The end of the second field season for zooplankton

Rhian Taylor

Somehow, I’m now coming to the end of my second season in the Falkland Islands (having been here since mid-October). The last few months have been insanely busy, and now that I’m into my last week, there seem to be so much left to do! This has included going rock pooling for small fish, helping out with World Ocean Day, and making sure that I have got all the data that I need from my samples. Things seem to be falling into place though, which is always nice. Now I just need to make sure everything gets to Aberdeen so I can continue the work!
Stall at the World Oceans Day Event
At the end of March, I completed the final zooplankton collection for my PhD – going out with a bang, as we hit a swarm of post-larval lobster krill on the last repeat! This meant we were all quickly trying to find as many big jars as possible, and make sure there was enough formalin to preserve everything. I was definitely not expecting to get the highest biomass of zooplankton out of any samples on this trip, as I would have guessed that spring would have the high biomass. Another unexpected thing from this trip was the number of small squid larvae we caught. Initially, I was going to do a PhD chapter on squid larvae, but we found so few that that plan had to be scrapped! At the time of this collection, I had sorted through around 175 samples and found a grand total of 7 squid larvae. In the first sample from this collection, I more than doubled that count. It’s nice to see that the final collection was consistent to all the others: we didn’t know what to expect, and what we got was a surprise. Oh, and I suppose the Peal’s dolphins showed up at the expected time- when I had to focus on filtering the zooplankton through a small sieve. It’s good to know that we can always count on them to show up on schedule!
Squid larvae
Big-eyed lantern fish larvae
The last few collections all involved games of “tweezer ninja” (where we try to collect as many fish larvae from the sample so I could look at them separately), but on this occasion, there were only three small larvae to pick out. Based on the work I did on last year’s samples, it looks like these ones could be more of the deep-sea lantern fish larvae. It was very exciting to find them in last year’s collections but getting them again at the same time of year is even more interesting.
In the first week of June, I hit a major milestone of my PhD – I finished sorting through my 214 zooplankton samples! I have no idea how many hours I’ve spent in the lab counting everything under the microscopes, though I’ve spent the better part of a year going through them all. I sometimes now wake up with a vague feeling of having been counting things in my dreams. I really enjoy looking at the overall numbers for these samples because they sound ridiculous. According to my huge spreadsheet of results, I have counted around 120,000 animals which collectively have weighed… about 500g. Zooplankton is really tiny. To continue the scale of reference from my blog post from the last Southern Currents – my zooplankton weighs the equivalent of 3.3 chocolate oranges. The analysis I’m actually doing for my PhD is slightly more technical, but less fun to think about than that!

On return to the UK, I need to collect my zooplankton samples, as they got to take the more interesting route back to the UK on the RSS Sir David Attenborough (thank you BAS). I did get to have a tour of the ship before they left the Falklands, which was incredibly exciting! Once I get my samples back to Aberdeen, I will continue spending my time in the lab trying to identify zooplankton, but this time I will be identifying the animals using DNA barcoding and phylogenetic analysis. To do this, I will essentially be making a family tree of my unknown species and comparing these with the DNA of animals already identified. This way I can see what species my sample is closely related and determine what it is. It sometimes feels like combining science with detective work.
214 Sample sorted! 
Visit to the RRS Sir David Attenborough
This project is hosted by the University of Aberdeen and SAERI. Collaborators and sponsors include Fortuna LTD, Darwin Plus, Shallow Marine Surveys Group, Falkland Island Fisheries and the Environmental Studies Budget (Falkland Islands Government). Rhian’s PhD supervisors include Dr Jesse van der Grient and Dr Paul Brickle at SAERI and Professor Stuart Piertney and Dr Alex Douglas at the University of Aberdeen.
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