Diatoms Prove That Not All Algae Are Ugly

Think algae are gross? A new website will make you take a closer look. Dedicated to Lake Mendota’s diatoms – single-celled members of the brown algae classification – the website serves as a field guide of sorts to the beautiful, microscopic organisms in the picture above. Diatoms are quite amazing. They produce around 20% of the oxygen in Earth’s atmopshere. They are Lake Mendota’s primary photosynthesizers – in other words, they convert sunlight to food and then serve as a foundation of the food web. Oh, and they are made of glass.
We asked Tommy Shannon, the UW-Madison undergraduate behind the Mendota Diatoms website a few questions about how he fell in love with algae and how he got such amazing photographs.
So, For Starters, What Is a Diatom?
Tommy: Diatoms are a kind of algae. Technically, brown algae is their classification which sort of lumps them into the same category as seaweed. They can be in the open water and free-floating or they can also exist on the bottom, growing on plants and rocks. Diatoms are single celled, often times they’ll clump together and grown in colonies, but they’re unicellular. And an interesting thing about them is that their outside cell wall is made of glass. They take glass, or silica, from the sediments and incorporate it into their cell walls which gives them protection and still allows photosynthesis to happen. It’s really cool.
I like to think of diatoms as the grassy plains of the lake. They are kind of at the very base of the food chain and they are the main photosynthesizer of the lake. And then other small zooplankton like Daphnia and other copepods will eat diatoms and then small fish eat them and then on up the food chain.
How Did You Get into Diatoms?
Tommy: I started working with diatoms with (CFL graduate student) Mike Spear on a project researching the impacts of the invasive zebra mussels in Lake Mendota. Zebra mussels came in around 2015, or that’s when we detected them, but we think they were here earlier. So we were trying to measure their progress and also as they expanded their population, to see how that is going to have an effect on all the rest of the lake. So we were looking at a lot of different things and one of those was diatoms.
One of the things we’re actually looking for in the study I’m doing with Mike is how are the percentages of open water diatoms and bottom dwelling ones changing. Zebra mussels draw a lot of nutrients down to the bottom of the lake, which provides a lot of structure for other algae and plants. That, in turn, produces a lot of habitat for bottom-feeding, or benthic, diatoms. They also filer feed on a lot of the free-floating diatoms. So it looks like we’re seeing an increase in benthic populations and a decrease in the open water populations of diatoms.

In case of emergency, don’t break glass. Tommy Shannon collecting diatoms in Lake Mendota.

What Led You to Create the Mendota Diatoms Website?
Tommy: We brought in Rex Lowe who was a professor at Bowling Green University and lives here now to come and talk to us and show us how to prepare the samples, what to look for in the samples and then he volunteered to prepare some samples and identify what was in them for us. And I became the person who worked really closely with Rex all the time. And eventually he invited me up to the University of Michigan Biological Station to learn all of the diatom identification protocols and take a whole bunch of photos. They do a lot of work on diatoms up there and had a specialized camera attached to their microscope that was all set up to take these kinds of images. T
So I spent ten days up there and sat in on one of Rex’s classes and in the long run, what ended up happening was we produced hundreds of really high resolution pictures of these beautiful diatoms. But it was all going to just go into this data set and I thought, well we should do something more than just turn them into numbers. They’re absolutely eye-popping and everyone I showed them to was like “Oh my God you have to do something with these.”
So what I did is I kind of made a field guide to Lake Mendota’s diatoms. I’ve gone through all the pictures and ID’d them down to species level when I can and built a website that acts in part as a way to say – “Here’s all the things you could expect to find in this lake.” And I provide other pictures and a bunch of descriptions and links to other websites that might have more information.
The project also turned into my senior capstone project for the environmental science degree and so that was a really nice way for me to be able to take a lot of research experience and class experience and bring them together.
Do You Think Algae Get a Bad Rap?
Tommy: As it stands right now, a lot of algae are vilified because the lake turns green and it’s nasty and you have to keep your dog out of it and stuff like that, but I think this project will hopefully show they’re more complex than that. I want to tell short stories about diatoms and how they’re part of the ecosystem and talk about how they are doing these other things and how they’re built and how they reproduce.
But in addition to that part of the website, I just want to talk about how cool this stuff is. There are a lot of people who might not care that diatoms are doing this or that or that zebra mussel populations are exploding in Lake Mendota. But they would totally care about some really awesome looking photos.