Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

This dataset was utilized for Waggoner et al. (submitted) Figure 2 and supplementary figure 2. See "Related Datasets" section on this page for other closely-related data from this study published in Waggoner et al. (submitted).  They are also listed under the BCO-DMO Project Page: https://www.bco-dmo.org/project/747715.

Synechococcus Growth– Axenic Synechococcus WH8102 (open ocean strain) and WH5701 (coastal strain) were obtained from the National Center for Marine Algae and Microbiota (NCMA, Bigelow Laboratories, East Boothbay, Maine). Both strains were grown in batch culture using SN media (Waterbury et al. 1986) made with aged, filtered (0.2 µm), and autoclaved (120°C, 30 minutes) seawater from station ALOHA (A Long-term Oligotrophic Habitat Assessment). At the late-exponential phase, cultures were transferred in triplicate to one of two SN media: (1) +Pi (45 µmol L^-1 KH₂PO₄, following Waterbury et al. (1986)) and (2) -Pi (no KH₂PO₄ added; Pi below detection limit). All cultures were incubated at 25°C on a 12h:12h light cycle at 130 µmol m^-1 s^-1 in sterile culture flasks with a vent cap (0.22 µm hydrophobic membrane).

DOP Hydrolysis– Representative phosphoester (P-ester) and polyphosphate (PolyP) hydrolysis rates were determined as in Diaz et al. (2018). The nucleotide AMP was used as a model P-ester, 3-PolyP as a model PolyP, and ATP as a representative containing both P-ester and P-anhydride bonds. Two separate experiments were conducted with both Synechococcus strains to determine DOP hydrolysis in the presence (whole cell) and absence (cell-free filtrate) of cells (Diaz et al. 2018, 2019). The +Pi and -Pi cultures were subsampled approximately every three days over ~20 days to obtain whole cell and cell-free DOP hydrolysis results along each phase of the cellular growth curve. To prepare cell-free filtrates, the +Pi and -Pi culture aliquots were aseptically filtered (0.2 µm) at each subsampling day. To determine DOP hydrolysis rates, the production of Pi was measured over time. Aliquots (200 µL) of +Pi and -Pi treatments were amended with a single DOP substrate (3-PolyP, ATP or AMP; 20 µmol L^-1 P, final concentration) in triplicate wells of a non-treated standard 96-well transparent microplate and incubated over 6-hours. An unamended control treatment to track Pi concentrations in the cultures over time were prepared in triplicate and monitored in parallel. Pi (or soluble reactive phosphorus) was measured using a standard colorimetric protocol (Hansen and Koroleff 1999) on a multimode plate reader (SpectraMax® M2, Molecular Devices). Absorbance read at 880 nm was calibrated using a standard curve of monopotassium phosphate (0, 0.5, 1, 2, 5, 10, 20, 40, 50, 75 µmol L^-1; KH₂PO₄). The average detection limit of Pi using this method, defined as three times the standard deviation of the triplicate blank measurements, was 0.125 ± 0.005 µmol L^-1. The calibration curve was prepared with 0.2 µm filtered ALOHA seawater with a Pi background concentration below the detection limit.

Organism identifiers (Life Science Identifier, LSID):
Synechococcus, urn:lsid:marinespecies.org:taxname:160572

* Sheet 1 of submitted file "Synechococcus_DOPHydrolysisExperiment_HydrolysisRates.xlsx" was imported into the BCO-DMO data system for this dataset.

* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores.  Can not start with a number]

NSF Award Abstract:
Phosphorus (P) is an essential building block for life. Because P is in short supply over vast areas of the ocean, P availability may control biological productivity, such as photosynthesis and carbon fixation, which has implications for uptake of the greenhouse gas carbon dioxide and thus climate regulation. Marine microorganisms must satisfy their nutritional requirement for P by obtaining it from seawater, where P is present in a variety of chemical forms, from simple phosphate ions (Pi) to complex dissolved organic phosphorus (DOP) molecules. The concentration of DOP vastly exceeds Pi over most ocean areas, therefore DOP is a critically important source of P for marine microbial nutrition and productivity. However, much remains unknown about the contribution of specific DOP compounds to the P nutrition, productivity, and structure of marine microbial communities. In this project, the investigators will conduct field experiments in the Atlantic Ocean and perform a series of controlled laboratory studies with pure enzymes and microbial cultures to determine how and to what extent different DOP compounds are degraded to Pi in the marine environment. Furthermore, the contribution of these compound-specific DOP molecules to microbial P nutrition, carbon fixation, and community structure will be determined, thus advancing the current state of knowledge regarding the factors that control the activity and distribution of microbial species in the ocean, and the ocean?s role in the climate system. This project will support two female junior investigators, a postdoctoral researcher, and graduate and undergraduate students. The undergraduate students will be recruited from the Marine Sciences program at Savannah State University, an Historically Black Colleges and Universities. In addition, results will be incorporated into new hands-on K-12 educational tools to teach students about microbial P biogeochemistry, including a digital game and formal lesson plans with hands-on demos. These tools will be validated with K-12 educators and will be widely accessible to the public through various well-known online platforms. These activities will thus reach a broad audience including a significant fraction of underrepresented groups.

P is a vital nutrient for life. Marine microorganisms utilize P-hydrolases, such as alkaline phosphatase (AP), to release and acquire phosphate (Pi) from a wide diversity of dissolved organic P (DOP) compounds, including P-esters (P-O-C bonds), phosphonates (P-C), and polyphosphates (P-O-P). Compound-specific DOP transformations have the potential to exert critical and wide-ranging impacts on marine microbial ecology (e.g. variable DOP bioavailability among species), biogeochemistry (e.g. P geologic sequestration via formation of calcium Pi), and global climate (e.g. aerobic production of the greenhouse gas methane by dephosphorylation of methylphosphonate). However, the mechanisms and comparative magnitude of specific DOP transformations, in addition to their relative contributions to microbial community-level P demand, productivity, and structure, are not completely understood. This study will fill these knowledge gaps by tracking the fate of specific DOP pools in the marine environment. Specifically, this project will test four hypotheses in the laboratory using recombinant enzymes and axenic cultures representative of marine eukaryotic and prokaryotic plankton from high and low nutrient environments, and in the field using observational and experimental approaches along natural Pi gradients in the Atlantic Ocean. In particular, the investigators will reveal potential differences in the hydrolysis and utilization of specific DOP compounds at the community- (bulk enzymatic assays), taxon- (cell sorting of radiolabeled cells in natural samples), species- (axenic cultures) and molecular-levels (pure enzyme kinetic studies and cell-associated proteomes and exoproteomes). Results from our proposed work will provide a robust understanding of the enzymatic basis involved in the transformation of specific forms of DOP and create new knowledge on the relative contribution of these specific P sources to Pi production, marine microbial nutrition, community structure, primary productivity, and thus global carbon cycling and climate. In particular, our refined measurements of the concentration of bioavailable DOP and our unique estimates of DOP remineralization fluxes will provide critical new information to improve models of marine primary production and P cycling.