Co-occurring Synechococcus ecotypes occupy four major oceanic regimes defined by temperature, macronutrients and iron

• Published in: The ISME Journal Vol. 10; no. 2; pp. 333 - 345
• Main Authors: Sohm, Jill A, Ahlgren, Nathan A, Thomson, Zachary J, Williams, Cheryl, Moffett, James W, Saito, Mak A, Webb, Eric A, Rocap, Gabrielle
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2016; Nature Publishing Group
• Subjects: 45/77; 631/158/2446/2447; 631/158/852; 631/181/735; Biogeography; Biomedical and Life Sciences; DNA Primers - genetics; Ecology; Ecotype; Ecotypes; Evolutionary Biology; Iron; Iron - analysis; Iron - metabolism; Life Sciences; Microbial activity; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Oceans; Oceans and Seas; Original; original-article; Pacific Ocean; Phylogeny; Prochlorococcus; Prochlorococcus - genetics; Prochlorococcus - metabolism; Seawater - chemistry; Seawater - microbiology; Surface water; Synechococcus; Synechococcus - classification; Synechococcus - genetics; Synechococcus - isolation & purification; Synechococcus - metabolism; Temperature
• ISSN: 1751-7362; 1751-7370
• DOI: 10.1038/ismej.2015.115

Marine picocyanobacteria, comprised of the genera
Synechococcus
and
Prochlorococcus
, are the most abundant and widespread primary producers in the ocean. More than 20 genetically distinct clades of marine
Synechococcus
have been identified, but their physiology and biogeography are not as thoroughly characterized as those of
Prochlorococcus
. Using clade-specific qPCR primers, we measured the abundance of 10
Synechococcus
clades at 92 locations in surface waters of the Atlantic and Pacific Oceans. We found that
Synechococcus
partition the ocean into four distinct regimes distinguished by temperature, macronutrients and iron availability. Clades I and IV were prevalent in colder, mesotrophic waters; clades II, III and X dominated in the warm, oligotrophic open ocean; clades CRD1 and CRD2 were restricted to sites with low iron availability; and clades XV and XVI were only found in transitional waters at the edges of the other biomes. Overall, clade II was the most ubiquitous clade investigated and was the dominant clade in the largest biome, the oligotrophic open ocean. Co-occurring clades that occupy the same regime belong to distinct evolutionary lineages within
Synechococcus
, indicating that multiple ecotypes have evolved independently to occupy similar niches and represent examples of parallel evolution. We speculate that parallel evolution of ecotypes may be a common feature of diverse marine microbial communities that contributes to functional redundancy and the potential for resiliency.