Salter I.,University Pierre and Marie Curie |
Bottjer D.,SOEST |
Bottjer D.,Center for Microbial Oceanography |
Christaki U.,University Pierre and Marie Curie |
Christaki U.,University of Lille Nord de France
Environmental Microbiology | Year: 2011
The effect of inorganic particle concentrations on bacteria-virus-nanoflagellate dynamics in an oligotrophic coastal system was investigated using a model aluminosilicate, kaolinite, with a modal size of 2.1μm. Virus-only, bacteria-only and bacteria-virus-nanoflagellate incubations were carried out at increasing kaolinite concentrations to elucidate the microbial response. The sorption of bacteria and viruses to kaolinite particles was negligible over a concentration range of 1-50mgl -1. In contrast, the abundance of heterotrophic nanoflagellates was negatively correlated with kaolinite concentrations following both 48 and 96h incubations. Calculated nanoflagellate bacterial ingestion rates were reduced by 5-35% depending on kaolinite particle concentration. In the bacteria-virus-nanoflagellate incubations viral production increased by 56×10 3 to 104×10 3VLPsml -1h -1 as a function of kaolinite particle concentration. Our results demonstrate for the first time that the interaction of microbial populations with inorganic particles can shift the balance between protist and virally mediated mortality of marine heterotrophic prokaryotes. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.
Kaupp L.J.,1776 University Avenue |
Measures C.I.,SOEST |
Selph K.E.,SOEST |
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2011
The concentrations of dissolved Fe and Al were determined in the upper waters of the eastern Equatorial Pacific (EEP) between 5°N and 4°S at 110°W and along the equator from 115°W to 140°W between 3 December 2004 and 2 January 2005. The most notable feature is a distinct Al maximum that appears as a 100-150. m thick layer that corresponds closely to the Equatorial Undercurrent (EUC). The origin of this enrichment is likely from sediment resuspension processes in the source water regions of the EUC in the western Pacific. There is no corresponding feature in dissolved Fe but vertical profiles of Fe show typical nutrient-like distributions. Concentrations of dissolved Al decline slightly within the EUC along its advective flow path, but concentrations of Fe decline much more significantly at all depths along the section as a result of particle scavenging. Upwelling of the upper part of the EUC is the main source of Fe to the surface waters of this region, since eolian deposition, calculated from surface water dissolved Al, is minimal. The continual depletion of Fe in the source waters feeding the upwelling results in a decline of the Fe supply to surface waters. At 140°W in the surface waters, the N:Fe ratio (∼15,000:1) implies the presence of sufficient Fe to allow full utilization of upwelled nitrate. By 110°W, the N:Fe ratio is >60,000:1, implying surface waters that are severely Fe-limited. The change in the status of the surface waters from Fe-sufficient to Fe-limited appears to be largely the result of the inorganic scavenging of Fe from the water column by the vertical particle rain rate, which itself is produced in surface waters by the upwelling of nutrients and Fe. Thus the progressive depletion of Fe from west to east appears to be directly related to production stimulated in the surface waters by the Fe-rich upwelling in the west. The large loss of Fe over this relatively short spatial scale in a rapidly moving water mass implies an extremely short residence time under these conditions and also suggests that the EUC might provide a natural laboratory for studying the relative scavenging rates for a variety of trace elements. These results imply that the persistent high-nutrient, low-chlorophyll conditions in the EEP are a result of Fe-limitation, but that changing climatologic conditions in the source regions of the EUC may result in temporal variation in the amount of that Fe supply. © 2010 Elsevier Ltd.
News Article | November 1, 2016
SOEST, Pays-Bas, November 1, 2016 /PRNewswire/ -- En février 2017, le Musée militaire national des Pays-Bas (NMM) accueillera en première européenne l'exposition « Gengis » qui retrace l'histoire et l'impact de l'un des plus grands empires de tous les temps. « Gengis » s...
