Variations In Deep-sea Hydrothermal Vent Communities On .
DEEP-SEA RESEARCHP art IPERGAMONDeep-Sea Research I 48 (2001) 1325-1346www.elsevier.com/locate/dsrVariations in deep-sea hydrothermal vent communitieson the Mid-Atlantic Ridge near the Azores plateauD. Desbruyères3’*, M. B iscoitoi J.-C. Caprais3, A. Colaçoc, T. Comtetd,P. Crassous3, Y. Fouquet3, A. Khripounoff3, N. Le Bris3, K. Olu3, R. Risoe,P.-M. Sarradin3, M. Segonzac3, A. Vangriesheim3aCentre de Brest de VIFREMER, BP 70, 29280 Plouzané, FrancehIMAR - Museu Municipal do Funchal (Historia Natural), Rua da Mouraria, 31, 9004-546 Funchal, Madeira, PortugalCIMAR - Laboratorio Marítimo da Guia, Faculdade de Ciencias de Lisboa, Estrada do Guincho, 2750 Cascáis, PortugaldPlymouth Marine Laboratory, Citadell Hill, Plymouth PLI 2PB, UKeUFR Sciences et Techniques, 6 av. Le Gorgeu, B.P. 809, 29285 Brest, FranceReceived 9 August 1999; received in revised form 24 May 2000; accepted 31 July 2000AbstractN ear the Azores Triple Junction as the Azores Plateau is approached, the ridge axis becomes shallower; its depthdecreases from ca. 2400m in the R a in b o w vent field (36 13/N) to ca. 850 m in the M e n e z G w e n vent field (37 35/N). Inthis area, extensive mussel beds of the mytilid Bathymodiolus azoricus dominate the hydrotherm al vent fauna, along withpopulations of three shrimps (Rimicaris exoculata, Mirocaris fortunata and Chorocaris chacei). The main physical andchemical characteristics of the vent habitat were studied by discrete sampling, in situ analysis and sediment trapmoorings. The vent fauna is distributed along a variable band where the vent fluids and seawater mix, with R. exoculataliving in the m ost concentrated areas and Bathymodiolus azoricus in the m ost diluted zones. Various non-endemicspecies live at the border of the vent field. The variations observed in structure and composition of the communitiesalong the depth gradient are m ost likely due to changes in vent fluid toxicity (metallic and sulphide content) andsuspended mineral particles, which render the fluids harsher for species living there. The m ain faunal differences observedbetween L u c k y S t r ik e and M e n e z G w e n hydrotherm al fields are due to an impoverishment in the hydrotherm alendemic species and to the penetration of bathyal species. The com parison of the three studied vent fields suggests theexistence of a succession of several biogeographic islands rather than a single province. 2001 Published by ElsevierScience Ltd.Keywords: Deep-sea; H ydrotherm al vents; Mid-Atlantic Ridge; Azores Triple Junction; Ecosystems; H abitat character isation* Corresponding author. Fax: 33-2-98-22-4757.E-mail address: ddesbruy@ifremer.fr (D. Desbruyères).0967-0637/01/ -see front m atter 2001 Published by Elsevier Science Ltd.PIE S 0 9 6 7 - 0 6 3 7 ( 0 0 ) 0 0 0 8 3 - 2
