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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Geodia belongs within the Demospongiae, and is an extremely species-rich genus (see<br />
http://www.marinespecies.org/aphia.php?p= taxdetails&id=132005). Differences between species<br />
generallylie in the finer detailsof the skeleton,or spicules,and therefore these usuallycannot be<br />
identified with certainty from pictures or videos.Geodiasimplicissimais regardedas a speciesof<br />
uncertain st<strong>at</strong>us. The following is an extract from the Intern<strong>at</strong>ional Marine SpeciesIdentific<strong>at</strong>ion<br />
Portalhttp://species-identific<strong>at</strong>ion.org/species.php?species_group=s ponges&id=234)<br />
SpeciesOverview<br />
GeodiasimplicissmaBurton (1931)is known only from a few fragmentsfrom Northern Norway.The<br />
differencewith the more commonG.barretti and G.cydoniumis microscopical:it hasan ectosomal<br />
palisadeof smalloxeaslyingperipheralto the crustof sterrasters.<br />
TaxonomicDescription<br />
Colour: Unknown.<br />
Shape,size,surfaceand consistency: Knownonly from a few fragments,so no detailsof the habit<br />
areknown.<br />
Spicules: Megascleres: Huge oxeas:2200 x 32 µm; "microxeas"(= cortical oxeas):250 x 4 µm;<br />
orthotriaenes:shaft1700x 48 µm, cladi320µm; a singlean<strong>at</strong>riaenewith cladiof 150µm wasfound.<br />
Microscleres: Sterrasters,spherical:70 µm; pycnasters:4 µm.<br />
Skeleton: (Geodiasimplicissimaskel) Ectosomal: a palisadeof microxeasis erectedon the sterraster<br />
layer, which in its turn is carriedby the cladi of the orthotriaenes.Choanosomal : radial bundlesof<br />
oxeasandorthotriaenes.<br />
Ecology: In fjords,10-75 m.<br />
Distribution: NorthernNorway.<br />
Etymology: The name presumably refers to the rel<strong>at</strong>ively simple spicule complement.<br />
Typespecimeninform<strong>at</strong>ion: Thetype is in the N<strong>at</strong>uralHistoryMuseum,London:BMNH1913.6.1.36.<br />
Remarks<br />
Thedescriptionis uns<strong>at</strong>isfactoryandthe specificdistinctnessisdoubtful.<br />
3.5 Sponges as ecosystem engineers<br />
Sponges,corals and also sea-pens have long been acknowledgedfor their role as autogenic<br />
(individual-based) ecosystemengineers (Miller et al., 2012 and numerous references therein).<br />
Ecosystem engineersprovide living spacefor other organisms(Figure14), or they may alter the<br />
physicalpropertiesof the immedi<strong>at</strong>ehabit<strong>at</strong> (in the caseof sponges,they filter large quantities of<br />
w<strong>at</strong>er daily, and provide small-scale shelter from bottom currents). Thus they can alter the<br />
biodiversityin areaswhichthey occupy,andhavea role in influencingsea-floor ecosystemfunction.<br />
ThelargeGeodiasponges,andalsoother unidentifiedbranchingforms,in the south-westernBarents<br />
Seaevidentlyprovidehabit<strong>at</strong> for organismssuchassqu<strong>at</strong> lobsters.Thesecanbe seenin burrows<strong>at</strong><br />
the baseof the sponge,with clawsextended.Alsoother invertebr<strong>at</strong>esareexpectedto takeshelterin<br />
this way. During filming, fish were frequently seen to feed from the bases of the sponges<br />
(presumablypreying on the resident invertebr<strong>at</strong>es),but they seldom did damageto the actual<br />
sponges.However,occasionally,fish were seento "accidentally"bite off a chunkof a sponge,and<br />
then l<strong>at</strong>er ejectit from their mouths.Personalobserv<strong>at</strong>ions,S.Cochrane.<br />
<strong>Detailed</strong> <strong>site</strong> <strong>survey</strong> <strong>at</strong> PL531 Darwin<br />
Akvaplan-niva AS Rapport 6051 - 1 19
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