The night the krill eggs hatched…
Setting sail from the Falklands and heading into the open water, I was slightly apprehensive, with little knowledge of what to expect of the upcoming 40 days at sea on my first research cruise. A barrage of thoughts hit me in sync as I boarded the ship. How rough would the sea be? Would it make me ill? What would the people on board be like? Questions I’d perhaps put to the back of my mind beforehand as I was so focused on preparing for the scientific tasks ahead. Amongst the chaos of preparing the ship for leaving port, I paused to reflect on the first Antarctic expeditions aboard the Discovery, with Captain Scott. The apprehensions of the living conditions and weather worries were immediately put into perspective… I was as ready as I’d ever be!
With so many helping hands, the ship was transformed much faster than I had anticipated. The laboratories, previously blank canvases with nothing but wooden desktops had entirely transformed and were fully functioning with microscopes, light sources, weighing scales and everything else one might imagine needing for conducting zooplankton surveys, all screwed or tied in place to prevent them moving or falling with the rolling and pitching of the ship in rough seas. Finally, with the ship prepped and ready to, I could focus on my purpose for being on board.
The deck lab prior to unpacking. Photographic credit: Sophie Fielding
So what is ‘nanoplastic’? It’s a term much less heard than ‘microplastic’, crowned word of the year in 2018. Microplastics are categorised as small plastic particles under 5mm. Nanoplastic, unseen by the human eye, is even smaller! It describes tiny pieces of plastic less than 0.001 mm in size, that’s at least 2000 times smaller than a grain of sand! Because of their extremely small size, nanoplastics interact differently with the water particles in the sea and within the bodies of animals that eat them, compared to how bigger plastics behave.
We don’t yet know how much nanoplastic there is in Antarctic waters and we know little of how they impact zooplankton such as Krill. Krill are tiny animals that are hugely important for the Antarctic marine food web as they are eaten by larger animals such as penguins, sea birds and even whales. These are the things I hoped to address with my research on board.
The first hurdle for my research was catching pregnant female krill, so that I could look at how nanoplastics would impact the eggs that they produce. This was no easy task. Every day, midwater fishing nets were deployed and hurled by four people back onto the ship.
Recovery of the RMT fishing net. Photographic credit: Alejandro Ariza
The nets, especially with a big catch, are pretty heavy – and when the contents come aboard they were emptied into buckets. Everybody crowded around the buckets with each scientist searching for their focus species whilst trying not to block the little artificial light we had, since fishing often took place throughout the night when the ship was surrounded by darkness.
Sorting the catch from an RMT net. Photographic credit: Alyasa Hulbert
When the day came in which pregnant females were found, we quickly moved them to holding tanks and the waiting game began. Now it was just a case of waiting for the females to release their eggs. The jars in which they were kept were checked day and night, looking for eggs sunken below the protective mesh which was added to prevent the mother eating them. I waited with bated breath and finally….there were eggs! After checking under the microscope we knew they were fertilised eggs that given the right care, would develop into adult krill. I was ready to set-up my experiment.
All set-up, my next job was to document how the eggs developed by taking photographs every 12 hours. In the early stages krill eggs develop very quickly, and it was exciting to see the cells dividing each time I checked from early stages of two cells or four cells to later stages of 32 cells or more. Soon the development of krill eggs slows and my observations at 2am, in a temperature controlled laboratory set at 2 degrees Celsius (we called it the cold lab) with tired eyes became more tedious. At this time the developmental rate is so little between observations it’s difficult to tell whether the eggs are still alive!
On day four of my experiment, at 2am in the morning, when everybody had gone to bed, I put on my salopettes and thermal coat and headed into the cold lab, expecting to do my usual assessment. With tired eyes, I attempted to focus the microscope and noticed a blurry blob moving amongst the eggs. Coming into focus, there it was, a tiny baby krill had hatched and investigating further, there were many more too! Never seeing this in real life before and with little expectation of the krill eggs developing to this stage beforehand (as the eggs from the last year’s cruise had failed to develop to this stage), I was incredibly excited.
Krill babies! (C) Emily Rowland
After finishing my observations (with lots of extra time spent taking video footage of the baby krill), I left the cold lab and went into the main lab, a busy environment during working hours in which everybody is typing away on their computers waiting for instructions to put on their thermal clothing and head on deck for the next round of fishing. Now it was eerily quiet. I took out my laptop and sent some emails to friends back home, to share what to me was an extremely exciting day, though amused by the fact that they may not find it quite so exciting.
The next morning, I showed the video footage of the baby krill to the other scientists on board who were just as excited as I had been the night before. We celebrated the hatching of the krill, and that’s when I realised that one of the greatest things about being on a biology research cruise in the Southern Ocean was being with others just as passionate about the Antarctic marine ecosystem as I am.
Emily Rowlands is a PhD student at Exeter University, studying the effects of nanoplastic on Antarctic Zooplankton. To find out more about her research – give her a follow on twitter: @EmilyRowlands89