1326D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-13461. IntroductionThe discovery of hydrotherm al vents on ocean ridge crests occurred in 1977, off the G alapagosIslands (Lonsdale, 1977), b u t the exploration of the m id-A tlantic Ridge only started in 1985 (seeV an D over (1995) for details). Several ecological studies (Segonzac, 1992; V an D over, o.c.) on thetwo m ain deep hydrotherm al vent fields, T A G (26 N) and Snake P it (23 N) ca. 3500 m deep,showed faunal assemblages very different from those found on the E ast Pacific Rise. C arideanshrim ps, in particular Rimicaris exoculata, dom inate populations in these deep A tlantic fields.Conversely, alvinellids and tube-w orm s are n o t observed.In 1992, during the U S m ission FA ZAR, a new site was discovered a t 37 18'N, 1700 m deep( L u c k y S t r i k e ) . A prelim inary study of the com m unities’ com position a t this site was done duringsix dives of the U S deep research subm ersible A L V IN 1 and suggested the existence of two distinctbiogeographical provinces on the M id-A tlantic Ridge (Van D over et al., 1993). Follow ing the firstdiscovery, the E uropean U nion program m e M AST 2 — M A R FL U X /A T J,2 the diving cruises3 ofthe French subm ersible N A U T IL E , the M AST 3 A M O R E S4 program m e and the PortugueseFrench SA L D A N H A 5 cruise, continued and com pleted the exploration of the Azores TripleJunction area, establishing its depth limits. F ro m 1993 to 1998, the hydrotherm al vent com m unitiesthriving in three m ajor vent fields located on three segments of the southeastern lim b of the AzoresTriple Junction ( R a i n b o w , L u c k y S t r i k e and M e n e z G w e n ) w ithin 2 of latitude, were explored andstudied.The deep-sea hydrotherm al vent com m unity com position and structure are affected (1) bylinking and isolating m echanism s betw een vent fields (Hessler and Lonsdale, 1991; Tunnicliffe,1991), (2) by local conditions (chemistry and particle content of fluids and substratum patterns)(Johnson et al., 1988), and (3) by instability of venting, which induces an extinction-colonizationdynam ics (C ann et al., 1994; Desbruyères, 1998; C hevaldonné et al., 1997). In the Azores TripleJunction area, as the Azores P lateau is approached, the ridge axis gets shallower; its depthdecreases from ca. 2400m in the R a i n b o w vent field (36 13'N) to ca. 850m in the M e n e z G w e n ventfield (37 35'N). Because of phase separation processes, the accom panying d rop in hydrostaticpressure directly affects the chem istry of the high-tem perature effluents and their m ineral particlecontent. Source rocks hosting the hydrotherm al convection also affect the chem istry of the effluentsand deposits. The R a i n b o w ultram afic hosted system produces acidic fluids enriched in m etals andgases (H 2 and C H 4) and relatively im poverished in H 2 S (C harlou et al., 1997). The physical settingsof the area studied provide a unique opportunity to describe the influence of a wide range ofchemical and physical factors on the com position, distribution and dynam ics of vent com m unitiesat slow spreading ridges w hen geographical isolation by transform faults is absent or reduced.1Lucky Strike Cruise, M ay-June 1993, Chief-Scientist, Charles Langmuir.2 C oordinator Henry Bougault, IFR EM ER , France.3 DIVA 1 Cruise, May 1994, Chief-Scientist Yves Fouquet and DIVA 2 Cruise, June-July 1994, Chief-Scientists DanielDesbruyères and Anne-M arie Alayse.4 FLO R ES Cruise, July-A ugust 1997, Chief-Scientist Yves Fouquet; MARVEL Cruise, A ugust-Septem ber 1997,Chief-Scientists Daniel Desbruyères and Anne-M arie Alayse and PIC O Cruise, June-July 1998, Chief Scientist andProgram m e Coordinator, Daniel Desbruyères.5 July 1998, Chief-Scientist Fernando Barriga.
