Endless Winter - Field expedition during the International Polar Year, July - September 2008
Seven of us are deploying in July for our field season which will be operated out of Palmer Station, on the Antarctic Peninsula. The basic plan is to interrogate the wintertime bacterioplankton assemblage to understand them better – as few studies have been conducted on the plankton in winter and we want to see if they are the same organisms as the summer time ones just in some form of hibernation, or if they are adapted to the long dark days of winter in which there is little organic carbon to support growth. We are planning on doing the following:
- Sampling:
- Large scale seawater sampling events from near-surface waters in which we’ll concentrate 400-1000L of seawater for transcriptomic and proteomic analyses. These samples will be collected by zodiac boat or by skiing to sampling sites depending on the condition of the sea ice. We’ll use a submersible pump to harvest the water.
- Sample from the RV Lawrence M. Gould to get further offshore of Anvers Island where we can collect profiles of the bacterioplankton using a rosette that holds lots of sampling bottles in which you close bottles at specific depths.
- Experiments:
- A series of seawater mesocosm studies (10 days ea.) will be conducted in which we will test the ability of the wintertime bacterioplankton community to utilize and adapt to different carbon and inorganic nutrient regimes. We also plan to study the community dynamics as we “turn on the lights” and simulate a spring/summer ecosystem with the addition of phytoplankton.
- Dilution experiments to artificially change bacterial richness and evaluate its importance in bacterial activities. Questions are : To which extend does artificial diminution of bacterial richness influence the community activity? Are abundant taxa doing the entire bacterial activity? What is the relative importance of richness and eveness in bacterial community activity?
- Analyses (Abundance, chemistry, activity, and lmolecular biology)
- Abundance of bacteria, archaea, and protists will be determined on station microscopically using fluorescent probes which bind specifically to the ribosomal RNA in these organisms, in addition all samples will be preserved for flow cytometric analyses for direct counts back in Hugh Ducklow’s laboratory at MBL. We’ll also determine the living vs. dead cell counts in the seawater.
- Conduct water chemistry analysis for phosphate, nitrate, nitrite, and ammonium, and dissolved organic carbon.
- Conduct different kinds of biological activity assays to understand different facets of growth and substrate utilization
- Leucine incorporation into protein
- Carbon fixation into biomass
- Microbial respiration (oxygen consumption)
- Hydrolysis of simple and complex carbon compounds
- The abundance and expression of targeted genes from organisms of interest will be detected using real time PCR - a precise method to quantify gene copy numbers of these genes in the natural samples.
- Bacterioplankton community structure will be profiled using a PCR-DGGE approach to amplify DNA and RNA so that we can determine how things change while we’re in the field, and evaluate the effect of the mesocom experimental treatments on the community structure. The RNA gives us a relative indicator of which organisms are more active.