LA JOLLA, Calif., July 28, 2015 /PRNewswire-USNewswire/ -- A team of ocean researchers led by those at the J. Craig Venter Institute (JCVI) and Scripps Institution of Oceanography (SIO) have uncovered a series of complicated relationships among marine microbes and their fight for important resources such as iron, light and VitaminB12. These relationships appear to have critical consequences for coastal Southern Ocean food webs. JCVI and SIO, along with those at the University of Southern California (USC), and the Virginia Institute of Marine Sciences (VIMS) published their research today in the Proceedings of the National Academy of Sciences (PNAS).
Microscopic organisms, phytoplankton (single celled photosynthetic algae) and bacteria, which live suspended in seawater form the base of global marine food webs and underpin the success and health of the water and other animals that live there. The Southern Ocean around Antarctica is home to massive phytoplankton populations, and scientists have long considered their growth to be controlled largely by availability of iron and light. However, the research published today shows that the picture is much more complicated.
Scientists from JCVI ventured to the US Antarctic Program's McMurdo Station at the south tip of Ross Island. They conducted expeditions over the frozen sea to the ice edge where they collected surface water samples and analyzed them back at the McMurdo Station. The researchers learned that although the water appeared teeming with a particular type of phytoplankton called diatoms, the diatoms displayed cellular signatures of malnourishment. Unlike most regions of the global ocean which do not contain sufficient nitrogen or phosphorous for sustained phytoplankton growth, diatoms in the remote waters of McMurdo Sound, adjacent to the Ross Sea, were starving from lack of iron and deficiency of vitamin B12.
The researchers also identified a range of different bacteria growing in the water, but it wasn't clear what role the various types of bacteria might play in driving or alleviating the starvation exhibited by the diatoms. Were they competing for the scarce resources and exacerbating the starvation conditions or were they somehow cooperating to effectively share these resources? By looking at how these microbial groups changed the expression of their genes in response to shifts in micronutrient availability, the researchers could begin to untangle these questions.
The team, along with other collaborators at the University of Rhode Island and the Marine Biological Laboratory, further confirmed that a large portion of the B12 supply in the Southern Ocean appears to be produced by a particular group of gamma proteobacteria bacteria belonging to the Oceanospirllaceae.
Senior author Andrew Allen, a joint Associate Professor at JCVI and SIO, said: "Through a combination of field manipulation experiments and next generation sequencing, we've obtained a new view of the microbial interactions underpinning a highly productive ecosystem. Although oceanographers have long recognized that iron fertilization in the Southern Ocean will drive phytoplankton blooms, it is now evident that particular groups of bacteria, perhaps specifically cultivated by the phytoplankton, are important for regulating the magnitude of the blooms as well as sustaining them through supply of the critically limiting micronutrient vitamin B12."
Erin Bertrand, Ph.D., former JCVI and SIO researcher, now an Assistant Professor at Dalhousie University in Halifax, Nova Scotia, and lead author of the study added, "Just like humans, phytoplankton require vitamins, including vitamin B12, to survive. But this precious resource is being competed for by three groups of microbes which, due to the extreme remoteness of the Southern Ocean, is a scarce and consequently invaluable resource. Allen added, "I think this study also illustrates the eye opening sensitivity of marine phytoplankton and bacteria to very minor additions of scarce micronutrients over very short, hourly, time scales."
With this new understanding of the nature of these interactions and the careful balance of competitive and cooperative behaviors that exist in this key ecosystem, researchers can work towards predicting how these relationships might change in the future, as temperatures begin to rise in the Southern Ocean.
This research is funded in part by the Gordon and Betty Moore Foundation through Grant GBMF3828 to Scripps, A.E. Allen, and National Science Foundation, Antarctic Sciences Section Grant 1043671 to JCVI, A.E. Allen and 1103503 to E. M. Bertrand.
About J. Craig Venter Institute
The JCVI is a not-for-profit research institute in Rockville, MD and La Jolla, CA dedicated to the advancement of the science of genomics; the understanding of its implications for society; and communication of those results to the scientific community, the public, and policymakers. Founded by J. Craig Venter, Ph.D., the JCVI is home to approximately 200 scientists and staff with expertise in human and evolutionary biology, genetics, bioinformatics/informatics, information technology, high-throughput DNA sequencing, genomic and environmental policy research, and public education in science and science policy. The JCVI is a 501 (c)(3) organization. For additional information, please visit http://www.JCVI.org.
SOURCE J. Craig Venter Institute