D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-134613272. Materials and methods2.1. Animal collection, mapping and microdistributionThe present study is based on in situ observation with the subm ersible N A U T IL E , video recordanalyses and fauna sam pling during dives. D a ta are provided by four cruises, in sum m er 1994(DIVA2), 1997 (M ARVEL) and 1998 (P IC O & V ictor Première). M apping of vent sites was donewith N A U T IL E ’s acoustic navigation records on high-resolution EM 12 bathym etric m aps (fromF l o r e s cruise), and the G IS analysis ArcView software. At selected hydrotherm al sites, videoanalysis was used to describe the m icrodistribution of each species and its relationship withsubstratum and fluid escaping structures.2.2. Chemical and thermal characterisation o f the habitatsFluid samples were obtained with two sam plers m anipulated by the subm ersible N a u t i l e : 750 mltitanium syringes (Von D am m et al., 1983) associated w ith an autonom ous tem perature probe forthe h ot fluids and a new m ultisam pler unit using four 200 ml titanium bottles associated with anautonom ous tem perature probe. Sam pling was done betw een and inside the populations m arkedwith q u adrats 0.5 x 0.5 m in size as topographic benchm arks. W ater sam pling locations werechosen in relation to faunal assem blages and m icroenvironm ents: (1) fluid diffusion or ventproxim ity, (2) w ithin R. exoculata swarms, (3) inside Mirocaris fortunata populations, (4) onmussel-beds (small- or large-sized) and (5) associated or n o t w ith shrim ps (M. fortunata andChorocaris chacei).D uring the “V IC T O R P R E M IÈ R E ” cruise, a new chemical analyser (Le Bris et al., 2000) wassuccessfully tested in the L u c k y S t r i k e area, and a series of in situ ES (total dissolved sulphide),nitrate and tem perature d a ta were obtained. This in situ analyser, called A L C H IM IS T , is based onflow injection analysis and colorim etric detection. Sample processing and analytical m ethods aredisplayed in Table 1.Discrete tem perature m easurem ents were m ade w ith the probe operated by the subm ersible, andtem peratures over a time series were obtained a t different p opulation beds w ith HOBO and MICREL probes (F ornari et al., 1994). C alibration was done w ith a standard reversingtherm om eter.2.3. Particulate fluxesAt M e n e z G w e n and R a i n b o w (“Flores 5” vent) vent fields, triple sedim ent traps (see K hripounoffand Albéric (1991) for description) were deployed by the subm ersible N A U T IL E during theM A R V EL cruise for 10 and 16 days, respectively. O n both occasions the trap was set close to anactive vent. At L u c k y S t r i k e vent field, a triple trap was deployed 1.5 m south of a sm oker calledS i n t r a during the DIV A 2 cruise. In order to obtain a pelagic flux reference, another triple trap wasalso m oored during the M A R V EL cruise outside M e n e z G w e n hydrotherm al field. P rio r todeploym ent, the sam pling bottles were filled w ith filtered seawater. N o poison was added becausebacterial decom position was considered to be negligible during the m ooring tim e ( 2 x 5 days atM e n e z G w e n , 4 x 4 days a t R a i n b o w and 1 x 25 days a t L u c k y S t r i k e . After recovery, samples were
1328D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-1346Table 1Sample treatm ent and analytical methods used in the study of microenvironmentsParam eterProcessingAnalytical methodRemarksPHAnalysis on board25 C TRIS bufferES (H 2S HS )Analysis on boardPotentiom etry electrode forsulphide-rich mediumColorimetry (Fonselius, 1983)z c o 2, c h 4Analysis on boardN utrients’5Cu, Pb total dissolvable metalFreezingF1N 03 suprapur , 20 pi in20 ml, am bient TIn situ analysis A l c h im istZS and N O y N O yH ead space-GC-HW D F ID(Sarradin and Caprais, 1996)Colorimetry, segmented flowPotentiom etrie strippinganalysis (Riso et al., 1997)FIA (Le