoda(Crabs) o Decapoda(Hermitcrabs) o Gammaridae(smallshrimps) o Isopoda o Munida(Squatlobster) o Pandalus(the commercialshrimp) Echinodermata o Asteroidae(starfish) o Holothuroidae(seacucumbers) o Ophiuroidae(brittle-stars) o (pillow-stars) Fish Mollusca(shells) o Otherobservations Litter (objectsspecified) Macroalgae(recordedto showconnectionsbetweenthe shoreandthe offshore shelf) Akvaplan-niva AS, 9296 Tromsø 12 www.akvaplan.niva.no
3 About sponges and challenges for assessment 3.1 OSPAR habitat classification of sponges Offshore sponges in the south-western Barents Sea are classified under the OSPAR habitat descriptionas"DeepSeaspongeaggregations". Thefollowingtext is modifiedfrom OSPAR(2005): Deepseaspongeaggregationsare principallycomposedof spongesfrom two classes:Hexactinellida andDemospongia.Glasssponges(Hexactinellidae)tend to be the dominantgroupof spongesin the deep sea although demospongidssuch as Cladorhizaand Asbestoplumaare also present. The massivespongesthat dominate some areas include Geodia barretti, G. macandrewi,and Isops phlegraei.Theycan occurat very high densities,particularlyon the slopein areaswhere substrate and hydrographicconditionsare favourable.Surveymaterial from a spongefield in the northern North Seaand other locationshad a comparablediversityanddensityof spongeswith tropical reefs (Konnecker,2002). The spongesalso influence the density and occurrenceof other speciesby providingshelterto smallepifauna,within the osculaand canalsystem,and an elevated perch,e.g. for brittlestars(Konnecker,2002).Deep-seaspongeshavesimilarhabitat preferencesto cold-water corals,and henceare often found at the samelocation.Researchhasshownthat the densemats of spiculespresent around spongefields may inhibit colonisationby infaunal animals,resulting in a dominanceof epifaunalelements(Gubbay,2002).Information indicatesthat dominant speciesare slow growingtaking severaldecadesto reachlargesize(Klitgaard& Tendal,2001).Thehabitat and the rich diverse associatedfauna is therefore likely to take many years to recover if adversely affected(Konnecker,2002). Theyoccurbetweenwater depthsof 250-1300m(Bett & Rice,1992),where the water temperature rangesfrom 4-10°Candthere is moderate currentvelocity(0.5knots).Deep-seaspongeaggregations may be found on soft substrataor hard substrata,suchas bouldersand cobbleswhich may lie on sediment.Icebergplough-mark zonesprovidean ideal habitat for spongesbecausestableboulders and cobbles,exposedon the seabed,providenumerousattachment/settlementpoints(B.Bett, pers comm.). However,with 3.5kg of pure siliceousspiculematerial per m 2 reported from some sites (Gubbay,2002),the occurrenceof spongefields canalter the characteristicsof surroundingmuddy sediments.Densitiesof occurrenceare hardto quantify,but spongesin the classHexactinellidahave been reported at densitiesof 4-5 per m², whilst ‘massive’growth forms of spongesfrom class Demospongiahavebeenreported at densitiesof 0.5-1 per m 2 (B.Bett,pers. comm.). 3.2 Sponges in the south -western Barents Sea Spongesare found in most sea-floor (benthic)faunalassemblages,both on hard andsoft substrates. In the south-westernpart of the BarentsSea(precisearea not specifiedhere),spongescompriseup to 57 % of the benthic biomass(Ereskovsky,1995).Slightlyfarther east,along the Murman coast, almost80%of the recordedbiomasswasdue to sponges(Propp,1971).Extremelyhigh densitiesof spongesalso have been recorded in the Tromsøflaketarea west of the Troms/Finnmarkarea in northern Norway(Figure7). Detailed site survey at PL531 Darwin Akvaplan-niva AS Rapport 6051 - 1 13
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 18 and 19: Figure7. Over4 tonnesof sponges(pre
Page 20 and 21: Figure10. BarentsSea.Spongebycatchi
Page 22 and 23: Somespongesform densereefs,and prov
Page 24 and 25: Figure14. Photosfrom Mercier(2012)s
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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