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- Title
Co-existence of distinct Ostreococcus ecotypes at an oceanic front.
- Authors
Clayton, Sophie; Lin, Yun ‐ Chi; Follows, Michael J.; Worden, Alexandra Z.
- Abstract
Western boundary currents support high primary production and carbon export. Here, we performed a survey of photosynthetic picoeukaryotes in the North Pacific Ocean in four transects crossing the Kuroshio Front. Prasinophyte algae comprised 85% of 18S rRNA gene sequences for photosynthetic taxa in the <5 μm size fraction. The picoplanktonic (<2 μm) genera Micromonas and Ostreococcus comprised 30% and 51% of the total photosynthetic 18S rDNA sequences from five stations. Phylogenetic analysis showed that two Ostreococcus ecotypes, until now rarely found to co-occur, were both present in the majority of samples. Ostreococcus ecotype OI reached 6,830 ± 343 gene copies mL−1, while Ostreococcus ecotype OII reached 50,190 ± 971 gene copies mL−1 based on qPCR analysis of the 18S rRNA gene. These values are higher than in studies of other oceanographic regions by a factor of 10 for OII. The data suggest that meso- and finer-scale physical dynamics had a significant impact on the populations at the front, either by mingling ecotypes from different source regions at fine scales (∼10s km) or by stimulating their growth through vertical nutrient injections. We investigate this hypothesis with an idealized diffusion-reaction model, and find that only a combination of mixing and positive net growth can explain the observed distributions and overlap of the two Ostreococcus ecotypes. Our field observations support larger-scale numerical ocean simulations that predict enhanced biodiversity at western boundary current fronts, and suggest a strategy for systematically testing that hypothesis.
- Subjects
OCEANIA; NORTH Pacific Ocean; SCALE insects; EUKARYOTES; NUCLEOTIDE sequence
- Publication
Limnology & Oceanography, 2017, Vol 62, Issue 1, p75
- ISSN
0024-3590
- Publication type
Article
- DOI
10.1002/lno.10373