Placing the microsensor on the exact surface of the rhodolith was my greatest challenge during the project. Many microsensor were broken. :(
Microsensors Group Lab Rotation I Max Planck Institute for Marine Microbiology, Bremen, Germany March 6, 2017 - April 28, 2017 Advisor: Lauria Hofmann, PhD
Project: Monitoring surface pH of Arctic rhodolith crustose coralline algae during exposure to continuous darkness March 6, 2017 - April 30, 2017 Crustose coralline algae (CCA) live in a variety of habitats in oceans across the world. CCA both photosynthesize and calcify, or deposit a skeleton. Several mechanisms of calcification have been proposed, one suggests the decreased pH conditions resulting from photosynthesis enable calcification to occur. Others suggest an ion gradient generated from a mechanism independent of photosynthesis results in calcification. During the high winter, CCA in the Arctic are exposed to continuous darkness for months. However, rings of calcification during these time periods have been measured. Recently, a trial experiment detected an elevated surface pH on rhodoliths (compared to the water column) from the Akia fjord in Greenland has been measured after continuous darkness for 24 hours. This suggests some process is occurring that keeps the pH higher on the surface to allow the CCA to calcify. If photosynthesis is not occurring, the surface pH decreases due to respiration. My project expanded this trial experiment. I measured the surface pH profiles of rhodoliths exposed to continuous darkness for 20 days, using pH microsensors. Individuals exposed to continuous darkness for 20 days, simulating the Arctic's high summer season, were also measured for comparison.
Placing the microsensor on the exact surface of the rhodolith without breaking the microsensor was insanely difficult for me. I could never see the tip clearly. If I was merely 5 microns above the rhodolith's surface, my measurements would differ dramatically. But I couldn't simply lower the sensor until I felt it touch the individual because this usually broke the sensor. With my already poor eyesight, I broke quite a few sensors in the process.
My friend measuring tropical rhodoliths and I kept tally of how many sensors we broke each week. At the end of the week, we had to take as many shots that weekend as sensors we broke. While I got better over the duration of the rotation, I managed to break 8 sensors one week. Ahhhhh!
Attached below is a report in which I summarized my project and results.
The picture below on the right is the setup of taking microsensor measurements. A fancy motor controlled the movement of the microsensor using an in-house computer program. A separate computer program recorded the measurements. The picture on the left shows a profile measurement recording. The x-axis represents pH, and the y-axis represents depth, increasing from the surface of the rhodolith to the seawater column.