June 22, 2009
55° 17.789 N
Science in the field is more difficult than in the controlled setting of the lab. Science in the middle of Bering Sea is exponentially more difficult. Samplings conducted over the past 24 hours have not exactly gone as planned.
Last night saw no change in the weather. High seas and sustained winds are making the deploying of instrumentation a very tricky task. When devices such as the CTD, multi-core, grab, or sediment traps are launched, the ship has to maintain its position to keep the apparatus directly below the ship. To accomplish this task the ship is equipped with a dynamic positioning system. A bow thruster and two independently controlled multidirectional propellers in the stern allow the ship to constantly reposition itself to avoid the drifting problems that would plague most fixed propeller vessels. However, technology can only do so much to resist Mother Nature.
The multi-core was dropped to the bottom late last night in rough weather. The multi-core looks like a Martian lander, and eight-legged conical device that takes samples (or cores) of the ocean floor. Once positioned on the seabed, a weight stack releases and drives sample tubes into the mud and sand capturing a cross section of the sediment in the area. The deployment went well enough but the retrieval did not. Just as the multi-core was brought to the surface the ship raised high on a passing swell and yanked the multi-core from the water. Suspended in mid-air with no resistance to its 2000 lb. weight, it slammed into the stern of the ship, bending 4 of its 8 steel legs and some of the vertical pistons. Needless to say, no samples were recovered from the ocean bottom and the multi-core now sat on deck, leaning to one side.
After breakfast, it was time to retrieve the sediment traps. The ARGOS unit secured to the buoy had communicated to the ship that the traps were about 12 nautical miles away from our current position. They had traveled 32.6 nautical miles over a time period of 24.4 hours. The traps were soon spotted and the Thompson was positioned for capture. The buoy was hooked by a member of the crew on the starboard side to a rope line, which ran around the back of the ship to the large a-frame crane located on the stern. The ship then repositioned to bring the traps around to the rear for recovery. Meter by meter, the trap line was brought on deck. One of the sediment tubes located at 25 meters had been destroyed (most likely during cracked during deployment) and the 3 of 4 set at 60 meters were missing, their steel frames bent significantly. The remaining tube hung loosely to the frame. Pat said that this most likely happened when the traps were being set out yesterday. The ship had a difficult time keeping its position constant and too much drag on the line would have ripped the tubes right out of their frames. Of the 20 possible data points, only 15 would be usable.
The acrylic tubes were brought back to the main lab and allowed to settle for two hours. Even though they were filled to the brim with brine when deployed, only about 1/8 of the brine remained. The top layer or seawater was siphoned off and the filtering began. I measured the salinity of each sample with a refractometer as a comparative measurement to see how well the brine layer was captured. Regular seawater has a salinity of around 35 and brine about 85. The samples ranged from the mid 40s to the upper 70s. Bad news was soon delivered by the marine biologists though. Apparently the traps had passed through a Phaeocystis bloom. These small autotrophic flagellates bloom to form large colonies and give off a mucus-like precipitate. These phytoplankton would soon clog the filters and significantly increase the filtration time to somewhere between 24 and 48 hours for only a 300 mL sample.
The filtrations were started and I wandered around the ship a bit. Thankfully as the day progressed the seas calmed. The sun even came out for a brief period of time. They say up here is you don't like the weather, just wait an hour. Still no sign of whales but I can now add a short-tailed albatross to my list and then cross that off too. It seems they are critically endangered as only about 2000 of them remain in the wild. Since there is little to do right now, I am going to head back to my stateroom. It is 19:00 and I will set my alarm for 12:30. We are scheduled to sample off the standard CTD and Prod CTD at about 05:00 and I have yet to see the bongo nets deployed for krill sampling. This is set for 02:00. I only have a few chapters left in The Lost Symbol and I intend to finish them off before going to sleep.