We’ve been dealt some tough hands on this cruise, but as I write this we just finished another series of net tows and wrapped up a few experiments in bright sunshine and light winds. The Memorial Day festivities appear to be in full swing on the pleasure craft, as evidenced by the sails dotting the horizon and clusters of sport fishing boats to the north of us. As nice as it would be to be attending a barbecue with the family or “sampling” the nekton with a rod and reel, it’s awfully nice to be out here with a great crew doing cool science.
It is Memorial Day, and it’s a good time to reflect on the sacrifices that have allowed our free society to flourish, and as result so has our science. It’s also worth noting that this project is funded by the National Science Foundation, which was created in 1950 and has its roots in cold war politics. The agency was formed “To promote the progress of science; to advance the national health, prosperity, and welfare; and to secure the national defense.” (Wikipedia)
As far as our science goes this lovely Monday morning, we seem to be seeing sulfide laden deep water. I’m not a marine chemist, but I’m pretty sure this is somewhat early for sulfidic water to be present, particularly this far south. We’ll try to get some samples to determine the amount of sulfides present, but we weren’t planning to do that so it may take some creative thinking.
So why do we care about that? Well, low oxygen can really stress organisms but sulfides are toxic. Our colleagues who work on these things are interested in what ions organisms use as electron receptors for energy. In simplest terms, everything but the tiniest microbes rely on oxygen because it has the highest energy per molecule. As oxygen gets used up, certain organisms can switch to lower energy compounds like nitrates and things like that. Once all the oxygen is used up there is a bit of a lag and then some of the organisms that can do it begin to switch to using sulfides as their terminal electron receptor. The byproduct of that chemical process is H2S, or hydrogen sulfide which is lethal to most organisms. Some microbes have mechanisms to deal with it, but metazoans (multi-cellular organisms including plants and animals) do not. In fact, even low oxygen is lethal to many metazoans before the switch to sulfide occurs. Hence the title of this post. Our deepest samples are nearly devoid of the copepods, fish larvae, and other zooplankton we are catching just a meter or so above the deep samples. So there might be microbes, but not much else alive down there.
I’ll try to get some more pictures up this afternoon. We’re going to finish up the net tows around dinner time and then try to get back some of our aborted Scanfish survey before heading home. Then we’ll hopefully get to enjoy some of those barbecue leftovers tomorrow evening. We did have some spectacular, and I mean truly scrumptious, brisket with fingerling potatoes and collard greens last night that seemed awfully appropriate. Our cook on this trip is sailing as relief for the regular cook, and her full time position is on a California research vessel, but the interesting part is that she has a blog about her life as a research vessel cook, food, and travels. Check it out here.