Seasonal and Geographical Transitions in Eukaryotic Phytoplankton Community Structure in the Atlantic and Pacific Oceans.

Autor:	Choi CJ; Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States., Jimenez V; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States., Needham DM; Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States., Poirier C; Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States., Bachy C; Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States., Alexander H; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States.; Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United States., Wilken S; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States.; Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands., Chavez FP; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States., Sudek S; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States., Giovannoni SJ; Department of Microbiology, Oregon State University, Corvallis, OR, United States., Worden AZ; Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.; Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States.
Jazyk:	angličtina
Zdroj:	Frontiers in microbiology [Front Microbiol] 2020 Sep 30; Vol. 11, pp. 542372. Date of Electronic Publication: 2020 Sep 30 (Print Publication: 2020).
DOI:	10.3389/fmicb.2020.542372
Abstrakt:	Much is known about how broad eukaryotic phytoplankton groups vary according to nutrient availability in marine ecosystems. However, genus- and species-level dynamics are generally unknown, although important given that adaptation and acclimation processes differentiate at these levels. We examined phytoplankton communities across seasonal cycles in the North Atlantic (BATS) and under different trophic conditions in the eastern North Pacific (ENP), using phylogenetic classification of plastid-encoded 16S rRNA amplicon sequence variants (ASVs) and other methodologies, including flow cytometric cell sorting. Prasinophytes dominated eukaryotic phytoplankton amplicons during the nutrient-rich deep-mixing winter period at BATS. During stratification ('summer') uncultured dictyochophytes formed ∼35 ± 10% of all surface plastid amplicons and dominated those from stramenopile algae, whereas diatoms showed only minor, ephemeral contributions over the entire year. Uncultured dictyochophytes also comprised a major fraction of plastid amplicons in the oligotrophic ENP. Phylogenetic reconstructions of near-full length 16S rRNA sequences established 11 uncultured Dictyochophyte Environmental Clades (DEC). DEC-I and DEC-VI dominated surface dictyochophytes under stratification at BATS and in the ENP, and DEC-IV was also important in the latter. Additionally, although less common at BATS, Florenciella -related clades (FC) were prominent at depth in the ENP. In both ecosystems, pelagophytes contributed notably at depth, with PEC-VIII (Pelagophyte Environmental Clade) and (cultured) Pelagomonas calceolata being most important. Q-PCR confirmed the near absence of P. calceolata at the surface of the same oligotrophic sites where it reached ∼1,500 18S rRNA gene copies ml -1 at the DCM. To further characterize phytoplankton present in our samples, we performed staining and at-sea single-cell sorting experiments. Sequencing results from these indicated several uncultured dictyochophyte clades are comprised of predatory mixotrophs. From an evolutionary perspective, these cells showed both conserved and unique features in the chloroplast genome. In ENP metatranscriptomes we observed high expression of multiple chloroplast genes as well as expression of a selfish element (group II intron) in the psaA gene. Comparative analyses across the Pacific and Atlantic sites support the conclusion that predatory dictyochophytes thrive under low nutrient conditions. The observations that several uncultured dictyochophyte lineages are seemingly capable of photosynthesis and predation, raises questions about potential shifts in phytoplankton trophic roles associated with seasonality and long-term ocean change. (Copyright © 2020 Choi, Jimenez, Needham, Poirier, Bachy, Alexander, Wilken, Chavez, Sudek, Giovannoni and Worden.)
Databáze:	MEDLINE
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