title: Newly discovered deep-branching marine plastid lineages are numerically rare but globally distributed.
abstract: Ocean surface warming is resulting in an expansion of stratified, low-nutrient environments, a process referred to as ocean desertification [1]. A challenge for assessing the impact of these changes is the lack of robust baseline information on the biological communities that carry out marine photosynthesis. Phytoplankton perform half of global biological CO2uptake, fuel marine food chains, and include diverse eukaryotic algae that have photosynthetic organelles (plastids) acquired through multiple evolutionary events [1-3]. While amassing data from ocean ecosystems for the Baselines Initiative (6,177 near full-length 16S rRNA gene sequences and 9.4 million high-quality 16S V1-V2 amplicons) we identified two deep-branching plastid lineages based on 16S rRNA gene data. The two lineages have global distributions, but do not correspond to known phytoplankton. How the newly discovered phytoplankton lineages contribute to food chains and vertical carbon export to the deep sea remains unknown, but their prevalence in expanding, low nutrient surface waters suggests they will have a role in future oceans.
authors.affiliation: Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA.
authors.forename: Chang Jae
authors.initials: CJ
authors.lastname: Choi
authors.affiliation: Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Bachy
authors.affiliation: Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
authors.forename: Gualtiero Spiro
authors.initials: GS
authors.lastname: Jaeger
authors.affiliation: Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA.
authors.forename: Camille
authors.initials: C
authors.lastname: Poirier
authors.affiliation: Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Sudek
authors.affiliation: National Institute of Oceanography, Visakhapatnam, India.
authors.forename: V V S S
authors.initials: VVSS
authors.lastname: Sarma
authors.affiliation: Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
authors.forename: Amala
authors.initials: A
authors.lastname: Mahadevan
authors.affiliation: Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Giovannoni
authors.affiliation: Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA; Integrated Microbial Biodiversity Program, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada. Electronic address: azworden@mbari.org.
authors.forename: Alexandra Z
authors.initials: AZ
authors.lastname: Worden
mesh_terms: D005075:Biological Evolution; D002244:Carbon / Q000378:metabolism*; D057231:Climate Change; D017753:Ecosystem; D009792:Oceans and Seas; D010839:Phytoplankton / Q000166:cytology* / Q000502:physiology; D018087:Plastids / Q000145:classification / Q000235:genetics* / Q000502:physiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S; D002244:Carbon