Bris et al., 2000)D L 3 0.5 p m o lF 1rsd 5%10%rsd 5%Cu rsd 5%Pb rsd 5%1.5%3D L detection limit.bN H Î, N O 3 N O 2 .stored in the dark a t 4 C pending analyses. In the laboratory, m acro- and m eio-organism s wererem oved from the particle samples. Samples were then rinsed w ith M illi-Q purified freshwater(pH 7), freeze-dried and weighed. T otal carbon and nitrogen contents were m easured in duplic ate w ith a Carlo-Erba N A 1500 auto-analyser. O rganic carbon content was m easured witha Leco W R12 elem ental analyser after rem oval of carbonates with a 2 N HC1 solution (Weliky etal., 1983). Inorganic carbon content was calculated as the difference between total and organiccarbon contents. T otal sulphur was determ ined w ith a Leco CS-125 auto-analyser. Elem entalanalysis of particles was undertaken by EDAX 1 DX-4i X -ray spectrom etry. Standards wereprepared in the lab o rato ry from pure chemical com pounds. The average accuracy of the analyseswas 15%.3. Results3.1. Physical settings and faunal characteristicsF ro m n o rth to south, three distinct vent fields were visited (Fig. 1).M e n e z G w e n is situated in the volcanic segm ent betw een 37 35'N and 38 N. The m ain system isform ed by a 700 m high volcano, 17 km in diam eter (Fouquet et al., 2000). A 2 km wide axial grabensplits its summ it. Several active sites were located on the southeast and east slopes of one smallvolcano growing at the n o rth ern end of the b ottom of the graben (Fig. 2) a t depths ranging from840 to 865 m. At “P P 10/F 11” sites hydrotherm al precipitates cover an area of ab o u t 50 m indiam eter. A nhydrite chim neys up to 2 m high are present a t the sum m it of this low elevatedhydrotherm al m ound. A few patches (500 cm 2 each) of mussels were present. A few geryonid crabs(Chaceon affinis) were present in the vicinity. A second and m ore im p o rtan t site (m arkers D 9, P P
D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-13461329x u r c h a to vMenez Gwen 850mAzoresLucky Strike (1700m) PiHjRainbow (2320m" . FamousBroken Spur (3090m) pAtlantisCanariesTAG (3650m)Snake Pit (3500m ) KaneCape VerdeLogatchev (3000m)V FifteenTwen y70“W60“Fig. 1. General location m ap of the eight active hydrotherm al vent fields known to date on the Mid-Atlantic Ridgebetween E quator and the Azores Archipelago. The m ajor transform faults, which constitute the principal isolationstructures, are also drawn on the map.11, F 12) is located in an escarpm ent on the slope, between 860 and 842 m depth. It is bordered inthe upper p a rt by a field of pillow lava and laterally by crum bled rocks. H ydrotherm al deposits,from which a 10-40 C réfringent fluid diffuses, occupy the centre of the site. An active chimneysituated on the northw est escarpm ent belched o u t fluid at 277 C. The site’s periphery was occupiedby a little dense belt of hydroids. N um erous bathyal fishes have been found around the site:Chaunax sp., Trachyscorpia cristulata echinata, Neocyttus helgae, Epigonus telescopus and Beryxsplendens (Saldanha and Biscoito, 1997). In the lim it between lava and the anhydrite deposits, therewere im p o rtan t m ussel’ colonies. Specimens sam pled showed a m axim um shell length of 111 mm.There were no com m ensal scale-worms inside these mussels. N um erous patelliform gastropodswere present on the m ussels’ shells, in particular Protolira valvatoides and one new species of thegenus Lepetodrilus. These m ytilid populations consisted m ainly of large individuals (/ 40 mm),but the two younger cohorts (modes 4 and 18 mm) were also present and represented ca. 20% of thepopulation (Com tet and Desbruyères, 1998). Extensive bacterial m ats covered some of thesepopulations. O n the active deposits (chimney walls) and am ongst mussels, im p o rtan t populationsof C. chacei and M. fortunata were found. S. mesatlantica was the dom inant indigenous predator,while m any C. affinis came to feed on the mussels.
