Web­lo­g7

Chief sci­en­tist leg 3
Ant­je Boe­ti­us
a.boe­ti­us.d at me­ri­an.brie­se-re­se­arch.de
Weblog 7
12.11.-14.11.09


Diving into diversity

Thank you, to all of you who kept their fin­gers cros­sed. This worked at least for the 12th No­vem­ber (Dive 248), when the ROV came up with an in­tact ca­ble, rai­sing the hope to have found an im­me­dia­te so­lu­ti­on preven­ting twists and turns in the ca­ble. Howe­ver, dive 249 and 250 both re­qui­red more ca­ble cut­ting, de­s­pi­te dif­fe­rent pro­ce­du­res to avo­id the ca­ble twists, in­clu­ding chan­ging the po­si­ti­on of the floats, ta­ping the ca­ble and ke­eping a fi­xed hea­ding and dis­tan­ce to the wire du­ring the dive.

Thank­ful­ly, the ROV team has worked very hard to help us com­ple­te the sci­en­ti­fic pro­gram of the first leg. By ta­king turns in ca­ble cut­ting and ROV pre- and af­ter dive checks, and by al­lo­wing two di­ves du­ring the night they ma­na­ged to get us 2 ad­di­tio­nal di­ves in 3 days. Of cour­se dive 250 was a spe­cial one: This num­ber me­ans that QUES­T4000 has now com­ple­ted 250 di­ves, and pro­bab­ly more than 2000 hours at the deep sea floor.
Left: Cable cutting - in the heart of the wiring is the fine glass fiber cable which transport images and data from the ROV to the ship. Here, ROV pilot Werner Schmidt’s hands are busy lapping the glass fiber. (Source: Christian Borowski)
Middle and right:
The 250th dive of ROV QUEST4000 (MARUM). The ROV is coming up. Scientists waiting for their samples. The ROV team is waiting for their ROV. (Source: Gabi Schüssler)
We used the­se di­ves main­ly to com­ple­te our bio­di­ver­si­ty sam­pling sche­me, for all bent­hic size clas­ses from mi­cro­me­ter- to cen­ti­me­ter-si­zed or­ga­nisms. For the EU pro­ject HER­MIO­NE we will com­pa­re the bio­di­ver­si­ty of three che­mo­syn­the­tic eco­sys­tems of the Eas­tern Me­di­ter­ra­ne­an, se­pa­ra­ted by 60 to 200 mi­les from each other. In each eco­sys­tem we have cho­sen three dis­tinct re­du­ced ha­bi­tats, of which two are only a few tenths of me­ters away from each other, and a third one is se­veral hund­red me­ters away. All of the­se sites are sam­p­led in re­pli­ca­ti­on, al­lo­wing us to test the spa­ti­al sca­ling of the bio­di­ver­si­ty and struc­tu­re of the com­mu­nities of mi­cro­or­ga­nisms, meio- and ma­cro­fau­na. As­so­cia­ted with this sam­pling sche­me, we mea­su­re the in situ bio­geo­che­mis­try of each spot, to be able to test whe­ther the en­vi­ron­men­tal con­text, for ex­amp­le the en­er­gy avail­a­bi­li­ty, ex­plains more of the si­mi­la­ri­ty bet­ween com­mu­nities than the geo­gra­phic dis­tan­ce.

Spea­king about bio­di­ver­si­ty and sca­les, Hei­ko Sah­ling and Chris­ti­an Bo­row­ski made a re­al­ly in­te­res­ting ob­ser­va­ti­on. The frac­tu­red na­tu­re of the re­du­ced ha­bi­tats seems to in­crea­se di­ver­si­ty tre­men­dous­ly. For ex­amp­le, a small black spot of less than 20 cm wide in the midd­le of a vast area of pel­agic se­di­ments was po­pu­la­ted so den­se­ly by a di­ver­se com­mu­ni­ty that a net samp­le caught some 8 spe­cies of worms and 3 dif­fe­rent cru­stace­an spe­cies, all ag­gre­ga­ting in this tiny but, high­ly sul­fi­dic spot. None of the­se or­ga­nisms can be found outs­ide of the spot in the vast oxic seaf­loor sur­roun­ding this mini-ni­che – but some of them oc­cur in the lar­ger bac­te­ri­al mat are­as some 50 m away from the tiny spot. How the­se high­ly ad­ap­ted but op­por­tu­nis­tic or­ga­nisms find and po­pu­la­te their ha­bi­tats and how they sha­re such a small ni­che re­mains un­k­nown – si­mi­lar as the wood bo­ring or­ga­nisms, they ap­pe­ar to have nu­merous lar­vae floa­ting in the wa­ter, able to sett­le in re­du­ced set­tings via spe­ci­fic cues.
Christian Borowski sieving macrofauna samples (Source: Gabi Schüssler). A net haul of one small sulfidic spot…. (Source: MARUM)…proving to be a biodiversity hotspot: each vessel holds several species of worms and crustaceans extracted by sieving (Source: Christian Borowski)
Bet­ween di­ves we con­ti­nued map­ping the seaf­loor and the flu­id es­cape struc­tu­res by a com­bi­na­ti­on of Mul­ti­beam, Pa­ra­sound and ca­me­ra tran­sects. It is ama­zing to see what a lar­ge frac­tion of the seaf­loor is co­ve­r­ed by car­bo­na­te ce­ments, and again, what a di­ver­si­ty of or­ga­nisms hide in the crusts. Fur­ther­mo­re, the car­bo­na­te crusts ap­pe­ar to keep a re­cord of extinct com­mu­nities. We have vi­si­ted some sites, which are lit­te­red with bi­val­ve and sea ur­ch­in shells which may have ac­cu­mu­la­ted over thousands of ye­ars. Other crusts are par­ti­al­ly com­po­sed of ce­men­ted bi­val­ve shells. The­se bi­val­ves also re­pre­sent che­mo­syn­the­tic spe­cies, in­di­ca­ting that this who­le area has pro­bab­ly been ac­tive for geo­lo­gi­cal time sca­les.
Shells from the seafloor and cemented in crusts (Source: Heiko Sahling). Remnants of echinoderms (Source: MARUM; University Bremen)
Con­side­ring this, it seems up­set­ting that so­me­thing else also ac­cu­mu­la­tes on the seaf­loor: the trash of ci­vi­liza­t­i­on. Du­ring our di­ves, we have esti­ma­ted that we find one pie­ce of trash every 100m in the deep Eas­tern Me­di­ter­ra­ne­an. This in­clu­des plas­tic bott­les, bags, cans and other lit­ter, which ends up in the sea. Plas­tic is not de­gra­ded by mi­cro­or­ga­nisms, hence it re­mains fo­re­ver at the seaf­loor – what an un­plea­sant sight.
We hope for more plea­sant sights when pre­pa­ring for our last dive for this leg to­mor­row morning … Dive 251, which will be de­di­ca­ted to car­bo­na­te crust and fla­re map­ping.


Ant­je Boe­ti­us
Litter at the seafloor – typical items to be encountered during a 300m transect across the seafloor at 1700 m water depth: a can, a milk bottle, a plastic bag (Source MARUM)
 
 
 
 
 
 
 
 
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