Running Diary of Flux Chambers, Mini Me and a Marathon Day in the Field

Necessity, of course, is the mother of invention. And scientific fieldwork is often the mother of necessity. Researchers are constantly having to invent new ways to collect data in challenging environments. What follows is a running diary of a marathon day of monitoring carbon dioxide (CO2) emissions and testing new equipment on Lake Mendota.
But, first, a little background – Angela Baldocchi is the Long-Term Ecological Research intern in Professor Ankur Desai’s lab in the department of Atmospheric and Oceanic Sciences. Earlier this spring, she spent a 28-hour period taking measurements every four hours while testing a new flux chamber (no, not flux capacitor for you Back to the Future fans) prototype developed by the undergraduate engineers in the Insight Wisconsin program.
A flux chamber is a piece of equipment with a sensor inside that is placed on top of the water to measure gases that come out of the water column and into the atmosphere (or vice versa). Referred to as “hats” the traditional model is basically made out of a Tupperware bowl with a styrofoam noodle (like the ones kids use in swimming pools) strapped to it and a Sensair CO2 sensor inside. The bowl gets placed on the water like a hat so that the sensor can directly measure gases as they diffuse from the water surface inside the chamber.
The problem is, every so often, these hats need to be lifted out of the water to clear the accumulated gases and reset the chamber to ambient air and point them properly into the wind. And it takes a person to do this. 
The modified flux chamber, dubbed ‘Mini Me’ by the Insight Wisconsin team, has an air pump that is programmed to reset the chamber at regular intervals. That means it’s only hindered by its ability to stay afloat, its battery life, and the amount of data that the sensor can hold.  That is, if it works.
Such an invention would let scientists take more measurements of lake emissions over longer periods of time and, as Angela’s running diary will show us, to also get some much-needed rest!
We’ll let Angela take it from here:
Monday April 23, 2018

The Insight Wisconsin team – Galen Giese, Calvin Henderson, Max Roth, and Shuai Zhang – and Mini Me. Photo: A. Baldocchi.

As I head to Lake Mendota to meet up with the Insight Wisconsin team at Hasler Lab, I am excited for them, and for myself if this works! We are going to test their prototype of a modified flux chamber “hat” during my diel, or 24-hour, cycle run with our traditional hats.
Our traditional hats are being used to take measurements of Lake Mendota’s to better understand carbon cycling. Mendota is one site of the Global Lake Ecological Observation Network (GLEON) project. GLEON aims to “Understand, Predict and Communicate the Role and Response of Lakes in a Changing Global Environment”.
But, back to the prototype. We are going to first make Mini Me floats and then take it out during my first measurement at 8:00am and secure it 20 feet downwind of David Buoy (Editor’s Note: David Buoy is the Center for Limnology’s big yellow buoy in the middle of Lake Mendota) with a 80’ mooring line. We have a 25lb weight to hold it in place and a weight to counter balance the probe and hopefully keep it from flipping over in the wind.
Remember April? Photo: A. Baldocchi.

Winds are going to mainly from the E and NE with a maximum velocity of 6 to 7 mph. Temps will range from 37 to about 60 degrees F. 
What should I expect as far as data goes? Well, we just experienced another snow event last week. I took a picture at 3:45pm when I left Science Hall on Friday April 18th. I remember it well the bus was late and had trouble getting traction. I didn’t get home until 6:30pm.
This late warm up may influence the start of photosynthesis, which would in turn influence how gases move in and out of the lake as small plants, like diatoms and other algae, take in CO2 from the atmosphere.
7:11am Shuai, Max, Galen, and Calvin – “It floats, let’s proceed with deployment!”

Alright! We have some data. This 474ppm of CO2 is raw data ONLY. We have to account for the chamber dimensions and get the actual temps, wind speed, and wind direction from the buoy and the pressure data from Jonathan at Atmospheric and Oceanic Sciences.
Noon: It’s noon, our 2nd trip to the buoy to take readings, and mini me is still afloat. It hasn’t moved away from the buoy.  It seems a little breezy this time but Mini Me is doing well. We should take a video for the Insight team, so they can see how their probe handles the waves. Now I’d better get to class!
4:00pm: 4 O’clock and all is well!  I saw CFL professor Emily Stanley today in the lab. She said there are a lot of diatoms in the lake right now and she wouldn’t be surprised if they are taking in carbon from the atmosphere. Boy oh boy! This could go either way and be a carbon sink or source. I cannot wait to find out! Ah, but I must. This is only measurement #3 and we have 4 more to go in order to complete the cycle.
Bird and buoy. Photo: A. Baldocchi.

Lake Mendota is very beautiful at sunset. There is a calm at days end and yet a flurry of activity. This weather has brought everyone out into the fresh air. Students line the piers to de-stress during the last few weeks of the semester. I recall from our October monitoring campaign that the seagulls prefer David Buoy at night. I wonder how Mini Me will fare?
Madison at midnight. Photo: A. Baldocchi.

12:01am: Ok, it’s midnight and not too dark . . .there is a very slight wind at our backs, a half moon glistening in the sky and the city lights illuminating the way toward the buoy’s beaconing flash. But what’s with the noise? Where’s the party?! The water is calm but there must be a flock of seagulls at Picnic Point. Is it mating season? Maybe they are nocturnal? They are active, it sounds like crying, or puppies or something.
 4:00am: I got about an hour of sleep and I want more! It’s cold. . . and dark . . .   I‘m going to need more sleep and some coffee before my presentation this morning. But, just this reading and one more. Then we can take Mini Me out of the water and see how it did. I hope it works out, that way we can rely on a less laborious method and get more continuous data in the future.
Ok, I’ll take a shower instead of more sleep but I’m not skipping the coffee.  Whoa! Look at this sunrise! If I wasn’t here right at this moment I would have missed this surreal vision.
Sunrise on Lake Mendota. Photo: John Maginnis.

8:00am: I’m dragging but the prospect that this works and the worry that I won’t get my presentation done in time have me wide awake (or maybe it’s the coffee!) Let’s do this. . . Last measurement and get that probe out of the water and into the shop!!!
9:00am: DONE! Got some data files. Time for class! I’ll get the pressure data from Jonathan and process after I get some sleep.
Final Report: The prototype (or, rather, Mini Me’s) data shows the need for further review and programming improvements to correct the timestamp and calculations based on the chamber size. For example, there are three measurements that we know the time for based on my monitoring using the traditional hats, and the prototype measurements are off by one order of magnitude.
Sadly, I found out after our run that, sometime during our testing, Mini Me passed away. Still, overall, it was a success and what we learned will help us fine-tune Mini Me version 2.0! Here’s to a future of more automated carbon flux measurements and less sleepless nights for us interns!