Bottles and bottles of seawater
April 3, 2009
Sea temperature: 0.3°C
Air temperature: -2.2°C
In the late evening, the ship left iceberg C-18A and traveled east in search of an area away from the influence of icebergs. The principal investigators monitored the ship’s data systems during the transit to select the study area. When the ship reached a suitable location about 75 kilometers away, a suite of sampling began to characterize the area. First, the MOCNESS net system was deployed for several hours and recovered before sunrise. While the MOCNESS crew sorted samples in the lab, other research teams conducted water collections with trace-metal-clean Niskin bottles, surface mapping, and CTD casts throughout the day. Just after dinner, a Langrangian sediment trap was lowered into the water and started on a three-day drift at 600 meters depth. After completing the last set of surface mapping measurements late tonight, the ship will transit south back toward a zone rich with small icebergs for the next study area.
Bottles and bottles of seawater samples were processed in the research labs today. In addition to collections, the Vernet and Murray labs sub-sampled the phyto- and bacterioplankton incubation cultures that began more than two weeks ago (see log 03-19-09). Maria Vernet, Diane Chakos, Karie Sines, and Adrian Cefarelli handled the phytoplankton cultures. While working with samples, they turned off overhead lights to keep the phytoplankton inside from photosynthesizing light from additional sources beyond the controlled light van. They prepared and ran a suite of tests, including chlorophyll measurements, microscopy, and primary production using special instruments on the ship. They also saved samples to be analyzed upon their return to Vernet’s lab at Scripps.
Just like land plants, phytoplankton need nitrate, phosphate, and ammonium to grow. Two additional nutrients, nitrite and silicate, also contribute to the growth of some phytoplankton. To accurately analyze phytoplankton growth, the Vernet lab has nutrient technician Lindsey Ekern measure the concentrations of these nutrients from all seawater samples, which includes the experimental cultures in the light van, CTD casts, trace-metal-clean Niskin casts, towfish deployments, and samples collected by the ROV.
—Debbie Nail Meyer