We're in a new location now after a few days of steaming around looking for Ehux. Plankton hunting is a science, but I've learned that it's also an art. The team uses really high tech satellite data to point them in the right direction. Satellites can measure chlorophyll content of the water, currents and the height of the ocean. They can generate a picture of the region we're in, and how much phytoplankton is there (for more on how that works, check out a previous post). On the ground, erm, sea, the boat is equipped with a fluorometer that reads how much chlorophyll is in the water (a rough measure of how many phytoplankton there are). The genetics team on board can sample, and do analyses to see whether Ehux and its virus's genes are in the water. Other scientists can look under the microscope and identify the coccolithophores that are there.

Here's the most recent satellite image the scientists have. It shows the big red patch, which they hope is a bloom of Ehux - and the green labels are where the ship has stopped. It also shows a weird little doughnut hole of low chlorophyll (now officially named "da hole" by the science team). Yesterday we swooped down to da hole to see what was going on, and now we're back up at the northernmost green spot there.

But there are limitations to all these methods. The satellite data they're using is about 24 hours old. By the time we get there, the booming plankton population could be gone. And those big red patches don't necessarily mean Ehux. They could be a bloom of some other kind of plankton, like diatoms. The fluorometer has the same problem: it tells the scientists how much chlorophyll there is, but chlorophyll is found in all sorts of phytoplankton -- not just Ehux.

The units on the Y-axis there is voltage (measured in mV). The spike in the evening happens almost every night, since the daylight quenches some of the fluorescence of the chlorophyll before it can get to the fluorometer.

There are also less scientific measures. For instance, the water where we're at today looks far greener than the water did where we were earlier. That's not such a terrible measure of how many plankton are there. But are they the right plankton?

Our last stopping place (left) compared to this one (right).

And then, when they pause to scope out an area, how much Ehux is enough to stop the boat and spend four days sampling? There's a fine balance between chasing after the biggest bloom, and settling for a middle-of-the-road level of plankton. Do you spend the whole cruise looking for the perfect spot, or do you stop at a few averages places, and work with what's there?

So finding the blooms and deciding when to stick around is a big part of the success of this cruise - but it's not an entirely scientific process. Gut and intuition play a role too. We've just stopped the boat here -- where the northern most green dot is on the satellite map -- for a few days. It's not a huge bloom, but there are Ehux here and the scientists have decided that it's better to get some data than keep on chasing plankton waterfalls (which, as TLC explains, is unwise).


During this trip, I’ll be answering your questions about the science, this boat, and life onboard. Want to know how we search for plankton, why we’re here, or what the food is like? Just ask me! And if you’re wondering how I got here, check out the groups that made this adventure possible: Mind Open Media and COSEE NOW.

Previously in this series:

All Aboard: how you can be a part of our research blog

You wanted to know: what are these phytoplankton?

You wanted to know: what am I bringing to sea?

Greetings from Ponta Delgada! We set sail tomorrow.

Steaming North: how the scientists are trying to find plankton

The superstar sensor: what is a CTD?

Status Update: Day 3 at the Cyclonic Eddy

You wanted to know: what is this virus that infects the phytoplankton (Part One)

You wanted to know: what is this virus that infects the phytoplankton (Part Two)