At Sea, Part 1: Science

Apr 17 2012 Published by under Uncategorized

I thought about calling this Science at Sea—how’s that for a vague title?

 

Of course it would be a fairly misleading title, since there’s actually a huge variety of science done at sea.  For example, MyU has a large geophysics program, one that uses a lot of remote sensing devices.  And most people who talk about “science at sea” are thinking of people who study whales or dolphins.  But I don’t know anything about that sort of science.

 

The scientists I want to talk about are the ones I know: people who study water (or microbes in the water).  If you are one of these scientists, you can skip this blog post altogether because it will all be very  basic to you.  I am writing this because it’s rather surprising how little people (even many scientists) know about how the science of oceanography works.

 

First, I should say that if you want to do oceanography, you need a ship.  That sounds like a dumb thing to say, but getting ship space can be one of the hardest parts of doing oceanography.  Dr. Hand-Waver says it’s a catch-22: when you write a grant, they want to know which ship you’re going to be going out on; but when you try to reserve space on a ship, they want you to be funded before they actually write your name in for sure.  It helps if you are at a university with a research vessel.  Alas, Dr. Hand-Waver and I live and work in Colorado, so we get on board whichever cruise we can.

 

A research vessel in dock.

 

If you don’t work for a university that owns a ship, you reserve ship time through the UNOLS system.  And hopefully they grant it to you.

 

So now you’re at sea.  To do chemical oceanography, you definitely need water samples.  Most people use a CTD-rosette, more commonly called a CTD.

 

a CTD

A CTD rosette.

 

Each rosette is a little bit different, but they all have the same basic parts: a cage to hold everything together; a bunch of Niskin bottles around the outside; and some sensors that measure the Conductivity, Temperature, and Density (hence the name “CTD”) of the surrounding water.  The Niskin bottles are programmed to open at given depths—yes, each individual bottle can be opened at a different depth—which is determined by density.

 

The CTD is lowered into the ocean by cable.  If you attempt this when the seas are too rough, you take the risk of the cable snapping: bye-bye CTD, bye-bye 1.5 million dollars.  Calm seas are a good thing.

CTD overboard!

 

When the CTD comes back on deck, everyone gets their water.  Usually there’s some sort of pecking order; you’re told which bottles you can sample from, and who gets water from that bottle first.

Getting water out of the CTD. I did not intentionally fuzzify the picture--that just tends to happen a lot at sea if you have a mediocre camera.

 

If you just need a few bottles’ worth of water, you can attach Niskin bottles directly to a line—which is definitely not as efficient as a CTD, but quite a bit less unwieldy.  You can use also use Go-Flo bottles the same way; these are close cousins to Niskin bottles but are designed to minimize trace metal contamination, which makes a huge difference for some analytical methods.

Go-flo bottles hanging in the lab. These are the smallest size--some are almost as large as I am.

 

That really is me on the right, getting the GoFlo bottle on the line.

 

Go-Flo bottles (and individual Niskin bottles) have no depth sensors attached.  Instead they’re triggered by “messengers”—basically, weights that slide down the line and hit the button that snaps the sampling door shut.   It’s actually a rather ingenious system.

 

So now you have your water.  Now what do you do with it?  Obviously, it depends on what sort of science you do.

 

There are people who look at nitrate and nitrite production.  There are people who look at primary production (i.e. turning CO2 into organic carbon).  There are people who look at how global warming affects ocean acidification.

 

There are folks who do DNA analysis on the microbes in the water.  I love these people: I want to know what’s doing chemistry in the water, but I only have theoretical knowledge of how to determine who’s there.  So it’s good to be on a cruise with people who will do the DNA analysis for you.

 

And of course there are people who look at—well, what I look at.  But as far as I know, there are only about four groups in the world who do that at sea, so I’ll keep my mouth shut.  Just suffice it to say that I think that what I do is really, really cool and cutting edge.  I love what I do!

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