AME 56:227-239 (2009)  -  DOI:

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

David J. Suggett1,*, Noga Stambler2, Ondrej Prášil3, Zbigniew Kolber4, Antonietta Quigg5, Evaristo Vázquez-Dominguez6, Tamar Zohary7, Tom Berman7, David Iluz8, Orly Levitan2, Tracy Lawson1, Efrat Meeder9,10, Boaz Lazar9,10, Edo Bar-Zeev2, Hana Medova3, Ilana Berman-Frank8

1Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK
2Department of Geography and Environment, Bar-Ilan University, Ramat-Gan 52900, Israel
3Photosynthesis Laboratory, Institute of Microbiology ASCR, Opatovicky mlyn, 379 81 Trˇebonˇ, Czech Republic
4Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, USA
5Department of Marine Biology and Oceanography, Texas A&M University, Galveston, Texas 77551, USA
6CSIC, Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 39-43, 08003 Barcelona, Spain
7Kinneret Limnological Laboratory, Israel Oceanographic and Limnological Research, PO Box 447, Migdal 14950, Israel
8The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
9The Interuniversity Institute for Marine Sciences Coral Beach, PO Box 469, 88103 Eilat, Israel
10Institute of Earth Sciences, The Hebrew University Edmond J. Safra Campus, Jerusalem 91904, Israel
*Email: co-authors contributed equally to the data collection

ABSTRACT: Bioassay experiments were performed to identify how growth of key groups within the microbial 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 phytoplankton 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) photochemical 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 addition 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. Productivity of obligate heterotrophic bacteria exhibited the greatest increase in response to a natural (deep water) 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 heterotrophy) is critically dependent upon the nature of transient nutrient enrichment.

KEY WORDS: Phytoplankton · Aerobic anoxygenic photoheterotroph · Bacterial · Fast repetition rate fluorometry · Chlorophyll a · Nutrient limitation · Gulf of Aqaba

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Cite this article as: Suggett DJ, Stambler N, O Prášil, Kolber Z and others (2009) Nitrogen and phosphorus limitation of oceanic microbial growth during spring in the Gulf of Aqaba. Aquat Microb Ecol 56:227-239.

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