The great zooplankton count!

Rhian Taylor

The last few months of zooplankton work have been largely lab-based, as I continue to sort and count all my samples. I have now reached over 150 samples sorted through, with around 50 left to go. Sometimes I try and visualise how much zooplankton I’ve sorted and counted out, and turns out to date I have counted over 95,000 animals, which have weighed a grand total of… 350g. Well, it’s slightly less than that, but to make the visualisation more fun, that means the total weight of zooplankton I’ve gone through is around 2 chocolate oranges, with a few segments of a third!

In the samples I have gone through, I have completely sorted through 7 seasonal collections. From this, I can make a start at analysing my data – so rather than just talking about looking at how the zooplankton community changes between seasons, I can actually make a start at comparing the seasons. What’s exciting is that even after 150 samples, I still find the occasional new thing in a sample!
Image left:  A very hungry arrowworm - you can see through its body its recent dinner!
Image middle: Even after 150 samples - something new!
Image right:  All the larval stages of lobster krill
Although I still have a lot of work to do on my project, the sampling period is winding down. Currently, the plan is to do one final collection of zooplankton as soon as the wind dies down, and then I will have collected all the samples for my PhD! These have been collected across the seasons since October 2022, and from these I should be able to get a good idea of what species of zooplankton are present in the near-shore environment of the Falkland Islands in the different seasons, and how the community composition changes. Even ahead of doing statistical analysis on these samples, I can already see some differences – in spring, the samples are completely dominated by the larvae of lobster krill at the full range of life-stages and several crab species (decapod crustacean larvae), but by late summer these have almost completely gone, and their numbers stay low until spring comes around again. In the months without large numbers of decapod crustaceans, other organisms take on a more dominant role – sometimes it’s jellyfish, other times arrow worms (which are always fun to see in the samples due to their big teeth and tendency to feed on other things in the net) or it’s copepods.
Many crustaceans to count
Aside from continuing to go through my samples, I’ve been planning ahead to figure out what work I need to do for the rest of this field season. Hopefully I’ll be able to find some days where the tide is good to do some rock pooling and collect some adult crabs and fish to help with by DNA barcoding work in Aberdeen. 

Some of the tasks are very different, like preparing for a university conference next month. This is a good opportunity to think about how I can use and talk about the data I have. 
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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