D. Desbruyères et al. / Deep-Sea Research 148 (2001) 1325-1346133031 31.8W3F31.631 31.431 31.231 3131 30.831 30.631 30.431 30.231 30PP30, PP31PP32, PP33PP10F ilD9, PP11F12- 37 51.437 5005001000 mFig. 2. M ap of the M e n e z G w e n vent field (“EM 1 2 ” bathymetric survey — FLO RES cruise). The small (young) volcanois growing on the bottom of the axial graben, which split an 800-m tali circular volcano situated at the centre of thevolcanic segment adjacent to L u c k y S t r i k e segment.At the P P 32/33 m arkers, the faunal characteristics were sim ilar to the above. M ussel pop u la tions were very im p o rtan t and covered virtually all-available rock surfaces. In contrast withpreviously studied sites, the size of mussels in this population was heterogeneous. Some musselscarried the com m ensal Branchipolynoe seepensis. N um erous gastropods were present on themussels. G eryonid population around and inside the site was im portant. A single fish of the genusGaidropsarus was observed inside a crevice am ongst mussels.L u c k y S t r i k e is one of the largest know n active fields in the m odern ocean. The hydrotherm alfluid, with a tem perature ranging betw een 170 and 324 C, has fluid characteristics (tem perature,chlorinity and gas concentration) varying from site to site w ithin the field (C harlou et al., 2000a,b).The hydrotherm al vent sites of this field are distributed around a lava lake (Fig. 3), in particular inthe southeastern and northw estern zones. W ell-defined active chimneys such as Eiffel Tower, Y3 orElizabeth, belching out very h o t fluids and zones where hydrotherm al activity is m ore diffuse canb o th be found at L u c k y S t r i k e . F o r practical reasons, an equivalence of vent site nam es givenduring French and A m erican cruises corresponding to passive m arkers is proposed (Table 2).The fauna is described from the biggest and m ost studied site E i f f e l T o w e r considered asexample of the Lucky Strike field. In fact, no noticeable difference was observed in the dom inantspecies com position or m icrodistribution except at the Y3 site. Except for the flaky anhydriteand barite-clad steep slopes, which were inhabited by m ore or less extensive populations of M.fortunata, the edifice walls of E i f f e l T o w e r were covered by Bathymodiolus azoricus. The Polynoidae
D. Desbruyères et al. / Deep-Sea Research 148 (2001) 1325-134632 17'1532 17'32 16’4532 16'2932 16'15133132 16’WPP12 (Elisabeth)PP7 (Bairro Alto)P P 8 2 2 z2 /yPP25, F29M US1 (Statue of liberty)PP21 \ XFIS US3 (Sintra)Crystal Bk pp6S7X US4Montségur —-0 6001200 mFig. 3. M ap of the L u c k y S t r ik e vent field showing the location of the active sites (“EM 12” bathymetric survey— FLO RES cruise). The central topographic high is made up of a composite volcano 13 km long, 7 km wide and 430 mhigh and divided into two parts separated by a N -S valley. The eastern p art has a semicircular shape with three volcaniccones at its summit. The L u c k y S t r ik e vent field is situated around a circular lava lake between these three cones.B. seepensis was present in alm ost all mussels collected. M ussel distribution at E i f f e l T o w e r was ofparticular note. A simple direct observation showed size segregation in the mussel beds (Com tetand D esbruyères, 1998; C om tet, 1998) within the same site. In the samples collected on isolatedsubstrates (sulphide blocks and fragments) inside an active site, size spectrum analysis showed th atsmall individuals colonised less active zones, whereas large individuals were found in active areas,on the sm okers’ walls, near the vent apertures. This is the reason why certain samples weredom inated (75%) by individuals belonging to the first cohort (mode 4.35 mm) whilst in others 63%of the individuals belonged to older cohorts (modes 13-91 mm). Dense m ats of filam entous bacteriacovered certain areas of mussel beds of both sites. In the samples taken from mussel beds, severalaccom panying species were found, in particular gastropods belonging to genera Protolira, Pelto spira, Lepetodrilus and Shinkailepas and the am phipod Luckia striki. O n the walls of small activediffusers of low and m edium tem perature (30-90 C, e.g. in a small diffuser), several tens of veryactive individuals of C. chacei were observed. N um erous S. mesatlantica and pycnogonids werepresent on the mussel beds, a large p ro p o rtio n of which was covered by filam entous bacteria.N um erous shrim ps, m ostly juveniles of M. fortunata or C. chacei, were aggregated around flangestrapping hydrotherm al fluid at the base of the edifice. C. chacei was also ab u n d an t am ong mussels.
