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Meteor-Blog 28. July 2008: Megafauna from depth!

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The previous dive with QUEST promised success: the focus of today's Meteor-Blog is the marine fauna at REGAB station. The PhD student of the French research institute IFREMER, Carole Decker, reports about her scientific passion for the deep-sea clam Calyptogena and the benthic way of life.

Planetearth Blog

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 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 and an overview of all contributions to the Meteor-Blog and expedition M76/3B:

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28. July 2008 (Author: Carole Decker)

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Today's blog is contributed by:

carole decker“Hello, my name is Carole Decker. I have just finished my Master studies in Marine Biological Sciences at the Institut Universitaire Européen de la Mer in Brest, Brittany, France. I will start my PhD next November in the Deep Sea Laboratory at IFREMER. The subject deals with the study of diversity, ecology and adaptation of Vesicomyid bivalves (“clams”) associated with reduced deep-sea environments, and mainly cold methane seeps. During the cruise I plan to sample different species to investigate if they are distributed according to chemical parameters (methane, sulphide and oxygen).”

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Picture 1: A species of the genus Calyptogena abundantly found at REGAB

Megafauna from depth!

28. Juli 2008: shiptrackDuring the two last dives we have sampled a first habitat at REGAB dominated by a new species of the genus Calyptogena (Picture 1) using a net. We also deployed two types of benthic chambers to measure the respiration rate of the bivalves and the methane fluxes coming from the seafloor (Picture 2). When we removed the chamber we sampled the sediment using blade core (Picture 3) and bivalves to count, measure and weight them. These bivalves are adapted to the harsh environment at seeps and we will study the respiratory pigments in the blood. Some of the species have haemoglobin, which binds the sulphide, a poison for the organisms. Indeed, these clams need sulphide for the symbiotic bacteria living in their gills and nourishing them. The different pigments also have a variable affinity for oxygen, which can be limited at seeps.

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Picture 2: The benthic chamber CALMAR deployed on a patch of clams

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Picture 3: Sampling clams with the large blade core

For these studies of host and symbiont physiology, and of their reproduction, we dissect each individual and store the different parts: blood, gills, mantle, muscle, gonad to study them in the lab. There are also many other organisms living with these bivalves (Picture 4) and most of them are of very small size (less than one millimetre). To separate them from the sediment, we pass them through different sizes of sieves, from 250 µm to one millimetre (Picture 5). We will sort the organisms in the lab after the cruise and send them to several specialists for the taxonomy of each group, as most of the species are new to science.

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Picture 4: Patches of living Calyptogena north of the active centre of the REGAB pockmark

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Picture 5: Carole Decker sieving sediments to collect small organisms