Table of Contents

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

Sampling Dates:
2021:
Gump Station, Moorea, French Polynesia
Aug 10 to Aug 19, 2021
Chief Scientist - Linda Wegley Kelly (SIO, lwegley@ucsd.edu)

2022:
Gump Station, Moorea, French Polynesia
Mar 29 to Apr 15, 2022
Chief Scientist - Linda Wegley Kelly

2023:
Gump Station, Moorea, French Polynesia
Aug 17 to Aug 25, 2023
Chief Scientist - Linda Wegley Kelly

Sample Collection. At every site on the fore- or backreef, salinity and temperature were measured using Manta Probes multi-parameter sondes (Eureka Instruments). Approximately 1.2 liters (L) of reef water was collected via peristalsis through 0.2 micrometer (µm) polyethersulfone filter cartridges (Sterivex, Millipore, UK) directly into durable, food-grade, flexible pouches (1.5 liter, blended foil and EVOH (ethylene vinyl alcohol) plastic, AstraPouch) before being transported to the laboratory for further processing. Ten milliliters (mL) of whole seawater was also collected into a syringe using peristalsis and immediately fixed with paraformaldehyde at a final concentration of 0.5% for subsequent flow cytometry analysis of microbial abundances. The Sterivex filtrate was used to rinse bottles to collect samples for inorganic nutrients, which were frozen and stored at -40 degrees Celsius (°C). For dissolved organic carbon (DOC) measurements, Sterivex filtrate was used to triple sample-rinse borosilicate vials with Teflon septa caps before collecting 40 mL (for deployment 2 and 3 in duplicates). Additionally, 500 mL of filtrate was transferred to triple-rinsed polycarbonate bottles for solid-phase dissolved organic matter (DOM) extraction. DOC and DOM samples were acidified to pH 2 using trace metal grade HCl. Acidified DOM samples were solid-phase extracted using the multichannel pump operating at a flow rate of 18 mL per minute onto Bond Elut PPL resin cartridges (200 milligrams (mg) bed mass, Agilent 2105005, USA). After desalinating the resin with LC-MS grade water (Fisher Chemical, Belgium), the cartridges were dried using Ultra High Purity compressed N₂ gas and kept frozen at -40°C.

Biogeochemical Measurements. Inorganic nutrients were analyzed using a Seal AA3 Segmented Flow Injection Autoanalyzer at the University of Hawai'i SOEST Laboratory for Analytical Biogeochemistry: Nitrate+nitrite (N+N) and silicate concentrations, ammonium, phosphate. Additionally, total dissolved nitrogen and total dissolved phosphorus were determined through separate injections, with UV and alkaline or acid persulfate in-line oxidation, respectively. DOC samples were analyzed using high-temperature platinum catalytic oxidation on a Shimadzu TOC-V at the University of Hawaii SOEST Laboratory. The analysis of fluorescent dissolved organic matter (fDOM) was conducted using a Horiba Aqualog scanning fluorometer. Samples for microbial cell concentrations were thawed and 200 microliters (µL) of each sample was stained with SYBR Green I stain for a final concentration of 1X. Bacterial cell counts were enumerated using an Attune Acoustic Focusing Cytometer (Applied Biosystems).

Note that while the instruments were the same from year to year, samples were not all run at the same time.

The shared data is unprocessed.

- Imported three original CSV files, Diel2021_BCODMO_Wegley_Kelly_Nelson.17Dec2025.csv, Diel2022_BCODMO_Wegley_Kelly_Nelson.17Dec2025.csv, and Diel2023_BCODMO_Wegley_Kelly_Nelson.17Dec2025.csv into the BCO-DMO data processing system.
- Treated "NA" as a missing data value (missing data are empty/blank in the final CSV file).
- Added a constant integer column Survey_Year with values 2021, 2022, and 2023 to their respective rows.
- Renamed multiple columns to standardize names across files and to comply with BCO-DMO naming conventions.
- Concatenated all three tables into a single combined table, mapping all 40 columns by name.
- Computed a new "ISO_DateTime_Local" datetime column by combining "Time" (format %H:%M) and "Date" (format %m/%d/%Y) columns, output formatted as %Y-%m-%dT%H:%M.
- Computed a new "ISO_DateTime_UTC" datetime column by combining the same "Time" and "Date" columns, interpreting the input as HST timezone and converting output to UTC, formatted as %Y-%m-%dT%H:%MZ.
- Added constant Latitude column ("-17.47722") and Longitude column ("-149.84258") to all rows, representing the general sampling area coordinates.
- Saved the final file as "1003286_v1_moorea_n_shore_diel_2021-2023.csv".

This project develops a core understanding of diel microbial ecology and biogeochemistry in coral reef ecosystems. It contextualizes how crucial nutrient recycling processes vary across gradients of coral cover and nutrient availability, two factors highlighted as the main drivers of reef decline in the Anthropocene, making the results useful to managers seeking to enhance ecosystem-based approaches to reef restoration. The investigators are collecting diel measurements of microbial and biogeochemical processes at coral reefs around Mo’orea at the Long Term Ecological Research site there (MCR-LTER). They are using established spatial gradients of benthic cover, from coral to macroalgal dominance, and nutrient inputs. Overall the research improves our understanding of how these key environmental factors influence diel microbe-DOM interactions and nutrient recycling. The ongoing macroalgal phase shifts observed at Mo’orea are hypothesized to be related to nutrient pollution, and this work directly informs understanding of how these changes are impacting nutrient cycling in the reefs of Mo’orea. The training of several undergraduate students and two graduate students, one in Biology and one in Oceanography is shared between two minority serving institutions of higher education. The project also supports active outreach programs with the Ocean Discovery Institute focused on engaging underrepresented high school students in ocean-oriented careers in San Diego, and with the UH College Sea Grant Program to support coral reef resilience initiatives locally in Hawai‘i.

Coral reefs exhibit some of the highest rates of primary production and decomposition of any ecosystem type yet persist in some of the most oligotrophic waters on the planet, implying tight recycling of macronutrients through organic matter. The last half century of work on the biogeochemistry of reefs have highlighted this bacterial decomposition of organic matter as a likely mechanism for maintaining nutrient retention and reef productivity. This project applies modern metagenomics and untargeted metabolomics to test clearly defined hypotheses of how diel microbe-DOM interactions drive nutrient recycling and retention in reefs. The investigators are first resolving coupled in situ diel dynamics of organic and inorganic C, N and P (using bulk elemental and spectroscopic methods), microbial abundances and population structures (using DNA sequencing and flow cytometry) and the chemical composition of DOM (using untargeted tandem mass spectrometry) in multiple reef habitats across a gradient of benthic cover and nutrient availability. These patterns inform the second in situ diel sampling campaign resolving the dynamic coupling of metabolic pathways (using metagenomics), exoenzymatic activity (using transcriptomics and enzyme assays) and transformations of specific metabolites (tracked via molecular networking) to distill common mechanisms of microbial organic matter decomposition that play a role in nutrient cycling. This project is being conducted within the Moorea Coral Reef Long Term Ecological Research program, leveraging a wealth of time series data on multiple reef habitats as well as contextualizing our in situ sampling with ongoing physical, geochemical and biological monitoring programs. By integrating cutting edge molecular approaches with well-established techniques in field ecology and microbial oceanography, this research program identifies key microbial and molecular players in the nutrient decomposition and remineralization processes long hypothesized to be central to maintaining healthy reefs.

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.