We Blogged It!

The Eyes and Nose are Chemists!

06/09/2010, 3:34 PM by Lollie Garay
The RV Knorr at Night.<br/><br/>Credit: lollie garay
The RV Knorr at Night.
Photo Credit: lollie garay

June 9

Lat/Long: 04.58N 052.10W

Off the coast of French Guiana

Air Temp:28.5C 83.3F

Surface: 28.4C 83.16F

Salinity: 34.34

 

 

We are anchored a couple of miles off the coast of Cayenne, French Guiana! Early this morning a small boat came out to the ship, bringing 2 students who are joining the cruise.

Brandon Russell(UC,Santa Cruz) will be working on Ed Carpenter’s team and John Fleming (USC)who will join Will Berelson’s team. While we welcome them aboard, we also bid “safe travels” to Doug Capone and Ed Carpenter who are leaving the cruise. We are only here for a short time (no port call) and then head out back to sea. The decks were full this morning with people armed with cameras anxious to see land again. As we approached someone said “can you smell it?” And you could!

 

Last night we had another PITS trap recovery. (The photo featured shows the stark difference between the night on the sea and the lights on the ship.) Unfortunately, only 2 of the 3 traps were recovered. The third one was damaged, likely by another vessel. However, the floats and the satellite transmitter were salvaged.

 

We turn now to a guest blog by Will Berelson:

 

"During station 11, the ship was sampling the ocean in relatively shallow water, we were on the

'shelf' off the coast of French Guiana in 75 m of water.  The biologists

were finding all kinds and huge quantities of phytoplankton in these waters.

We geologists wondered "how much of this 'pea soup' makes it down to the bottom and falls

to the sea floor?"  So we did what we do...we cored."

 

"However, as any beach-goer knows, it is really, really difficult to get your beach

umbrella to penetrate the sand.  Well, it's really really hard to collect a core

in sandy sediment, and that's what we found.  The sediment on the shelf was

primarily a fine sand with bits of shells and a little mud mixed in--but primarily, it

was sand.

 

"We drove the corer into this sediment and collected a core, all of 5" long! (we like

cores > 2')  But we looked at this sediment, and the eyeballs became chemists.  The sand

core was about 2-3" of reddish-brown color and then 2-3" of

dark grey-black color.  The dark sand was a curious sight.  So we used our

Nose-chemists....smell the sand.  The light sand smelled like.....sand.  The dark sand

smelled.....stinky.  The dark color and smell indicate the presence of sulfides

mixed into the sands.  There are various ways this could occur, but it seems most likely

that large amounts of organic matter (the 'pea soup') get pumped into the sand, between

the grains, and the degradation of this organic matter yields sulfide.  The sulfide

produces both the smell and the dark color (as an admixture of sulfide and iron).  This

sort of thing happens commonly in salt marsh environments, but are not common on open

marine shelves, like where we were."

 

"We need to investigate this further, but our Eye and Nose chemists are reliable and

useful as a first stab at sediment geochemistry!!"

 

Thanks Will! Until tomorrow,

Lollie

 

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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.