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A Potpourri of News

09/26/2011, 11:06 PM by Lollie Garay
Moon Drawing from the Melville<br/><br/>Credit: Michael Oliveri
Moon Drawing from the Melville
Photo Credit: Michael Oliveri

There’s a frenzy of activity onboard the ship as the science teams make use of the dwindling time at sea. Michael Oliveri reports that’s its hard to get interviews while everyone works so hard, but images are easy to capture! I’ve posted quite a few with this blog to give you an idea of the daily happenings and people on the ship.

 The featured image on this post is a “drawing “ by Michael. He explains:

“I am taking long exposure “drawings “of Jupiter and the moon. I am
calling them drawings because with the boat rocking it is like using
light to draw it - light that is already 43 minutes in the past.”  Nice!

 Chief Tish weighs in with some insight on the hunt for the DDAs in response to some questions I had. (If you recall, in an earlier post Tish mentioned how the changes in salinity determined what organism could live successfully in those areas.)

  “Based on last spring's observations and the observations from the three previous cruises to this area - we expected to find DDAs in 32-33 ppt salinity.  We are not finding a lot of water with that salinity right now.  Most of the plume is more like 30-31, and we have seen much fresher (26-29) and much saltier (35.5 - 36) on the first leg.   The salinity gradients (plume edges) seem sharper...   perhaps driven by the strength of the current underneath us.”

 “There are DDAs mixed up with Tricho in the 30-31 salinity water here in the SE corner, but they aren't blooming like they were in the spring.  We may just be in the wrong place and we will continue to monitor the communities as we steam.    And yes - Trichodesmium likes clear blue calm water, generally speaking.   Finding it in fresher plume water is a bit of a surprise.”

 “This morning we found (salinity) at 33.5 in a broad band - but we still see mostly Tricho.  Something has shifted to allow Tricho to out compete the DDAs here.  Might be a shift in the Phosphorous or perhaps the CO2 concentration, or maybe there is some seasonality as you mention.  The pCO2 is not very low here at all, despite the plume influence.  That's the impact of Tricho - it doesn't draw the co2 down as much, for the same relative amount of n-fixation.”

 And Will Berelson, who joined the cruise midway, tells us more about the coring his team is doing:

“The USC gang from my group is at it again.   We are deploying floating
traps, arrays that hold 12 tubes, each tube 4" diameter and about 1 m
long acts as a particle trap.  Hence, one array has 12 particle traps attached.
We hang these traps on a line, one array at 150 m and another at 250m.  The 'hanging' part comes from flotation; large rubber ball floats from which the traps
hang.  The purpose of two depths is to capture particles sinking past
150 m but also those sinking past 250 m.  There will be a difference in what and how much gets to each depth and we are after that sort of information.  At each
'drifter' station, we deploy two of these arrays.  They each have a GPS buoy attached, which tell us where they are and where they've been.  We leave them floating
for 48-72 hours, then grab them with a line and grappling hook, pull them up and each tube gets processed.  One of the major processing steps involves looking at
the trap material and deciding if it fell in or swam in.  This job falls to Debbie
Steinberg, she 'picks out' the 'swimmers', organisms that she thinks
don't belong as part of the sinking flux. Further analyses of this material are made back at USC.”

“Another thing we are doing as we did last year is collect cores from
the sea floor.  Eventually, the material made in the surface ocean is
recycled or it sinks to the bottom. If it makes it to the bottom, we'd like to know how much, so we collect cores.  Our coring device of choice is the multicorer.  This
can retrieve 8 cores, each with 30-70 cm of mud from the bottom.  Once collected, we extract the pore water from that mud.  As reactions take place in the mud, the pore water chemistry is a sensitive monitor of what's happening and how fast it happens.  Thus the pore water chemistry from a core lets us interpret how much carbon and nitrogen has fallen to the sea floor in a given area.  We must place our cores in a cold van to get them back to temperatures like the sea floor, thus we must do our work on them in this cold van, wearing winter clothes while it's summer near the equator!!  It takes about 4 hours to extract pore waters from the cores, then we sample the mud itself and store a core for transport back to USC.”

“Something else we're doing this year that we didn't last year is collecting mud using a gravity corer (GC).  A GC is a long piece of irrigation pipe, 15-20', with a stack of weights on the top and a nose cone on the bottom.  As this tube enters the mud, like an arrow piercing a target, the mud enters the tube and a long, several meters, section of mud can be obtained.  The longest core we've collected thus far is almost 4 m.  This is so important that NSF gave us 3 extra days of ship-time to collect these cores. It's so important for this reason, it collects mud from 1000's and 1000's of years ago, perhaps 40,000 years ago or longer.  This was a time when the globe experienced much colder temperatures, the ice age, so sediment obtained from this period tells us how the ocean used to operate and how the Amazon interacted with the Atlantic Ocean at this time.  We also extract pore waters from these cores.”

 That’s a lot of science for one night!


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Question of the Day

  • Do the bacteria in the water make us sick?

    Only a few of them.  Bacteria are in every habitat on Earth, growing in soil, hot springs, radioactive waste, water, as well as in organic matter and the live bodies of plants and animals. Bacteria recycle nutrients, with many steps in nutrient cycles depending on these organisms, such as nitrogen fixation.