July 6, 2006 Options

[Betty_Carvellas]

July 6, 2006

I mentioned the XBT yesterday, and told you that XBT stands for eXpendable BathyThermograph, and that it is launched hourly round the clock. The expendable part means that the device goes to the bottom and the connecting wire is cut to release it. Because the ship doesn't have to stop for each launch, and because the XBT is relatively inexpensive at about $50/XBT, the XBT provides a great way to supplement the CTD temperature data. The CTD is a far more complex and expensive piece of equipment which measures temperature and much more. I'll have pictures and more information about it in an upcoming journal entry. This particular XBT is a T4 XBT which means that it goes to a depth of 460 meters. Once launched, it sinks to the bottom at a constant rate, transmitting temperature data vertically to depth and sending the information to a computer on board the ship.

While on deck this morning, I asked Kate Darling to take pictures of my temporary work with the bongo nets. She got great shots of Rebecca and me as we sent the bongos overboard, but my camera batteries died right after that. So, you can check out Kate's picture to see what they look like going in and you can also see the picture I took yesterday of the copepods (a type of zooplankton-small aquatic animals) which seemed to be filling our samples for the past two days. Twice a day we drop the two nets over the side and bring them back to the surface vertically. The nets take two samples simultaneously. In the picture, you can just see the small filter bottles (called cod ends) at the bottom of each net. We rinse the nets as they come close to the ship to make certain all the zooplankton are washed into the cod ends. Once the nets are on the deck, we detach the cod ends, dump their contents into buckets, and filter the samples into jars, one preserved in formalin and the other in ethanol.


Here I am lowering the weights attached to the bongo nets as they go into the water.


Once we dump out the contents of the cod end of the bongo nets, this is what we find. If you look closely, you can see individual copepods.

While working at my computer this afternoon, Rebecca came in to tell me to quit immediately because weather like this is rare and I'd better take advantage of it. I knew she was right, so I headed up to the flight deck where we were soon joined by Ian and Kate Darling, and Rebecca Woodgate, all seeking a few minutes in the sun before dinner. Ian told us about the large bird, a fulmar that was around the ship. The fulmar is a seabird which only comes to land to nest; it evens drinks seawater, extruding the salt through a tube on its beak. Females lay one egg/year, and the chicks have an interesting defense mechanism. If disturbed (by an Arctic fox, for example), the chick will regurgitate an oily, foul smelling substance that drives away all but the most determined predator. Their numbers have increased as commercial fishing has expanded. The fulmars follow the boats, feeding off the discarded fish waste. During my last two cruises on the Laurier, we spent the majority of our time in fog, rain, or otherwise unpleasant weather. This afternoon was a real treat!


Days lke this are rare, so Kate Darling, Ian Darling, and Rebecca Woodgate took a few minutes to enjoy the sunshine and warm temperatures.

[Samantha_Dassler_Barlow]

Hi Betty,
I have been reading your journals and I think you are doing an excellent job. Keep up the good work and enjoy your expedition.
Samantha Barlow

P.S. Please tell Lee and Jackie that I said hello.