Award: OCE-1948042

Award Title: Collaborative Research: Assessing the role of compound-specific phosphorus hydrolase transformations in the marine phosphorus cycle
Funding Source: NSF Division of Ocean Sciences (NSF OCE)
Program Manager: Henrietta N. Edmonds

Outcomes Report

The chemical element phosphorus is a natural resource that we depend on in our daily lives. For example, it is a key building block for life in the ocean, where phytoplankton require it to produce half the oxygen that we breathe. However, phosphorus is relatively scarce over wide areas of the ocean surface where phytoplankton live. Some of this scarcity is natural, while some of it is due to human activities, which may exacerbate phosphorus scarcity in the future. As a result, phytoplankton have developed innovative strategies to acquire phosphorus from seawater. These strategies may become more and more important to safeguarding global oxygen supply and planetary health, if the future oceans experience heightened levels of phosphorus stress, as predicted. In this project, we have studied the strategies that marine microbes use in order to acquire phosphorus from the pool of complex phosphorus-containing molecules in seawater called dissolved organic phosphorus (DOP). DOP is composed of several major types of phosphorus, depending on the chemical bonds that are present. In P-esters (~80% of DOP), phosphorus and carbon are bound together through an oxygen atom (P-O-C), while in P-anhydrides (~10%), oxygen helps bind multiple phosphorus atoms to each other (P-O-P). Based on experiments with live microorganisms in the laboratory and natural ocean settings, we discovered that phytoplankton may prefer the P-anhydrides, or polyphosphates, over the P-esters as a nutritional source of phosphorus for growth. This preference could contribute to the much lower prevalence of P-anhydrides in DOP. In contrast, bacteria do not seem to share this preference for P-anhydrides and instead utilize them just as much as P-esters. This observation may be driven by the high requirement that bacteria have for organic carbon. Indeed, our results from the California Current Ecosystem point to bacterial carbon demand as a key factor underlying paradoxically high rates of DOP cycling that exist there, despite sufficient levels of phosphorus that are available in seawater. Our results also demonstrate that marine microbes acquire DOP through a diversity of enzymes that depend on metals such as iron, zinc, and manganese. Overall, our project shows that microbial cycling of phosphorus in the oceans is highly dynamic, regardless of overall phosphorus availability, and intricately linked with the cycling of carbon and trace elements. If phosphorus stress increases in the future oceans due to human activity, our results suggest that the microbial demand for trace elements, which are already in short supply, may increase as well. This project provided training and educational opportunities for two postdocs, two PhD students, and multiple undergraduate students, including individuals from underrepresented backgrounds in environmental science. Through this work, we have developed preliminary components of an educational app to teach K-12 students about the marine phosphorus cycle. Results have been communicated to scientific and general audiences through publications, conference presentations, seminars, outreach events, and videos. Last Modified: 01/23/2023 Submitted by: Julia M Diaz
DatasetLatest Version DateCurrent State
Bioavailability factor of polyphosphate, nucleotides, and methyl phosphonate in bioassay experiments with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 2019 2021-11-02Data not available
Phytoplankton and heterotrophic bacterial cell abundance over the incubation period ​in bioassay experiments with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 20192021-11-02Data not available
Concentrations of particulate phosphate in treatments amended with dissolved organic phosphate compounds in bioassay experiments (incubation 48h) with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 2019 2021-11-02Data not available
Concentrations of soluble reactive phosphate in treatments amended with dissolved organic phosphate compounds in bioassay experiments (incubation 48h) with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 2019 2021-11-02Data not available
Turnover time and uptake rates of phosphate in treatments amended with dissolved inorganic and organic phosphate compounds in bioassay experiments (incubation 48h) with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring 2019 2021-11-02Data not available
Alkaline phosphatase activity over bioassay experiments with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 20192021-11-02Data not available
Alkaline phosphatase activity (APA) Michaelis-Menten kinetic parameters (Vmax and Km) in both whole and filtered seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Bioavailability factor of polyphosphate, nucleotides (ATP and AMP) and phosphonate in seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Concentrations of particulate phosphate in seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Phytoplankton and heterotrophic bacterial cell abundance in seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Optical density and cell counts from flow cytometry of Ruegeria pomeroyi laboratory cultures2023-06-09Final no updates expected
Dissolved organic phosphorus (DOP) hydrolysis rates from Ruegeria pomeroyi laboratory cultures2023-06-09Final no updates expected
Hydrolysis rates from dissolved organic phosphorus (DOP) hydrolysis experiments with marine cyanobacterium Synechococcus laboratory cultures (WH8102 and WH5701) from 2018-20232024-05-28Final no updates expected
Laboratory-cultured Synechococcus (WH8102 and WH5701) growth (vivo fluorescence) on dissolved organic phosphorus (DOP) from experiments between 2018-20232024-06-03Final no updates expected
Laboratory-cultured Synechococcus (WH8102 and WH5701) MUF-P hydrolysis inhibition by dissolved organic phosphorus (DOP) from experiments between 2018-20232024-06-06Final no updates expected
In vivo fluorescence and flow cytometry cell counts from dissolved organic phosphorus (DOP) hydrolysis experiments with marine cyanobacterium Synechococcus laboratory cultures (WH8102 and WH5701) from 2018-20232024-06-06Final no updates expected

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Principal Investigator: Julia M. Diaz (University of California-San Diego Scripps Inst of Oceanography)