Bioluminescence and Biodiversity Expedition 2007
July 27 - August 1, 2007
July 29, 2007
Leanne Birden writes: Last night when the ROV came up there was a kink in the wire so they had to cut it off and reattach it to the ROV. This took most of the morning so we decided to do trawls until it could be deployed. The trawl net is a Tucker Trawl. I am in charge of setting up the net and deploying it. The net is set up so there is a double trip mechanism on it. The bars that form the top and bottom of the mouth of the net are both weighted and have chains to attach them to the trip mechanism. The net is put in the water and sent to depth, then a "messenger" is sent down the line to trip the bottom bar to fall so the net will open. The messenger is a metal weight that attaches around the wire and slides down it. After the net has been fishing open for an hour the closing messenger is sent. Then the net is brought back up.
We did three trawls today because of the ROV being out of the water for most of it. The first trawl was to 400m. It caught a few small squid and lots of amphipods, which are what I am studying. The second trawl was to 1000m, and was disappointing because we were hoping to catch fish for Dan. Luckily the evening trawl to 300m had several fish for him and plenty of amphipods as well as a few squids in good condition. In every trawl there are also copepods and krill as well as numerous gelatinous organisms. The mesh size of the net is pretty small so we can get some really tiny things. When we bring up the net we pour it out into a big square container with pre chilled seawater and then we sort through it with spoons. It can be rather difficult to sort when the boat is moving a lot.
I store the amphipods I collect overnight in filtered seawater so they have no food. Then the next day I will put them in chambers to collect data on their oxygen consumption. This is a good indicator of metabolism because the amount of oxygen an organism consumes is proportionate to the amount of energy it is using.
We were hoping to scuba dive on this trip as another method to collect animals, but the wind has been too fast (so far no less than 20 knots) and the water has been too rough to dive. Hopefully the weather will improve so we can get in the water soon.
The ROV made it into the water for a short dive in the afternoon. It caught a few jellies and siphonophores and a squid. We all took a quick break at sunset to watch the sun go down, that was the first we had seen it this trip. Tomorrow we should be back to the normal ROV schedule.