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This dataset includes data from nutrient manipulation experiments aimed at relieving or inducing nutrient stress in phytoplankton and quantifying these responses using metatranscriptomic sequencing. Experiments were conducted by adding key macronutrients (N, P, Si) and Fe in different combinations over different growth periods, simulating potential alleviation of in situ nutrient stress or the induction of nutrient stress. Experiments were conducted on the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) cruise DY131 in the North Atlantic during May of 2021. 

This dataset includes trace metal (iron, manganese, cobalt, nickel, copper, zinc, cadmium, lead) and macronutrient (nitrate&nitrite, nitrite, phosphate, silicic acid) concentration data from incubation experiments conducted on board the RRS Discovery during the EXPORTS North Atlantic campaign at the Porcupine Abyssal Plain-Sustained Observatory (PAP-SO) site (DY131). In these experiments, additions of macronutrients (N, P, Si) and Fe were used to assess the level of Si, N, and Fe stress being experienced by the phytoplankton and to contextualize taxa-specific metatranscriptome responses for resolving gene expression profiles in the in-situ communities. This research project focuses on the vertical export of the carbon associated with a major group of phytoplankton, the diatoms in the North Atlantic near the Porcupine Abyssal Plain. The major objective is to understand how diatom community composition and the prevailing nutrient conditions create taxonomic differences in metabolic state that combine to direct diatom taxa to different carbon export pathways. The focus is on diatoms, given their large contribution to global marine primary productivity and carbon export which translates into a significant contribution to the biogeochemical cycling of carbon (C), nitrogen (N), phosphorus (P), iron (Fe) and silicon (Si). It is hypothesized that the type and degree of diatom physiological stress are vital aspects of ecosystem state that drive export. To test this hypothesis, combined investigator expertise in phytoplankton physiology, genomics, and trace element chemistry is used to assess the rates of nutrient use and the genetic composition and response of diatom communities, with measurements of silicon and iron stress to evaluate stress as a predictor of the path of diatom carbon export. The EXPORTS field campaign in the North Atlantic sampled a retentive eddy over nearly a month in May 2021, which coincided with the decline of the North Atlantic Spring Bloom. 

Each spring, the North Atlantic experiences one of the largest open‐ocean phytoplankton blooms in the global ocean. Diatoms often dominate the initial phase of the bloom with succession driven by exhaustion of silicic acid. The North Atlantic was sampled over 3.5 weeks in spring 2021 following the demise of the main diatom bloom, allowing mechanisms that sustain continued diatom contributions to be examined. Diatom biomass was initially relatively high with biogenic silica concentrations up to 2.25 μmol Si L⁻¹. A low initial silicic acid concentration of 0.1–0.3 μM imposed severe Si limitation of silica production and likely limited the diatom growth rate. Four storms over the next 3.5 weeks entrained silicic acid into the mixed layer, relieving growth limitation, but uptake limitation persisted. Silica production was modest and dominated by the >5.0 μm size fraction although specific rates were highest in the 0.6–5.0 μm size fraction over most of the cruise. Silica dissolution averaged 68% of silica production. The resupply of silicic acid via storm entrainment and silica dissolution supported a cumulative post‐bloom silica production that was 32% of that estimated during the main bloom event. Diatoms contributed significantly to new and to primary production after the initial bloom, possibly dominating both. Diatom contribution to organic‐carbon export was also significant at 40%–70%. Thus, diatoms can significantly contribute to regional biogeochemistry following initial silicic acid depletion, but that contribution relies on physical processes that resupply the nutrient to surface waters.

 

Diatoms serve as the major link between the marine carbon (C) and silicon (Si) biogeochemical cycles through their contributions to primary productivity and requirement for Si during cell wall formation. Although several culture-based studies have investigated the molecular response of diatoms to Si and nitrogen (N) starvation and replenishment, diatom silicon metabolism has been understudied in natural populations. A series of deckboard Si-amendment incubations were conducted using surface water collected in the California Upwelling Zone near Monterey Bay. Steep concentration gradients in macronutrients in the surface ocean coupled with substantial N and Si utilization led to communities with distinctly different macronutrient states: replete (‘healthy’), low N (‘N-stressed’), and low N and Si (‘N- and Si-stressed’). Biogeochemical measurements of Si uptake combined with metatranscriptomic analysis of communities incubated with and without added Si were used to explore the underlying molecular response of diatom communities to different macronutrient availability. Metatranscriptomic analysis revealed that N-stressed communities exhibited dynamic shifts in N and C transcriptional patterns suggestive of compromised metabolism. Expression patterns in communities experiencing both N and Si stress imply that the presence of Si stress may partially ameliorate N stress and dampen the impact on organic matter metabolism. This response builds upon previous observations that the regulation of C and N metabolism is decoupled from Si limitation status, where Si stress allows the cell to optimize the metabolic machinery necessary to respond to episodic pulses of nutrients. Several well-characterized Si-metabolism associated genes were found to be poor molecular markers of Si physiological status; however, several uncharacterized Si-responsive genes were revealed to be potential indicators of Si stress or silica production.

