I was invited on a research cruise by my Marine Science advisor and Oceans professor, Jim Bishop last week. We were calibrating newly received Particulate Inorganic Carbon (PIC) sensors which utilize cross polarized light to detect the presence of CaCO3 particles (namely coccolithophores and other primary producers). The cross polarizing equipment is very sensitive and any change in angle between the laser and the detector may drastically change results.
We departed out of Moss Landing to follow a finger of the deep Monterey Canyon to depths more than four thousand meters in which we could safely test our equipment. We also sought out a location with relatively low PIC so that we could regulate and monitor the reproducibility of our results. This way, we could compare our three sensors and verify that each reflected equal, but low values of PIC in the water column.
Here we can see that our old and reliable PIC sensor, PIC001, shown in blue, continued to yield believable data. However, our new sensors, PIC006 and PIC007, especially PIC006, shown in yellow, strayed from the data we expected to have. The sensor shown in yellow reacted to the change in pressure as the CTD (Conductivity Temperature and Depth) rosette reached depths of more than 700 meters. Because the sensor stuck to this course on the way up the water column, we believe that the pressure caused the cross polarizers to move in relation to each other and reflect an incorrect reading. We worked to increase the performance of this new sensor and Professor Bishop filled the gap between the pressure case and polarizer lens with silicon oil to minimize the effect the pressure would have on the sensor. Within days we saw the improvement in data. As seen below, the yellow PIC006 was less and less affected by the increase in pressure until the gap had closed completely by the evening of October 11th.
Our sensors were back in order to detect the more productive waters closer to shore in the Monterey Bay Canyon. (shown below) The profile was taken on October 13th at 8:30AM.
Another subject of interest on the vessel, for me personally, was the great biodiversity we observed. We saw brown sea nettle jellies, moon jellies, salps, common dolphins, and humpback whales. The video below was taken at night as salps, euphausids, copepods, and pteropods and other vertically migrating zooplankton were traveling upwards to feed in the safety of darkness on the phytoplankton dwelling near the surface which had been producing carbohydrates in the light of day.
I gave a lecture to my Oceans class about a piece of equipment on the ship, called the Acoustic Doppler Current Profiler (ADCP), which can be used to track the migration of these organisms as it sends out a sound wave which is scattered by the vertical migrators. It can also be used to determine the speed and direction of the current by using these same acoustic scatterers and the Doppler effect which modifies the frequency of a sound wave bouncing off another object based on its motion toward or away from the source. Below, we can see the layer of migrating organisms meeting the layer of light-dependent primary producers which dwell in the surface waters.
We were met by the hospitality and good cooking of the Point Sur crew. Some of my favorite meals are shown below.
Tara, our cook, in her element.