CD179: Deep-sea biology of the Portguese canyons


Daily diary

Thursday 11 May 2006

Teresa writes:

"As it is my turn to write this diary, I will finally explain a bit of the work I intend to do during my postdoc. The objective of my research is to determine the feeding strategies of the sea cucumbers (holothurians) that inhabit the Portuguese canyons. In more detail I will try to answer the following questions:

1) What do the deep-sea holothurians eat?
2) Is the digestive tract of deep-sea holothurians an appropriate microenvironment for the proliferation of the bacteria in the deep sea?
3) Are the bacteria that exist in their guts responsible for the degradation of the organic matter (OM)? What is their role in the nutrition of deep-sea holothurians?

For this study, I will use the guts of Molpadia sp. (a burrowing sea cucumber species that is very abundant in the Nazaré Canyon off Portugal) and compare the bacterial community present in each gut with that in the sediment. Due to the fact that not many Molpadia are collected in each Megacore deployment, I am using an Agassiz trawl to collect lots of the holothurians and will have to assume that the sediment they feed on is collected by the Megacore and is comparable to the material in the holothurians’ guts.

The night shift began with a Megacore from the 3500m site at the Nazaré Canyon. Once all gear was safely and secure on board, our “chief” allowed us to start our work. We always had a very organized sequence that always worked very well. It always happened as follows:

-Emily looked at the best Megacore and took a picture with the station number on;
-Xana measured each core and Nina wrote it down on our log book;
-Our “chief” and myself took the core tubes out of the Megacore;
-Emily or Nina or Xana put it safely on a corer holder.

Unfortunately at this particular station, we realized that we only had sediment in three megacore tubes (100mm diameter) out of a possible nine, and two multicore tubes (58mm diameter) out of a possible three. This meant that as we had to slice two multicores for Jeroen, I could use only the 3 megacore tubes to search for the elusive Molpadia.

While slicing one of the megacore tube samples between 2 to 4 cm depth I found one of “my” Molpadia. I became so happy that I left my team outside and I went straight to the lab to sample part of the sediment that was still in its guts! It was great to work on an animal in such good condition and to be able to sample the sediment in its immediate vicinity. While I was in the lab we began the long steam to the next site of interest, a CTD/SAPS station. As it took us sometime to get there, we all had time to finish our work. While waiting we decided to take a nice picture of the “night shifters”...

The night shift: Xana, Nina, Teresa, Emily, Dário and Lee.

Unfortunately our “chief” is not present in the picture because somebody had to take the picture!!!! Dário was with us because that night he decided to give us a hand with the Megacore. I would like to take this opportunity I also want to thank Lee for helping us sieving some mud! He has been great and we all appreciated his help! I also would like to thank Dave, our chief scientist who tries to fit in the program every single request. He has done a great job! Also, I have to thank him for putting Emily, Xana, Nina and myself together in the same shift. We got along really well and I have to say that we are a real working team. As I am thanking everybody I should not forget to thank our “chief” that works hard to get us some good samples and tries every night to be integrated with “his” girls. He has almost succeeded!!!!

At around 6 am in the morning we arrived at the 715 m station where we deployed the CTD and SAPS. After a couple of hours CTD and SAPS was retrieved and we sampled the surface waters at 20m in the chlorophyll maximum over the Nazaré Canyon. With the CTD and SAPS again. We then repeated the CTD and SAPS at a deeper station (1160 m) where the day shifters did the last CTD/SAPS. At about 1600H we started moving again to our 3500m Megacore station. It was just 2000H and the “night shifters” were ready again for megacoring. Our team started working as described above with eight good megacores and 2 good multicores. Another Megacore deployment at the same site and another 8 good megacores and 2 multicores for Kostas Kiriakoulakis at the University of Liverpool. Sadly Kostas could not be with us on this cruise because he was busy studying deep-water corals off Sweden. Although I did not get any cores this time, I have found another Molpadia trapped at the end of one of the megacores. It is time to go to the CT lab to see what it has been eating!!!!"

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April 2006
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