 

This dataset includes data from the nutrient amendment experiments. In these experiments, tracer additions (14C, 32Si) were used to quantify the level of Si, N, and Fe stress being experienced by the phytoplankton and to contextualize taxa-specific metatranscriptome responses for resolving gene expression profiles in the in situ communities. Seawater samples were collected on EXPORTS cruise DY131 during May 2021. This research focuses on the vertical export of the carbon associated with a major group of phytoplankton, the diatoms in the North Atlantic near the Porcupine Abyssal Plain. The major objective is to understand how diatom community composition and the prevailing nutrient conditions create taxonomic differences in metabolic state that combine to direct diatom taxa to different carbon export pathways. The focus is on diatoms, given their large contribution to global marine primary productivity and carbon export which translates into a significant contribution to the biogeochemical cycling of carbon (C), nitrogen (N), phosphorus (P), iron (Fe) and silicon (Si). It is hypothesized that the type and degree of diatom physiological stress are vital aspects of ecosystem state that drive export. To test this hypothesis, combined investigator expertise in phytoplankton physiology, genomics, and trace element chemistry is used to assess the rates of nutrient use and the genetic composition and response of diatom communities, with measurements of silicon and iron stress to evaluate stress as a predictor of the path of diatom carbon export. The EXPORTS field campaign in the North Atlantic sampled a retentive eddy over nearly a month. At the beginning of the cruise, nitrate was abundant while silicic acid was nearly undetectable. Such low dissolved Si concentrations significantly limit diatom silicification resulting in diatoms with reduced mineral ballast and low Si:C and Si:N ratios that would reduce sinking rates and competition for Si can alter diatom taxonomic composition. Both factors can the path cells follow through the food web ultimately altering diatom carbon export. Within each ecosystem state examined in the EXPORTS program, nutrient biogeochemistry, diatom and phytoplankton community structure, and global diatom gene expression patterns (metatranscriptomics) are characterized in the ocean. Nutrient amendment experiments with tracer addition (14C, 32Si) are used to quantify the level of Si, N, and Fe stress being experienced by the phytoplankton and to contextualize taxa-specific metatranscriptome responses for resolving gene expression profiles in the in situ communities. 

This dataset includes depth profiles in the euphotic zone of nutrient (nitrate, silicate, phosphate) concentrations and profiles of silicic acid uptake rates from seawater samples collected on EXPORTS cruise DY131 during May 2021. This research focuses on the vertical export of the carbon associated with a major group of phytoplankton, the diatoms in the North Atlantic near the Porcupine Abyssal Plain. The major objective is to understand how diatom community composition and the prevailing nutrient conditions create taxonomic differences in metabolic state that combine to direct diatom taxa to different carbon export pathways. The focus is on diatoms, given their large contribution to global marine primary productivity and carbon export which translates into a significant contribution to the biogeochemical cycling of carbon (C), nitrogen (N), phosphorus (P), iron (Fe) and silicon (Si). It is hypothesized that the type and degree of diatom physiological stress are vital aspects of ecosystem state that drive export. To test this hypothesis, combined investigator expertise in phytoplankton physiology, genomics, and trace element chemistry is used to assess the rates of nutrient use and the genetic composition and response of diatom communities, with measurements of silicon and iron stress to evaluate stress as a predictor of the path of diatom carbon export. The EXPORTS field campaign in the North Atlantic sampled a retentive eddy over nearly a month. At the beginning of the cruise, nitrate was abundant while silicic acid was nearly undetectable. Such low dissolved Si concentrations significantly limit diatom silicification resulting in diatoms with reduced mineral ballast and low Si:C and Si:N ratios that would reduce sinking rates and competition for Si can alter diatom taxonomic composition. Both factors can the path cells follow through the food web ultimately altering diatom carbon export. Within each ecosystem state examined in the EXPORTS program, nutrient biogeochemistry, diatom and phytoplankton community structure, and global diatom gene expression patterns (metatranscriptomics) are characterized in the ocean. Nutrient amendment experiments with tracer addition (14C, 32Si) are used to quantify the level of Si, N, and Fe stress being experienced by the phytoplankton and to contextualize taxa-specific metatranscriptome responses for resolving gene expression profiles in the in situ communities. 

This dataset includes concentrations of dissolved (<0.2 micrometers (µm)) manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in surface (~2 meters) samples collected between 15 August 2018 and 6 September 2018 during the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) cruise aboard R/V Roger Revelle cruise RR1813 at Ocean Station PAPA (Station P). 

This dataset includes concentrations of dissolved (<0.4 micrometers (µm)) and labile particulate (0.4-5 µm and >5 µm) phosphorus (P), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in shipboard incubation samples collected during the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) North Pacific (NP) cruise RR1813 on the R/V Roger Revelle near Ocean Station PAPA (Station P). 

This dataset includes concentrations of dissolved (<0.2 micrometers (µm)) manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in depth profile samples collected on 8 September 2018 during the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) cruise aboard R/V Roger Revelle cruise RR1813 at Ocean Station PAPA (Station P).