By Breena S Riley

Me: “I work with diatoms.”

Other person: “What are diatoms?”

I get a lot of confused looks when I tell most people about what I work with. In short, diatoms are a type of golden-brown algae with an outer layer made of organic silicon. The outer layer is a called a “frustule,” and the frustule is made of two valves. They stack neatly into each other like origami boxes. Each diatom species has unique markings, which are used for identification.

Diatoms live in water bodies all over the world. Each species has specific habitat requirements such as needing a certain temperature to grow or certain surfaces to grow on. These factors make them useful for environmental monitoring programs. This is because changes in the species that grow at a location can give clues to how the environment is changing. For example, if cold-loving diatoms used to be found at a given location but now warm-loving diatoms are now found, then it can be assumed that temperatures in the water are becoming warmer.

The European Union uses diatoms as part of its aquatic environmental monitoring programs. In Sweden, diatoms are sampled at sites annually across the country. Samples are sent to and processed at universities like the Swedish University of Agricultural Sciences in Uppsala, Sweden. Before they can be counted and identified under a light-emitting microscope, diatoms must be chemically processed to remove all organic matter. Otherwise, organelles like chloroplasts inside the frustule hide the special markings on the outside of the algae that are used to identify them to species. It can take a professional diatomist (scientist who studies diatoms) one full day to process and count the diatoms in a sample. They count diatoms on a prepared slide until they count at least 400 diatom valves, or halves.

From what I have seen, it seems like some parts of Sweden have a high concentration of monitoring stations. Other parts of the country, like the region around Abisko, Sweden, have very few stations. I think this is because stations are set probably set up in areas with high human impacts upon the environment (like around cities and other highly populated areas). Northern Sweden has very few people. Abisko’s only station is at the mouth of the river at Abisko Nationalpark where it drains into Torneträsk Lake. This can be both good and bad for research in the region.

There is a yearly record for one single spot at one time of year (about every September or October) at Abisko. What else lives here, though? What lives in the mountain streams? What lives in the forest streams? The answer will change depending on the time of year and location.

We care about diatoms and answering these questions because we care about climate change. How can we know how the whole area is changing or is affected by climate change when we do not even know what diatoms live here?

Site to search for environmental monitoring sites and data (site is in Swedish, but  you can use the Google Translate web browser extension to automatically translate it to English or another language): http://miljodata.slu.se/mvm/Search.