1332D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-1346Table 2Equivalence between vent site names given during French and American cruisesNameStatue of LibertySintraL’aiguille/M. SoaresP etit chimisteFantôm eEiffel TowerChimisteIsabelM arkers P PPP21PP4PP1P P 3-P P 23PP2PP22M arkers DivaM arkers FlorèsF15F24DII, IV, V, VID iliDVIIIM arkers USUS1US3F16F 22F30U S6US7US4M ontségurHélènePicoN unoBairro Alto (ex. Pagodes)ElisabethY3PP6PP5F17-F18DXP P 7 -P P 8 PP25PP12-PP 13PP24W hite CastelCrystal ventF19F29-F21JasonDIF142608 siteIn the crevices w ithin the site perim eter, several filter-feeding species were observed in low densities,such as pedunculate cirripeds, as were small sessile carnivores such as Candelabrum phrygium(hydroid). T here was an ab u n d an t bathyal ichthyofauna aro u n d the sites, which m ake frequentintrusions. The chim erid Hydrolagus pallidus was quite frequent; two or three individuals ofCataetyx laticeps were always present a t E i f f e l T o w e r base as well as several Gaidropsarus n. sp.living a t a sm oker’s base inside crevices of the edifice. Lepidion schmidti was also frequentlyobserved (Saldanha and Biscoito, 1997, 2000).The Y3 site is distinguishable from other L u c k y S t r i k e sites by the occurrence of Rimicarisexoculata in the upper and m ost active p a rt of the edifice, m ostly aggregated in crevices, whenmussels are concentrated a t the base of the structure.The R a i n b o w vent field (36 13'N) is situated in the n o rth AM A R segment (Fig. 4). It is the deepestactive segment of the A TJ area (2270-2320 m). The m ost active sm okers are located a t the westernand eastern ends of the hydrotherm al field. The west zone has the roughest relief, while the sites ofthe eastern zone are located on a sedim entary plateau. The highest developed sites are located atthe field centre (PP 28/35 and P P 29/37) and are either active edifices o r nearly “extinct” smokers.H ydrotherm al sedim ents border the vent field.The youngest and m ost active sites (e.g. E ast sites and W est sites) in this field were nearly azoic,with the exception of the periphery of the w estern sites, where some sessile species were found.H ydroids form ed fairly dense covers over the surrounding h ard substrates. In the eastern region,
D. Desbruyères et al. / Deep-Sea Research 148 (2001) 1325-134633 54.5W33 543X53.533 53133333 52.52100,H ydrothermalfield2050WJJnAQllíílir iDonnées bathymétriques campagne FLORES 19971--------133 54'20W33 54'102350"I ' ' Mt '1----- 33 54'230036 i0100200 mFig. 4. M ap of the R a i n b o w vent field. Left, the distribution of active sites. Right, topography of the overall area (EM 12bathymetric survey — FLO RES cruise). The Rainbow vent field is situated on the Rainbow Ridge in the north of AMARsegment.the polychaete Spiochaetopterus sp. form ed dense and patchy populations inside hydrotherm alsedim ents near the site. O n the active crest to the west of the field, M. fortunata was observed inrelatively dense aggregations along with some individuals of i?, exoculata and C. chacei. N o mussels
1334D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-1346Table 3F aunal composition of the vent communities at the three vent fields (M e n e z G w e n , L u c k y S t r i k e and R a in b o w )PhylumPoriferaCnidariaAnnelidaMolluscaA cheliplumaA nthozoaStegolariaH niceCf. io)PrionospioM onoplacophora RokopellaG OrbitestellaOrbitestellidaen. cosuraH peciespennatulainfundibulumaff. slutzisp.aff. seepensissp.norvegicasp.n. sp.sp.n. rquesMarquesVervoortDesbruyèresK n. sp.1***PetersenDesbruyèressp.2**idsp. 3n. sp.n. sp.acuticostataobesulacomtetisp.n. sp.n. sp.n. sp.nitidunilamarshallin. sp.n. sp.*n. sp.n. sp.n. sp.valvatoidesthorvalldssonimidatlanticaazorican. sp.brychian. *************************************idW arén & BouchetidididValdes & BouchetW arén & BouchetidididididididididididWarénW arén & BouchetididididVon Cosel, Com tet et al.Child & SegonzacBartschBartsch
