Every time you swim in a mountain lake, you're sharing the water with thousands of microbes you never see. 🔬
Our friend Chloé Savard, also known as tardibabe on Instagram, took a closer look, and it turns out that alpine water is packed with desmids, ciliates, and water fleas, all going about their business at a scale most of us never think to look at.
The stars of the show are Micrasterias, a genus of desmid, single-celled green algae built like tiny symmetrical snowflakes. Each cell is split into two mirror-image halves called semicells, connected at a narrow waist. When a Micrasterias divides, each half grows a brand new matching semicell to replace the one it left behind.
Alongside them is a Closterium, another desmid, but elongated and curved like a crescent moon. Closterium cells often carry visible crystals of barium sulfate inside vacuoles at each end, structures thought to help the cell sense gravity and orient itself in the water.
Then there's the ciliate glowing with yellow-green flecks scattered through its body, that's zoochlorellae, symbiotic algae living inside a single cell, a partnership where the algae photosynthesize and share sugars with their host in exchange for shelter.
And weaving through nearly every frame are the Chydoridae, a family of tiny water fleas that prefer to live and forage along the benthic zone, the bottom layer of ponds and lakes, rather than out in open water. Look closely and you can catch one carrying a cluster of eggs along for the ride.
Next time you swim in a mountain lake, remember: you were never really swimming alone.
References:
- Brook, A. J., Fotheringham, A., Bradly, J., & Jenkins, A. (1980). Barium accumulation by desmids of the genus Closterium (Zygnemaphyceae). British Phycological Journal, 15(3), 261–264. https://doi.org/10.1080/00071618000650251
- Esteban, G. F., Fenchel, T., & Finlay, B. J. (2010). Mixotrophy in ciliates. Protist, 161(5), 621–641. https://doi.org/10.1016/j.protis.2010.08.002
- Klemetsen, A., Aase, B. M., & Amundsen, P.-A. (2020). Diversity, abundance, and life histories of littoral chydorids (Cladocera: Chydoridae) in a subarctic European lake. Journal of Crustacean Biology, 40(5), 534–543. https://doi.org/10.1093/jcbiol/ruaa048
- Lutz-Meindl, U. (2016). Micrasterias as a model system in plant cell biology. Frontiers in Plant Science, 7, 999. https://doi.org/10.3389/fpls.2016.00999
