It doesn’t happen often enough, but when the sun shines in Scotland it is spectacular – so what better way to soak up the sun than searching for copepods in glorious Loch Etive?! I (Jen) joined fellow Arctic biologists from the Scottish Association of Marine Science (SAMS) aboard the Seòl Mara for this special fishing trip. Here’s what we got up to…

Perfect conditions for the Seòl Mara

I was pleasantly surprised that our equipment was fairly straight forward for the task at hand: one large plankton net (with a very fine mesh for catching the tiny animals), a few buckets, temperature recorders and a trusty teaspoon (for removing pesky copepod-eating jellyfish!) and we were all set. Luckily we had a 40 minute trip to our site, so we enjoyed the stunning views of Glen Etive and even spotted some seals and a sea eagle!

Now for some work. First things first, we lower a CTD (conductivity-temperature-depth) profiler into the water and wait till it reaches 100m deep. This records the temperature and salinity of the water column to tell us what sort of conditions our copepods are experiencing. Also attached to the CTD is a circle of six containers that, when fired, will close and collect water at specific depths. This water will be used for keeping the copepods happy back in the laboratory.

The CTD profiler and water bottles, ready to be deployed

Next up to be deployed is our plankton net. To catch these zooplankton we need to follow their daily rhythm. During the day, copepods tend to migrate to deeper, darker water to avoid encountering their predators so we drop our net to 150 metres and collect our first sample. The “cod end” (a container at the bottom of the net which everything drops in to) was satisfyingly full of life! Not only had we caught copepods but jellyfish and larger crustaceans.

A plankton net and a happy biologist!

We repeat these net hauls several times and at several depths to make sure we have plenty data because there is more than one important reason for collecting these animals. First, we preserve some in small bottles for genetic analyses. These are going to be analysed by researchers of team CHASE who are interested in their biological clocks. By studying which genes are switched on at different times of the day, the researchers hope to better understand how copepod migratory behaviour is controlled.

This moon jelly was caught in our net and released afterwards (thanks to the teaspoon)

Other copepods were taken to the lab, sorted, and prepped for some pretty cool experiments.  Individual copepods were placed inside small glass tubes and then neatly placed inside a LAM (Locomotor Activity Monitor). This scientific circuit board is fitted with hundreds of tiny light beams that surround each tube – if a copepod moves up or down, a light beam is broken, and the information is recorded on a computer. Now we will record their movements over the course of a week and under different light environments. We hope this data will help tell us how changes in light affect their behaviour – something that is affecting their copepod cousins in the North Atlantic and Arctic as warming ocean temperatures shift their habitat further north.

With sampling complete, experiments set up, and meetings finished, all that’s left to do is enjoy a brew and these fantastic views. Thanks to Kim, Jon, Jordan, Michela and others at SAMS for a fantastic week chasing copepods. Next stop: the Arctic!

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