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Title: Nanophytoplankton Diversity Across the Oligohaline Lake Pontchartrain Basin Estuary: A Preliminary Investigation Utlizing psbA Sequences

item LAKEMAN, M.B.
item Evens, Terence

Submitted to: International Phycological Congress
Publication Type: Abstract Only
Publication Acceptance Date: 4/25/2009
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The Lake Pontchartrain basin estuary is shallow, wind-driven and comprised of two large embayments (1645 km2). Salinities range from freshwater in the west to 8 ppt in the east near the Gulf of Mexico. Phytoplankton investigations spanning this salinity gradient or examining small photoautotrophs are few in number. Molecular approaches using rRNA sequences cannot distinguish photosynthetic and heterotrophic organisms. However, psbA encodes the photosystem II D1 protein in both cyanobacteria and eukaryotic algae and is used successfully in marine studies. Therefore, this study investigates psbA sequences for assessing nanophytoplankton biodiversity (<10 µm) spanning this oligohaline estuary. Samples were taken during October 14-20 (21-24°C) and December 12-17, 2003 (10-12°C) from 14 and 12 sites, respectively. Four were selected for psbA analyses at salinities of 0.51 ppt (14 October) and 3.10 ppt (20 October), 1.52 ppt (15 December) and 5.78 ppt (16 December). Cloned PCR products were digested with AluI. DNA sequences were determined for each unique RFLP pattern and compared to the Genbank database; 57 sequences were identified. Of these 59.7% were viral, 15.8% cyanbacterial, 10.5% diatom and 8.8% chlorophyte. Although some PCR products had distinct RFLP patterns, five sequences gave best database matches that were common to all four samples: one diatom, a cyanobacterium and three phages. No clear geographic distribution pattern was observed. These data are presented within the context of system-level physical/chemical parameters, including nitrogen and phosphorus, and overall phytoplankton composition (as derived from suites of diagnostic photopigments).