Instruments working together for long-term monitoring
November 17, 2012
Today marked the final day at Station M, which means several instruments were returned to continue monitoring the area until the next Smith lab cruise. The camera tripod and sediment traps were the first instruments redeployed today. Review of the last five months’ deployment showed records of changes in sea cucumber, urchin, and sponge behavior; animal abundances; jelly blooms; changes in current speed and direction; and food pulses to the seafloor.
Meanwhile, correlations between the activity on the seafloor and what is raining down from surface waters above are possible because of the sediment traps moored above the camera tripod. Traps located 50 and 600 meters above the seafloor act like rain gauges for marine snow, collecting falling particles to see how much carbon, or food, reaches the seafloor. Abundances of many different animals on the abyssal plain do correlate with changes in the amount of carbon falling from above: sea cucumbers, urchins, macrofauna living within the sediments, and sponges are all found to increase when the amount of incoming food increases, but with a time lag. The time lag occurs because it takes time for the food to sink, so the time that surface waters produce more food and the time when that food reaches the seafloor can be months apart.
Next, the sediment event sensor (SES) was redeployed. The SES provides greater resolution to the information obtained from the sediment traps: one can measure the quantity of carbon sinking to the seafloor with the sediment traps, but the SES adds information about the quality of that carbon: whether it comes from photosynthetic organisms or zooplankton, and if its source can be distinguished from a photo.
Meanwhile, the free vehicle grab respirometer (FVGR) was acoustically recalled to the surface and was brought back on the ship, along with the floats and spar buoy that make up the mooring. The spar buoy is a giant floating flag and beacon that help the crew find the instrument at the surface. The spar buoy, all of the floats, and the FVGR are connected with lines. To bring the FVGR back on the ship, a grappling hook was used to capture the line between the spar buoy and the first block of foam. That line was connected to a winch on the ship and everything was carefully pulled up on board.
The elevator holding the respiration chambers was sent down at the beginning of the cruise, then sat at the seafloor until it was recovered today, with the help of the ROV Doc Ricketts.
This cruise, however, has come to a close; the Western Flyer will head back to Moss Landing tonight and will arrive at MBARI tomorrow. All hands will help unload the ship, then everyone will disperse, but all will work up the data from the expedition in the coming months. Thank you to everyone for reading and following along with our expedition! To learn more about Station M, the research conducted by the Smith lab, or the different instruments deployed, check out the equipment, people, and background sections of this cruise log website.