Eukaryotic metatranscriptome profiling identifies the unique responses of phytoplankton functional groups to deep water upwelling at station ALOHA

Harriet Alexander1, Monica Rouco-Molina2, Sheean Haley2, Sonya Dyhrman2

1 MIT/WHOI Joint Program in Oceanography2 Earth and Environmental Science, Lamont-Doherty Earth Observatory, Columbia University

Stochastic blooms of large phytoplankton balance NCP at Station ALOHA

Image credits: SeaWIFS Global Chlorophyll

North Pacific Subtropical Gyre

Station ALOHA

(Karl and Church, Nature Rev. Microbiol., 2014)

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Sampling at Station ALOHA coupled with bloom simulations

+ 10% DSW

700m0.2 μm filtered

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Deep seawater amendment

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Start date of experiment

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S = In situE = Experimental

Sampling at Station ALOHA coupled with bloom simulations

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8/6 8/10 8/14 8/23 8/27 8/31 9/89/4

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What are the biogeochemical constraints on the oligotrophic large phytoplankton? What are the functional group transcriptional responses to deep seawater (DSW) upwelling?

S = In situE = Experimental

Sampling at Station ALOHA coupled with bloom simulations

E1

Sampling and processing for metatranscriptomes

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8/6 8/10 8/14 8/23 8/27 8/31 9/89/4

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Filter (>5μm)

Extract RNA

Poly-A selection

Sequence(Illumina 60M 100bp PE)

Map to custom reference database (MMETSP)

Pool counts by functional group

MMETSP=Marine Microbial Eukaryotic Transcriptome Sequencing Project

S1 S2 S30

20

40

60

80MMETSP

Genome

Reads mapped to reference (%)

Mapping to genomes misses dinoflagellates,which comprise >30% of in situ mRNA

Community composition stablein an oligotrophic environment

S1 S2 S3

DSW addition alters functional group composition; shift similar across replicated experiments

Dinoflagellates Diatoms Haptophytes

Little changein species composition

Significant changes in species composition

DIA HAP DIN

ENVIRONMENTAL INFORMATION

PROCESSING

ENERGY METABOLISM

CARBOHYDRATE AND LIPID

METABOLISM

NUCLEOTIDE AND AMINO ACID

METABOLISM

GENETIC INFORMATION

PROCESSING

METABOLISM

Metabolic fingerprint differs between groups

and shifts after DSW addition

DIA HAP DIN

ENVIRONMENTAL INFORMATION

PROCESSING

ENERGY METABOLISM

CARBOHYDRATE AND LIPID

METABOLISM

NUCLEOTIDE AND AMINO ACID

METABOLISM

GENETIC INFORMATION

PROCESSING

METABOLISM

Metabolic fingerprint differs between groups

and shifts after DSW addition

95% confidence intervals indicated

DIA HAP DIN

ENVIRONMENTAL INFORMATION

PROCESSING

ENERGY METABOLISM

CARBOHYDRATE AND LIPID

METABOLISM

NUCLEOTIDE AND AMINO ACID

METABOLISM

GENETIC INFORMATION

PROCESSING

METABOLISM

Metabolic fingerprint differs between groups

and shifts after DSW addition

For each gene determineSignificance Post-p > 0.95 for 2-fold change

Experiments coupled with field sampling identify metabolic response to DSW addition

Experiments coupled with field sampling identify metabolic response to DSW addition

Phosphate and amino acid transport

Metallic and B12 transport

Replicated experiments highlight consistency of response to DSW addition

E3

E2

E1

Transcriptional response to DSW addition unique

Down-regulation following DSW addition

Up-regulationfollowing DSW addition

No major shifts in metabolism; most regulation

post-transcription?

Biogeochemical drivers of observed metabolic shifts

Urea transporter

Nitrate/itetransporter

Phospho-diesterase

Adenosyl-homocysteinase

Iron transporter

DIA

HAP

N P Vitamins Fe

Down in DSW

Up in DSW

No significant change

Complex co-limitation?Drivers not consistent across functional groups

Transcriptional response to DSW additionunderscores functional group traits

Diatoms “the scavengers”; r-selected

Haptophytes “the survivalists”; K-selected

Down-regulation following DSW addition

Up-regulationfollowing DSW addition

Functional group specific traits drive ecology of the system… balancing NCP

Functional group specific traits drive ecology of the system… balancing NCP

What are the biogeochemical constraints on the oligotrophic large phytoplankton?

Vary by functional group (Fe, N, P, vitamins)Possible complex co-limitation

What are the functional group transcriptional responses to deep water upwelling?

Dinoflagellates: Little/no transcriptional responseDiatoms: Broad down-regulation indicative of “scavenger”; r-selectedHaptophytes: General up-regulation indicative of “survivalist”; K-selected

Acknowledgements

o Dyhrman Lab

o Captain, crew of R/V Kilo Moana

o Science party of HOE-DYLAN

o Bethany Jenkins

Funding:o CMORE

o MMETSP/Gordon & Betty Moore Foundation

o NSF

o NDSEG

o MIT Presidential Fellowship

o MIT/WHOI Joint Program