Meteor-Blog 29. July 2008: High tide!
Changing alkalinity, sulfate concentration or amount of hydrocarbons in porewater or sediments are important indicators for processes and fluxes in the sediment and the pore water. They are measured best directly where they happen: at the sea-floor. André Gassner, PhD student at the MARUM/Bremen developed an instrument that is able to perform such in situ measuremnts - today's blog deals with its first deployment during a dive with under water robot QUEST4000.
Aktion Ausgeführt von Datum und Uhrzeit Kommentar Veröffentlichen Dr. Astrid Ahke 30.07.2008 18:21 Keine Kommentare
Does the biodiversity of deep-sea organisms play a role for the climate on Planet Earth? Questions all about marine research will be answered directly aboard of the German research vessel Meteor by cruise leader Prof. Antje Boetius and her crew. In cooperation with the geoportal planeterde.de from 17.07.08 to 24.08.08 they contribute a Science-Blog of METEOR expedition M76/3 GUINECO – MARUM research of fluid and gas seeps on the Westafrican continental margin. Technical highlight of the cruise is the remote-controlled under water robot QUEST4000 by MARUM that will be deployed for taking fauna and sediments samples and conduction of in situ experiments. Go on a dive down to places no other human being has ever seen before: explore the fascinating deep-sea fauna and watch the scientists’ work at gas and fluid seeps deep down on the ocean bottom.
Expedition M76/3b is a collaboration of MARUM – Center for Marine Environmental Sciences at Bremen University and its associated institutes MPI and AWI as well as the French research institute IFREMER and the University of Paris.
More information of the Meteor-Blog, an overview of all contributions to the blog and expedition M76/3B:
29. Juli 2008 (Autor: André Gassner)
Today's blog is contributed by:
Hi! I am
André Gaßner. I am a PhD student at MARUM-Center for Environmental Sciences at
the University of
Bremen (Picture 1). In my
thesis I work on the geochemistry of interstitial waters in cold seep areas. I
focus on several geochemical key parameters such as alkalinity, sulphate and
sulphide concentrations and the amount of hydrocarbons in the sediments (for
example methane). These are important indicators for processes and fluxes in
the sediment and the pore water.
To achieve a quantitative understanding of these processes I have designed and built a unique sampling tool. The so-called In Situ Pore water Sampler (ISPS) is capable of sampling the pore water of sediments directly at the seafloor, prior to any disturbance caused by core recovery. The ISPS can be deployed by the ROV Quest 4000 or other submersibles. The robot brings the ISPS down to the seafloor, operates the sampler and retrieves it after sampling. Afterwards the samples are directly taken to the onboard geochemistry lab and are analyzed. Besides the in situ pore water sampling, me and three other colleagues are working on the geochemical analysis of sediment cores. We measure different pore water constituents, mineral composition and the quantity of gaseous hydrocarbons. The West African margin is known for an abundance of gas emitting geostructures, and our plan is to investigate in detail some of the giant pockmarks of this region.
Picture 1: The ISPS is ready to be mounted on the ROV front porch by André Gaßner
When I woke up today I felt this certain feeling of butterflies in my stomach. Finally my self- developed and constructed device to obtain pore fluids under in situ conditions should get the opportunity to be deployed by ROV QUEST 4000. After having mounted the tool on the front porch of the vehicle under the tropical Congolese sun, it was ready to go. QUEST descended down to a water depth of approximately 3000 meters. After a closer observation of the cable connecting the ROV to the ship by the ROV cameras, we were all really disappointed. The cable was twisted several times and formed a wire bundle just next to the vehicle. To avoid further possible damages to the ROV, we had to decide to ascend immediately (Picture 2). At the moment the ROV crew is working really hard to fix the problems with the cable. Now I am really looking forward to the next dive and I hope that the ISPS is then able to start its work at the seafloor. Greetings on behalf of all cruise participants –
Picture 2: The ROV brings the device back on deck of RV Meteor
Using the bottom water samples ISPS, continued…
I reported on the unsuccessful attempt to take the ISPS down to the seafloor.
Today, we were able to take the ISPS down and place the sampler in the
sediment. Everything was looking good. Still, I had to wait for several hours
until the sampler could be recovered to check if everything went fine.
Unfortunately it did not. Onboard I quickly realised that the enormous pressure
of 320 bar lead to the collapse of the installed samplers the so called
rhizones. Thus, no pore water could be retrieved on this dive. In the following
days I will fix the ISPS and hope for more luck next time.
Best wishes from the RV Meteor.
Picture 3: The ISPS is deployed on the seafloor and should be ready to start work.