OPERATION - Inventory of the benthic fauna and flora
- 10 mai 2017
- 2 min de lecture
The benthic operations will focus on completing an inventory of the living organisms, both flora and fauna, that live in close relationship with, or buried in, the substrate bottom on and around the Walters Shoal. The operation will target in particular: echinoderms, algae, crustaceans, molluscs, sponges, worms, fish and corals. Several sample collection techniques, depending on depth, will be used. From 0 to 50 m, the maximum depth at which divers are allowed to descend, sampling takes place in three ways. Divers can collect by sight (by hand) large organisms visible to the naked eye. They also use a technique of brushing the substrate with a 50 micron recovery net. The aim is to recover living specimens in the cracks and cavities in the substrate blocks. Finally, a submarine vacuum cleaner equipped with a 500 micron net is used to sample the tiny individuals in the more inaccessible cavities. The contents of the collections are sorted in the ship's laboratory.
Préparation du Diodon Préparation plongéé Préparation plongée Equipe de plongée Sas plongée Sas plongée Descente au Diodon Départ des plongeurs
Collecte à vue Collecte à vue Aspiration du substrat Descente des paniers de brossage Remontée des paniers de brossage Opération de brossage du substrat
Tri au labo Tri des annélides Labo Tri des algues Algues
In the non-diving zone, between 80 and 2 000 m deep, the 'benthic' team will use the Warén dredge as a sampling technique for hard substrates, and beam trawls for soft substrates. Anders Warén, the inventor of the drag which bears his name (1981), is on board with us!
Anders Warén
Once the dredge is lifted to the ship's aft deck and the contents are dumped into large tanks, hand sieving and sorting begin. Coarse substrate and the first organisms gradually start to be differentiated from the raw substrate. It is at this time that sorting by taxon or large zoological groups (sea urchins, molluscs, crustaceans ...) is done. As the sieving proceeds, the fraction is refined until a passage under the binocular microscope is necessary to identify the specimens. A few decks above - in the lab - a photographer takes stills of the remarkable organisms that will feed the databases of the Museum. Tissue sampling is performed on some molluscs selected for subsequent DNA sequencing.
Remontée de drague Tamisage Tamisage Tri Tri Tri Substrat
Tri sur le pont arrière Substrat Tri Tri des mollusques au labo Notre Commandant de bord au labo
A few meters away from the aft deck, in the laboratory, all the specimens collected by diving or by dragging gear are kept in ethanol. A finer identification of the samples will be carried out at the Museum, after the expedition, via its network of experts. It is expected that a number of specimens will be new to science. This expedition organized within the framework of the FFEM-SWIO project, also allows the researchers of the Museum to feed the Tropical Deep Sea Benthos (TDSB) programme.
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