D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-13461335Table 3 (continued)PhylumA rthropodaCirripedaCopepodaO stracodaA mphipodaD ecapodaEchino derm ataC hordataEchinidaO prisKrithe? hinuslongicarinataaurantiacrassan. scuvierimesatlanticaaff. iatustelescopusn. sp.MGLSRdéterm.*YoungidididElûmes & SegonzacElûmesElûmes & SegonzacCarbonelidididididididBiscoitoidididididG nianus ?Guttigaduslatifrons ?*LepidionschmidtiLycenchelysn. sp.*MoramoroNezumiasclerorhynchusPolyacanthonotus rissoanus*Simenchelysparasitica*Synaphobranchus kaupiTrachyscorpiacristulata echinata************TylerBiscoito & SaldanhaididididididididididBiscoito, Saldanha& DesbruyèresidididBiscoitoBiscoito & Saldanhaididididid
1336D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-1346were observed around these sites except a few small individuals of Bathymodiolus azoricus aroundthe P P 26 sm oker. Two com plex edifices (PP28/35 and PP37) were observed in the central p a rt ofthe field. They were com posed of several active (2-3) and inactive (5-10) chimneys. T em peraturesm easured a t the diffuser sum m it ranged from 22 to 63 C. Low diffusion occurred along the lowestp art of some clogging chim neys and all around the site through the sediment. These edifices werelargely colonised by M. fortunata on sulphide diffusers with higher densities on chim neys coveredby iron oxides (about twice as dense as on diffusers). Dense swarms of R. exoculata were located insmall depressions betw een chimneys. At the P P 37 site, a relatively large p opulation of mussels hadgrow n on the areas of low diffusion and on clogging chimneys. Small-sized mussels were located atthe base of the chim neys where low diffusion occurred, while large-sized individuals were locatedon the higher parts of the inactive chim neys covered by deposits. A bout 20% of the musselsharboured the com m ensal polynoid B. seepensis. Along the active walls, a few bythograeid crabs(S. mesatlantica) were observed, as well as some zoarcid fishes am ong mussels a t the base of the site.These proved to be a yet undescribed species of the genus Lycenchelys. O phiurids, gastropods(Phymorhynchus n. sp.) and pygnogonids also occured in this sedim ent covered area. Smallgastropods (Mitrella nitidunila, Protolira valvatoides, Lepetrodrilus n. sp., etc.), free polynoid andam pharetid polychaetes were sam pled a t this site (Table 3).3.2. Site characterisationIn order to characterise the different m icrohabitats, we took a total of 70 discrete w ater samplesand recorded tem peratures in the m ain m acrofaunal assem blages and w ithin diffuse ventingstructures in the three vent fields. W ithin the L u c k y S t r i k e vent field, three different sites ( E i f f e lT o w e r , B a i r r o A l t o and E l i s a b e t h ) were sampled. The averages and standard deviations oftem perature, pH and concentrations of chemicals th at fuel bacterial a u to tro p h y are show n inTable 4. Cross com parisons betw een the fluids am ongst habitats/sites were m ade using the Fishertest for variances and t-Student’s test for m eans of small samples w hen n 4 (p 0.05). At theR a i n b o w site, the m icrohabitats of Rimicaris and Mirocaris did n o t differ significantly. Them icroenvironm ent was significantly different for Rimicaris and Mirocaris vs. Bathymodiolus whenm ethane content, pH and tem perature were com pared. The L u c k y S t r i k e site was characterised bystrong differences in the variances. The site-to-site com parison, concerning the m ussels’ m icroen vironm ent, revealed significant differences between R a i n b o w , E i f f e l T o w e r ( L u c k y S t r i k e ) , B a i r r oA l t o ( L u c k y S t r i k e ) and M e n e z G w e n when pH was com pared. Significant differences were alsoobserved in the C O 2 and m ethane concentrations betw een E i f f e l T o w e r and B a i r r o A l t o on oneside and P P 24 on the other. A decreasing gradient in ES, C 0 2, C H 4 and tem perature was foundw hen these param eters were m easured a t the diffusers, in the