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Aquatic Microbial Ecology

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AME 62:85-97 (2011)  -  DOI:

Myrionecta rubra population genetic diversity and its cryptophyte chloroplast specificity in recurrent red tides in the Columbia River estuary

Lydie Herfort1,*, Tawnya D. Peterson1, Lee Ann McCue2, Byron C. Crump3, Fredrick G. Prahl4, Antonio M. Baptista1, Victoria Campbell1, Rachel Warnick1, Mikaela Selby1, G. Curtis Roegner5, Peter Zuber1

1Center for Coastal Margin Observation & Prediction and Division of Environmental & Biomolecular Systems, Oregon Health & Science University, Beaverton, Oregon 97006, USA
2Pacific Northwest National Laboratory, Richland, Washington 99352, USA
3Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, Massachusetts 21613, USA
4College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331-5503, USA
5Point Adams Research Station, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, Hammond, Oregon 97121, USA

ABSTRACT: For several decades, annually recurring blooms of the photosynthetic ciliate Myrionecta rubra have been observed in the Columbia River estuary in late summer. In an effort to understand the dynamics of these blooms, we investigated the genetic variability of M. rubra and its cryptophyte plastids within 3 large estuarine blooms formed in consecutive years (2007 to 2009), and conducted a broader spatial survey along the coasts of Oregon and Washington. Analysis of the ‘18S-28S’ sequences specific for Mesodiniidae uncovered at least 5 variants of M. rubra within the Columbia River coastal margin in spring and summer, but only one of these M. rubra variants was implicated in estuary bloom formation. Using a multigene approach, we show that the bloom-forming variant of M. rubra appears to harbor the same cryptophyte chloroplast in recurring blooms. Analyses of chloroplast 16S rRNA, cryptophyte RuBisCO and Photosystem II D2 genes together suggest that the plastid is derived from Teleaulax amphioxeia. Free-living cells of this species and of other cryptophytes were practically absent from the bloom patches in the estuary main channels based on 18S rDNA sequence analyses. The respectively low and high proportions of T. amphioxeia nuclei and chloroplast signals found in the M. rubra bloom of the Columbia River estuary in successive years supports the notion of an association (either endosymbiosis or kleptoplastidy) between T. amphioxeia and the bloom-forming M. rubra variant, with loss of cryptophyte nuclei. The genetic variability of M. rubra uncovered here is relevant to the controversy in the literature regarding the cryptophyte/M. rubra association.

KEY WORDS: Myrionecta rubra · Red tide · Cryptophyte · Diversity · Columbia River estuary

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Cite this article as: Herfort L, Peterson TD, McCue LA, Crump BC and others (2011) Myrionecta rubra population genetic diversity and its cryptophyte chloroplast specificity in recurrent red tides in the Columbia River estuary. Aquat Microb Ecol 62:85-97.

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