Sarah Bedolfe
Sarah continues her studies in the Netherlands, experimenting with temperature on mudflat diatoms.

Back in the Netherlands after the holidays, I was met with mild winter temperatures perfect for a beautiful walk in the Amsterdam Forest with my family. Later, upon returning to Groningen, I resumed work on the diatom research I had started in the fall.

A light brushing of early morning frost in the Amsterdam Forest.

In my effort to discover how mudflat diatom communities are affected by heat waves, I spent last autumn trekking out onto the mudflats of the Wadden Sea to collect samples of sediment and diatoms, as I described in a previous blog. I brought the samples back to the lab and placed them in climate chambers programmed to either heat wave or control temperatures. I now need to assess if there was a difference in how the diatoms reacted to the heatwave compared to the control. If they did differ, I need to know in what way and by how much.

There are a number of reasons that this type of research is important. Diatoms have several functions. For example, they produce oxygen, and they are a link in the mudflat foodchain. Another function they perform is helping keep the mud’s surface stable by creating mats. If my research shows that the heat wave affects the diatoms’ ability to do this, then climate change spells trouble for sediment stability. As more heat waves occur, the islands in the Wadden Sea could become more vulnerable to erosion – worsening the troubles of sea level rise for these low-lying areas.

The dark areas are mats of diatoms; they create bubbles by photosynthesizing and producing oxygen.

There are now a few ways for me to assess all of the data I collected during the experiment. Firstly, during the experiment, I used a device to measure how much fluorescence the algae were producing; this can give information on how much they are photosynthesizing. Secondly, over the course of the experiment, I removed samples and froze them for later analysis. The aim now is to measure how much chlorophyll a (another indicator of photosynthesis) and how much EPS there is in each sample. EPS stands for extracellular polymeric substance. Basically, it is a slimy secretion that helps the diatoms stick together and create a biofilm on the mud’s surface.

Measuring the chlorophyll a and EPS required many hours of processing in lab. For each sample, my lab partner and I had to separate the compound we were interested in from the sediment. First, precise amounts of sediment were scooped into test tubes. Then a complicated process involving chemicals such as acetone and ethanol, and tools such as centrifuges and fluorometers, allowed us to find out exactly how much EPS and chlorophyll a the diatoms produced.

Working under the fume hood, in the midst of endless pipetting.

Now, finally, all the data is in and I’m gearing up for the next step: statistical analysis. While sitting at a computer crunching numbers isn’t as fun as working in the field or lab, it’s important – and I’m super excited to find out what the results of my experiment exactly reveal. Does a heat wave harm diatom productivity? And might this destabilize the sediment? By the time of next month’s blog, I hope to be able to give a clearer answer to these questions!

In the meantime, I’m doing my best to enjoy the pretty winter scenery, and I’m grateful it’s not as cold here as it is for Melissa in Canada. The first snow day of the season came in late January and I had a gorgeous walk in the freshly fallen snow. However, entering the storm on a bike is another matter. Avoiding falls on the uneven soft and slick roads takes extra focus and my first day involved a few close calls. Here’s to hoping I make it to spring crash-free!

First snow day of the season in Groningen.


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