Rimicaris and the Mirocaris habitats,in the m ixed h a b ita t of Mirocaris and Bathymodiolus, in the mussel beds and the seawater. However,w hen adjacent pairs of different habitats were com pared, this gradient could n o t discern them icrodistribution.D uring the “V IC T O R P R E M IÈ R E ” cruise, the use of the in situ auto-analyser “A L C H IM IS T ”in the L u c k y S t r i k e vent field allowed a better description of the vent p o pulation environm ent(Fig. 5 and Table 5). Profiles of tem perature, sulphide and n itrate concentrations (Fig. 5) wereobtained as the probe and inlet were gradually m oved over the different anim al populations w ithina q u a d ra t (0.25 m 2), term inating in an area of visible diffusion. The data obtained indicate general
D. Desbruyères et al. / Deep-Sea Research 1 4 8 (2001) 1325-13461337Table 4Mean values and standard deviations for chemical factors, tem perature and pH as measured on discrete water samples atR a in b o w , L u c k y S t r ik e and M e n e z G w e n vent fields. The data in bold type were n ot used in cross com parisons
840 to 865 m. At “PP 10/F 11” sites hydrothermal precipitates cover an area of about 50 m in diameter. Anhydrite chimneys up to 2 m high are present at the summit of this low elevated hydrothermal mound. A few patches (500 cm2 each) of mussels were present. A few geryonid crabs (Chaceon affinis) were present in the vicinity.
Little is known about how deep-sea litter is distributed and how it accumulates, and moreover how it affects the deep-sea floor and deep-sea animals. The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) operates many deep-sea observation tools, e.g., manned submersibles, ROVs, AUVs and deep-sea observatory systems.
Investigation: Life on a Hydrothermal Vent. EDUCATOR GUIDANCE. Some common misconceptions students may share as they experience this phenomenon include: algae are plants plants and algae can photosynthesize in the dark animals in the hydrothermal vent ecosystem survive by only eating dead things that sink to the sea floor
Figure 1: Radar chart of "Deep Sea Fishing" Bug Hunt The "deep sea fishing" bug hunt process Sophisticated approaches have been tried-and-true, and experiences have been gathered in this area. To summarize, the "deep sea fishing" bug hunt process consists of these significant steps: 1. Identify formal experts who can help with the .
The National Oceanic and Atmospheric Administration (NOAA) Deep Sea Coral Research and Technology Program (Program) co mpiles, curates, and makes publically accessible a National Database of biogeographic data and i nformation on deep-sea corals and sponges - the most important habitat-forming organisms in the deep sea.
deep-sea benthic foraminifera intensifi ed with the beginning of scientifi c piston coring expeditions after World War II (e.g., Phleger et al., 1953), and of deep-sea drilling in the late 1960s (e.g., Berggren, 1972). At that time, little was known about the biology of foraminifera in general and deep-sea forms spe-
Deep Geothermal Review Study Final Report Atkins Deep Geothermal Review Study Version 5.0 21 October 2013 9.1. Rationale 58 9.2. Enhanced Geothermal System (EGS): Cornwall 60 9.3. Deep Hydrothermal (non- EGS) System: Weardale 67 9.4. Hot Sedimentary Aquifer (non-EGS) System: Crewe 72 9.5
15) A sea otter feeds on sea urchins. If the sea otter is removed, sea urchins would become a ravaging predator in the ecosystem. Sea urchins would consume the habitat’s kelp. Ultimately, the population of the sea urchins would be left uncontrolled. The sea otter is an example of a(n) _
Security activities in scrum control points 23 Executive summary 23 Scrum control points 23 Security requirements and controls 24 Security activities within control points 25 References 29 Risk Management 30 Executive summary 30 Introduction 30 Existing frameworks for risk and security management in agile software development 34 Challenges and limitations of agile security 37 a suggested model .
