Another step closer…

Hi guys, well another milestone has been reached on the long road to becoming a doctor of Oceanography!!!

Yesterday I did my “Présentation de résultats” at ULaval, which is a 35-45 minute presentation summarizing the results of your PhD. This talk (which takes place towards the end of the project), is graded by attending professors, and anyone else around campus who sees the emails and posters and is interested can also attend. It was great to see my past students come by for support :).

This is the second of three course presentations you give during your PhD studies, the first being the proposal of your project (which I did back in April 2013), and the third being your final defense (which I will probably do before April 2016). Looking back at the PhD project proposal, it’s awesome to see how far things have come. Maybe one day I will upload both project presentations (proposal and results) so you can see the development of things from beginning to near-end. Initially I had planned to do my whole thesis on arrow worms from the Canadian Arctic. In the end, my first chapter focused on arrow worms from the European Arctic (published), my second on those from the Canadian Arctic (manuscript), and my third contained results from the Canadian Arctic and the Chukchi Sea, Alaska!

I’m happy with how the thesis has come together. As we know, the role of chaetognaths in the Arctic food web has traditionally been overlooked, but my PhD has filled in some of the knowledge gaps, and introduced many more questions!!

The Arctic marine food web!! Arrows link prey to their predators, but does nothing eat chaetognaths?? Modified from Darnis et al. (2012)

Here is a quick summary of some of the unique features of my PhD:

  1. The first chapter is a study of how chaetognaths live slap bang in the middle of winter, when not much is known about many organisms, due to sampling difficulties. I was lucky to be a participant in the first ARCTOS Polar Night cruise around Svalbard in January 2012, just before I came to Canada. Then my buddy Carl went on the second cruise in January 2013, and brought me back some more chaetognaths so I could increase my sample size and compare between different locations and years. Thanks Carl!

  2. The other chapters compare the ecology of the 3 common species, from the same places (mostly the Amundsen Gulf) and same time (2007-2008), and literally included thousands of specimens. Such a nice long time series is really hard to come by, and it allowed us to see exactly what the different species do throughout the year. In the Arctic, animals often require very different strategies to survive through different seasons, due to extreme seasonality in their food availability. 

  3. Finally, in Chapter III, I was able to use 3 different types of analyses to look at what they eat, helping to overcome any potential weaknesses of using just one method. The first simply involved dissecting chaetognaths under the miscroscope and seeing what was in their guts. The other analyses required the extraction of chemical constituents to discover the presence of fatty acids that may have come from their food, and ratios of different isotopes of carbon and of nitrogen, which can also reveal diets.

The talk went very well. To be honest with you I was exhausted beforehand, having worked intensely on it since the previous weekend and being totally sleep deprived (although this has become the norm). However with the support of my team, especially Sophie and Moritz (two people I can always rely on whatever), I made it through with flying colors! If you have tuned into any of my internet communications on chaetognaths in the last couple of years, you will probably know that whilst I agree that chaetognaths are predators (on copepods and the like), I reckon that they are NOT ONLY PREDATORS. This became a theme in the talk. They may also “drink” / ingest seawater and whatever is in it (see this video from my friend Takuya Ohnishi, Kochi University, Japan):

Certain species also seem to grab and ingest detritus, including algae. Very high numbers of Eukrohnia hamata individuals contained large amounts of green matter in May (81% of 132 analysed specimens) and this increased towards the bloom period. So it doesn’t seem they only do this when weakened. These green gut contents also do not occur in Parasagitta elegans from the same locations, times and depths, so I reckon different species have different feeding habits: P. elegans seems more carnivorous. See comparative photos below (thanks Roxane at Aix-Marseille for the photos)!!

Eukrohnia hamata individuals from May 2008 in the Amundsen Gulf with lots of detritus in their guts.

Parasagitta elegans individuals don’t have these gut contents! All animals were dyed with a stain to help reveal gonads and prey.

This is really important (well… at least in chaetognath science)! If chaetognaths aren’t only predators and consume organic matter, then we could be missing a critical part of their ecological role and need to revisit it. This could mean that they have a role in a side food ‘loop’, called the microbial loop which also involves bacteria. What’s really interesting is that the guts of E. hamata individuals can contain highly visible green matter, even when they live quite deep (hundreds of meters down). Maybe grabbing falling detritus, or gulping organic matter, really helps E. hamata individuals to live here when (and where) their favorite copepod prey is not around so much. Incidentally, these omni/detritivores appear to be less seasonal restricted in when they reproduce (and grow) than P. elegans. Could a more flexible diet also ensure sustenance for parents and their offspring in winter? As you can see, there are a lot more questions to answer, and I really hope that these questions are pursued further after my PhD.

But what’s next for me?

Well, I’m really looking forward to going home to Scotland in a month from now, with a short trip to Toronto before. I also hope a first draft of the thesis will be ready, or almost ready, before that.

Then some chilling with the family, and back for the last stretch in mid-January. I’ve also been looking for jobs in science communication/education/outreach – I will keep you updated with any news. If you come across any positions like this, please let me know too! 

Shout out to Sophie, that girl is working non-stop too.

Take care guys, Jxx

P.S. If you missed my recent video on zooplankton, the “Underdogs of the Arctic”, here it is one more time: https://vimeo.com/139630398

Featured image: a copepod with a chaetognath, image taken by the LOKI underwater imaging system. 

Comments (8)
  • Name*Dave

    November 22, 2015

    Message*Lots of very hard work Jordy – well worth it – looking forward to the festive chilling !! x

    • Jordan

      November 22, 2015

      Thanks Dad 🙂

  • Eithne

    November 22, 2015

    Well done Jordon. Fascinating subject. Can’t wait to hear more! Lots of hard work went into this!!

    • Jordan

      November 22, 2015

      Thanks Eithne! 🙂

  • Erico

    November 22, 2015

    What a fun talk it was. Congratulations!

    • Jordan

      November 22, 2015

      Cheers Eric 🙂

  • Uncle Scott

    November 26, 2015

    Brilliant work and a great video Jordy. It almost made me interested in plankton. Just almost though!

    • Jordan

      November 27, 2015

      Hi Uncle Scott and Auntie Gill,
      thanks a lot for your comments! Don’t worry, at new year I will make sure you become interested in plankton!
      Cheers J 🙂

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