From the Field: Deploying a new pH and O2 Sensor!

Recently, I traveled to Tampa Bay/St. Petersburg, Florida for a short research trip with Professor Wade McGillis’s field course “Field Methods in Environmental Engineering.” What began as a trip to test a sensor became so much more!

Upon arrival, we went to our host’s house, Captain Jon, who welcomed us all into his home for the weekend.

The beginning of unpacking all 12 coolers of equipment!

We soon began unpacking all 12 giant coolers that we had checked under the plane, covering Jon’s driveway in random pieces of equipment and tools. After we finally got sorted, my partner and I started working on the final set-up and assembly of our sensor.

The sensor we built is a combination fast-pH, dissolved oxygen, and temperature sensor that we adapted to be

All smiles on the boat with new friend Liz Moskalenko!

able to be deployed at depths up to 60 meters.  We chose this depth because that’s where mesophotic coral reefs (coral reefs that get low amounts of  sunlight) are located. Recently, scientists have been exploring if mesophotic coral reefs could support resilience of other corals. What this means is that these deeper corals, as less exposed to human-driven changes like increased temperature, might seed the shallower coral reefs and help them resist global climate change effects.  Our thought is that having a cheap, but reliable fast sensor is a great way to monitor both shallow and deeper coral reefs. With better data, we can see how productive the ecosystem is and calculate rates of calcification (generally, the rate of making coral structure).

Soon after we started working, we realized that our data loggers (machines to record our data) were the wrong kind – they only measured whether or not there was power to the instrument, as opposed to the value that the instrument recorded.  After some panicking, Captain Jon offered to let us use his CR-1000, a top-notch data logger that he happened to have in his workshop. We started scrambling to learn the coding language, while also fixing up the final elements of the housing.  We needed to make sure that the housing we put our sensors in was fully sealed- otherwise, water would seep in and destroy our sensors.

As a group, we deployed the “spider” (a metal skeleton on which all the instruments were attached)…

While we worked on our sensor package, the field course had to go on, so we began helping other teams and leading side projects during the day, with our

Getting the “spider” on the boat! (photo credit – Liz Moskalenko)

sensor “pHOx it!” taking up our evenings. As a group, we deployed the “spider” (a metal skeleton on which all the instruments were attached) in a sea grass site and a smaller metal structure in the mangrove field site. In the mangrove, we had a light sensor and CO2 sensor attached to the platform, while we brought a methane sensor and YSI for testing on site.  Attached to the spider, we had slower dissolved oxygen and pH sensors, light sensors, a nitrate sensor, a velocity meter, and a SAMI CO2 sensor.


My partner specialized in the CO2 sensors, while I focused on taking water samples for testing alkalinity

Prepping alkalinity samples onboard (photo credit Liz Moskalenko)

and nitrate levels in the lab. The nitrate samples were to check and make sure that the nitrate sensor we put in the water was collecting accurate data.  As much as it is great to have sensors you can deploy in the ocean and (somewhat) forget about, it’s really important to check your data (often called “ground truthing”).  The alkalinity samples I won’t personally measure, but they will be processed by a collaborator at USGS in Tampa Bay.


Though we had very full days, the trip wasn’t all work, Our first night, after we missed lunch while on the

Loving the all-you-can-eat hot pot after a long day of work! (photo credit – Liz Moskalenko)

water, we went out for all-you-can-eat Korean hot pot  and we ate a TON of delicious food. Our second day, we had Captain Jon’s adorable 3 year-old daughter with us, which was challenging at times, but still so much fun! She loved being out on the water and was overjoyed when she got to go swimming at the mangrove station. She “saved” me multiple times, grabbing on to my bathing suit and pulling me back to the boat.

When we tried to get our sensor to the spider, located 6 feet below the surface in a sea grass bed, we found that our sensor wouldn’t sink!

Finally, on the last day, it looked like we would be able to get our sensor out.  We had data recording at 4 times

Our “pH-Ox it” sensor in process and then on its way to the boat!

a second and our housing had been thoroughly sealed. We wrapped up our sensor and brought it to Jon’s boat, the “NaviGator” (can you tell he’s a UF fan!) to launch it for a few hours before we had to pull up all the sensors and pack for New York. When we tried to get our sensor to the spider, located 6 feet below the surface in a sea grass bed, we found that our sensor wouldn’t sink! We hadn’t made our sensor neutrally buoyant, so it was bobbing up to the surface and refused to go down. Eventually, we strapped some scuba diving weights to it and sank it to the bottom.


The next morning, we went to download the data from all the sensors. Much to our surprise, our sensor only had 1kb of data stored in it! It turns out that our data logger’s program had a bug where it saved each new measurement over the previous measurement. This meant that we had 0 data from our few hour test deployment. I sat down with Jon and we figured out the problem. He re-programmed the data logger and we started to see our file size growing! We took the sensor for a quick test in his pool and found that everything was working great!

Even though it was disappointing that our sensor didn’t work during testing in Tampa Bay, I’m still so thrilled that we now have a working oceanographic sensor. My partner and I will be applying for funding from Lamont Doherty Earth Observatory (our research home) for further sensor development and a deployment with our collaborator from USGS. Hopefully, this sensor will see many uses in collecting fast pH, dissolved oxygen, and temperature data. Our hopes are to use it with USGS to look at the effects of sea grass beds on ocean acidification and the potential of mesophotic corals to buffer coral loss due to global climate change.

Check back for more updates on the sensor development or other science stories. You can also check out my photos on Instagram or follow me on Twitter!

A field biologist always has her/his hands full! Only thing not in view is the sharpie tucked in my braids 🙂   (photo credit – Anna Libbey)

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