Table of Contents

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

Field seawater samples for all incubation experiments were collected from the Gulf Stream off the Coast of Wilmington, North Carolina, in November of 2020. 

Samples were filtered through Whatman GF/F filters prior to analyses. A Horiba Aqualog Fluoromeeter was used to acquire the EEM spectra. All spectra were inner filter corrected, scatter corrected and normalized to the Water Raman peak area.

EEM data were collected using the Horiba Aqualog Fluorometer, and all Fluorescence spectra were blank corrected, inner filter corrected and normalized to the Water Raman scattering.   

Software: Horiba Aqualog software version 4.3

Data are presented in two separate zip packages:
982174_v1_CONTROL.zip = All EEM data of the triplicate controls at each time point (no Synechococcus DOM added).
982174_v1_VDOM.zip = All EEM data of the triplicate Synechococcus DOM added samples at each time point during the one-year incubation.

All files are the direct exported files from the Horiba Aqualog software and can be opened directly in MS Excel or other software. The first part of the file name is indicative of the sample collection time in days. For example, T0 means beginning of incubation, T01 means day 1 of the experiment and so on.  The s annotation is presenting the number of replicate. For example the control sample T0s1 is replicate one at the beginning of experiment, T0s2 is the second replicate, and T0S3 is the third replicate.  For the VDOM samples, the replicate numbering is T0S4 for the first replicate.T0S5 for the second, and T0S6 for the third replicate, as an example. The remaining attributes of the file naming indicates the processing of the file prior to export.  RM means scatter correction or Raleigh masking (RM), IFE corresponds to inner filter correction (IFE), which uses the simultaneously measured absorbance data, and NRM means it was normalized to the Water Raman Scattering. 

Version 1:
* Unix command "dos2unix" was used on the .dat files to fix some encoding issues in some of the files.
* .dat files zipped into two packages and attached to page 982174_v1_CONTROL.zip and 982174_v1_VDOM.zip
* File inventory with md5sum added as a supplemental file.

NSF Award Abstract:
This study focuses on the sources and composition of colored dissolved organic matter (CDOM) in the ocean. CDOM is a part of water that absorbs sunlight. This material is important because it filters out harmful ultraviolet radiation. Scientists use it to track the movement of carbon and other important biological and chemical processes in the ocean. Organisms such as algae living in the open ocean have been shown to be sources of CDOM, but the chemical composition of these algal natural products remains to be discovered. Recent results from studying common algae show that viruses may break down algal cells and release material that looks like CDOM. This study will use new tools to find out if viruses and algae are creating this material and study its chemical makeup. This project will support two graduate students and provide summer internships for undergraduates through the NSF Research Experiences for Undergraduates (REU) program. The investigators will participate in a range of education and outreach activities.

The sources and structural nature of marine CDOM within the oceans remain unclear and continue to be a subject of debate. Marine in situ sources of CDOM have been suggested and some have been confirmed, but thus far none could explain the ubiquitous appearance of the so called "humic-like" CDOM component. Unique features of this component include its unusual exponential behavior in ultraviolet-visible (UV-Vis) absorbance with the absorbance extending well above 400 nm, and the large Stoke's shift in fluorescence spectroscopy. Picocyanobacteria are ubiquitous in the World's Oceans and make up 50 % of the autotrophic marine primary production. Preliminary results showed that the picocyanobacteria Synechococcus and Prochlorococcus release CDOM that matched the "humic-like" appearance of globally observed marine CDOM after virus-induced lysis. The main focus of this study is the characterization of the optical properties and molecular composition of viral-lysed DOM (VDOM) from different strains of Synechococcus and Prochlorococcus and additionally Trichodesmium which was shown in a previous study to also release CDOM. Associations between the chemical characterization information and metagenomics and transcriptomics data will be investigated for picocyanobacteria in the Pacific and Atlantic Oceans. This study includes long-term incubation experiments to determine the persistence of picocyanobacteria-derived CDOM as well as changes in microbial communities and processes (gene expression) that are related to the degradation of VDOM during the incubation period.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.