From the sea along the coast of Belgium to the molecular laboratories in Germany

23 October 2018

Jon Lapeyra, MixITiN’s ESR10, reports from RV Simon Stevin

Running away from the European capital of Brussels, on an early morning in summer we arrive at the port of Oostende. Fresh air! The research vessel (RV) “Simon Stevin” from VLIZ is already waiting for us along with a very welcome cup of coffee. A big thank you to the crew!

As soon as we get our sampling equipment into the ship’s laboratory, our project briefing begins. We are going to sample nine stations along the Belgian coastal zone in 48 hours. Our aim? … sampling the planktonic community; especially mixotrophs, of course!

At each sampling station the RV Simon Stevin stops for 20-30 minutes, depending on the requirements of the different scientists on board. A range of different sampling equipment are deployed: a CTD (an oceanography instrument to measure Conductivity, Temperature, and Pressure), Niskin bottles to collect water and Secchi disks to measure the water turbidity. Also, we take surface water and benthic samples at different depths ranging from 10 to 35m. Why? Because within MixITiN one of our aims is to understand the impact of environmental conditions on the mixotrophic plankton communities and one of my jobs is to carry out monthly sampling throughout the year off the Belgian coast.

Alongside the field sampling, in the ship’s laboratory we carry on identifying, sorting and preserving samples for later analysis. Through the microscope we look at the living organisms as soon as we get them out of the water. In this way, we can have an overview of what is present in the water so that we can isolate what we need for the analysis of their genes. Also, we always hope to get lucky and observe some mixotrophs predating over what one may consider to be their predator!

Filters of the seawater ‘content’ are collected and quickly frozen; DNA from these was going to be extracted at the ‘Université Libre de Bruxelles’ and finally sequenced at the Alfred Wegener Institute (AWI) in Germany; both MixITiN consortium institutes where I am conducting my research as a Marie Sklodowska Curie Actions Early Stage Researcher (ESR). While I carry on sampling on RV Simon Stevin, I wonder…. how diverse and abundant are the mixotrophs among the planktonic community going to be?  What functional types will I find in the Southern North Sea?

Sampling done, on our way back to the shore, we spot a ‘red tide’ not far from our last sampling station. A Noctiluca bloom! A great opportunity to get fresh samples of one of the most iconic species of the plankton community. Noctiluca scintillans form bioluminescent blooms in our seas and oceans globally. So we were very excited – are these particular cells bioluminescent?

We test them in the dark, however unfortunately these particular Noctiluca were not bioluminescent. Off this coast of Belgium we only see the heterotrophic Noctiluca, but increasingly in the Indian Ocean and West Pacific they see a mixotrophic version (“Green Noctiluca”), harbouring intact green algae actively growing inside their erstwhile predator. Perhaps with climate change we will eventually see this form in the English Channel? Almost at the end of our journey, the Captain of the RV Simon Stevin announces through the speakers that a ‘man over board’ manoeuvre was going to take place. Good for us in that this is a warm and sunny day and that we are going to have a chance to swim in the middle of the North Sea, where the land is just a distant memory…..

John Lapeyra Martin