Hedwig Ens

“Thank you”, I whispered in a soft voice while driving by the rayon and plating factories surrounding Lake Orta. “Thank you for giving me a PhD”.

The wastewater of those factories polluted the lake with copper and ammonium sulphate from approaching the mid-nineteen hundreds until the end of the last century. This history of pollution makes Lake Orta an interesting ecosystem to study, and sets the perfect stage for my PhD: the life-history responses of the rotifer Brachionus calyciflorus to past environmental changes (i.e. industrial pollution) and the underlying eco-evolutionary processes.

To study this, I (try to) resurrect rotifers from up to 80 year old lake sediments that contain their resting eggs, and compare the performance of these rotifers under different experimental treatments. As I have had some difficulties getting resting eggs from the post-pollution conditions, I decided to go to Lake Orta to get the most recent Brachionus calyciflorus: the ones that are currently swimming around.

Together with Diego Fontaneto of the ‘Istituto per lo Studio degli Ecosistemi’, I drove around the lake, and found five spots to easily enter the lake to collect zooplankton with a plankton net. This net made of fine nylon mesh is pulled through the water horizontally and the animals are captured in a vial at the bottom of the net.

A quick look together with Diego revealed that we captured tons of animals, but probably no Brachionus. A more thorough look together with our summer research assistant Conor Waldock confirmed this suspicion, but we have still some bottles of water to go through, so we keep on hoping. And otherwise, our hope lies in the sediment samples of Lake Orta that I also brought back from the trip.

The reason why we didn’t find any Brachionus in our water samples? Probably because the water was still too cold due to the relatively bad summer, and there have been no big algae blooms yet of which Brachionus could profit. I guess this means I have to go back next month to again sample Italian ice cream… Ehm, Lake Orta I mean.

Sometimes Science is nothing more than checking assumptions. This holds true whether you are a theoretical biologist (e.g. checking model assumptions), experimental biologist (e.g. checking assumptions of experimental design), or just love doing statistics (as we all do). During the first weeks of my PhD, I found out that I perhaps needed to check the basic assumption my supervisor has about me: that I would be able to let eggs hatch in the lab. Until now, I have been unable to let the desired rotifer eggs hatch, but I can proudly announce that since five days we have some pets in our office: Triops! These crustaceans are considered ‘living fossils’, and just as the rotifers I’m investigating, their eggs can remain in a state of diapause for a prolonged period of time.

Assumption “I have the capacity to let resting eggs hatch under laboratory conditions”: Check!

Pfieuw

Today I felt like going on a first (blind) date: being nervous and excited at the same time. Or perhaps this is more what marriage feels like: eager to be tied to your partner(s) for the coming years while knowing it has a high change of being a love-hate relationship. Today, my diapausing females arrived.

They were brought to our lab by Diego Fontaneto and Stefano Gerli of the Istituto per lo Studio degli Ecosistemi. Just like a first date I didn’t know what to expect, and I couldn’t trust that the outside would be a representation of the inside (which of course is the most important part): I was given bags of mud.

The mud comes from different layers of the sediment cores obtained from Lake Orta in Italy. This mud harbours the resting eggs (diapausing females) of the rotifers I will be using to investigate the relative contribution of ecological and evolutionary processes involved in the populations’ responses to changing environments. More information on how I will use resurrection ecology to address this topic will follow hopefully relatively soon.

Diego and Stefano taught us the necessary knowledge and skills on how to extract the eggs from the sediment. As I expected to find a lot of eggs in the mud, I had already designed a small experiment to be able to put the females directly to scientific use. However, in the small sample we investigated, we could only find 2 resting eggs of the rotifer species I will be using (Brachionus calyciflorus). As this is by far not enough for a proper experiment, we decided to put the females on hold: we stored them in the fridge.

To make up for the non-exciting mud picture, hereby a picture of what everyone thinks Science is about: green bubbly liquid. This is how we culture our algae, which we use as a food source for the rotifers.