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1. RSV James Clark Ross

2. Chlorophyll concentration

From: Gerard McCarthy
Date: Wed, 28 Nov 2007 23:50
Subject: Update from Stanley

Hi there,
We are due to depart the Falkland Islands on tomorrow, Thursday, afternoon. It will be great to finally get going after being delayed for nearly a week. But the news is good: the delay will not affect us directly. Some of the other scientists on board have had some of their work postponed due to the delay.

This sort of last minute chopping and changing of cruise plans is all part of being an oceanographer. It is my first scientific cruise and I was expecting everything to go according to plan. Some of the more experienced scientists told me to get used to delays and plans changing.

The delay did give us more time to get the rest of our equiptment set up. We added an oxygen sensor, a fluorometer and a PAR to the CTD frame.

Measuring the ammount of oxygen in seawater can tell oceanographers when the water was last at the surface. Wind mixes air in with the water making it rich in oxygen. But oxygen-rich water doesn't just exist at the surface. Some of the oxygen-rich water from the Drake Passage spreads into the South Atlantic where is sinks to a depth of roughly 1000 metres. This water can be detected all the way from Brazil to South Africa and beyond.

The fluorometer and the PAR, though they sound complicated, are really just used to tell us about phytoplankton (and phytoplankton aren't too complicated either, I promise!). Phytoplankton are the 'grass' of the ocean: they are the first link in the food chain that all marine life depends upon. Like the grass on land, phytoplankton contain chlorophyll, so they can 'harvest' sunlight energy. The fluorometer gives us an idea of how much chlorophyll is in the water. The PAR measures Photosythethically Available Radiation - the intensity of the type of sunlight that plants can use to grow. Together these instruments therefore give us an idea of where phytoplankton will be growing and producing food. And where the food is, that's where you will find all sorts of other sea life.

We have tested some of our instruments while in port. Some of them we cannot test until we are at sea. Here's hoping they all work when we leave...

Gerard