Showing papers by "Zbigniew Kolber published in 2009"

Nitrogen and phosphorus limitation of oceanic microbial growth during spring in the Gulf of Aqaba

Abstract: Bioassay experiments were performed to identify how growth of key groups within the mi- crobial community was simultaneously limited by nutrient (nitrogen and phosphorus) availability during spring in the Gulf of Aqaba's oceanic waters. Measurements of chlorophyll a (chl a) concentration and fast repetition rate (FRR) fluorescence generally demonstrated that growth of obligate phototrophic phyto- plankton was co-limited by N and P and growth of facultative aerobic anoxygenic photoheterotropic (AAP) bacteria was limited by N. Phytoplankton exhibited an increase in chl a biomass over 24 to 48 h upon relief of nutrient limitation. This response coincided with an increase in photosystem II (PSII) pho- tochemical efficiency (Fv/Fm), but was preceded (within 24 h) by a decrease in effective absorption cross- section (σPSII) and electron turnover time (τ). A similar response for τ and bacterio-chl a was observed for the AAPs. Consistent with the up-regulation of PSII activity with FRR fluorescence were observations of newly synthesized PSII reaction centers via low temperature (77K) fluorescence spectroscopy for addi- tion of N (and N + P). Flow cytometry revealed that the chl a and thus FRR fluorescence responses were partly driven by the picophytoplankton (<10 µm) community, and in particular Synechococcus. Produc- tivity of obligate heterotrophic bacteria exhibited the greatest increase in response to a natural (deep wa- ter) treatment, but only a small increase in response to N and P addition, demonstrating the importance of additional substrates (most likely dissolved organic carbon) in moderating the heterotrophs. These data support previous observations that the microbial community response (autotrophy relative to hetero- trophy) is critically dependent upon the nature of transient nutrient enrichment.

Seawater pH sensor based on the long period grating in a single-mode-multimode-single-mode structure

Abstract: A pH sensor is developed based on the long-period grating (LPG) inscribed into a single-mode–multimode–single-mode (SMS) structure in order to measure the pH in seawater. The LPG is formed by using a focused CO2 laser at LPG's critical period (1 mm). The transmission characteristics are similar to that of a multimode fiber. However, the SMS structure has a higher sensitivity because mode coupling only happens between the fundamental mode and higher-order modes in the SMS structure. The pH-sensitive hydrogel is made by the thermal cross-link of poly vinyl alcohol and poly acrylic acid. This sensor has been utilized in seawater pH sensing in the range of 6–8. Experiments have confirmed that the sensor is sensitive and repeatable.

Consequences of high CO2 and ocean acidification for microbes in the global ocean

Abstract: CONSEQUENCES OF HIGH CO2 AND OCEAN ACIDIFICATION FOR MICROBES IN THE GLOBAL OCEAN Ian Joint*, David M. Karl*, Scott C. Doney*, E Virginia Armbrust, William Balch, Michael Beman, Christopher Bowler, Matthew Church, Andrew Dickson, John Heidelberg, Debora Iglesias-Rodriguez, David Kirchman , Zbigniew Kolber, Ricardo Letelier, Claudia Lupp, Stephen Maberly, Susan Park, John Raven, Daniel J. Repeta, Ulf Riebesell, Grieg Steward, Philippe Tortell, Richard E Zeebe, Jonathan P. Zehr. a)Plymouth Marine Laboratory, UK, b)Center for Microbial Oceanography, University of Hawaii at Manoa USA, c)Woods Hole Oceanographic Institution, USA d)University of Washington, USA e)Bigelow Laboratory for Ocean Sciences, USA f)Ecole Normale Supérieure, Paris, France g)Scripps Institution of Oceanography, USA h)University of Southern California, USA i)National Oceanography Centre, Southampton, UK, j)University of Delaware, USA k)Monterey Bay Aquarium Research Institute, USA l)Oregon State University, USA m)Nature Publishing Group, London, UK n)Centre for Ecology and Hydrology, Lancaster, UK, o)National Research Council, Washington DC, USA p)University of Dundee, UK, q)IFM-GEOMAR, Kiel, Germany, r)University of British Columbia, Canada s)University of California, Santa Cruz, USA * The steering committee that organized the workshop (irj@pml.ac.uk, dkarl@hawaii.edu, sdoney@whoi.edu)