Bacterioplankton Samples

This is my first research cruise in over ten years, and I am quite excited by the great opportunity.  I once went out to sea fairly routinely when I worked at Harbor Branch Oceanographic Institution (HBOI), but the goals were much different then. This time for DEEPEND, we focus on the pelagic mid water column organisms in the Gulf of Mexico, which remains a fairly new habitat for me to explore.
 
My role for DEEPEND on this DP05 cruise is to ensure proper collection of new bacterioplankton samples from Gulf of Mexico seawater at various depths.  I am basically following the same procedures as past cruises for consistency.
 
The main instrument for collecting water is the CTD (conductivity, temperature, and depth) which is loaded with a rosette (circular arrangement) of twelve Niskin bottles that can each hold 12 L. These traditional aquatic water collectors close at precise depths which I can control from the ship. R/V Point Sur crew member, Marshall Karmanec, helped get me accustomed to running and deploying the CTD on this cruise. With the controls, I can designate where and when bottles are opened at specific depths. Once the bottles are filled and back on deck, I am able to drain 4-5 L of seawater and bring them into the lab.  I share a filtering station corner of the ship’s lab with FWC/USF technician Tess Rivenbark.  While most of the other DEEPEND scientists are identifying charismatic deepwater megafauna, I filter marine microbiomes onto special sterile 0.45 micron filters. “Sterile” is the operative word here, since the lab is not the optimal place for traditional “microbiology” methods. Essentially I am preserving the communities on the filter by careful handling, freezing and recording, so they can all be brought back intact to my molecular lab at the NSU Oceanographic Center for DNA extractions and sequencing that will eventually illuminate the distribution and dynamics bacterioplankton in much greater detail.
 
The CTD also measures where the very important oxygen minimum and chlorophyll maximum zones occur vertically within the water column.  These zones represent important parameters for oceanographic work since they can delimit where food chains begin or end, where maximum photosynthesis (the production of oxygen from cyanobacteria) happens, and we also have found distinct microbial communities (also known as “microbiomes”) associated with each zone. With DEEPEND postdoctoral scientist Cole Easson, we have been characterizing these microbiomes from past cruises, and our current results point to significant depth stratification of microbiomes in DEEPEND Year 1 data, which among other interesting findings will be submitted in a forthcoming manuscript.  This year 3 sampling adds to the temporal dimension of the project and is also very exciting.