Aquatic Sciences Meeting, Albuquerque 2001
| SS14 Microbial Diversity (Disciplinary Connections) |
| Date: Tuesday, February 13, 2001, Time: 12:15:00 PM |
| Location: Mesilla |
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| Post, A, F, Marine Biology Lab., Hebrew University, Eilat, Israel, anton@vms.huji.ac.il |
| Penno, S, , Marine Biology Lab., Hebrew University, Eilat, Israel, spenno@gmx.de |
| Lindell, D, , Marine Biology Lab., Hebrew University, Eilat, Israel, debbie@vms.huji.ac.il |
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| NITROGEN STRESS AND PROKARYOTIC PHYTOPLANKTON DIVERSITY IN THE GULF OF AQABA, NORTHERN RED SEA. |
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| N-availability in the Gulf of Aqaba changes drastically over the winter mixing and summer stratification seasons. These changes are accompanied by shifts in picophytoplankton communities with cyanobacterial species dominating during N-deplete periods. A multiyear analysis of seasonal succession among picophytoplankton establishes the dominance of eukaryotic algae during winter when nitrate is mixed in the surface layers. Prochlorococcus numbers are low in winter and fall below detection when mixing reaches deeper than 400 m. A Synechococcus spring bloom, with cell counts of 400,000 cells per ml, is characteristic for the early phase of stratification when nitrate becomes deplete. Prochlorococcus, reported incapable of utilizing nitrate, reaches maximum abundance in late summer with different, poorly characterized Prochlorococcus ecotypes coexisting at the nitracline. These observations raise questions about N-sources utilized by Synechococcus and Prochlorococcus during the different seasons, which we attempt to ascertain from their genetic potential. We identified the nitrogen regulatory gene, ntcA, and nitrate transporter gene, napA, both specific for cyanobacteria among marine plankton. Sequences amplified from natural DNA templates were used to construct the genotypic makeup of Synechococcus and Prochlorococcus over the seasons. Spatial and temporal variation among Prochlorococcus populations and their potential to utilize nitrate-nitrite are discussed. |
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