News Article | November 15, 2016
Prochlorococcus, the most abundant photosynthetic microbe on the planet, is found in the Pacific Ocean (shown) and around the globe. Credit: Tara Clemente, University of Hawaii SOEST Researchers from David Karl's laboratory at the University of Hawai'i at Mānoa (UHM) and from Professor Jens Nielsen's laboratory at Chalmers University of Technology in Göteborg, Sweden, developed a computer model which takes into account hundreds of genes, chemical reactions, and compounds required for the survival of Prochlorococcus, the most abundant photosynthetic microbe on the planet. They found that Prochlorococcus has made extensive alterations to its metabolism as a way to reduce its dependence on phosphorus, an element that is essential and often growth-limiting in the ocean. Revolutionary developments in gene sequencing technology have allowed scientists to catalog and investigate the genetic diversity and metabolic capability of life on Earth—from E. coli bacteria to humans, and much in between. Ocean monitoring and advances in oceanographic sensors have enabled a more detailed look than ever before at the environmental conditions that are both the consequence of microbial activity and act as stressors on the growth of microbes in the ocean. This new metabolic model represents a window to the inner workings that enable microbes to dominate Earth's chemical and biological cycles, thrive in the harshest conditions, and make the planet habitable—a black box, in a sense. Microbes are known to employ three basic strategies to compete for limiting elemental resources: cell quotas may be adjusted, stressed cells may synthesize molecules to make more efficient use of available resources, and cells may access alternatives or more costly sources of the nutrient. In the case of phosphorus, a limiting resource in vast oceanic regions, the cosmopolitan Prochlorococcus thrives by adopting all three strategies and a fourth, previously unknown strategy. "By generating the first detailed model of metabolism for an ecologically important marine microbe, we found that Prochlorococcus has evolved a way to reduce its dependence on phosphate by minimizing the number of enzymes involved in phosphate transformations, thus relieving intracellular demands" said John Casey, an oceanography doctoral candidate in the UHM School of Ocean and Earth Science and Technology and lead author of the recently published study. Prochlorococcus has an extremely minimal genome. If it were to lose the function of any one metabolic gene, its survival would be nearly a coin toss. To their surprise, Casey and co-authors discovered that the world's most abundant microbe has performed, through a process called "genome streamlining"—the concerted loss of frivolous genes over evolutionary time—a comprehensive re-design of the core metabolic pathways in response to the persistent limitation of phosphorus. "The dramatic and widespread change in the metabolic network is really a shock," said Casey. "However, we're seeing that these changes provide a substantial growth advantage for this ubiquitous microbe in phosphorus-limited regions of the ocean, so it seems that where there's a will there's a way." The computer model is built from an enormous library of genetic data compiled from researchers around the world, and the results are validated with data from numerous laboratory culture experiments and field studies. "We're interested in the underlying principles guiding metabolism and physiology in marine microbes, and that is going to require a deep understanding of not only the 1-dimensional genetic code, but also the 4-dimensional product it codes for," said Casey. "So we're looking to a systems-level approach to incorporate a great variety of physiological and 'omics studies all in one computational structure, with the hope that we can start to learn from the design and interactions of these complex systems." In the future, the researchers plan to expand the model to include more representatives of the marine microbial community and to look deeper into micro-diversity within the Prochloroccocus genus. "This will allow us to simulate marine microbial community metabolism at an unprecedented level of detail; embedding these fine-scale simulations within global ocean circulation models promises to deliver insights into how microbial assemblages interact with their environment and amongst each other," said Casey. Explore further: To understand the oceans' microbes, follow function, not form
News Article | September 22, 2016
A new paper in the Journal of Geophysical Research shows that sea level rise in the northern Indian Ocean rose twice as fast as the global average since 2003. This represents a stark contrast to the previous decade, when the region experienced very little sea level rise at all. The science team led by Philip Thompson, associate director of the University of Hawai'i Sea Level Center in the School of Ocean and Earth Science and Technology (SOEST), analyzed two and a half decades of ocean surface height measurements taken from satellites. The satellite data showed a substantial and abrupt increase in decade-long sea level trends in the Indian Ocean region, which prompted the oceanographers to investigate the cause of the shift using computer simulations of ocean circulation. "Wind blowing over the ocean caused changes in the movement of heat across the equator in the Indian Ocean," said Thompson. "This led to suppression of sea level rise during the 1990s and early 2000s, but now we are seeing the winds amplify sea level rise by increasing the amount of ocean heat brought into the region." When trade winds in the Indian Ocean are weaker north of the equator compared to the south, warmer water at the ocean surface is driven out of the Northern Hemisphere, and colder, deep water is moved in. This has a net cooling effect on the ocean, leading to the suppression of sea level rise. This is what occurred early in the satellite record, but recently the situation reversed, causing heat to build up in the northern Indian Ocean and enhancing the rate of sea level rise. Many of the world's most vulnerable populations to sea level rise can be found in these parts of the Indian Ocean, including those in Bangladesh and Jakarta. "What we are learning is that the interaction between the ocean and atmosphere causes sea level to rise like a staircase instead of a straight line – starting and stopping for many years at a time. What we've done here is described one stair, which will help us better understand and plan for the future," said Thompson. The science team members will continue their work using similar techniques to understand sea level variability in the South Indian Ocean, investigating how heat is exchanged between the Indian and Pacific Oceans.
News Article | November 2, 2016
SOEST, Niederlande, November 2, 2016 /PRNewswire/ -- Im Februar 2017 eröffnet das Nationale Militärmuseum der Niederlande (NMM) Europas erste "Genghis"-Ausstellung. Diese Ausstellung erzählt die Geschichte eines der größten Reiche unserer Geschichte und beleuchtet den Einfluss, den die...
News Article | November 1, 2016
SOEST, Germany, November 1, 2016 /PRNewswire/ -- In February 2017, the National Military Museum of the Netherlands (NMM) stages the European premiere of the exhibition 'Genghis'.This exhibition tells the story of one of the greatest empires that ever was and the impact it had....
News Article | November 1, 2016
SOEST, Países Bajos, November 1, 2016 /PRNewswire/ -- En febrero del año 2017, el National Military Museum of the Netherlands (NMM) llevará a cabo la presentación europea de la muestra titulada 'Genghis'. Esta muestra cuenta la historia de uno de los mayores imperios que jamás existió...